Document: JOH-3-6-4

NPP and biodiversity: Contrasting traditional community ecological approaches with those developed from soils.

MOORE, J.*

Department of Biological Sciences, University of Northern Colorado, Greeley, CO, USA ¹

Abstract:
Productivity, the energetic efficiencies of consumers, habitat heterogeneity, and the frequency of disturbance have formed the basis of hypotheses to explain patterns in trophic structure and species richness at local, regional and global scales. Models of the trophic interactions within soil demonstrate that species richness is a function of how productivity (rate of production) and how different types of primary producers and resources (diversity of production) affect trophic structure, community organization, and patterns of energy utilization by species. The diversity of consumers is controlled by two factors: 1) the interactive influences of productivity and population dynamics on the likelihood of a system forming and persisting (feasibility), and 2) the diversity of resources that systems are based on. Net primary productivity, trophic structure and trophic dynamics are inter-related in a non-linear fashion. This relationship limits any attempt to make general statements about how diversity might be affected along a productivity gradient. The inter-relationship between productivity and dynamics operates in a way that the likelihood of a system being feasible (F[sys]) at a given level of productivity is the result of sufficient energy in the system to support all species (F[NPP]) and given that there is enough energy, that the dynamics of the system (F[dyn]) are biologically reasonable (i.e., F[sys] = F[dyn]:F[NPP]). This confirmed the observation that over a wide gradient of productivity more systems (and species) are likely to be at intermediate levels of primary productivity. Communities are shaped by the diversity of production as well as the rate of production. Theory and empirical evidence indicated that communities are organized into assemblages of species that begin with different food types and separated by different rates of utilization. At low levels of productivity, diversity is low due to the dearth of available energy for higher trophic levels (low F[NPP]). At high levels of productivity, diversity is low due to the trade-offs between different life history strategies and the instabilities associated with oscillatory dynamics (low F[dyn]). The increase in diversity at the intermediate levels of productivity occurs through the potential for a higher number of stable assemblages.

Keywords: Biodiversity, models, NPP, soils

This abstract is being presented at: 11:30 AM in session:
Symposium # 21: The Rhizosphere: Top-Down and Bottom-Up Approaches.