Elucidating the effect of anthropogenic land management on soil nematode community structure

Abstract

Nematodes as a taxonomic phylum are incredibly diverse and play an important role in soil biology, nutrient cycling, and soil food web function. Nematodes can be categorized into five major trophic groups including bacterivores, fungivores, herbivores, predators, and omnivores. Plant-parasitic nematodes (PPNs) affect soil food web resources through direct herbivory, while free-living (non-pathogenic) bacterivores and fungivores graze on microbes and contribute significantly to soil nutrient pools. Predatory nematodes regulate the soil food web by preying on other nematodes and invertebrates in the soil. An unbalanced soil food web community can lead to unintended impacts to other species and create a cascading effect. In agriculture, this impact can lead to low crop production and reduced revenue by means of soil ecological degradation. The goal of this project was to elucidate the nematode community structure changes under different management strategies in both agricultural and range settings. The hypotheses we tested were 1) that crop rotations eliminating fallow would positively and significantly impact the soil nematode community that would in turn self-regulate the PPN population and 2) native sagebrush steppe would have a more diverse nematode community than converted sagebrush steppe managed for livestock grazing or other uses. We did so with the following studies: 1. Quantitatively assessed nematode community structure under barley monoculture and barley-fallow vs. barley-pea rotations using multiple ecological measures and indices and correlated those measures and indices with soil chemical and physical properties as well as agronomic parameters of each system. 2. Quantitatively assessed nematode community structure under wheat-tilled fallow, wheat-no-till fallow, and no-till wheat monoculture vs. several no-till wheat-pulse rotations using multiple ecological measures and indices to evaluate long term impacts of cropping system to the nematode community. 3. Quantified taxonomic diversity and ecological indices of disturbed and undisturbed sagebrush steppe in the Bangtail Mountains west of Wilsall, Montana to evaluate disturbance regimes in a reclaimed environment.