荒漠绿洲土壤生态系统结构和功能对景观格局变化的响应及尺度效应

In temperate desert ecosystems in Northwest China, the ecotone between desert and oasis is thought to be an important link between desert and oasis ecosystems as well as an ecological buffer zone in which plays a key role in maintaining the stability of the oasis ecosystem. In recent decades, the human-induced rapid expansion of artificial oases in desert landscape has led to changes in landscape patterns in the desert-oasis ecotones,with consequences of fragmentation of native desert landscape into small and isolated patches consisted of farmland as well as woodland and shrubland plantations. This landscape pattern change in turn causes substantial alterations in the environment, structure, and functions of soil ecosystems. However, how changes in landscape patterns through replacement of natural desert landscape with different land use types such as farmland and shrub/tree plantations affect the soil ecosystem environment, structure, and functions is poorly understood. Using a typical artificial oasis habitat in the Hexi Corridor, Gansu province, northwestern China, we assess the scale-dependent responses of the soil ecosystem environment, structure, and functions to changes in landscape patterns. The main objectives of this study are to quantify: (1) the effects of landscape pattern changes on soil biological, chemical, and physical conditions of the oasis ecosystem; (2) the effects of landscape pattern changes on soil food web composition, abundance, and diversity of the oasis ecosystem; (3) the effects of landscape pattern changes on the functioning and services of soil ecosystems; and (4) the mechansims underlying how differences in soil food web composition and abundance resulting from changes in landscape patterns affect the functioning of soils and the ecosystem services that they deliver. Understanding the influence of landscape change on the soil food web composition and the ecosystem functions by altering vegetation type, microclimate, and soil physical-chemical-biological properties as well as quantifying general associations between soil biota and ecosystem functions may have important implications for the development of appropriate land use management strategies for conserving soil biodiversity and ecosystem functioning in this desert oasis ecosystem.

在荒漠生态系统，荒漠绿洲过渡带是连接戈壁荒漠、人工绿洲的重要纽带，也是重要的生态缓冲带，对维持人工绿洲生态系统稳定性起着关键作用。近年来人工绿洲扩张导致过渡带景观格局变化已对人工绿洲土壤生态系统环境、结构和功能产生重要影响。然而，尚缺乏对过渡带景观格局变化在不同尺度上影响人工绿洲土壤生态系统环境、结构和功能的研究。本项目以甘肃河西走廊典型人工绿洲为研究对象，采用样带调查、定位观测与建模和理论分析等方法，拟在不同时间（季节、年际）和空间（样方、景观）尺度上系统研究和定量评估过渡带景观格局变化对人工绿洲土壤生态系统环境、结构（土壤食物网组成及其多样性）和功能（如碳和养分循环与积累）的影响，从多层面解析景观格局变化与土壤生态系统环境、结构和功能演变之间的耦合关系及互馈机制。研究成果将提升对人工绿洲生态系统响应高强度人类活动系统行为的预测能力，并为人工绿洲景观格局优化设计和调控提供新知识和新思路。

中国内陆干旱区分布着数量众多大小不同的人工绿洲，这些人工绿洲是人类定居、生存、繁衍的重要场所。近60年来，人工绿洲快速扩张，扩张方式主要包括：农地扩张，即绿洲边缘天然草地开垦为农田；林地扩张，即绿洲边缘天然草地转变为乔木防护林；灌木地扩张，即荒漠-绿洲过渡带天然草地转变为防风固沙灌木林。3种扩张方式反映了荒漠绿洲景观格局的变化状态。项目以河西走廊张掖绿洲边缘典型天然荒漠草地及其转变的人工梭梭灌木林（雨养）、人工杨树林（灌溉）和农田（灌溉+施肥）为研究对象，围绕绿洲扩张方式对土壤食物网的影响，人工灌木林类型（梭梭纯灌木林、柽柳纯灌木林和梭梭+柽柳混播灌木林）对地栖甲虫物种多样性的影响，作物种植模式（单作玉米和春小麦、玉米和春小麦间作套种）对地栖和土居农业节肢动物害虫及其天敌多样性的影响等关键科学问题开展深入研究。. 项目取得如下原创性成果：阐明了土壤微生物和节肢动物优势类群组成、数量、多样性受绿洲扩张方式影响的差异响应及其适应性变化特征，发现绿洲扩张方式灌溉管理水平的差异是导致土壤食物网结构变化的重要原因；揭示了不同绿洲扩张方式对土壤生态系统重要服务功能属性的差异影响；确定了地栖甲虫优势种在不同人工灌木林的分布特征及其季节活动模式，发现混播灌木林的甲虫多样性显著高于纯灌木林；阐明了作物种植模式对地栖和土居重要农业节肢动物害虫及其天敌多样性和数量的影响及其调控机理，发现玉米/春小麦间作套种的害虫生物防治功能显著优于单作。. 研究成果对于深入理解荒漠绿洲生态系统土壤食物网结构、功能受人类活动影响的响应方式、适应能力及其变化规律具有重要意义；为人工绿洲可持续发展路径的抉择提供了理论依据；为创建可促进昆虫多样性保护的绿洲防护林体系及可提升害虫生物防治功能的环境友好型农业生产体系提供了技术支撑；为全球变化背景下荒漠绿洲生态系统的环境、结构、功能协同演变及其驱动机制研究提供了重要的信息。. 项目发表原创性研究论文13篇,9篇发表在《Plant and Soil》、《Agriculture, Ecosystems and Environment》、《Science of the Total Environment》、《Catena》、《Insect Conservation and Diversity》等国际主流学术期刊。培养博士生2名、博士后1名。