Effects of disturbance of great gerbil （Rhombomys opimus）on soil

荒漠鼠类对植物群落、土壤特性有着显著影响。其采食显著影响着植被演替和被采食植物的丰富度。其掘洞影响着土壤的质地和结构、肥力、渗透性，这些环境因素的改变又影响着植被结构和物种组成。国外就荒漠鼠类扰动对土壤、植被的影响已经作了广泛、深入的研究，国内针对该领域的研究却少见报道。大沙鼠广泛分布于新疆准噶尔盆地，为荒漠地典型鼠种之一，其对荒漠植物群落和土壤的扰动效应尚不清楚。研究其对荒漠土壤和植物的影响有助于深入理解鼠类在荒漠生态系统生态过程中的作用。2005年9月～2006年5月，作者3次赴古尔班通古特沙漠采集土样和植物样方数据。利用常规实验室方法对比分析了10组大沙鼠洞区和对照区表层（0～5cm）、深层（20～30cm）土壤含水量、养分、盐分等20项指标的差异性。调查了大沙鼠洞区、过渡区、对照区的植物种类、密度、盖度，并利用方差分析比较其差异性。结果如下： 1） 大沙鼠的扰动，导致水分渗透能力发生变化。大沙鼠洞区表层土壤含水率低于无扰动对照区，深层高于对照区。 2） 大沙鼠掘洞、排泄导致土壤养分含量变化。洞区表层土壤全N、全P含量增加，全K、速效N、速效P、速效K含量降低；洞区深层土壤全N、全P、全K、速效N含量减少，速效P、速效K含量增加。 3） 大沙鼠的扰动促进了土壤微生物的发育，洞区土壤深层细菌、放线菌、真菌数量均高于对照区，其中真菌数量约为对照区的5倍。 4） 大沙鼠采食、掘洞行为促进了草本植物，尤其是一年生草本植物的发育，抑制了小半灌木的生长。 5） 大沙鼠的扰动改变了生物结皮的演替格局，导致生物结皮始终处于初级演替阶段。扰动程度的差异对生物结皮的种类、盖度产生不同的影响。Rats can strongly influence soil and vegetation in desert. In particular, they can affect vegetation succession and species richness by foraging. Also, the burrowing mammals can affect soil texture, fertility and penetrability which made patten of species richness and community structure changed. Despite considerable international research on soil and vegetation, the interactions of these desert rats with soil and vegetation have been received only limited attention in our country. Great gerbil is abroad distributed in sinkiang Zhungeer basin, however, little is known about the effect of great gerbil on plant community and soil. Therefore, to study the effect of great gerbil on soil and vegetation can help us further understand the contribution of rats’ activities to desert ecosystem. We sampled soil and vegetation during 2005 Sept. to 2006 May in Gurbantonggut desert. Using a paired sample design, We chose 10 burrows of great gebil and matched them ten locations in the matrix. It was used general laboratory measures to analyze soil moisture, nutrient and other 20 soil characters of surface layer (0~5cm) and deep layer (20~30cm). Also, using ANOVA, we compared the difference of plant species, density, coverage etc. among burrow sites, transition regions and control plot. The results as follows: a) Because of activities of great gerbil, soil water content changed. Soil moisture of surface layer tended to be lower for the burrowing sites, On the contrary，it was higher than random sites in deep layer. b) Soil nutrient content had changed considerable for the excavation and excretion of great gerbil. Totle nitrogen and phosphorus content of burrowing sites of surface layer have increased, however, total potassium, available nitrogen, phosphorus and potassium have reduced. In the deep layer, the main effect was an increase of available phosphorus and potassium and a decrease of total nitrogen, phosphorus, total potassium and available nitrogen. c) Disturbance by great gerbil favored soil microorganisms. The quantities of bacteria, actinomycete and fungal colonies of burrowing sites were higher than random sites. Especially for fungi, the quantity was five times as many as that of random sites. d) The flora on burrowing sites was dominated by annuals. But the burrow system of rats was not advantageous to the growth of small shrubs. e) Great gerbil destroyed succession of biological crust and it was remained on the state of primary stage. The components and coverage of biological crust were influenced by disturbance in degree