西南喀斯特区生态恢复过程中植被与土壤养分的协同演变机制

Attributed to the ecological restoration projects and rocky desertification control projects, the degradation trend of karst ecosystem has been reversing, and the vegetation cover is substantially improving in Southwest China recently. However, soil restoration is slow. Particularly, the recovery processes of soil organic carbon and soil mineral nutrients are very slow, which definitely limited the net primary productivity (NPP) and ecosystem sustainability in this region. Through the integration of large-scale field survey, multi-point monitoring experiment, and remote sensing data, the objectives of this project were to 1) analyze the relationship between soil mineral nutrients and environmental factors to document the spatial pattern of soil mineral nutrients at large-scale and figure out its primary factor(s), 2) compare the status of soil mineral nutrients over vegetation succession under different geological background and integrate with the key ecological processes that affect soil nutrients to reveal how environmental factors affects the accumulation of soil nutrients, and 3) explore the response of plant community structure and its ecological functioning to soil nutrients via a fertilization experiment and a germination experiments to reveal the mechanisms of how soil nutrient levels affects and maintains the plant community construction and productivity. The project will potentially improve the ecological services of soils of karst ecosystems, provide scientific basis for managing of vegetation recovery and for optimizing of artificial inputs to karst ecosystems under mid- and late-succession stages.

随着大规模石漠化治理与生态建设工程的实施，西南喀斯特地区植被覆盖率持续提高，生态系统退化趋势发生逆转。然而由于土壤属性恢复滞后，植被恢复的可持续性面临挑战，其中土壤有机质积累缓慢，养分供给能力不足成为植被恢复中后期的关键限制因子之一。本研究拟基于大尺度野外调查、多样点观测试验和遥感数据，分析区域尺度土壤养分与喀斯特环境因子之间的关系，探明土壤养分的空间分布格局及其主要影响因子；在景观尺度结合土壤养分变化的关键生态过程（凋落物归还、微生物群落结构等）研究，阐明不同地质背景下土壤养分随植被恢复的变化特征，揭示植被恢复过程中土壤养分积累对环境因子的响应规律；通过养分添加试验和土壤种子库萌发试验，探讨植物群落结构对土壤养分库特征的差异响应，阐明土壤养分对植物群落构建和生产力形成的影响，揭示土壤养分与植被的协同演变机制，为喀斯特生态系统服务提升与植被重建的中后期调控措施制定提供科学依据。

随着大规模石漠化治理与生态建设工程的实施，西南喀斯特生态系统退化趋势发生逆转。然而由于土壤属性恢复滞后，生态工程建设成效缺乏有效评估，植被恢复的可持续性面临挑战，其中土壤有机质积累缓慢，养分供给能力不足成为植被恢复中后期的关键限制因子。本研究针对这一问题，基于区域遥感监测、大尺度野外调查和多样点定位观测，研究了西南喀斯特地区生态恢复背景下植被与土壤养分的协同演变过程特征及其机制。结果发现，生态工程实施以来，西南喀斯特地区植被叶面积指数和地表植被固碳速率显著增加，首次证实了大规模生态保护与建设工程的投入显著促进了区域植被覆盖、碳固定等生态服务提升，降低了土地石漠化退化风险和生态系统对气候扰动的敏感性；明确了退化生态系统自然恢复有利于土壤碳氮较快积累，自然恢复方式的土壤碳氮固定效应和微食物网结构优于人工恢复，复合种植优于单一人工林种植，阐明了恢复前土壤氮库大小、氮固定速率和交换性钙离子水平是土壤碳固定的主要控制因子；探明了生态恢复过程中植被群落主要限制性养分的变化规律，恢复初期植被生产力主要受氮限制，恢复中后期主要受磷限制，并揭示了根际有机酸分泌和苔藓结皮定殖对养分循环的促进机制。研究结果为喀斯特地区后期重大生态工程实施和植被稳定持续恢复提供了重要科学依据。