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United States Department of Agriculture

Agricultural Research Service

Title: Spatiotemporal Distributions of Bacterivorous Nematodes and Soil Resources in a Restored Riparian Wetland

Authors
item Ettema, Christian - UNIVERSITY OF GEORGIA
item Coleman, David - UNIVERSITY OF GEORGIA
item Vellidis, George - UNIVERSITY OF GEORGIA
item Lowrance, Robert
item Rathbun, Stephen - UNIVERSITY OF GEORGIA

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 1998
Publication Date: November 12, 1998
Citation: Ettema, C.H., Coleman, D.C., Vellidis, G., Lowrance, R.R., Rathbun, S.L. 1998. Spatiotemporal distributions of bacterivorous nematodes and soil resources in a restored riparian wetland. Ecology 79:2721-2734.

Interpretive Summary: Soil ecosystems are made up of diverse communities of microorganisms, soil flora and soil fauna. Free-living nematodes (not plant parasitic forms) are among the most diverse and widespread of the groups of soil organisms. Many nematodes feed on bacteria which in turn respond to changes in soil properties such as organic matter content and nutrient content. Understanding complex soil ecosystems, especially in restored wetlands, requires an understanding of relationships among soil resources and soil organisms such as nematodes. The complexity of these assemblages of soil organisms can be used to assess both the health and maturity of soil ecosystems. An understanding of nematode populations and their relation to other soil properties will provide valuable information on the success of restoring riparian wetlands and other wetland ecosystems to their origianal condition. In a restored riparian forest wetland in the Gulf-Atlantic Coastal Plain, nematodes of different taxonomic groups that feed on soil bacteria were correlated with different nitrate-N levels in the soil and with different levels of soil moisture. As the newly restored riparian wetland matures and exhibits characteristics more similar to mature wetlands of the region, it is likely that there will be clearer spatial distribution patterns. These patterns may provide recognizable characteristics associated with ecosystem health and maturity and will provide an assessment tool for general ecosystem sustainability.

Technical Abstract: Spatial and temporal variability in soil biotic populations reflect heterogeneity in soil resources, affect patterns of soil process rates and facilitate eoexistence of diverse biota. These relationships were investigated in a 0.7 ha restored riparian wetland in the Gulf-Atlantic Coastal Plain (Georgia) for an abundant and diverse group of soil fauna, the bacterivorous nematodes. We quantified spatial distributions in four different seasons for the eight most dominant bacterivorous taxa in the wetland and related their individual distributions to patterns of microbial respiration, inorganic nitrogen, moisture and soil organic matter. Geostat- istics were used to quantify spatial aggregation and draw isopleths. For all variates except two nematode taxa, 36-99% of sample population variance was spatially dependent over ranges of 11-84m. Spatial trend analysis showed that different nematode taxa aggregated into different clusters in the wetland. Individual nematode distributions did not correspond well to the more static soil resource patterns except occasionally for soil nitrate and soil moisture. Lace of correlation between nematod distributions and soil resource patterns may be due in part to transitional nature of restored wetland going from a wet pasture to a riparian forest. Observed spatiotemporal divergence of populations of nematode taxa has important implications for our understanding of soil ecosystem and community processes, notably the spatiotemporal distribution of nematode-influenced nitrogen cycling rates and maintenance of field-scale nematode diversity.

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