戈壁荒漠捕食强度和降雨变化对土壤动物营养结构的影响及调控机制

The Gobi desert is the main natural landscape unit in northwest of China, covering 6.9% of the total land area of China. Vegetation is dominated by a few xerophytic and super-xerophytic shrub species in the Gobi desert, such as Reaumuria songarica (Pall.) Maxim. (Tamaricaceae) and Nitraria sphaerocarpa Maxim. (Zygophyllaceae). Shrubs as “Ecosystem engineers” affect the diversity and trophic structure of soil animals by modifying abiotic (e.g. soil water available and soil temperature) and biotic factors (e.g. litter production and quality) in the Gobi desert ecosystem. However, our knowledge of the effects of shrubs on trophic structure of soil animals by changing predation intensity and precipitation change remains limited in these severely water-limited Gobi desert ecosystems. Hence, there is a need for a more thorough exploration onthe mechanisms underlying how predation intensity and precipitation changes affect the trophic structure of soil animals and their top-down and bottom-up controls in the dry and wet seasons in the Gobi desert ecosystem. In this project, we used a typical Gobi desert ecosystem in the middle Heihe River Basin as a research model, and considered four dominant soil animals (spiders, beetles, mites, and springtails) in this system. A removing lizard and changing rainfall manipulative experimental approach is applied to address the three key questions: 1) the effects and regulatory mechanisms of the predation intensity on the trophic structure of the soil animals; 2) the effects and regulatory mechanisms of the precipitation changes on the trophic structure of the soil animals; and 3) the mechanisms underlying the interactive effects of both predationin tensity and precipitation changes on the trophic structure of the soil animals and their ecological functions. This research will help us to understand the mechanisms of how the shrubs, predators and rainfall combined to drive the changes on the trophic structure of soil animals in the Gobi desert ecosystem. The results will provide important information on predicting the effects of future climate change on the diversity and ecological function of soil animals in the Gobi desert ecosystem.

戈壁荒漠是我国西北主要的自然景观单元，其面积约占我国国土面积的6.9%。戈壁荒漠植被以旱生和超旱生小灌木为优势类群。灌木是戈壁荒漠重要的生态调控者，它主要通过改变生物、非生物资源再分配影响土壤动物多样性及其营养结构和功能。然而，对灌木如何通过改变捕食强度和降雨再分配影响土壤动物营养结构及功能的机制尚不清楚。本项目以黑河中游戈壁荒漠蜘蛛、甲虫、螨类和跳虫等土壤动物优势类群为研究对象，通过排除沙蜥（戈壁荒漠主要的捕食者）和模拟降雨变化的控制试验，重点开展以下3方面研究：1）排除沙蜥对土壤动物营养结构的影响及调控作用；2）降雨变化对土壤动物营养结构的影响及调控作用；3）排除沙蜥与降雨变化对土壤动物营养结构的耦合影响及相互作用调控机制。该研究对认识灌木、捕食者和降雨三个因子驱动的土壤动物营养结构及功能的变化规律有重要意义，并为进一步研究戈壁荒漠土壤动物多样性与生态功能对气候变化响应提供理论基础。