【Objective】 This study aims to explore the characteristics of surface runoff and sediment yield of economic forest land with different planting and management measures in the hilly region of Southern Jiangsu. 【Method】 Analyzing the process of runoff and sediment yield on the slope based on the observation data of runoff plots in Wuxi Yixing City in 2021. 【Result】 ① In the hilly region of Southern Jiangsu, the runoff and sediment yield of economic forest mainly occurred from May to August, in which the runoff and soil erosion yield of different runoff plots accounted for more than 72.5% and 68.7%, respectively. ② The comparison of slope runoff and erosion in different runoff plots is as follows: Ⅰ-peach forest (with grass) <Ⅱ-peach forest (weeding), and compared with Ⅱ, the annual runoff reduction of Ⅰwas 156.3% and the annual soil erosion reduction was 122.9%; Ⅴ-tea garden (cross slope) < Ⅳ-tea garden (along slope), and compared with Ⅳ, Ⅴ had an annual runoff reduction of 57.0% and erosion reduction of 41.5%. In addition to it, the annual runoff of different economic forest slopes was reduced by 50.6%-380.4%, and the annual soil erosion was reduced by 155.3%-513.1% compared with Ⅲ-bare slope (blank). ③ The maximum runoff and erosion of the Ⅰ-Ⅴ plots accounted for 15.3%, 14.5%, 10.8%, 12.5%, 14.4% and 7.9%, 6.3%, 4.5%, 7.1%, 8.0% of the total, respectively. It can be seen that high-intensity rainfall has an important impact on slope soil erosion. 【Conclusion】 Soil erosion in runoff plots of different economic forests was significantly positively correlated with rainfall, average rainfall intensity, I30 and runoff depth, and the correlation with soil water content before rainfall was complex, in which soil erosion had the closest relationship with runoff depth (R2=0.553).
【Objective】 The aims of this research are to elucidate the effects of simulated nitrogen (N) and phosphorus (P) deposition and litter treatment on soil organic carbon (SOC) components in Pinus koraiensis forests, to provide a theoretical basis for improving soil fertility, ecosystem productivity and stability of P. koraiensis forests. 【Method】 Taking broad-leaved P. koraiensis forest and P. koraiensis piantation in Liangshui National Nature Reserve of Heilongjiang Province were studied. Each forest type was set with three plots of 20 m×30 m, and 12 quadrats were set in each plot. Each quadrat was subjected to treatments. (1) Litter treatment: three levels were removed (R), addition (A) and unchanged (CK1) were tested in October 2017, and three replicates were set for each level. (2) Simulated N and P deposition treatment: from May to October in 2018 and 2019, the experiment was carried out once a month. Four levels were set: low (L) (N and P supplemental levels are 5 g/m2), middle (M) (N is 15 g/m2, P is 10 g/m2), high (H) (N is 30 g/m2,P is 20 g/m2), and no N and P (CK2), and three replicates were set for each level. The amounts of N and P were 2 L for each quadrat, and the same volume of stream water was sprayed for the control. In May, August and October of 2018 and 2019, three sampling sites were randomly selected in each quadrat. Collected the soil samples at 0-20 cm soil layer, and pick out plant roots, rocks larger than 2 mm and soil animals, then put it in a cool and ventilated place for natural air drying. After that it was extracted according to the extraction method of SOC for each component and measured using a TOC elemental analyzer. Finally, SPSS 21.0 and Canoco 5.0 were used for statistical analysis. 【Result】 (1) In the first year of the experiment, the low dose N and P deposition treatments significantly affected the SOC components. (2) In the second year, the middle dose significantly affected the SOC components. (3) For the two years, the SOC content was the highest in the broad-leaved P. koraiensis forest. The contents of mineral-bound, easily oxidized organic carbon, and total organic carbon were the highest in August. Litter removal and addition treatments had no effect on the SOC components. 【Conclusion】 (1) In the first year of the experiment, the low dose of N and P promoted the accumulation of SOC components. (2) In the second year, the middle dose treatments promoted the mineralization of SOC components. (3) In the second year of the experiment, the broad-leaved P. koraiensis forest was beneficial to the accumulation of SOC components. Environmental conditions in August is favorable for the formation of mineral-bound, easily oxidized organic carbon and total organic carbon. Litter removal and addition can promote the release of SOC components.
【Objective】 This research aims to investigate the effects of different organic matters on soil organic carbon and soil respiration in Pinus tabuliformis forest. The results can provide reference for predicting soil carbon budget of P. tabuliformis forest ecosystem in Taiyue Mountain, Shanxi Province, China.【Method】A random block design was used to add biochar (BC), maize straw (JG), Quercus mongolica leaf (LD) and P. tabuliformis leaf (YS) to 0-20 cm soil of P. tabuliformis forest in Taiyue Mountain, with no addition as control check (CK). Li-8100 automatic measurement system for CO2 flux was used to continuously measure soil respiration rate under organic matter addition, and the contents of soil organic carbon (SOC), microbial biomass carbon (MBC), readily oxidized carbon (ROC) and dissolved organic carbon (DOC) in each treatment were monitored. Based on the relationship between soil respiration and soil organic carbon and its components, the effects of organic matter addition on soil respiration and soil carbon components of P. tabuliformis forest in Taiyue Mountain were investigated. 【Result】 (1)The addition of biochar significantly reduced the soil respiration rate, and the soil respiration rate was significantly increased by 11.67% after adding JG compared with CK, while there was no significant difference between other treatments and CK. (2)In August 2014, the addition of JG significantly increased the soil SOC, MBC, ROC and DOC contents, the addition of BC significantly increased the soil MBC content, and the addition of LD and YS significantly increased the soil SOC and MBC contents. In October 2014, the addition of JG significantly increased soil SOC, MBC, ROC and DOC contents, the addition of LD significantly increased soil MBC and ROC contents, and the addition of YS significantly increased soil SOC and MBC contents. In March 2015, the addition of JG significantly increased soil SOC, MBC and ROC contents, while the addition of LD significantly increased soil ROC contents. In May 2015, JG supplementation significantly increased soil MBC content.(3) Compared with CK, soil respiration at 10 (R10) was significantly decreased by 18.01% after BC addition, and increased by 30.88% after YS leaf addition. Other organic compounds had no significant effect on soil respiration temperature sensitivity (Q10) and R10. (4) Soil respiration rate was significantly positively correlated with soil temperature, SOC, MBC, ROC and DOC. 【Conclusion】 The addition of organic matter significantly affected soil carbon dynamics and soil temperature and humidity, which all had significant effects on soil CO2 emissions. The addition of JG had the most significant effect on soil organic carbon and its carbon components, but the soil respiration rate was the highest, which was not conducive to carbon storage. The addition of LD could increase soil active organic carbon content and significantly improve soil organic carbon pool quality in a short term, while the addition of BC could increase soil microbial biomass carbon content in a short term, and significantly reduce soil respiration rate, which has the best effect on reducing soil CO2 emission.
【Objective】 Inorganic carbon constitutes a large proportion of soil carbon storage in the coastal area of northern Jiangsu; therefore, estimating the soil inorganic carbon (SIC) content with precision and accuracy is a prerequisite for further study.【Method】Soil samples at different depths (i.e., 0-10, ≥10-20, ≥20-40, ≥40-60, ≥60-80, and ≥80-100 cm) were collected from a poplor plantation and a Spartina alterniflora wetland. The SIC content as well as its recovery rate were then estimated using a calcimeter, carbon dioxide (CO2) absorption and indirect methods, respectively. This was done to compare the precision and accuracy of the three methods. 【Result】 The ranges of the SIC content estimated by the calcimeter, CO2 absorption and indirect methods were 4.25-9.93, 6.18-11.50 and 5.50-12.60 g/kg with the average of 8.11, 9.58 and 9.54 g/kg, respectively. When the amendment rate of exogenous calcium carbonate was 2.35-12.90 g/kg, the averaged recovery rates of SIC content estimated by the calcimeter, CO2 absorption and indirect methods were 96.9%, 105.0% and 71.5%, respectively. According to the SIC content corrected by the recovery, the SIC contents measured by the indirect method were significantly higher than those measured by the other two methods, indicating that the recovery of SIC measured by the indirect method was underestimated. The coefficients of variation of the SIC content in the parallel soil samples estimated by the calcimeter, CO2 absorption and indirect methods were 1.19%-4.99%, 0.52%-3.34% and 1.51%-6.79% with averages of 2.44, 1.36 and 3.25 g/kg, respectively. 【Conclusion】 The calcimeter, CO2 absorption and indirect methods can all be used to determine the SIC content of coastal soils from Northern Jiangsu, although the SIC estimated by the CO2 absorption and indirect methods were both higher than those measured by the calcimeter method. However, the SIC recovery rate estimated by the indirect method was underestimated, and this was mainly due to the overestimation of the organic carbon content of the acid-treated soils by the potassium dichromate oxidation method. The accuracy of the CO2 absorption method was the highest, followed by that of the calcimeter and indirect methods. However, the calcimeter method is time-saving, whereas the indirect method can quantify the contents of soil organic carbon and SIC simultaneously. In the future, researchers should choose a method that is in line with their specific research purposes.
【Objective】 The composition of bacterial and fungal communities in rhizosphere soil is not only affected by plant species and varying growth periods, but also by the introduction of foreign genes. The contents of betaine or late-embryogenesis-abundant proteins could be increased in transgenic poplar with betA and TaLEA genes, which were obtained by genetic engineering technology. Drought resistance and salt tolerance were also enhanced in these transgenic poplars. PsnWRKY70 is a negative regulator of the salt stress response signal transduction network. Salt tolerance of WRKY70 inhibitory expression line was significantly higher than that of the line wild type (WT). To clarify the drought resistance and salt tolerance of transgenic poplar with betA, TaLEA and WRKY70, the composition of rhizosphere soil bacterial and fungal communities of transgenic poplar was analyzed to provide a reference for its environmental and ecological security evaluation. 【Method】 In this study, rhizosphere soil was collected from a two-year-old poplar with modified TaLEA, betA and WRKY70 genes, and WT plants were used as controls. The 16S rRNA and ITS sequences of microorganisms in the rhizosphere soil were sequenced using the Illumina-MiSeq highthroughput sequencing platform. The population structures and community compositions of the bacteria and fungi in the rhizosphere soil were then determined and analyzed. The purpose of this study was to understand how transgenic poplar influences the composition of soil microbial communities before the subsequent environmental release. 【Result】 For the composition of bacterial communities, Alpha diversity showed that the Simpson index of betA transgenic poplar was significantly lower than that of the WT, the Shannon and Simpson indexes of WRKY70 transgenic poplar were also significantly lower than that of WT. The fungal indices of the transgenic poplars were significantly lower than those of the WT. The Venn diagram, principal component analysis, and cluster heat map showed that there was little difference in the microbial community structure between TaLEA and WT plants. The microbial communities of transgenic betA and WRKY70 poplars were similar. Based on the composition and abundance analysis at the genus level in the rhizosphere soil collected from transgenic poplars, the abundance of beneficial bacteria, such as Rhodanobacter and Gemmatimonas, increased to varying degrees. The abundance of the beneficial mycorrhizal fungi Inocybe in TaLEA and betA plants was significantly higher than that in the other two samples. The abundance of Sphaerosporella, Hebeloma and Laccaria significantly increased only in TaLEA plants. Conversely, the abundance of pathogenic fungi, such as Didymella and Cadophora, decreased by more than 85% compared with the WT. 【Conclusion】 The diversity of rhizosphere microorganisms was influenced by transgenic poplars, which may be beneficial to plant growth and enhance stress resistance. However, more research is needed to prove whether these microorganisms play a vital role.
Saline-alkaline soil is not suitable for farming because of its low fertility, consolidation, poor biological activity, low temperature, high salt content and other obstacles. However, the national food security strategy of “Secure the rice bowl in China” requires more efforts to “ask for grains from saline-alkaline land”. Practical experiences have proved that the application of natural or industrial by-product gypsum can effectively improve the properties of saline-alkaline soil, thus increasing the productivity of saline-alkaline land.This study compares the progress of related research at home and abroad for more than 100 years, reviews and summarizes the existing research results of gypsum improvement of saline-alkaline soil, and intends to providea theoretical basis for the improvement and comprehensive promotion of the gypsum improvement technology system. It is intended to provide a theoretical basis for the improvement and comprehensive promotion of the gypsum technology system for improving saline-alkaline soil.The analysis suggests that numerous studies conducted since 1895 have revealed the mechanisms based on the cation exchange process and immobilization process, established several formulas for calculating the suitable application amount, shown that soil bulk density, thickness of soil modification layer, exchangeable sodium percentage and soil cation exchange capacity are representative factors influencing the appropriate amount of gypsum application, and the method of gypsum application based on the degree of saline-alkaline soil was developed. The beneficial effects of gypsum application on soil physical and chemical biology were clarified. At present, the application of gypsum to improve saline-alkaline soil needs to be accompanied by irrigation measures, and the quota is generally 150-200 m3 of gypsum per 666.67 m2. The best method is the continuous irrigation such as sprinkler irrigation or drip irrigation, and different saline-alkaline soil and crop characteristics require different application amounts and irrigation methods. The existing research and practical results provide strong support for the efficient use of saline-alkaline soil. However, there is still a need to further integrate and unify the appropriate application formula. The calculation formula of suitable application amounts should be further integrated and unified, and the calculation method should be established across regions and applicable to various scenarios. The biogeochemical processes of passively introduced elements should be studied in depth, and the response mechanism of soil ecosystem should be revealed; the monitoring level of ecological and environmental risks brought by gypsum application should be improved, and the long-term dynamic quantitative assessment should be carried out.
【Objective】 The growth adaptability of Rhododendron moulmainense in different environments in Shenzhen urban parks was studied to provide a reference for its introduction into urban areas as an ornamental tree species. 【Method】 Ten-year-old R. moulmainense with the same growth statuses, and three planting environments, including waterfront, highland and flatland, were selected in Shenzhen Xiangmi Park. These trees were planted under two irradiance environments, such as half-light and full light, and divided into six experimental plots. The trees flowering rate, growth rate, chlorophyll content, changes of light response curves and diurnal changes of photosynthetic characteristics were determined. 【Result】 (1) Different planting environments had different effects on the morphology and growth of R. moulmainense. The number of flower buds, thickness of new shoots, volume of new shoots and number of new shoots of R. moulmainense in the waterfront half-light plot were significantly higher than those in other test plots (P < 0.05). (2) The content of the chlorophyll a(Chla), chlorophyll b(Chlb) and total chlorophyll(Chlt) in the leaves of R. moulmainense on the flatland-full light plot were significantly higher than those on other test plots, while the Chla, Chlb and Chlt in the flatland half-light plot showed the lowest values. The carotenoid content(Car), Chl a/Chl b(mass ratio, the same below), and Chlt/Car in the highland half-light plot were significantly higher than those on other plots. (3) The maximum net photosynthetic rate(Pn,max), light compensation point(LCP), and light saturation point(LSP) of leaves in the waterfront full-light plot were higher than those on other test plots, the apparent quantum efficiency(AQY) of highland half-light was the highest, and the dark respiration rate(Rd) of leaves in flatland half-light was the highest.【Conclusion】 The chlorophyll content of R. moulmainense will decrease when the soil water content is high or the drainage is not smooth. The plant height and the number of flower buds and new shoots decreased when the light intensity was too high. On the contrary, the growth of new shoots and the formation of flower buds of R. moulmainense were promoted when the light intensity in the environment was weakened, indicating that the soil environment with appropriate shading and water permeability should be considered when planting R. moulmainense in urban parks.
【Objective】 This research aims to explore the effects of different storage time on the separation effects of soil animals under the condition of soil low temperature storage, so as to provide a reference for a large number of collection and separation of soil animals.【Method】 On October 6, 2018, the natural Mongolian oak (Quercus mongolica) forest in Songhua Lake Nature Reserve, Jilin City, the soil at different depths was drilled by the five point sampling method, brought back to the laboratory and stored in the indoor 4 ℃ refrigerator. The Berlese-Tullgren method was used to separate the soil animal samples of Oribatida and Collembola on the same day, 7, 14, 21 and 28 days later. The species and genera of Oribatida and Collembola were determined according to the morphological characteristics under the microscope.【Result】 With the increase of preservation time, the individual number and the number of species of soil animals of Oribatida and Collembola showed a downward trend; Under the same preservation time and different depths, the species of Oribatida and Collembola had significant differences with other depths (P<0.05), and showed a downward trend. The number of species of Oribatida and Collembolan collected in litter layer was significantly different from that in 5, 10 and 15 cm soil layers (P<0.05), and also showed a downward trend.【Conclusion】 Increasing the soil preservation time under cold storage will reduce the separation efficiency of medium-sized soil animals. The separation effect of Oribatida is the best on the day of soil collection, and the isolation of Collembola was not affected by soil storage time. Oribatida and Collembola animals were mainly collected in the litter layer. The soil depth increased while the soil animals decreased.
The water conversion process of the soil-plant-atmosphere continuum (SPAC) system is an important research topic in ecological hydrology. Stable isotopes, as natural tracers, can effectively trace, integrate and indicate water input, output and transformation processes in the SPAC system. Based on a brief introduction of the application principle of stable isotopes, this study reviewed the progress of research within the context of vertical water transport at the soil-root interface; fractionation in plant water transport; and water exchange at the plant canopy-atmosphere interface based on stable isotope techniques. This study explored the limitations of stable isotopic techniques in terms of elucidating fractionation processes, temporal resolution and spatial heterogeneity in water transformation studies of SPAC systems. Finally, we conclude by providing corresponding suggestions for the future application and development of stable isotope technology. Specifically, we recommend that future research within the context of spac water conversion based on stable isotopes should focus on the following three aspects:(1)In situ observation of the isotopic composition of various isotopic pools with the help of portable isotopic analyzers. (2) Multi isotope analysis of pool isotope composition to analyze the water transport process at the soil root interface, to further determine the water source of trees, and subsequently improve the accuracy of source identification and division, and improve the stable isotope application model. (3) Using isotope labeled pot experiments to accurately control the water source of leaf water absorption, and to analyze the location and time of leaf water absorption at a more fine level. (4) Using controlled isotope labeling and centrifugal technology to extract juice from xylem vessels, the isotope deviation of each pool was compared and analyzed to further study the isotope fractionation mechanisms.
【Objective】 The effects of different thinning retention densities and different ratios of N and P fertilizers on the growth and timber assortment structure of middle-aged Chinese fir (Cunninyhamia lancelata) forests were analyzed.【Method】 Nine standard plots were set up in a 9-year-old Chinese fir plantation with 23 site indices at the Yangkou National Forest Farm in Fujian Province. An orthogonal experimental design was used to carry out matching experiments of thinning and fertilization. The thinning retention density was 1 200, 1 500 or 2 250 trees/hm2; the N fertilizer application rate was 0, 100 or 200 g per tree; and the P fertilizer application rate was 0, 250 or 500 g per tree,this experiment lasted for four years.【Result】 The results show that different thinning densities and N and P application rates had no significant effect on tree height growth. Different thinning retention densities had a greater impact on the average DBH growth of Chinese fir forests, and revealed a significant difference between the minimum density and the maximum density. The application rate of N fertilizer and P fertilizer had little effect on the average DBH growth of Chinese fir forest, and there was no significant difference between different N and P application rates. There was a significant difference in the average volume increase per plant among different thinning retention densities, and the application of N and P fertilizers had little effect on the average per tree volume increase. The increase in stand volume among stands of different densities was not significant, but higher levels of N and P application rates could promote a significant increase in stock volume increase. The low thinning retention density significantly affected the large-diameter wood yield, and it was highest under the retention density of 1 200 trees/hm2. Higher yields of medium diameter timber were obtained at retention densities of 1 500 and 2 250 trees/hm2. A high level of N fertilizer application promoted an increased large-diameter wood output, while a high level of P fertilizer application promoted an increased medium-diameter wood output, but the result was not significant.【Conclusion】 In general, compared with the application of N and P fertilizers, the effect of density regulation on the growth and timber structure of Chinese fir middle-aged forests is more significant. The lower forest density is key for cultivating large-diameter fir timber, and the effects of N and P fertilizer application require long-term observation.
【Objective】 The effects of foliar spraying of medium and trace element fertilizers on the growth, fruit yield and quality of Xanthoceras sorbifolium were studied in order to screen the most suitable medium and trace element fertilizers for X. sorbifolium.【Method】 Based on the field experiment and the 4-year-old X. sorbifolium as the experimental material, the foliar surface was sprayed with medium and trace element fertilizer on the basis of soil fertilization and five fertilization treatments, including boron (B), iron (Fe), zinc (Zn), molybdenum (Mo) and silicon (Si) were set; the spraying mass concentrations were 150, 65, 300, 10 and 210 mg/L, respectively. With foliar spraying of the same amount of clear water as the control (CK), there were six treatments in total. Foliar spraying was carried out three times. Growth and physiological indices such as tree height growth, ground diameter growth, crown width growth and chlorophyll content of X. sorbifolium before and after leaf fertilizer application were measured. After the fruit matured, fruit yield and quality indices such as fruit diameter, number of fruits per plant, number of seeds per fruit, 1 000 seeds mass, seed kernel yield and 100 leaves dry matter mass were measured. Based on the measured indices, the fertilization effect was evaluated by a principal component analysis, and then the effects of different medium and trace element fertilizers on X. sorbifolium were analyzed. 【Result】 The effects of medium and trace elements on the growth of X. sorbifolium are mainly reflected in the following aspects: tree growth, 100 leaves dry matter mass, chlorophyll content, fruit yield, and quality; different elements have different effects. In terms of tree growth, Zn fertilizer significantly increased the tree height and crown width growth of X. sorbifolium, with an increases of 25.53 and 22.33 cm, respectively (1.40 and 1.46 times that of CK treatment); Si fertilizer significantly increased the tree height, ground diameter and crown width growth, with increases of 22.60 cm, 7.66 mm and 21.17 cm, respectively (1.24, 1.36 and 1.38 times that of CK treatment; P<0.05). Mo fertilizer increased 100 leaves dry matter mass of X. sorbifolium, while Mo fertilizer and B fertilizer increased the chlorophyll content. Zn fertilizer significantly increased the fruit diameter of X. sorbifolium, the fruit yield per plant, the number of seeds per fruit, 1 000 seeds mass,and seed kernel yield, which were 1.33, 1.19, 1.22, 1.29 and 1.16 times higher than those of CK treatment, respectively. Other medium and trace elements also showed certain promotional and improvement effects on tree growth, fruit yield and quality of X. sorbifolium. The principal component score of each fertilization treatment showed that the effect of Zn fertilizer was the best, followed by Si, Fe, B, Mo fertilizer and CK treatment.【Conclusion】 Appropriate medium and trace element fertilizers can effectively promote the tree growth of X. sorbifolium, enhance its physiological function on leaves, and improve the yield and quality of seeds.
【Objective】 The effects of soil water content on the leaf physiology and fruit quality of blueberries were studied. 【Method】 In this study, a 5-year-old Vaccinium ashei plant was used to analyze the effects of different soil water content on the plant physiology and fruit quality of blueberries using a manual control test. 【Result】 The results showed that the contents of malondialdehyde (MDA), proline and soluble sugar in blueberry leaves initially decreased and then increased with an increase in soil water content, while the activity of the superoxide dismutase (SOD) showed an “M”-type trend, and the chlorophyll content initially increased and then decreased. The single fruit weight of blueberry fruits showed an “S”-type change trend, the contents of anthocyanin and vitamin C (VC) in fruits increased initially and then decreased, and the content of soluble solids (SSC) decreased initially and then increased. The leaf physiology and fruit quality of blueberries were significantly affected when the soil relative water content was lower than 35%-40% or higher than 95%. The MDA, proline and soluble sugar contents in the leaves significantly increased; however, the chlorophyll and SOD contents decreased, and the chlorophyll content decreased significantly. The accumulation of anthocyanins and VC in fruits decreased significantly, whereas SSC increased. The weight of the blueberry fruits increased with soil water content. When the soil water content reached 65%-70%, the weight of the blueberry fruits did not increase significantly. Based on the membership function method, a soil moisture content of 65%-70% was considered suitable for the blueberry growth. Among the four blueberry varieties, the difference between the normal growth gradient of ‘Gardenblue’and ‘Baldwin’ in T3 treatment (65%-70%) and strong stress conditions of T1 (35%-40%) and T5 (95%-100%) was greater than that of ‘Brightwell’ and ‘S13’.‘Gardenblue’ and ‘Baldwin’ had slightly lower stress resistance to soil water, while ‘Brightwell’ and ‘S13’ had slightly better stress resistance. In the fruit growing stage, the increasing soil water content was beneficial to improve the quality of ‘Gardenblue’ and ‘Brightwell’ fruits. A comprehensive analysis showed that plants of all varieties were in the optimum water environment in T3 treatment. 【Conclusion】 Both too high and too low soil water content could affect the physiological and biochemical characteristics of blueberry leaves and fruit quality. Considering the requirements of the high yield and fruit quality, the optimal soil water content was 65%-70%.
【Objective】The main objective of this study is to comprehensively evaluate the soil fertility characteristics and spatial distribution of street trees in Shanghai City, to promote their effective management by improving health and soil quality, optimizing fertilization, and ensuring the sustainable development of green infrastructure.【Method】We collected tree soil samples from 136 roads across 16 administrative districts in Shanghai, China and measured soil fertility indices, such as soil bulk density, pH and main nutrient contents. Combining single factor analysis and GIS spatial distribution, we evaluated the soil fertility characteristics of street trees in Shanghai. 【Result】The results showed that street tree soil in Shanghai was predominantly silt loam, highly alkaline, and had a high average soil bulk density. Except for available potassium, main nutrient indices contents such as organic matter, total and available nitrogen, and available phosphorus were low, and soil nutrient spatial distributions varied greatly. Available calcium content in street tree soil was much higher than that of the highest planting requirements in Shanghai overall; however, it was considered to be low level based on the integrated fertility index (IFI) of street tree soils, which showed a general trend of being low in the middle and high in the periphery. The IFI showed a significant positive correlation with organic matter, total nitrogen, available nitrogen, available phosphorus and available sulfur, whereas it had significantly negative correlation with pH and available calcium. 【Conclusion】The IFI of street trees in Shanghai was generally low, and soil fertility differed significantly between administrative regions; however, no clear correlation was found. The street tree soil management and improvement should consider spatial distribution characteristics and practical measures such as reducing soil pH and increasing soil organic matter according to local conditions to improve street tree soil fertility.
【Objective】The purpose of this study was to investigate the soil nutrient and stoichiometry characteristics of different vegetation restoration modes in the context of Karst landscapes within the water source area of the South-to-North Water Diversion Project and to evaluate the soil nutrient supply status of woodland habitats at the northern edge of the contiguous southern Karst distribution area, with the aim of providing a theoretical basis for the forest management, restoration and reconstruction of degraded ecosystems, and rock desertification management in the water-supporting area of the South-to-North Water Diversion Project. 【Method】The soil under Quercus variabilis natural secondary forest, Platycladus orientalis plantation, and Cunninghamia lanceolata plantation in the Karst area of Xichuan County of Henan Province was investigated in this study. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) contents were determined through laboratory experiments, and the stoichiometric ratios of each element were calculated to analyze the soil nutrient balance in forest habitats with different restoration modes. 【Result】The contents of SOC, TN and TP in different vegetation restoration modes in Karst area ranged from 10.23 to 28.99 g/kg, 0.89 to 2.42 g/kg and 0.43 to 0.77 g/kg, respectively; the mean values of soil stoichiometric ratios as C∶N, C∶P and N∶P were 10.41 to 11.89, 13.69 to 80.00 and 0.18 to 6.61, respectively. The soil nutrient contents and stoichiometric ratios were influenced by vegetation types and soil depth, and were higher in the surface soil (0-10 cm) than in the subsoil (>10-30 cm). Except for TP content, the soil nutrient content of the natural secondary forests was higher than that of the artificial forests. The correlation analysis showed that there were significant correlations among SOC, TN and TP contents under different vegetation restoration modes, indicating that the spatial distribution of the three had a more consistent variation pattern. 【Conclusion】In the water source area of the South-to-North Water Diversion Project, the naturally restored Q. variabilis secondary forest is an ideal vegetation restoration model, and all three stands were limited by nitrogen or phosphorus during the growth process. In the future stand management, nitrogen supplementation should be moderately strengthened for natural forests, phosphorus fertilizers should be applied to plantation forests, and the nutrient uptake efficiency of vegetation should be improved through measures such as inter-cultivation to promote coordinated development among vegetation soils.
【Objective】As a famous royal garden and world cultural heritage site, monitoring and evaluating the soil quality of the Summer Palace is of great significance for maintaining and protecting the health and safety of the park ecosystem.【Method】In this study, soil surface (0-20 cm) samples from a representative vegetation coverage area in the Summer Palace were collected, and 11 evaluation indices: soil bulk density, pH, electrical conductivity, the content of the soil organic matter, total nitrogen, total phosphorus, total potassium, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, and bacterial diversity were measured. The minimum data set was established using a principal component analysis, and the soil quality index was calculated using the membership function value and weight assignment method. The soil fertility quality of different vegetation coverage areas was analyzed and evaluated through a linear correlation analysis of the soil quality index of the total and minimum data sets.【Result】Using the principal component analysis method, the indices finally entered the minimum data set were total phosphorus content, electrical conductivity, bulk density, and the Shannon index. There was a significant positive correlation between the soil quality index calculated using the total and minimum data sets, and R2 was 0.877. The soil quality of the Summer Palace was divided into three levels: the soil quality of peony planting land was good (SQI≥0.80); the soil quality of deciduous broad-leaved forest, perennial flower land, and wild shrub and grass clusters was medium (0.40≤SQI<0.80); and the soil quality of trampled lawn and mixed conifer-broad-leaved forest was poor (0.20<SQI<0.40). The soil in the park was generally neutral to alkaline (pH 6.83 and 8.71), and the organic matter content was generally low (the average value was between 8.83 and 17.06 g/kg). The spatial distribution of available phosphorus was extremely unbalanced, with a coefficient of variation of 161.55%, and 76.00% of the samples were extremely deficient.【Conclusion】Human disturbance had a significant impact on the soil quality of the Summer Palace. Owing to the application of chemical fertilizers, the soil quality index in the peony planting land was high, and the soil quality in other areas was medium to low. The soil organic matter content in the park was low, and the spatial distribution of alkali-hydrolyzable nitrogen and available phosphorus was unbalanced. It is suggested that soil quality can be improved by retaining litter and applying organic and phosphorus fertilizers.
【Objective】 Water is the main factor limiting the sustainable stability of forest vegetation in semi-arid regions. The purpose of this study was to characterize evapotranspiration and its components in a larch (Larix principis-rupprechtii) plantation on the north side of the Daqing Mountains in Inner Mongolia, thereby providing a theoretical basis for forest management based on forest-water relationships. 【Method】The sap flow, canopy interception, forest floor evapotranspiration, and soil water content in a larch plantation stand, along with meteorological factors were monitored simultaneously in the north side of the Daqing Mountains of Inner Mongolia, China. Then, the variations in total stand evapotranspiration and its components as well as the relationship between evapotranspiration and environmental factors were analyzed. 【Result】On the seasonal scale, the evapotranspiration values in 2016 and 2017 were 522.57 and 583.67 mm respectively, accounting for 120.13% and 167.34% of the precipitation in the same period. This interannual difference was influenced by both the air temperature and water content of the soil. The percentage of canopy transpiration to total stand evapotranspiration was 45.44%, that of forest floor evapotranspiration was 40.28% and that of canopy interception was 14.28%. On the monthly scale, canopy transpiration and interception accounted for 37.30%-52.43% and 8.61%-21.81% of total evapotranspiration, respectively, whereas 31.52%-48.15% of the total stand evapotranspiration was caused by forest floor evapotranspiration. Air temperature, wind speed, and water conditions were the main factors influencing total stand evapotranspiration and canopy transpiration. Interception of the stand was mainly determined via precipitation and air humidity. Variations in forest floor evapotranspiration were closely dependent on solar radiation, saturated vapor pressure deficit, and water content of the soil. Additionally, the total evapotranspiration was 28.06 mm lower than the precipitation in July 2016, and the ratio of precipitation to evapotranspiration in other months was 0.55-0.92 under the monthly scale. 【Conclusion】In the mountain plantation ecosystem of typical rain-fed forestry in a semi-arid region, the amount of precipitation cannot meet the water consumption demand of the plantation. Therefore, in future research, it is necessary to pay more attention to the effects of precipitation types and time patterns on evapotranspiration.
【Objective】The black soil region of northeast China is an important commercial grain production base in China, however, long-term traditional mechanical production has destroyed the soil structure and decreased aggregate stability, intensifying soil erosion and degradation. The aim of this study is to determine the effects of exogenous organic materials on the aggregate stability of farmland black soil and provide a basis for the restoration of eroded and degraded black soil.【Method】A constant temperature-humidity culture experiment was conducted by adding three kinds of exogenous organic materials (straw, biochar and swine manure) with different content gradients (small, actual returning and large amounts) to black soil cultivated for 60 years in northeast China, and the constant mass-supplementation water method was used in a 25 ℃ incubator for 180 days. Soil aggregate distributions and stability differences caused by three aggregate disintegration mechanisms [fast wetting (FW), slow wetting (SW) and wet stirring (WS)] were compared using the Le Bissonnais method for different types and amounts of organic materials. FW, SW and WS based on the Le Bissonnais method, were adopted to simulate the field environmental conditions of rainstorms, heavy and light rain, and runoff, respectively.【Result】(1) The three disintegration mechanisms of adding small, actual returning and large amounts of biochar, straw and swine manure could significantly improve soil aggregate stability by increasing large aggregate proportion, improving the average weight diameter (MWD) and reducing the percentage of aggregate destruction (PAD); however, improvement efficiency differed: for FW, adding biochar in small amounts and straw in actual returning and large amounts was the best; for SW, adding swine manure in small amounts and straw in actual returning and large amounts was the best; for WS, adding swine manure in any amount was always the best.(2) Exogenous organic materials cannot change the aggregate disintegration mechanisms; FW disintegration was the predominant mechanism, followed by the mechanical disintegration of WS, and SW mechanical disintegration characterized by clay expansion had the least destructive effect on aggregates.【Conclusion】During the field environmental conditions of rainstorms or heavy as well as light rain, runoff, biochar, straw and swine manure can improve soil aggregate stability and anti-erodibility to different degrees, effectively restoring degraded black soil. Considering the natural conditions and material capitalized costs, swine manure was most appropriate for black soil restoration.
【Objective】Analyzing distribution suitability of forest protection tree species in seven coastal cities of Shandong Province can comprehensively reflect the impacts of different site factors on each forest protection tree species, thereby enabling further scientific forest protection tree species planning. 【Method】The distribution suitability of the tree species in protection forests within seven coastal cities of the Shandong Province was analyzed with the LandUSEM model using survey data of ‘One map’ of forest resource management in Shandong Province, as well as the 1∶106 digital soil map and DEM data as auxiliary data. 【Result】There were 26 species which were significantly affected by geomorphological factors. Furthermore, it was found that the soil types were relatively sensitive to the influence of dominant tree species and that the suitability of dominant tree species varied greatly depending on the different forest types. The average relative weights of the seven factors on the 49 dominant tree species were as follows: landform (0.19) > soil type (0.15) = slope (0.15) = soil thickness (0.15) > forest species (0.14) > slope position (0.13) > slope aspect (0.09). In the protection forests dominated by Pinus thunbergii, P. densiflora and Robinia pseudoacacia, the relative suitabilities of the first two species were higher than that of the latter; 90.48% of R. pseudoacacia forests were not suitable or critically suitable. This suggests that Pinus thunbergii, P. tabulaeformis, Quercus acutissima, Crataegus pinnatifida, Eucommia ulmoides, Q. mongolica, Q. spp., Cerasus pseudocerasus, Cerasus pseudocerasus, Ziziphus jujuba var. spinosa and other tree species should be mixed in low mountains and hilly areas where R. pseudoacacia forests have poor distribution suitability to improve the ecological benefits of R. pseudoacacia forests. 【Conclusion】 The distribution suitabilities of tree species in the protective forests within the seven selected cities along the coast of the Shandong Province are generally good, and the LandUSEM model analysis provides reliable information on tree species distribution suitability.
【Objective】The complexity of different forest types was evaluated to determine the main factors affecting stand structure and provide a theoretical basis upon which the precise forest management can be developed.【Method】A total of 30 permanent sample plots comprising different stand types (Betula platyphylla forest, Larix gmelinii-Betula platyphylla mixed forest and Larix gmelinii forest) in Cuigang Forest Farm, the Greater Khingan Mountains were investigated and 13 indicators selected to consider four aspects, namely stand structure, forest tree size diversity, forest dynamic and soil conditions. The stand complexity was evaluated using the radar chart method.【Result】The diameter distribution of the three stand types was found to be in the form of an inverse “J” pattern, with the overall tree distribution generally random; however, slight uniformity was observed. The tree size differentiation was inferior and middling, while stand density varied from medium to dense. The maximum stand mixing, Simpson diversity, Shannon-Wiener and Pielou evenness index results were obtained for L. gmelinii-B. platyphylla mixed forest, while the maximum stand volume and healthy wood proportion were observed in L. gmelinii forest. No significant differences were observed in terms of natural regeneration, soil organic matter, and soil humus layer thickness in different succession stages (P>0.05). The forest structure complexity was observed in the order of L. gmelinii-B. platyphylla mixed forest (0.45) > L. gmelinii forest (0.37) > B. platyphylla forest (0.31), during which the stand mixing, the Simpson diversity index, and the healthy tree proportion were the main factors affecting complexity. 【Conclusion】 The overall complexity of the forest structure is inferior. For the subsequent forest management, increasing the species diversity and improving the forest environment can promote positive progress in forest restoration and succession.
【Objective】Soil arthropods are important components of soil biodiversity and play a critical role in ecosystems. Although afforestation with poplar plantations can improve soil properties in the saline soils of coastal area, little is known about the impact of plantation stand development on soil arthropods.【Method】In this study, we determined the community dynamics of soil dwelling arthropods across three aged poplar plantations (i.e., 5-, 10-, and 21-year-old) through a randomized block design with three repeated blocks over the course of one year, which included four sampling dates (i.e., spring, May; summer, August; autumn, November; and winter, February) in a coastal area of northern Jiangsu Province, China. 【Result】Prostigmata, Oribatida, Hymenoptera, Collembola, and Coleoptera comprised the dominant orders and together accounted for 89.4% of the total individuals. On average, both total number and those richness were the highest in the 10-year-old stands and the lowest in the 5-year-old stands and were higher in May and August than species in November and February. The abundance, Order richness, and community composition of soil arthropods were significantly affected by stand age, sampling date and their interaction. The total abundance showed strong age-dependent trends in May and August but not in February and November. Order richness was the highest in both 10- and 21-year-old stands observed in May and August. Permutational multivariate analysis of variance demonstrated that Order composition also differed strongly with sampling date and stand age, with 10-year-old stands sampled in May distinct from other sampling dates. 【Conclusion】The abundance and richness of soil arthropods in 10-year-old stands were higher than number in 5-year-old stands, and impact of stand age on the soil arthropod community depended on the seasonal changes. Our results highlight that both stand development and climate seasonality act strongly on soil arthropod community dynamics in the poplar plantations, while the related mechanisms need a further study.
【Objective】The Black Soil Region is an important food base, which has a vital strategic position to ensure the food security in China. However, due to the long-term unreasonable utilization, the black soil resources suffered from serious water erosion. The objective is to clarify the spatio-temporal characteristic of soil loss on cropland and discuss the feasibility of evaluating soil erosion by magnetic susceptibility. 【Method】Magnetic susceptibility (MS) had been proved to be a rapid, reliable, economic and nondestructive method in estimating hillslope soil redistribution. In this paper, three typical black soil slope transects were selected in Heshan Farm, Heilongjiang Province, and collected soil profile samples from surface to 60-100 cm depth, measured soil magnetic susceptibility. The MS was used as a tracer to analyze the spatio-temporal heterogeneity of soil susceptibility at slope scale and discussed the soil erosion patterns in Black Soil Region. 【Result】The results showed that MS of topsoils on all the slope were generally high, and decreased with the increasing of soil depth. MS at parent layers become stable, which was in line with the MS characteristics of temperate soil developed from weak magnetic parent materials. The average MS at upperslopes and middleslopes were less than that of reference sites, which were 24.1×10-8 m3/kg and 24.8×10-8 m3/kg, respectively, the average MS of lowerslopes were greater than that of reference sites, for 39.71×10-8 m3/kg. It conformed to the general soil erosion pattern on hillslope that soil material deposited from its original position to the lower position. The whole slope were divided into erosion area and deposition area according to the topsoil MS of reference sites. The topsoil MS at the erosion area was lower than that of reference sites, while the topsoil MS at the deposition area was higher than that of reference sites. The topsoil particles were removed and transported at upperslopes and middleslopes, deposited at lowerslopes. With the increasing of cultivation periods, the MS between upperslopes and lowerslopes varied significantly which showed strong slope heterogeneity, and the cultivation periods were positively correlated to the soil redistribution. The range of MS on cropland reclaimed for 110 years was 1.7×10-8-88.7×10-8 m3/kg, which was about 1.4 and 1.9 times of cultivated for 60 and 30 a, respectively. 【Conclusion】The MS at topsoils of the black soil slope presented heterogeneity, that is, upperslopes and middleslopes located in the erosion area while lowerslopes were located in the deposition area. The longer the cultivation period, the higher the degree of soil redistribution on slope. Soil erosion was the most intense on the slope reclaimed 110 years ago. In view of the soil erosion in Black Soil Region, we should vigorously carry out the quality protection and improvement of cultivated land, encourage contour farming and strengthen the monitoring and investigation of soil conservation of black soil under a longer spatio-temporal series. The results can provide a theoretical basis for the prediction and prevention of water conservation and controlling soil erosion in Northeast China, which is conducive to the sustainable development of regional agriculture and ecological environmental protection.
【Objective】 This study explored the influence of sampling interval on the measurement accuracy of urban soil magnetic susceptibility. 【Method】 Taking typical forest land in Nanjing and its suburbs as the research object, four representative sample plots (suburban forest farms, urban forest farms, undisturbed land and disturbed road green belts) were selected, and 0-30 cm topsoil samples were collected. Taking soil magnetic susceptibility as the main index, five topsoil sampling intervals (2, 5, 10, 15 and 30 cm) were set. The profile variation characteristics of surface soil mass susceptibility and percentage frequency susceptibility at different sampling intervals were analyzed. 【Result】Soil low frequency mass susceptibility (χlf) of the four sample plots ranged from 59.2 × 10-8 to 1 210.0 × 10-8 m3/kg, with a peak value of 5-7 cm. Low frequency magnetic susceptibility of soil profiles in all plots basically followed the pattern of first increasing and then decreasing and fluctuating. Fine sampling intervals (such as 2 cm) better captured the peak value and abnormal values of soil magnetic susceptibility; the 5 and 10 cm soil sampling intervals reflected the general variation trend of soil magnetic susceptibility; the soil sampling interval of 15 cm showed no detail in the soil magnetic susceptibility changes. Mixed soil samples at 0-30 cm soil sampling intervals only indicated the mean value of magnetic susceptibility of various surface soils. 【Conclusion】 During the sampling process, appropriate sampling intervals should be set according to the research purpose in order to improve the accuracy of experimental data.
【Objective】This study aims to reveale the law of soil quality variation caused by water erosion provides scientific data support for soil erosion control and low-efficiency forest transformation in hilly red soil region of southern china.【Method】The small watershed of Qingyuan Mountain in Ji ’an City, Jiangxi Province was selected as a typical area of red soil hilly area in southern China. According to the typicality and representativeness, the small watershed was divided into slope positions, and three sections were set up to collect soil repeatedly. The composition of soil aggregates was analyzed, and the correlation analysis was used to explore the relationship between various indicators in the process of water erosion.【Result】Water erosion changed the spatial distribution pattern of bulk density and soil porosity, resulting in weaker soil anti-erodibility in erosion area and less influence in deposition area, which accelerated the occurrence of soil erosion. Soil bulk density increased after long-term erosion. Compared with other slope positions, soil bulk density at slope toe increased significantly by 0.16 g/cm3 (P < 0.05), while saturated water holding capacity and capillary porosity decreased significantly (P < 0.05). After water erosion, the composition of soil texture also changed, soil sand content increased significantly, clay and silt content decreased significantly (P < 0.05). The water erosion process had different effects on soil nutrients at different slope positions. The soil total nitrogen, available phosphorus, organic carbon content and carbon-nitrogen ratio decreased on the upper, middle and lower slopes, and the content on the slope decreased significantly (P < 0.05). Compared with other slope positions, the nutrient content at the toe of the slope increased, and the available phosphorus increased significantly by 39.31% (P < 0.05). After water erosion, the mass fraction (R0.25), mean mass diameter (MWD) and geometric mean diameter (GMD) of water-stable aggregates at different slope positions showed a decreasing trend, and the change at the foot of the slope was not obvious, and the stability of soil structure was the highest.【Conclusion】The ecosystem of red soil hilly area in southern China is fragile. Long-term water erosion can reduce the stability of red soil aggregates. The water erosion process causes spatial differentiation of soil physical and chemical properties in erosion-deposition sites. Vegetation coverage and litter thickness are the main environmental factors.
【Objective】Beetles, as important biological components of forest ecosystems, can regulate litter decomposition and soil ecological processes. The authors aims to reveal the diversity characteristics of surface beetle communities in different aged poplar plantations and provide scientific support for exploring the structure, function and productivity maintenance for poplar plantations ecosystems.【Method】Poplar plantations of different stand ages (i.e., 6, 9, 12, 15 and 18 years) in the Yellow Sea Forest Park in Dongtai City of Jiangsu Province were selected for research conducted from 2020 to 2021. A pasteurized pot inducement method was used to collect different soil beetles. We investigated soil beetle community composition, structure and diversity characteristics in select poplar plantations.【Result】A total of 1 460 soil beetle specimens were collected during the study period, belonging to seven families and 28 species. The dominant species were Dolichus halensis, Agonum gracilipes, Harpalus chalcentus and Amara gigantea, which accounted for 79.11% of the total individuals. Common species were Harpalus calceatus, Harpalus griseus, Hypera conmaculata, Chlaenius micans, Harpalus amplicollis and Chlaenius costiger, accounting for 15.82% of the total number of individuals, and the remaining 18 species were rare populations, accounting for only 5.07% of the total number of individuals. The 12-year-old poplar plantation had significantly more beetle species and total individuals than other stand ages, while the 18-year-old poplar forest had the lowest. The species diversity of soil beetles varied by 33.83% across all plantation ages. Diversity increased first and then decreased with age of poplar plantation, with maximum and minimum values in the 12-year-old and 18-year-old plantations, respectively. There was no significant difference in beetle diversity in 6-, 9-, and 15-year-old poplar plantations.【Conclusion】Our study clarified that the individual number and species diversity of soil beetles are closely related to the growth and development stages of poplar plantations. Middle-aged stands in the rapid growth and development stage have higher beetle species diversity while mature stages or older stands have lower beetle species diversity. This study provides a theoretical basis for the protection of soil biodiversity in poplar plantations and the sustainable management of plantations.
【Objective】 Artificial standard soil was used to investigate the potential stimulatory effects of low-dose C, N, and P additions on soil respiration and Hormesis under heavy metal stress. 【Method】The four treatments were: GC (glucose), NP (nitrogen and phosphorus), GC+NP (glucose, nitrogen and phosphorus), and, no additions (CK). The soil samples were inoculated with soil microorganisms from forest land to determine the potential Hormesis effect of exogenous addition of glucose, N and P on soil respiration under Cd stress. 【Result】In the case of the NP and GC+NP treatments, the soil respiration rate was significantly higher than that of the control at Cd doses of 0.02, 0.10, 0.40, 2.50, and 13.00 mg/kg, respectively. There was a significant alternating phenomenon of multiple hormetic effects with stimulation amplitudes between 66.6% and 262.6%. When there was no Cd added to the soil, the sum of the soil respiration rates in the GC and NP treatments was greater than that in the GC+NP treatment. The interaction between C source and NP addition on soil respiration showed an antagonistic effect. When the Cd dose was 0.01 to 0.20 mg/kg, the sum of soil respiration rates in GC and NP treatments was lower than the corresponding rates in GC+NP treatments, and the effects of C source and NP additions on soil respiration showed a synergistic effect. Synergistic and antagonistic effects appeared alternately when the Cd dose was over 0.20 mg/kg. 【Conclusion】The Cd-induced soil respiration rate had a significant Hormesis effect under exogenous NP addition. With increasing Cd stress, the interaction between the C source and NP addition on soil respiration changed from antagonistic to synergistic effects.
【Objective】This paper elaborated upon the changes in soil total nitrogen and mineral nitrogen ($\mathrm{NH}_{4}{ }^{+}$-N and $\mathrm{NO}_{3}{ }^{-}$-N) contents, the nitrogen form characteristics and their spatial patterns in lightly, moderately and severely burned areas, which comprehensively reflected the characteristics of soil nitrogen nutrition habitats during the early restoration period of burned forest areas in the Greater khingan Mountains. This study aimed to provide a reference for the renovation and ecological restoration of burned coniferous forests in cold temperate zones.【Method】In the Ledum palustre-Rhododendron simsii-Larix gmelinii forest, fixed sample plots were set up with the grid method, and the intensity of the forest fire was controlled by artificial ignition. Soil samples were collected by auger boring before and one year after burning. The soil total nitrogen, $\mathrm{NH}_{4}{ }^{+}$-N and $\mathrm{NO}_{3}{ }^{-}$-N contents were measured, the change rate of each index and the ratio of mineral nitrogen forms were calculated, and the spatial patterns were drawn.【Result】A year after the burning: (1) Soil total nitrogen content changed, and its change rate was divided into two stages. In the lightly and moderately burned areas, soil total nitrogen content increased. Its spatial pattern was not obviously correlated with the fire intensity spatial pattern, but its change rate spatial pattern was. In the severely burned area, the soil total nitrogen content decreased. The spatial and change rate spatial patterns were both negatively correlated with the fire intensity spatial pattern. (2) Soil $\mathrm{NH}_{4}{ }^{+}$-N content increased in all burned areas; its spatial and change rate spatial patterns were not obviously correlated with the fire intensity spatial pattern. (3) Soil $\mathrm{NO}_{3}{ }^{-}$-N content increased significantly; its spatial and change rate spatial patterns were both positively correlated with the fire intensity spatial pattern. (4) The soil nitrogen form showed evident $\mathrm{NH}_{4}{ }^{+}$-N dominance, but its dominance (the content ratio of $\mathrm{NH}_{4}{ }^{+}$-N to $\mathrm{NO}_{3}{ }^{-}$-N) was reduced. The ratio spatial pattern and change rate spatial pattern were negatively correlated with the spatial pattern of fire intensity. 【Conclusion】During the early restoration period of burned areas in the Larix gmelinii forest, the change in soil nitrogen nutrition habitat did not constitute an obstacle to the restoration of native vegetation types; however, the decline of soil total nitrogen in the severely burned area may bring about the fall-off in nitrogen supply capacity in the long-term.
【Objective】This study aimed to investigate the dynamic changes of forest ecosystem structure, function, climate and site type factors during the restoration of natural forest ecosystems in northern Greater Khingan Mountains, screen out the key influencing factors, and use scientific methods to scientifically evaluate its forest ecosystem restoration capacity. This study provides a reference for exploring effective management measures to improve the ecological function of Greater Khingan Mountain natural forest. 【Method】Based on field survey data, discriminant validity test was used to determine the evaluation index system of forest ecosystem restoration capacity, and a structural equation model for forest ecological restoration capacity evaluation was established according to the conduction mechanism to determine the index weights. Based on K-means cluster analysis and the equidistant division method, a classification standard for the forest ecological restoration capacity in Greater Khingan Mountains was established. 【Result】The weights of four criterion factors in the evaluation index system of forest ecological restoration capacity in Greater Khingan Mountains-forest productivity, stand structure, climate factor and site type are 0.339, 0.192, 0.256 and 0.213 respectively; The comprehensive scores of the ecological restoration capacity evaluation of the two kinds of forest in the study area are in the range of 1.70 to 3.53, and the distribution of restoration capacity grades conformed to a normal distribution. The restoration capacity grades were mainly concentrated in difference, poor and good states. Overall, the ecological restoration capacity grades of the two forest types were as follows: mixed forest > pure forest. 【Conclusion】The forest ecosystem restoration capacity is mainly affected by forest productivity, whereas stand structure, climate factors and site types have relatively little impacts on ecological restoration capacity, and the ecological restoration capacity of some areas of the Greater Khingan Mountains is still poor.
【Objective】 The growth and photosynthetic characteristics responses of Acer rubrum following introduction to two kinds of purple soil were studied, to provide reference data for the development and use of a suitable variety of A. rubrum in the Chongqing area of China. 【Method】 A. rubrum ‘Marmo’ and ‘Aurea’ introduced into neutral purple soil (NS1) and callitic purple soil (AS2) were analyzed. Growth, leaf color, and photosynthetic characteristics of A. rubrum were compared in the two kinds of purple soil in summer, when their growth was vigorous. 【Result】 The net plant height, crown width, leaf area of ‘Marmo’ were positively correlated with alkali-hydrolyzed nitrogen, available potassium, carbon/nitrogen ratio, and organic matter, and negatively correlated with soil pH. Compared with the initial introduction, the plant height of ‘Marmo’ in the neutral and calcareous zones increased by 3.44 m and 1.18 m, respectively, ground diameter increased by 5.14 cm and 2.22 cm, respectively, and the leaf area and specific leaf area were significantly different. However, there were no significant differences of ‘Aurea’ in net plant height, net ground diameter, or specific leaf area. The chlorophyll a (ChlT), chlorophyll b (Chlb), total chlorophyll (ChlT), carotenoid (Car), L*, a* and b* values, maximum photochemical efficiency (Fv/Fm), electron transfer efficiency (ETR), light energy capture efficiency Y(Ⅱ), photochemical quenching coefficients (qP), leaf maximum net photosynthetic rate, light saturation point (LSP), apparent quantum yield (AQY), leaf carboxylation rate, leaf carboxylation rate (α), and photorespiration rate (Rp) of ‘Marmo’ in neutral zone were significantly higher than that of in calcareous zone (P<0.05). Compared with purple soil alkaline zone, Pn,max and intercellular CO2 concentration of (Cs) ‘Aurea, in the neutral zone were significantly increased, LCP, CO2 compensation point (CCP) were significantly decreased (P<0.05). Chla, ChlT, Chl a/b, L*, a*, b* Fv/Fm, ETR, Y(Ⅱ), qP, LSP, AQY, CCP, Rd and Rp of ‘Aurea’ in the neutral zone were not significantly different from those in the calcareous zone (P>0.05). 【Conclusion】 Among the two types of purple soil, ‘Marmo’ increased the photosynthetic electron transfer rate and photosynthetic rate of photosystem Ⅱ and reduced the consumption of organic matter by increasing the light energy capture area. The photosynthetic capacity was enhanced and growth was strong in the neutral region, while the performance of ‘Marmo’ was poor in the calcareous zone, indicating that this variety is not suitable for alkaline purple soil. The photosynthetic characteristics and growth of ‘Aurea’ showed strong adaptability to the two types of purple soil.
【Objective】 To provide a theoretical reference for urban green space construction under the “Dual Carbon” goal, we established a carbon neutrality performance evaluation system and analyzed the impacts of vegetation distribution on the carbon neutrality performance of green spaces. 【Method】 Based on life cycle assessments, green space construction was divided into three stages: material production and transportation, site construction and planting, and green space operation and maintenance, which were combined with open, semi-open, covered and closed vegetation types. Carbon emissions and sink simulations were performed to analyze the carbon neutrality performance.【Result】 When the vegetation type changed from openness to closedness, the total carbon emissions increased rapidly and the trend accelerated. The proportions of carbon sources in the three stages decreased, leveled out and increased, respectively. The total carbon sink and net carbon neutrality both increased gradually. The number of years of carbon neutrality decreased gradually, from 43.9 years for open vegetation to 24.6 years for closed vegetation. These trends implied that there was a limit to the degree of vegetation shading for improving the carbon neutrality performance.【Conclusion】 Vegetation type clearly has an impact on the carbon neutrality performance. In terms of carbon sources, strategies such as reducing machinery use, selecting environmentally friendly materials, controlling construction damage, and improving energy utilization efficiency are suggested. For carbon sinks, strategies such as selecting tree species that have dominant local carbon sinks, adjusting the structures of vegetation communities, and regulating and managing green spaces along with life cycles are suggested. Ultimately, we postulate that green space carbon neutrality performance can be achieved by adapting to local conditions.
【Objective】 The particle size composition, distribution, and water infiltration capability of soil in different soil layers of Phyllostachys edulis stands were measured. The response of soil particle size distribution and water infiltration capability to understory vegetation succession was revealed, which provides guidance for soil ecological management and vegetation renewal of P. edulis stands.【Method】 The understory vegetation successional ages of 21, 9 and 0 years in P. edulis stands were chosen for research. Soil particle size composition and fractal dimension of soil particle volume in different soil layers, as [0, 10) cm, [10, 20) cm, [20, 30) cm of stands land were measured. Soil water infiltration capability was simulated by using Kostiakov, Philip and Horton models. The relationships among soil fractal characteristics, particle composition, and water infiltration capability were analyzed. 【Result】 For P. edulis forests with the same understory successional years, soil clay content, silt content, fractal dimension, and water infiltration capability decreased with the increase of soil depth, while sand content increased gradually. With the extension of vegetation succession years, the content of clay and silt as well as fractal dimension decreased gradually in the [0, 10) cm soil layer, while the sand content increased gradually. The clay and silt contents and fractal dimension in [10, 20) cm and [20, 30) cm soil layers increased first and then decreased, but the sand content changed in the opposite direction. The initial infiltration rate and stable infiltration rate of all soil layers showed an increasing trend with the extension of successional age. Soil fractal dimension was positively correlated with clay particle content, initial infiltration rate, and stable infiltration rate (P<0.05), but negatively correlated with sand particle content (P<0.05). The Kostiakov and Horton models are more suitable for the simulation of soil water infiltration process in experimental P. edulis stands. 【Conclusion】 Vegetation succession under P. edulis stands can significantly improve soil water particle structure and enhance soil water infiltration capability, and the succession time effect is obvious. Soil water infiltration capability of P. edulis in the older 21-year successional understory age was better than that of the younger 9-year and pure bamboo stands.
【Objective】 The orchards in Dalian City suffer from soil erosion due to vigorous developmental activities. This study aimed to quantitatively analyze the status of soil erosion, determine the spatio-temporal characteristics of soil erosion in orchards in Dalian City, and explore the key factors that influence soil erosion. The results can provide significant insights for the healthy development and ecological protection of the orchard industry in Dalian City. 【Method】 The characteristics of soil erosion in orchards in Dalian City were assessed by using the Chinese soil loss equation (CSLE) model, based on geographic big data available online. The results were visually interpreted, and the dynamic changes and factors influencing soil erosion in the study area were subsequently analyzed. 【Result】 The area of soil erosion constituted approximately 40% of the total area of Dalian City, and the erosion was serious in the northern and southern mountainous and hilly regions. The average soil erosion modulus of the orchards in Dalian City was 1 230.29, 1 150.95, 2 311.36, 6 384.55, 3 399.60 and 3 484.24 t/(km2·a) in 2015, 2016, 2017, 2018, 2019 and 2020, respectively. Analysis of the intensity of soil erosion primarily revealed micro and slight erosion. Strong and above grade erosion was primarily observed in Ganjingzi, Jinzhou, and Lüshunkou District. Soil erosion was primarily observed in slope grades below 25° and in regions with rainfall grades ranging between 500 and 900 mm. The finding revealed that greenhouse coverage could reduce soil erosion in greenhouse orchards and open field/facility orchards, and vegetation coverage could effectively reduce soil erosion in open field orchards. 【Conclusion】 Soil erosion in the orchards in Dalian City exhibits obvious spatial distribution characteristics in that the intensity of erosion is high in the south and low in the north area. The successful control of soil erosion in orchards and the efficient promotion and sustainable development of the orchard industry can be achieved in future by increasing the area of greenhouse coverage, increasing the vegetation coverage of outdoor greenhouses, and selecting the location of orchards reasonably.
【Objective】 Climate change-induced drought restricts the distribution, growth and productivity of southern poplar plantations in the south of China. To explore adaptability to drought and provide reference for future sex-based poplar clone selection, we studied physiological responses to short-term intermittent soil drought between different sexes. 【Method】 Based on pot experiments by setting short-term intermittent soil water deficiency, four female and three male clones of southern-type poplar were used to compare sex-specific changes in physiological traits, including leaf plasma membrane stability, osmotic regulation, antioxidant system, and photosynthetic pigments. 【Result】 Short-term drought induced increases in electrical conductivity of leaves, malondialdehyde (MDA) and proline (Pro) contents, and antioxidant enzyme activities, but decreases in leaf chlorophyll content, for both male and female poplar clones, which indicated damage to leaf membranes and photosynthesis system with membrane lipid peroxidation. After drought relief by rewatering, these physiological traits all returned to substantially the same level as the (normal watering/non-drought) control treatment. Differences existed in the level and pattern of physiological responses to short-term soil drought between male and female clones. For female clones, the activity of antioxidant enzymes in leaves fluctuated greatly, and the contents of chlorophyll and proline remained at a high level under draught treatment; after drought relief by rewatering, chlorophyll content recovered rapidly, while membrane lipid peroxidation remained high. For male clones exposed to short-term drought, however, we detected stable POD activity and reduced chlorophyll content; this indicated higher drought resistance. Male clones, by maintaining membrane stability and reducing water loss. Therefore, female poplar clones showed relatively lower drought tolerance, but maintained a certain level of photosynthesis and growth, while male clones presented relatively higher drought tolerance. In addition, during short-term soil drought, three male clones showed relatively consistent physiological responses, while male clones had greater inter-clone variation. 【Conclusion】 Male poplar clones had relatively high and stable drought resistance, while female clones had generally weak but varied inter-clone drought resistance. However, female clones displayed rapid recovery of leaf physiological conditions after rewatering between short-term drought.
【Objective】 The study aimed to understand the health status of plantations in nature reserves for forest management and the construction of nature reserves. 【Method】 A total of 36 sample plots were surveyed in the pure Larix gmelinii var. principis-rupprechtii and Pinus sylvestris var. mongolica plantations in the Saihanba Nature Reserve of Hebei Province using the stratified random sampling method. A total of 17 indicators, including the five aspects of productivity, stand structure, species diversity, soil quality, and stability, were selected to establish an indicator system for assessing forest health. The forest health index was calculated by principal component analysis, and the forest health grades were classified using the K-means clustering method. The accuracy of the clustering results was verified by Fisher’s discriminant analysis. 【Result】 The forest health index of the study area ranged between -1.02 and 1.46. The soil quality and stand structure were the most important indicators that influenced forest health in the study area. The proportionate areas were in the following order: mid-health (50%) > unhealthy (25%) > sub-health (19%) > healthy (6%). The health status of L. gmelinii var. principis-rupprechtii forests was better than that of P. sylvestris var. mongolica forests for middle-aged (20-30 a) and near-mature (> 30 a) stands. The forest health indices of L. gmelinii var. principis-rupprechtii and P. sylvestris var. mongolica forests tended to decrease with increasing stand density. 【Conclusion】 The plantations in the Saihanba Nature Reserve were primarily in the mid-health and non-health states. Therefore, the findings revealed that effective management strategies are urgently necessary for improving forest health in the study area.
【Objective】 This study aimed to scientifically manage abandoned mine slopes, explore the application and promotion of the soil bacteria permanent greening method in restoration, optimize the fermentation conditions, and analyze the application effect of the isolated and screened high-efficiency solubilizing bacteria.【Method】 A variety of solubilizing microorganisms were isolated from the weathered rock wall soil in Nanjing Mufu Mountain, and a prominent solubilizing strain, NL-11, identified as Bacillus thuringiensis by 16S rRNA, was selected to optimize fermentation conditions, and its application effect was observed with the potting test. The three main factors affecting the growth of the strain (liquid volume, temperature, and time), were screened using the univariate and Plackett Burman tests; on this basis, the steepest climbing path was used to approximate the maximum response area; then, the Box-Behnken experimental design was used and the response surface analysis method was used for regression analysis. Finally, model reliability was verified by comparing the predicted values with the measured values. The optimized results were used to prepare the bacterial solution, and then adjusted to low (10 cfu/mL), medium (1 × 105 cfu/mL), and high (1 × 109 cfu/mL) concentrations and mixed into the substrate (T1, T2, and T3 treatments, respectively) for the pot experiments, and the treatment without the bacterial solution was set as a blank control (CK) to study the effects of the different bacterial solution concentrations on mineral weathering and plant and root growth.【Result】 The model was accurate and reliable, and the optimal fermentation culture conditions for NL-11 were as follows: a liquid volume of 19.51 mL, an inoculum level of 2%, an initial pH of 7.0, a temperature of 30.30 ℃, and a time of 22.07 h. The number of viable bacteria in the fermentation broth under these optimized conditions reached 1.47 × 1010 cfu/mL, which was 2.03 times higher than that before optimization. The results of the pot tests showed that strain NL-11 could promote mineral weathering, and the effect of the high concentration of the bacterial solution was the most significant. Furthermore, strain NL-11 could promote the dissolution of mineral nutrients, and the effect of the high concentration of the bacterial solution was the most significant. Strain NL-11 could also promote plant and root growth, and the effect of the medium concentration was the most significant. 【Conclusion】 The optimization test significantly improved the production of fermentation of the live bacteria of strain NL-11 and provided technical support for the application of the strain in the management of slopes. The suitable concentration of the bacterial solution in spraying practice is 1 × 105 cfu/mL by the comprehensive evaluation of the application effect and consideration of the production cost and other factors.
【Objective】 This study explored the effects of Serratia marcescens N1.14, X-45 bacterial fertilizer inoculated with different carrier substrates on the growth, photosynthetic characteristics, soil pH and available nutrients of Amorpha fruticosa. Based on this, bacterial fertilizer carriers that can effectively replace rare resource peat were determined in order to provide a theoretical basis for the development of microbial fertilizers.【Method】 Taking A. fruticosa seedlings as the object, the peat bacterial fertilizer (T0, CK), straw bacterial fertilizer (T1), wheat bran bacterial fertilizer (T2), straw and wheat bran as carrier bacterial fertilizer (volume ratio = 1∶1, T3), straw wheat bran and cotton seed hull as carrier bacterial fertilizer (volume ratio = 1∶1∶1, T4), and straw wheat bran and soybean cake as carrier bacterial fertilizer (volume ratio = 1∶1∶1, T5) were applied. Through comparative analysis, the effects of the application of different carrier bacterial fertilizer on the growth characteristics, photosynthetic characteristics and soil nutrients of A. fruticosa were explored, and treatment groups that can replace peat bacterial fertilizer were selected.【Result】 Compared with CK, there were three key findings. First, the growth statuses of T2, T3, T4, and T5 were significantly improved, especially T3. Second, the photosynthetic characteristic parameters of Amorpha fruticosa leaves under T1, T3, T4, and T5 improved to varying degrees. Among the gas exchange parameters, T5 had the most significant improvement effect, and T3 had the most obvious improvement effect on chlorophyll content. At the same time, the improvement effect of compound carrier bacterial fertilizer was better than that of single bacterial fertilizer. Third, the soil nutrient content of A. fruticosa under T3, T4, and T5 treatments increased.【Conclusion】 The straw, wheat bran and soybean cake as carrier bacterial fertilizers can promote the growth and development of A. fruticosa, improve photosynthetic characteristics, optimize the soil nutrient environment, improve soil fertility, and effectively replace peat carrier bacterial fertilizer.
【Objective】 This study explored the effects of acid rain-based changes in soil nutrient content and Chinese fir (Cunninghamia lanceolata) fine root growth, to provide a theoretical basis for improving soil acidification of C. lanceolata plantations in acid rain-stressed areas.【Method】 A one-year simulated acid rain field experiment was conducted at the Tongshan Forest Farm in Nanjing, Jiangsu Province. Three acid rain acidity levels (pH=4.5, 3.5, and 2.5) were applied with each of three acid rain types: sulfuric acid rain, with 5∶1 concentration ratio of sulfur (S, SO42-) to nitrogen (N, NO3-); mixed acid rain, with 1∶1 S/N ratio; nitric acid rain, with 1∶5 S/N ratio; and a control (CK, pH=6.6, local river water). There were thus 10 total experimental treatments. Outcome measures of acid rain stress included soil chemical properties, fine root physiological characteristics, and fine root element contents. Correlations and structural equation model analyses were used to explore the direct and indirect effects of acid rain type on C. lanceolata fine root growth.【Result】 With decreasing acid rain pH and S/N ratios, the fine root biomass and root activity of C. lanceolata decreased. The catalase activity of all strong acid rain treatments (pH=2.5) was lower than that of other acid rain treatments. Compared with nitric acid rain types, the catalase activity incrementally decreased and was lower than CK; Mg and Al content, as well as the c(Ca)/c(Al) and c(Mg)/c(Al) in fine roots also differed. Compared with CK, all acid rain treatments increased fine root Ca and Al contents, while K content decreased with acid rain stress. However, there were not significant differences in soil total C, total N, C/N ratio, total S, available P, or available K among S/N ratios or pH levels. Correlation analysis showed that soil pH was extremely significant positively correlated with c(Mg)/c(Al), root biomass, and root activity (P<0.01), and that root biomass was significantly positively correlated with peroxidase, catalase, but extremely significant negative correlated with Al content (P<0.05). 【Conclusion】 After one year of experimental acid rain stress, acidity significantly impacted both soil and C. lanceolata fine roots. Acid rain type affected fine roots more strongly than it affected soil. As the S/N ratio decreased, the inhibitory effect of acid rain on C. lanceolata fine root growth was more pronounced.
【Objective】 The aim of the present study was to investigate the changes of soil physical and chemical properties of Pinus massoniana plantations of different ages in Karst areas in southwest China, as well as comprehensively analyze the effects of topographic factors, stand characteristics and plant diversity on soil properties to provide reference for environmental management in degraded Karst areas.【Method】 In the present study, 11 P. massoniana plantations at three different ages, namely, middle-aged plantation, near-mature plantation, and over-aged plantation, were selected in Fenggang County, Zunyi City, Guizhou Province. The area of the plots was 25.82 m × 25.82 m. The species name, height and diameter at breast height (DBH) of the tree layer were investigated, and the altitude, position, slope and species composition of each plot were recorded. Five 2 m × 2 m shrub quadrats were set up in the southwest, northwest, northeast, southeast and middle areas of each plot to investigate the species name and number of plants in the shrub layer. A 1 m × 1 m herb quadrat was set up in each shrub quadrat to investigate the species name and coverage of herbs. The changes of soil physical and chemical properties were quantified, and the influencing factors were analyzed.【Result】 There were no significant differences in soil bulk density, porosity, water content, organic carbon content and total phosphorus content among the different age groups of the P. massoniana plantations (P>0.05). The total nitrogen content increased initially and then decreased with the increase in plantation age in the 0-20 cm soil layer, and the alkali-hydrolyzable nitrogen content decreased gradually with the increase of plantation age in the 20-40 cm soil layer. Moreover, the available phosphorus content decreased initially and then increased with the increase in plantation age in the 0-20 cm and 20-40 cm soil layers (P<0.05). No significant differences were found in the soil bulk density, porosity, and water content between the 0-20 cm and 20-40 cm soil layers within the same age group (P>0.05). The soil organic carbon content of the three age groups, the total nitrogen content and alkali-hydrolyzable nitrogen content of the near-mature and over-aged plantations, and the total phosphorus and available phosphorus content of the over-aged plantation were significantly different between the 0-20 cm and 20-40 cm soil layers (P<0.05). These contents decreased with the deepening of soil layer. Correlation analysis showed that topographic factors, stand characteristics, and plant diversity were the factors affecting soil physical properties and nutrient changes in the P. massoniana plantations. Stepwise regression analysis showed that stand density and plant diversity were the main factors affecting soil physical properties, while topographic factors, stand characteristics, and plant diversity were the factors affecting soil nutrients. Redundancy analysis (RDA) showed that stand characteristics, plant diversity, and topographic factors explained 36.60%, 27.00% and 10.30% of the variation in the soil physicochemical properties, respectively.【Conclusion】 The plantation age has a significant impact on the soil nitrogen and phosphorus contents of P. massoniana plantations, suggesting that nitrogen fertilizer and phosphorus fertilizer should be added appropriately with the growth and development to maintain the productivity and sustainable development of P. massoniana plantations. Changes in the plantation age has no significant effect on soil physical properties, while the stand density and tree height are the main factors affecting the soil physical and chemical properties in P. massoniana plantations.
【Objective】The aim of the present study was to investigate the soil physical properties, chemical properties, and enzyme activities under different Carya illinoensis ‘Pawnee’ and Paeonia ostii ‘Feng Dan’ planting modes, as well as analyze the effects of different modes and seasons on soil characteristics.【Method】The treatments included single cultivation of C. illinoensis (mode Ⅰ), compound cultivation of C. illinoensis ‘Pawnee’-P. ostii ‘Feng Dan’ (mode Ⅱ), and single cultivation of P. ostii (mode Ⅲ). Seasonal variation of soil physical properties, chemical properties, and enzyme activities were measured under different modes, and the minimum date set method and soil integrated fertility index (IFI) were utilized to evaluate the changes of soil fertility.【Result】The nutrient and enzyme activity in the surface soil were higher than those in the deep soil. The soil moisture content and bulk density gradually varied with the seasons of spring, summer and autumn. There was no significant difference on soil pH between the spring and summer seasons, and the lowest soil pH was observed in autumn. The soil catalase activity in summer was higher than that in spring and autumn. The soil organic matter content, total nitrogen content, available potassium content, sucrase activity, and urease activity increased during the seasonal variation of spring, summer, and autumn. In mode Ⅲ, the soil available phosphorus content in autumn was higher than that in spring and summer. The seasonal variation of the soil IFI was the lowest in summer and highest in mode Ⅱ.【Conclusion】There is a correlation among soil physical properties, chemical properties and enzyme activities. The soil fertility of the compound cultivation of C. illinoensis ‘Pawnee’-P. ostii ‘Feng Dan’ (mode Ⅱ) is significantly higher than single cultivation of either species, and the soil fertility quality is lower in summer than in spring and autumn. The soil fertility quality is directly affected by bulk density, total nitrogen content, available potassium content, available phosphorus content, sucrase activity, and urease activity. Further, sucrase activity is more sensitive in evaluating the soil IFI in all seasons.
【Objective】Increased nitrogen (N) deposition affects carbon (C) and N availability by affecting the litter decomposition process, after which it affects the C-nutrient balance of the biogeochemical cycle. In this study, the nylon mesh bag method was used to study the decomposition rate and nutrient content changes of Quercus aquifolioides litter under simulated N deposition, providing a reference for an effective Q. aquifolioides forest ecosystem management.【Method】The in situ litter decomposition test was carried out in the Q. aquifolioides forest of Mopanshan in Xinping County, central Yunnan Province. Four N levels were applied using the nylon mesh bag method, with urea (CH4N2O) as the N source for in situ decomposition of litter and N deposition treatment. The four N deposition levels were: control [CK, 0 g/(m2·a)], low N [LN, 10 g/(m2·a)], medium N [MN, 20 g/(m2·a)] and high N [HN, 25 g/(m2·a)]. Leaf litter and twig mass remaining, lignin, cellulose, and C, N, P and K contents were then measured.【Result】① After one year of decomposition, the N deposition treatment significantly increased the mass remaining rate (P<0.05) of leaf litter (0.84%-3.87%) and twig (1.67%-3.30%). The litter decomposition was inhibited, and the inhibition intensity was proportional to N content application. ② Variation coefficients of leaf and twig litter decomposition were 0.271-0.368 and 0.167-0.218 kg/(kg·a), respectively. The lhe C/N (69.02) and lignin/N (54.65) of twig litter were significantly higher compared with leaf litter (52.09 and 44.42, respectively). Leaf decomposition rate was faster compared with that of twig. ③ The chemical composition of the litter affected its mass remaining rate, which was negatively correlated with N and P contents of leaf and twig litters, and positively correlated with C, cellulose, C/N, C/P, lignin/N and cellulose/N.【Conclusion】The N deposition inhibits litter decomposition, and this effect is significantly enhanced by increased nutrient content. Initial nutrient content effects nutrient retention and litter release processes, among which N level, C/N and lignin/N are important influencing factors.
【Objective】The aim of this research is to determine the exposure characteristic and health risk of polycyclic aromatic hydrocarbons (PAHs) in soils and tobacco plants.【Method】Forty samples of soil and fresh tobacco plants were collected from tobacco-growing areas in Changping (CP), Taiping (TP), Pingtou (PT), Pujue (PJ), Panxin (PX) and Mengxi (MX) in Songtao County of Guizhou Province. A total of 16 PAH species were isolated from the samples. The characteristics of PAHs exposure were analyzed after ingestion, dermal administration, and inhalation. The carcinogenic and non-carcinogenic health risks on farmers were assessed.【Result】The total contents of seven kinds of carcinogenic PAHs [perylene (Chr), benzo(a) anthracene (BaA), benzo(b) fluoranthene (BbF), benzo(k) fluoranthene (BkF), dibenzo(a,h)anthracene (DahA), benzo (a) pyrene (BaP), and indeno(1,2,3-cd) pyrene (IP)] in the soil and tobacco samples were 70.97-365.71 and 293.53-1 730.72 μg/kg, and the mean values were 221.13 and 707.03 μg/kg, respectively. The total contents of nine non-carcinogenic PAHs [naphthalene (Nap), anthracene (Ant), phenanthrene (Phe), pyrene (Pyr), acenaphthylene (Ane), diacenaphthylene (Any), fluorene (Flu), fluoranthene (Fla), and benzo (g,h,i) pyrene (BghiP)] were 65.6-647.6 and 108.9-606.1 μg/kg, and the mean values were 379.6 and 304.2 μg/kg, respectively. Analysis of the exposure characteristics of the PAHs revealed that ingestion>dermal>inhalation in terms of the exposure risk. The total average daily exposure of the farmers to the seven carcinogenic PAHs in the soil and tobacco samples was 54.41-280.38 and 225.04-1 326.87 pg/(kg·d), and the mean values were 169.53 and 542.05 pg/(kg·d), respectively. The total average daily exposure of the farmers to the nine non-carcinogenic PAHs in the soil and tobacco samples were 146.70-1448.19 and 243.41-1355.33 pg/(kg·d), and the mean values were 848.91 and 680.22 pg/(kg·d), respectively. The average daily intake (ADI) of the carcinogenic and non-carcinogenic PAHs was the highest in MX. The total non-carcinogenic risk index of the PAHs in the soil and tobacco samples to the farmers ranged from 8.39×10-7 to 5.14×10-6, with a mean value of 2.18×10-6. The total carcinogenic risk index of the PAHs to the farmers varied from 8.39×10-7 to 5.14×10-6, with a mean value of 2.18×10-6. The total carcinogenic risk index of BaP was the highest among the PAHs, being 3.69×10-7 to 4.25×10-6, with a mean value of 1.58×10-6. The levels of BaP exceeded the recommended threshold published by the United States Environmental Protection Agency (USEPA) at 26 sites (65%), and the total carcinogenic risk of the seven carcinogenic PAHs was low at 90% of the sampling sites.【Conclusion】Ingestion and dermal exposure were the main exposure routes of the PAHs in the soil and tobacco samples. The carcinogenic risk of the non-carcinogenic PAHs was below the critical value recommended by the USEPA, and their values were at acceptable range. The carcinogenic PAHs had a low health risk to farmers at the majority of sampling sites. However, the carcinogenic PAH, BaP, requires further attention.
