Finlay B J, Black H I, Brown S, Clarke K J, Esteban G F, Hindle R M, Olmo J L, Rollett A, Vickerman K
Institute of Freshwater Ecology, Windermere Laboratory, Ambleside, Cumbria, UK.
Protist. 2000 May;151(1):69-80. doi: 10.1078/1434-4610-00008.
We have developed a method for determining the potential abundance of free-living protozoa in soil. The method permits enumeration of four major functional groups (flagellates, naked amoebae, testate amoebae, and ciliates) and it overcomes some limitations and problems of the usual 'direct' and 'most probable number' methods. Potential abundance is determined using light microscopy, at specific time intervals, after quantitative re-wetting of air-dried soil with rain water. No exogenous carbon substrates or mineral nutrients are employed, so the protozoan community that develops is a function of the resources and inhibitors present in the original field sample. The method was applied to 100 soil samples (25 plots x 4 seasons) from an upland grassland (Sourhope, Southern Scotland) in the UK. Median abundances for all four functional groups lie close to those derived from the literature on protozoa living in diverse soil types. Flagellates are the most abundant group in soil, followed by the naked amoebae, then the testate amoebae and ciliates. This order is inversely related to typical organism size in each group. Moreover, preliminary evidence indicates that each functional group contains roughly the same number of species. All of these observations would be consistent with soil having fractal structure across the size-scale perceived by protozoa. The method described will be useful for comparing the effects on the soil protozoan community of different soil treatments (e.g. liming and biocides).
我们开发了一种测定土壤中自由生活原生动物潜在丰度的方法。该方法可以对四个主要功能类群（鞭毛虫、裸变形虫、有壳变形虫和纤毛虫）进行计数，并且克服了常规“直接”法和“最大可能数”法的一些局限性和问题。通过光学显微镜，在特定时间间隔下，用雨水对风干土壤进行定量再湿润后，测定潜在丰度。不使用外源碳底物或矿质养分，因此发育的原生动物群落是原始田间样品中存在的资源和抑制剂的函数。该方法应用于英国苏格兰南部高地草原（索尔霍普）的100个土壤样品（25个地块×4个季节）。所有四个功能类群的丰度中位数与来自关于生活在不同土壤类型中的原生动物的文献中的数值相近。鞭毛虫是土壤中最丰富的类群，其次是裸变形虫，然后是有壳变形虫和纤毛虫。这个顺序与每个类群中典型生物体的大小呈反比。此外，初步证据表明每个功能类群包含大致相同数量种类。所有这些观察结果都与土壤在原生动物所感知的大小尺度上具有分形结构相一致。所描述的方法将有助于比较不同土壤处理（例如施石灰和使用杀生物剂）对土壤原生动物群落的影响。
