Abundance,diversity and connectance of soil food web channels along environmental gradients in an agricultural landscape |
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| Institution: | 1. Unidad de Productos Fitosanitarios, DTEVPF, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Ctra. Coruña km 7.5, 28040 Madrid, Spain;2. Department of Nematology, One Shields Avenue, University of California, Davis, CA 95616, USA;3. Department of Land, Air and Water Resources, One Shields Avenue, University of California, Davis, CA 95616, USA;1. National Institute for Agro-Environmental Sciences, 3-1-3, Kan''nondai, Tsukuba, Ibaraki 305-8604, Japan;2. Taiyo Keiki Co., Ltd., 1-12-3 Nakajujo, Kitaku, Tokyo 114-0032, Japan;1. State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China;3. Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China;1. Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, PR China;2. Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences, Huanjiang 547100, PR China;3. Graduate University of Chinese Academy of Sciences, Beijing, PR China;1. Institute of Ecology, Friedrich-Schiller-University Jena, Dornburger Str. 159, 07749 Jena, Germany;2. German Centre of Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany;3. Institute of Biology, University Leipzig, Johannisallee 21, 04103 Leipzig, Germany;1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183, Umeå, Sweden;2. School of Earth & Space Exploration and School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA;3. Department of Forestry, Michigan State University, East Lansing, MI 48824, USA;4. Department of Biological Sciences, Boise State University, Boise, ID 83725, USA;1. J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Göttingen, Berliner Straße 28, 37073 Göttingen, Germany;2. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany;3. Institute of Biology, University of Leipzig, Johannisallee 21, 04103 Leipzig, Germany;4. Department of Forest Resources, University of Minnesota, 1530 Cleveland Avenue North, St. Paul, MN 55108, USA;5. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW 2751, Australia;6. Institute of Biology, Humboldt University Berlin, Philippstr. 13, 10115 Berlin, Germany |
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| Abstract: | Soil food webs respond to anthropogenic and natural environmental variables and gradients. We studied abundance, connectance (a measure of the trophic interactions within each channel), and diversity in three different channels of the soil food web, each comprised of a resource-consumer pair: the microbivore channel (microbes and their nematode grazers), the plant–herbivore channel (plants and plant-feeding nematodes), and the predator–prey channel (predatory nematodes and their nematode prey), and their associations with different gradients in a heterogeneous agricultural landscape that consisted of intensive row crop agriculture and grazed non-irrigated grasslands in central California. Samples were taken at three positions in relation to water channels: water’s edge, bench above waterway, and the adjacent arable or grazed field. Nematode communities, phospholipid fatty acid (PLFA) biomarkers, and soil properties (NH4+-N, NO3−-N, total N, total C, pH, P, bulk density and soil texture) were measured, and riparian health ratings were scored. Environmental variables were obtained from publicly-available data sources (slope, elevation, available water capacity, erodability, hydraulic conductivity, exchangeable cation capacity, organic matter, clay and sand content and pH).The abundance and richness in most food web components were higher in grazed grasslands than in intensive agricultural fields. Consumers contributed less than their resources to the abundance and richness of the community in all channels. The association between richness and abundance for each component was strongest for the lowest trophic links (microbes, as inferred by PLFA) and weakest for the highest (predatory nematodes). The trophic interactions for the predator–prey and plant–herbivore channels were greater in the grassland than in the cropland. Fields for crops or grazing supported more interactions than the water’s edge in the plant–herbivore and microbivore channels. Connectance increased with the total richness of each community. Higher connectance within the microbivore and predator–prey soil food web channels were associated with soil NO3−-N and elevation respectively, which served as surrogate indicators of high and low agricultural intensification. |
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