土壤纤毛虫群落对不同退还模式生态恢复的响应

为了探究土壤纤毛虫群落对不同退还模式生态恢复的响应及利用其群落特征来评价退还效果,于2014年4月至2015年7月在甘肃省天祝藏族自治县朵什乡退耕还林区选取了3个不同退还林型样点(云杉、沙棘混交林A1,云杉林A2,沙棘林B1)和2个对照耕地样点(小麦地A0,豌豆地B0)为研究样地,采用"非淹没培养皿法"、活体观察法和培养直接计数法对土壤纤毛虫群落特征进行了研究,同时测定了各样点土壤的相关环境因子,并分析了不同恢复模式下土壤纤毛虫群落特征与植被群落参数、土壤环境因子间的相关性。研究共鉴定到125种土壤纤毛虫,隶属于9纲19目29科34属。结果显示:退还样点和对照样点的土壤纤毛虫群落结构特征存在明显差异(P0.05),退还样点间的物种相似性减小,群落组成复杂化;退还样点土壤纤毛虫物种数、密度、物种多样性指数、均匀度指数和丰富度指数均明显增高(P0.05),且各样点间表现为A1B1A2B0A0;各样点优势类群的演替趋势,由对照样点的肾形目演替为退还样点的散毛目。相关性分析和冗余分析结果表明,退耕还林后,对纤毛虫群落结构稳定影响最主要的是有机质、含水量和全氮的含量,不同林型间土壤纤毛虫群落组成差异较大,表明土壤纤毛虫群落结构可作为对退耕还林生态恢复的评价指标。

Response of soil ciliate community to ecological restoration of different return patterns

Rapid economic development in many countries is leading to global environmental degradation. Consequently, the restoration of degraded ecosystems has become an important component of modern ecological research. In the 1990s, China started the key project of returning farmland to forest in order to realize ecological restoration benefits. Benefits of ecological restoration include protecting and improving the environment and minimizing soil erosion, mitigating the threat of floods, and enhancing biodiversity. With the implementation of the project of returning farmland to forest, studies on returning farmland to forest (grass) have gradually increased, but there has been more emphasis on returning farmland to forests, ecological benefits, vegetation, and the soil environment. Microorganisms play a key role in driving biogeochemical cycles in ecosystems. However, knowledge of soil microbial communities is poor. It is therefore becoming increasingly important to gain a better understanding of soil microorganisms including microbial eukaryotes (protists). Ciliated protists (ciliates) play an important role in microbial food webs, controlling bacterial populations by predation, transferring carbon and energy through food chains, and releasing nutrients. In soils, the presence of ciliates and other heterotrophic protists is known to significantly increase levels of available plant nutrients, such as nitrogen and phosphorous. Furthermore, because of their rich species, short growth cycles, rapid community evolution and sensitivity to environmental change, they are often used as indicators of environmental quality. Current research on soil ciliates mainly focuses on classification, morphogenesis, and molecular information. Changes of soil ciliate community structure after returning farmland to forest and the use of ciliate community structure for evaluating environmental change have received only scant attention.This study investigates the response of soil ciliate communities to the ecological restoration of three different forest types in this region including A1 (Picea asperata×Hippophae rhamnoides), A2 (Picea asperata), and B1 (Hippophae rhamnoides). These forests had previously been destroyed for the growth of agricultural crops. Soil samples were collected from each of the three forest types and from two crops (A0:Triticum aestivum, B0:Pisum sativum) as controls. Ciliates were isolated from the samples using the non-flooded Petri dish method. Ciliate communities were characterized by observation of cells in vivo using light microscopy. Enumeration was by directing-culture counting. Physical-chemical parameters also were recorded. The main aim of the study was to relate soil ciliate community characteristics with vegetation and environmental factors under different restoration patterns. A total of 125 species belonging to 9 classes, 19 orders, 29 families, and 34 genera of ciliates were recorded. Significant differences in the community structure of soil ciliates (P < 0.05) were found between the restored forest soils and the control soils. The species richness, density, species diversity index, evenness index, and abundance index of soil ciliates were all significantly higher (P < 0.05) in the restored forest soils than in the soils from the control cultivars, which from high to low were A1 > B1 > A2 > B0 > A0. Furthermore, the dominant ciliate group in control soils (order Colpodida) was replaced by the order Sporadotrichida in the restored forest soils. Results of correlation analysis and redundancy analysis were similar with both showing that soil water content, organic matter and total nitrogen content were the main factors influencing the ciliate community structure in the restored forest soils.