降水脉动对干旱荒漠土壤动物分布及多样性的调控机理

In arid desert ecosystems, natural precipitation has a strong characteristic of pulse, namely strong variations in the frequency, intensity and quantity of precipitation. This precipitation pulse may have an important impact on the distribution and diversity of soil animal communities. However, our knowledge of the influence of precipitation pulse on the distribution, composition and diversity of soil animal communities remains limited in severely water-limited Gobi desert ecosystems of northwestern China. Hence, there is a need for a more thorough exploration of the mechanisms underlying how precipitation pulses affect the distribution and diversity of soil animal communities at different taxonomic levels. In this study, we used a typical arid desert shrubland in the Hexi Corridor of Gansu province as a model system. A manipulative experimental approach is applied to address the three key questions: (1) the responses of soil animal community and its main components to natural precipitation pulses; (2) the effects of the winter snow addition treatments on the distribution, abundance, and diversity of soil animal community and its main components; and (3) the effects of the simmer water addition treatments on the distribution, abundance, and diversity of soil animal community and its main components. Our aims of this study are to determine the underlying mechanisms of how precipitation pulses, summer water addition, and winter water addition affect differently the distribution and diversity of soil animal communities and to quantify whether the degree to which soil animals respond to precipitation pulse, summer water addition, and winter water addition is consistent across trophic and taxonomic groups. The findings may have important implications for supporting the development of suitable management strategies for the conservation of soil biodiversity and functioning in this arid desert ecosystem.

在干旱荒漠区，降水呈现强烈的脉动特征（即降水频率、强度及其数量的高度变异性），降水脉动变化对荒漠土壤动物群落的分布及其多样性有显著的影响。目前对降水脉动如何影响和调控荒漠土壤动物群落分布及其多样性形成与维持的生态机制的认识非常有限。本项目以甘肃河西走廊干旱荒漠为研究对象，通过一系列野外人工模拟冬季增雪、夏季增雨及降雨脉动的控制实验，结合室内分析和理论分析等方法，重点研究：⑴土壤动物群落及关键类群对自然降水脉动的响应特征，⑵冬季增雪对土壤动物分布及多样性的影响及调控机制，⑶夏季增雨及降雨脉动对土壤动物分布及多样性的影响及调控机制。通过研究，揭示冬季增雪、夏季增雨及降雨脉动驱动的微生境的生物和非生物环境因子变化对土壤动物分布格局和多样性形成的直接和间接影响及调控机理，为我国干旱荒漠生态系统生物多样性保护管理提供科学依据，促进荒漠生态系统生物多样性保育理论、资源脉动生态学理论和研究方法的发展。

在干旱荒漠区，降水呈现强烈的脉动特征（即降水频率、强度及其数量的高度变异性）并存在明显的季节变异，降水变化驱动的土壤水分及温度变化对荒漠土壤动物多样性及分布格局有深刻的影响。然而，我们对干旱荒漠不同大小节肢动物类群对降水脉动的响应认识仍非常有限。鉴于此，本项目围绕“土壤动物（节肢动物）分布及多样性对降水脉动的响应”这一核心问题，重点研究：（1）荒漠节肢动物（蜘蛛、甲虫、螨类和跳虫）对自然降雨的响应；（2）荒漠节肢动物对降雨增加的响应；（3）荒漠节肢动物对降雨脉动的响应。项目主要取得以下研究成果：.1）研究发现自然降雨出现的季节对节肢动物短期响应的影响较大，而降雨量及灌木种类对其影响较小。不同节肢动物类群对自然降雨的响应模式不同。干季捕获的甲虫数量最多，降雨后捕获的甲虫数量亦呈增加的趋势；湿季降雨捕获的蜘蛛数量最多，降雨后捕获蜘蛛的数量变化较小。湿季捕获螨和跳虫的数量明显高于干季，降雨后捕获的螨类数量呈降低的趋势，而捕获跳虫的数量短期变化较小。.2）确定了模拟增加不同大小降雨事件对小型节肢动物的短期影响不同，增加15 mm降雨对小型节肢动物群落的影响明显不同于自然降雨，而增加10 mm和5 mm降雨对小型节肢动物群落的影响与自然降雨相比差异不显著。此外，研究发现与自然降雨相比，增加15 mm降雨跳虫的数量提高了近100%，而增加15 mm降雨螨类的数量及类群丰富度降低了60%和55%。.3）确定了模拟降雨脉动（大降雨脉动：1次15 mm降雨；小降雨脉动：3次5 mm降雨）对蜘蛛和甲虫群落的影响较小（降雨处理仅解释了5.6%和7.3%的蜘蛛和甲虫群落变化），而对螨类和跳虫群落影响较大（降雨处理解释了16.2%和50.5%的螨类和跳虫群落变化）。在15天的试验期内，大降雨脉动使得螨类的数量及类群丰富度降低了100%和45%，小降雨脉动使得螨类的数量及类群丰富度降低了175%和26%；而大降雨脉动使得跳虫的数量及类群丰富度增加了519%和34%，而小降雨脉动使得跳虫的数量及类群丰富度提高了57%和68%。.4） 确定了降雨驱动的土壤温度和含水量的相互作用调控了螨类和跳虫群落对降雨脉动变化的短期响应模式。研究还发现土壤温度解释了88.8%和96.3%的螨类和跳虫群落变化，而土壤含水量仅解释了11.2%和3.7%的螨类和跳虫群落变化。