荒漠灌丛对土壤动物的“聚集—扩散”效应：过程与机制

It was found that there was an "assembly" effectiveness of shrub cover on soil arthropods in desert regions. Along with shrub growth and its stand succession, there was also a "dispersal" effectiveness of shrub cover on soil arthropod distribution. However, there was largely unknown about the formation process and mechanism of "Assembly-dispersal" effectiveness of desert shrub cover on soil arthropods in desert region. This project will take the desert shrub of different ages as the sampling subject in order to probe into the relationship between soil arthropods and shrub cover. An investigation on the abundance, diversity and trophic structure of soil arthropods between the microhabitats beneath the shrub cover and in the open space will be carried on together with soil properties and herbaceous performances in Shapotou region, Ningxia. (1) Taking the adjacent open space as control, the formation process and mechanism of "assembly" effectiveness of shrub cover on soil arthropods will be discussed. (2) The succession of "assembly" into “dispersal” effectiveness of shrub cover will be examined in order to probe into the formation process of "dispersal" effectiveness of shrub cover. (3) The mathematics models regarding the effect of shrub cover on soil arthropods will be constructed on the formal basis. (4) The conversion process between "Assembly" and "dispersal" effectiveness of desert shrub cover will be analyzed in addition to their effects on the distribution of soil arthropods between shrub microhabitats along with shrub growth and stand succession. (5) All these findings will reveal the relationship between aboveground and belowground biota along with shrub growth and stand succession, thus beneficial for the management on desert shrubs, biodiversity conservation, desertification control and recover assessment of degraded ecosystems.

荒漠灌丛对土壤动物的空间分布具有“聚集”作用，而随着灌丛林地演替，灌丛内土壤动物群落对灌丛间又表现出“扩散”效应。但是，关于荒漠灌丛对土壤动物“聚集-扩散”效应的形成过程与机制，尚不清楚。本项目以长时间年龄序列（2-60年）荒漠灌丛为调查对象，以灌丛和土壤动物分布间的作用关系为切入点，以灌丛外为对照，通过调查不同林龄灌丛内外土壤动物多度、多样性、生物量及功能群分布特征，结合土壤性质和地表植被特征调查，分析灌丛建植对土壤动物“聚集”效应的形成过程和机制，阐明灌丛林地演替对土壤动物“聚集”效应的演化进程及“扩散”效应的形成特征，构建灌丛与土壤动物分布间作用关系的数学模型，解析灌丛对土壤动物“聚集-扩散”效应间的转化关系及对土壤动物多样性分布的影响规律。研究结果旨在揭示灌丛建植与演化过程中地上和地下部分间的作用关系，为荒漠灌丛林管理、生物多样性保育、退化生态系统恢复评价以及沙漠化防治提供依据。

研究灌丛对土壤动物的“聚集”效应向“扩散”效应的转化过程，对于促进荒漠生态系统结构和功能恢复具有重要生态作用，对于人工灌丛林管理与利用、生物多样性保育、沙漠化防治均具有重要意义。取得的重要结果包括：（1）在腾格里沙漠扎设草方格和人工林建设，有利于改善土壤质地，促使土壤理化性质向良好方向发展。（2）流动沙地扎设草方格营造油蒿林能在短期内提高风沙土壤综合质量，而其他造林方式固沙效果有限。（3）沙地灌丛内外生境中节肢动物的空间分布，既与灌丛本身生理生态学特性相关，也与季节性降雨和温度等气象条件的改变密切相关。（4）灌丛林营造短期内，油蒿灌丛林对地面节肢动物多样性的保育效应要优于其他灌丛林地。（5）灌丛建植有助于地面节肢动物多样性恢复。但是，地面节肢动物多样性与多度分布对不同类型大小灌丛生境产生不同响应规律。（6）立地条件、灌丛微生境和季节变化不仅对地面节肢动物类群个体数产生深刻影响，而且亦影响到了地面节肢动物群落总个体数和优势度的时空分布。（7）立地条件对基于节肢动物个体数的灌丛“虫岛”效应分布影响较大，并受季节变化的调控，但对于基于节肢动物丰富度的灌丛“虫岛”效应影响较小。柠条灌丛对地面节肢动物多样性分布呈现正向性作用，受季节变化和立地条件的影响较小。（8）灌丛对地面节肢动物多样性的保育效应能够削弱放牧干扰的负向影响。（9）在宁夏荒漠草原，仅灌丛大小引起的微生境差异对枯落物分解率影响较小，但灌丛大小和土壤动物类群的相互作用对枯落物分解率的影响较大。（10）土壤动物是荒漠生态系统灌丛群落内不可或缺的一部分，它们大多数均处于土壤生态系统食物链的上端，在维持荒漠生态系统的食物网结构、物质循环和能量流动等方面扮演着重要的角色。荒漠灌丛土壤动物多样性分布及其生态功能对于荒漠生态系统灌丛林营造、土地资源管理及退化生态系统的恢复具有重要意义。