放牧对盐沼土壤生物功能群和碳氮过程的影响及其机制

Salt marsh is among the ecosystems of highest ecosystem value in the world, but it is also one of the most intensively disturbed systems. Although livestock grazing in salt marshes is very common worldwide, researches are very few compared to that of terrestrial ecosystems. Researches from terrestrial grazing systems in recent years have uncovered that the soil subsystem is the key intermediate to induce the ecological impacts aboveground. However, the investigation about the effects of grazing on salt marsh soil systems is still far from complete. This dampened our understanding of how salt marsh ecosystems response to grazing from the integrative ecosystem view and the aboveground-belowground linkage mechanisms. This study will conduct field investigations and fence exclusion experiments at Chongming Dongtan salt marsh, analyze the impacts of cattle grazing on important soil functional groups and carbon and nitrogen processes, reveal the plant and sediment deposition influential pathway, and discuss the possible feedbacks of soil system to underground plant systems. This study will provide basis for ecosystem management and restoration of the grazing salt marshes, and also provide new thoughts for improving the aboveground-belowground multitrophic interaction theories.

盐沼是世界上生态系统服务功能最强大的生态系统之一，但同时也是受人类干扰最强烈的生态系统之一。家畜动物的放牧活动在全球各大洲盐沼生态系统十分普遍，但相关研究和陆地生态系统相比还非常不足。近年来陆地系统的研究发现，放牧对植被的影响在很大程度上是通过对土壤的影响这一间接过程而实现的，因此了解土壤生态系统的响应非常关键。但迄今为止，国际上还缺乏有关放牧如何影响盐沼土壤的充分理解，尚没有从地上-地下生态系统联系角度，以及生态系统整体水平来剖析盐沼生态系统对放牧活动的响应与机制。本项目在长江口崇明东滩盐沼，以野外调查实验和围栏受控实验相结合，研究放牧对盐沼土壤生物功能群及生态系统碳氮过程的影响，并着重从地上植物、沉积物淤积两个方面揭示其影响机制，同时探讨土壤改变对地上部分植物等可能产生的反馈，为盐沼生态系统的管理和修复提供依据，也为完善有外源干扰情况下的地上-地下多营养级联系研究理论提供新的思路。