关键词: 人工林, 叶片, 凋落物, 土壤, 养分格局, 重吸收率, 黑龙江阿什河流域

Abstract:

【Objective】This study aimed to provide a theoretical basis for the recovery of the forest landscape and optimal management of plantations in the Ashi River Basin. The differences in leaf-litter-soil nutrient content and stoichiometric ratio, leaf-litter-nutrient resorption and soil available nutrients and their activation were investigated to explore the nutrient absorption and utilization strategies in plantations of six tree species. Differences in the nutrient distribution patterns between plantations of coniferous and broad-leaved species were also investigated, from the point of rational allocation and optimal utilization of nutrient resources, complementary tree species were inferred. 【Method】The study was conducted at the Forest Cultivation Experiment Station of the Northeast Forestry University in plantations located on secondary forest strip clear cutting land with the same site conditions. The study plantations were 29 years old and contained the following six species: Pinus koraiensis, Larix olgensis, Picea koraiensis, Fraxinus mandshurica, Phellodendron amurense and Juglans mandshurica. Applying the research method of ecological stoichiometry, the nutrient content and stoichiometric characteristics of the leaf-litter-soil system of each plantation were analyzed, and the nutrient resorption of the litter and the supply characteristics of soil available nutrients were confirmed. This was accomplished through field survey sampling and laboratory analysis. A Carbon and nitrogen analyzer was used to determine the carbon (C) content in leaves, litter, and soil and a Kjeldahl instrument was used to determine the nitrogen (N) content in leaves and litter. The soil N content as ammonium nitrogen ($NH_{4}^{+}-N$) and nitrate nitrogen ($NO_{3}^{-}-N$) was determined by using a continuous flow analyzer. Phosphorus (P) content was determined by sulfuric-perchloric acid digestion and molybdenum-antimony colorimetry. The soil P content was determined by sulfuric-perchloric acid digestion and molybdenum-antimony colorimetry. Soil available P was determined by HCl-H₂SO₄ extraction.【Result】① The leaf P content of the coniferous plantations (1.55 g/kg) was significantly lower than that of the broad-leaved plantations (2.02 g/kg) (P < 0.05, F =16.92, df=1) and the C and P content in the coniferous plantations (47.75, 1.17 g/kg) was significantly lower than in the broad-leaved plantations (76.35, 1.47 g/kg) (P<0.05, F_{C content}=75.15, F_{P content}=9.91, df=1). Within all six stands, the leaf N content (19.64 g/kg) (P < 0.05, F =5.26, df=5), C, N and P content in the litter (P < 0.05, F_{C content} =2.34, F_{N content} =1.60, F_{P content} =6.74, df=5) and the soil (P< 0.05, F_{C content} =154.84, F_{N content} =14.21, F_{P content}=53.55, df=5) of the F. mandshurica plantation was higher than those in the other plantations. Leaf P content of the P. koraiensis plantation (1.30 g/kg) (P < 0.05,F =36.71,df=5), litter C content of the L. olgensis plantation (P < 0.05,F =2.34,df=5) and litter N content of the P. koraiensis plantation (P < 0.05,F=1.60,df=5) was lower than those for the other plantations. ② The leaf C/P of the coniferous plantations (314.84) was significantly higher than that of the broad-leaved plantations (251.03) (P < 0.05, F =20.43, df=1) whereas the soil C/P of the broad-leaved plantations (53.20) was significantly higher than that of the coniferous plantations (40.71) (P<0.05, F=15.38, df=1). Within all six stands, the leaf C/P of the P. koraiensis plantation (359.24) was the highest (P < 0.05, F =35.02, df=5), and C/N in the leaves of the F. mandshurica plantation (24.15) was the lowest (P<0.05, F =11.42, df=5). The soil C/N of the J. mandshurica plantation (19.82) was significantly higher than that of the L. olgensis plantation (5.62) (P<0.05, F =12.40, df=5). ③ The N resorption efficiency (25.31%) was significantly higher than the P resorption efficiency (14.41%) in the coniferous plantations and the P resorption efficiency of the broad-leaved plantations (29.84%) was significantly higher than that of the coniferous plantations (14.41%) (P < 0.05, F =7.30, df=1). Within all six stands, the N resorption efficiency of F. mandshurica (P < 0.05, F =13.66, df=5) and the P resorption efficiency of P. amurense (P < 0.05, F =60.40, df=5) were higher than for the litter of the other stands. ④ The ratio of available P content and available P in the broad-leaved plantations (11.74 mg/kg, 8.22×10 ^-3) was significantly lower than that in the coniferous plantations (16.59 mg/kg, 14.24×10 ^-3) (P < 0.05, F_{available P content}=7.32, F_{available P ratio}=11.84, df=1). Within all six stands, the soil activation ability to N of the P. koraiensis plantation and the J. mandshurica plantation was stronger than those that of other plantations, and the soil supply ability and activation ability of available P in the P. koraiensis and the L. olgensis plantations was stronger than in the other plantations. 【Conclusion】The rate of P utilization in the leaves of coniferous plantation trees was higher than that in broad-leaved plantation trees, and the N resorption efficiency was higher than the P resorption efficiency. The C and P content in the soil of the broad-leaved plantations was higher than that of the coniferous plantations, while the available P accumulation ability was weak. The available P content and ratio of the broad-leaved plantations was significantly lower than for the coniferous plantations, but the P resorption efficiency was significantly higher than that for the coniferous plantations. From the point of optimal utilization of nutrients and rational allocation of nutrient resources, coniferous and broad-leaved tree mixes, such as P. koraiensis and F. mandshurica, and L. olgensis and F. mandshurica could create a complementary nutrient allocation and utilization pattern.

Key words: plantation, leaf, litter, soil, nutrient pattern, resorption efficiency, Ashi River Basin, Heilongjiang Province