Friday, August 7, 2009 - 8:40 AMCOS 114-3: Soil pH, ecological stoichiometry, and allometric scaling in soil biota
Christian Mulder, Dutch National Institute for Public Health and Environment and Jim Elser, Arizona State University.
Background/Question/Methods The factors regulating the structure of food webs are a central focus of community and ecosystem ecology, as trophic interactions among species have important impacts on nutrient storage and cycling in many ecosystems. Objectives of the present study were: to infer whether a correlation exists between the numerical abundance of soil organisms and environmental factors; and to provide empirical evidence for allometric scaling occurring in the belowground communities as related to the ecological stoichiometry of soil systems. We selected five taxocenes as the main subject of our study: Bacteria, Fungi, Nematoda, Arthropoda (lumping Acarina together with Collembola) and Oligochaeta. Monitoring activities were performed within the Dutch Soil Quality Network, a framework designed to obtain ecological insight on 166 sandy soil communities. Results/Conclusions For soil invertebrates in grassland ecosystems in the Netherlands, the site-specific slopes of the faunal biomass to organism body mass relationships reflected basic biochemical and biogeochemical processes associated with soil acidity and soil C:N:P stoichiometry. That is, the higher the phosphorus availability in the soil, the higher, on average, the slope of the faunal biomass size spectrum (i.e., the higher the biomass of large-bodied invertebrates relative to the biomass of small invertebrates). While other factors may also be involved, these results are consistent with the growth rate hypothesis from biological stoichiometry that relates phosphorus demands to ribosomal RNA and protein production. Thus our data represent the first time that ecosystem phosphorus availability has been associated with allometry in soil food webs. Our results may have broad implications, as soil invertebrates of different size have different effects on soil processes.