【目的】探究南水北调中线工程水源区内岩溶地貌背景下,不同植被恢复模式土壤养分与化学计量特征,评价南方岩溶连片分布区北缘林地生境土壤养分供给状况,以期为南水北调中线工程水源涵养区林分经营管理、退化生态系统恢复重建和石漠化治理提供理论依据。【方法】以河南淅川县岩溶区栓皮栎天然次生林、侧柏人工林和杉木人工林下土壤为研究对象,通过室内实验对土壤有机碳(SOC)、全氮(TN)、全磷(TP)、全钾(TK)、碱解氮(AN)、速效磷(AP)和速效钾(AK)含量进行测定,并计算土壤各元素的化学计量比,分析不同恢复模式林地生境土壤养分变异状况。【结果】岩溶区不同植被恢复模式下土壤SOC、TN、TP含量分别为10.23~28.99、0.89~2.42、0.43~0.77 g/kg;土壤碳氮质量比(C∶N)、碳磷质量比(C∶P)、氮磷质量比(N∶P)均值分别为10.41~11.89、13.69~80.00、0.18~6.61。土壤养分含量与化学计量比受植被类型与土层深度的影响,表现为表层土壤(0~10 cm)高于下层土壤(>10~20 cm、>20~30 cm)。除TP含量外,两种植被恢复模式土壤养分含量表现为天然次生林高于人工林。相关分析表明,不同植被恢复模式下土壤SOC、TN、TP含量间存在显著相关关系,说明三者空间分布有较一致的变化规律。【结论】在南水北调水源区,自然恢复的栓皮栎次生林是较为理想的植被恢复模式,而3种林分在生长过程中均受到氮或磷元素的限制。在日后的林分经营管理中,针对天然林可适度施用磷肥补给,对人工林添加氮肥,并通过抚育间伐等措施,提高植被对养分的吸收效率,从而促进植被土壤间的协调发展。

【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.