土壤纤毛虫群落对退耕还林生态恢复的响应——以侧柏林为例

为了了解土壤纤毛虫群落对退耕还林区生态恢复下土壤环境变化的响应及尝试利用土壤纤毛虫群落特征评价退耕还林生态恢复的效果,于2010年3月至9月采用"非淹没培养皿法"、活体观察法、蛋白银染色法和Foissner计数法对甘肃陇南武都退耕还林区5个不同恢复阶段的样点和1个荒草坡对照样点的土壤纤毛虫群落特征进行了研究,同时测定了p H值、温度、含水量及速效磷、有效钾、铵态氮、有机质和有机碳含量等土壤环境因子并分析了生态恢复条件下土壤纤毛虫群落特征与土壤环境因子的相关性。研究中共鉴定到71种纤毛虫,隶属于3纲、10目、22科、29属。研究发现,不同恢复年限的土样中土壤纤毛虫的物种分布存在明显差异,并随恢复时间的延长,样点间物种相似性减小,群落组成复杂化,物种数、种群密度和物种多样性指数总体均呈增长趋势。优势类群也发生了演替,由恢复初期的肾形目演替到后期的下毛目。相关性分析结果表明,在生态恢复条件下,土壤有机质和铵态氮含量是影响土壤纤毛虫群落结构稳定性的主要因素,不同纤毛虫类群对生态恢复的响应存在差异。冗余分析显示,土壤纤毛虫群落很好地响应了生态恢复过程中土壤环境条件的变化。

Response of soil ciliate communities to ecological restoration after the implementation of the conversion of cropland to forest and grassland program:a case study of Platycladus orientalis Forest

Soil ciliates are some of the most complex and highly differentiated soil unicellular eukaryotes and play an important role in soil ecosystems. The species richness and individual abundance of soil ciliates, and their unique cell structures and physiological characteristics means that soil ciliate communities are highly sensitive to environmental conditions and therefore can be used as bioindicators in natural and human-influenced soil ecosystems.In order to understand the response of soil ciliate communities to the soil environmental changes after the implementation of the Conversion of Cropland to Forest and Grassland Program, from March to September 2010, the community characteristics of soil ciliates in five sampling sites(Platycladus orientalis forests) at different stages of restoration, together with a control sampling site(a wild grass slope). The sites were located in Wudu District, Longnan City, and were studied using the non-flooded petri dish method, observation in vivo, protargol impregnation, and Foissner''s counting method. A total of 71 soil ciliate species were identified in this study, which belonged to 3 classes, 10 orders, 22 families, and 29 genera. Hierarchical cluster analysis showed significant differences in the distribution of soil ciliate species among the soils collected from forests at different restoration stages. Furthermore, the analysis indicated that as restoration progressed, the composition of soil ciliate species became more and more complex. The diversity of soil ciliate species in the soil samples collected from the restoration sites were all higher than that in the control soil sample. Multiple linear regression analysis revealed that there was a significant correlation between the ciliate species number and restoration stage(ŷ=2.714x²-10.820x+28.400, R²=0.940), and that there was an increase in the number of ciliate species as the restoration progressed. A statistical analysis of the number of the soil ciliate species showed a gradual succession of dominant soil ciliate groups over the course of ecological restoration. The dominant soil ciliate group Colpodida in earlier restoration soils was substituted by Hypotrichida in later restoration soils.In this study, the soil environmental conditions including pH, soil temperature, soil water content, soil available phosphorus, available potassium, ammonium nitrogen, organic matter, and organic carbon in different soil samples were also investigated using potentiometric determination, angle stem earth thermometer,high-temperature drying, Olsen''s method, sodium tetraphenylboron turbidimetry, indophenol blue colorimetry, and hydration heat-photoelectric colorimetry, respectively. The results of physicochemical analysis of the soil samples suggested that soil quality improved during the conversion from cropland to forestland. Bivariate correlation analysis showed that soil organic matter and ammonium nitrogen had the most important influence on soil ciliate community diversity. Finally, the redundancy analysis results suggested that the variation between soil ciliate communities had a significant correlation with changes to soil environmental conditions during the conversion from cropland to forestland. Therefore, the soil ciliates could be considered as indicator organisms for assessing the effects of ecological restoration after conversion of cropland to forest.