C. Ettema, I. D. Coleman, G. Vellidis
Dec 1, 1998
Spatial and temporal variability in soil biotic populations reflect heteroge- neity in soil resources, affect patterns of soil process rates, and facilitate coexistence of diverse biota. We investigated these relationships in a 0.7-ha restored riparian wetland in the Coastal Plain of Georgia, USA, 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. We used geostatistics 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 11-84 m. Isopleths and spatial trend analysis showed that individual bacterivorous taxa exhibited divergent spatial distributions, with populations aggregating into different hotspots in the wetland. Although these large-scale trends per- sisted at all sampling dates, small-scale patterning showed significant temporal variation due to rise and fall of local populations. Individual nematode distributions did not corre- spond well to the (temporally more static) soil resource patterns, except occasionally to soil moisture and nitrate content. We attribute the general lack of correlation between nematode and soil resource patterns in part to the young age (2.5-3.5 yr) of the investigated wetland site. Although nematode patterns remain inadequately explained, we suggest that the observed spatiotemporal divergence among populations of bacterivorous taxa has im- portant implications for our understanding of soil ecosystem and community processes, notably the spatiotemporal distribution of nematode-influenced nitrogen cycling rates and the maintenance of field-scale nematode diversity.