中国典型生态脆弱区生态化学计量学研究进展

在人类活动和自然环境变化的相互作用下，生态脆弱区生态系统随之变迁，荒漠化、盐碱化、水土流失、植被生产力下降等是生态脆弱区面临的重要问题。生态化学计量学作为当前多学科交叉研究的热点领域，强调从生态系统能量与元素平衡角度，揭示元素生物地球化学循环和生态系统对环境变化的调控机制。为了促进对生态脆弱区碳（C）、氮（N）、磷（P）生态化学计量的深入理解，本文重点总结了近年来有关我国典型生态脆弱区植物、凋落物、土壤和土壤微生物量C、N、P生态化学计量及其对环境变化响应的研究成果，并展望未来研究方向，以期促进生态化学计量学的发展和生态脆弱区生态保护与恢复研究。研究表明，植物-凋落物-土壤-土壤微生物系统C、N、P化学计量具有较强相关性，并受土壤因子、气候因子、生物因子和人类活动的显著影响。在生态脆弱区，我国北方荒漠及荒漠化地区由于较高的N∶P比值易受P限制，而青藏高原脆弱区、西南岩溶石漠化地区和黄土高原脆弱区等生态脆弱区更易受N限制；随着植被恢复，养分限制逐渐由N限制向P限制转变。生态脆弱区相对较低的养分含量和C∶N∶P比值或许可在一定程度上解释植被生产力较低的原因，而具有较高N、P化学计量内稳性的植物在贫瘠环境中具有较强竞争力和更高稳定性。今后可加强多尺度、不同生态系统植物-凋落物-土壤-土壤微生物系统生态化学计量和长期、多因子交互控制实验的研究。

Advances in ecological stoichiometry in typically and ecologically vulnerable regions of China

The ecosystem of ecologically vulnerable regions is changed by the interaction of human activities and natural environmental changes. The desertification, salinization, soil erosion and vegetation productivity decline are important problems faced by the ecologically vulnerable regions. As a critical issue of interdisciplinary research, ecological stoichiometry emphasizes to reveal the biogeochemical cycle of elements and the regulation mechanism of ecosystem on environmental change from the perspective of energy and element balance of ecosystem. It is of great ecological significance to carry out the research on ecological stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) elements in the ecosystem:(1) to judge the limitation of N and P on plants to reveal the mechanism of nutrient regulation and biogeochemical cycle in terrestrial ecosystem; (2) to promote the in-depth understanding of biological adaptability to the environment; (3) to reveal the mechanism of carbon cycle and response of ecosystem to environmental change. To understand the C, N and P ecological stoichiometry in typically and ecologically vulnerable regions (agro-pastoral ecotone, forest-grassland ecotone, desert-oasis ecotone, the Loess Plateau vulnerable areas, the Qinghai-Tibet Plateau vulnerable areas and southwest karst areas) of China, we mainly summarized the recently researches of C, N, and P ecological stoichiometry in plants, litters, soils and soil microbes, as well as their responses to environmental changes. Then, we proposed the possible direction in the further research. The aim is to promote the development of ecological stoichiometry and ecological protection and restoration in typically and ecologically vulnerable regions. The results show that the C, N, and P ecological stoichiometry of plants, litters, soils, and soil microbes present strong correlations, and is significantly affected by soil, climate and biological factors, and human activities. In the ecologically vulnerable regions, the deserts and desertification areas in north China with higher N:P ratio are more likely to be limited by P, while the ecologically vulnerable regions, such as the Qinghai-Tibet Plateau vulnerable areas, southwest karst areas, and the Loess Plateau vulnerable areas are more likely to be limited by N. With the vegetation restoration, the nutrient limitation gradually changes from N limitation to P limitation. The relatively low nutrient concentration and C:N:P ratio in the ecologically vulnerable regions may explain the reason for lower productivity of vegetation, while the plants with higher N and P stoichiometric homoeostasis have stronger competitiveness and higher stability in poor environment. Future research should focus not only on the ecological stoichiometry of plant-litter-soil-microbe system in different scales and ecosystems, but also on the controlled field experiments involving long-term and multi factors interaction.