Wageningen University, Department of Soil Quality, Wageningen, The Netherlands.
Ecology. 2010 Feb;91(2):460-73. doi: 10.1890/09-0666.1.
Understanding the impacts of agricultural intensification and extensification on soil biota communities is useful in order to preserve and restore biological diversity in agricultural soils and enhance the role of soil biota in agroecosystem functioning. Over four consecutive years, we investigated the effects of agricultural intensification and extensification (including conversion of grassland to arable land and vice versa, increased and decreased levels of mineral fertilization, and monoculture compared to crop rotation) on major soil biota group abundances and functional diversity. We integrated and compared effects across taxonomic levels to identify sensitive species groups. Conversion of grassland to arable land negatively affected both abundances and functional diversity of soil biota. Further intensification of the cropping system by increased fertilization and reduced crop diversity exerted smaller and differential effects on different soil biota groups. Agricultural intensification affected abundances of taxonomic groups with larger body size (earthworms, enchytraeids, microarthropods, and nematodes) more negatively than smaller-sized taxonomic groups (protozoans, bacteria, and fungi). Also functional group diversity and composition were more negatively affected in larger-sized soil biota (earthworms, predatory mites) than in smaller-sized soil biota (nematodes). Furthermore, larger soil biota appeared to be primarily affected by short-term consequences of conversion (disturbance, loss of habitat), whereas smaller soil biota were predominantly affected by long-term consequences (probably loss of organic matter). Reestablishment of grassland resulted in increased abundances of soil biota groups, but since not all groups increased in the same measure, the community structure was not completely restored. We concluded that larger-sized soil biota are more sensitive to agricultural intensification than smaller-sized soil biota. Furthermore, since larger-sized soil biota groups had lower taxonomic richness, we suggest that agricultural intensification exerts strongest effects on species-poor soil biota groups, thus supporting the hypothesis that biodiversity has an "insurance" function. As soil biota play an important role in agroecosystem functioning, altered soil biota abundances and functional group composition under agricultural intensification are likely to affect the functioning of the agroecosystem.
了解农业集约化和外延化对土壤生物群落的影响对于保护和恢复农业土壤中的生物多样性以及增强土壤生物在农业生态系统功能中的作用非常有用。在连续四年的时间里，我们调查了农业集约化和外延化（包括草地向耕地的转化以及相反的过程、矿物施肥水平的增加和减少、与轮作相比的单一栽培）对主要土壤生物群丰富度和功能多样性的影响。我们整合并比较了跨分类水平的影响，以确定敏感的物种群。草地向耕地的转化对土壤生物的丰富度和功能多样性都产生了负面影响。通过增加施肥和减少作物多样性进一步集约化种植系统对不同的土壤生物群产生了较小和不同的影响。农业集约化对体型较大的分类群（蚯蚓、真蚓、微节肢动物和线虫）的丰度产生的影响比对体型较小的分类群（原生动物、细菌和真菌）更负面。此外，较大体型的土壤生物的功能组多样性和组成受较大体型的土壤生物（蚯蚓、捕食性螨虫）的影响比对较小体型的土壤生物（线虫）的影响更大。此外，较大的土壤生物似乎主要受到转化的短期后果（干扰、栖息地丧失）的影响，而较小的土壤生物主要受到长期后果（可能是有机质的丧失）的影响。草地的重建导致土壤生物群的丰度增加，但由于并非所有群落在同一程度上增加，因此群落结构并未完全恢复。我们得出的结论是，较大体型的土壤生物对农业集约化比较小体型的土壤生物更敏感。此外，由于较大体型的土壤生物群具有较低的分类丰富度，我们建议农业集约化对物种较少的土壤生物群产生最强的影响，从而支持生物多样性具有“保险”功能的假设。由于土壤生物在农业生态系统功能中发挥着重要作用，因此在农业集约化下，土壤生物的丰度和功能组组成的改变可能会影响农业生态系统的功能。
