PARENT SESSION
Symposium 11: Digging Deeper or Scratching the Surface? Exploring Ecological Theories in Urban Soils.
Organized by: M Pavao-Zuckerman and L Byrne
Wednesday, August 4, 8:00 AM to 10:30 AM, Oregon Ballroom 203.
Urban ecosystems: Influences of altered resources, disturbance, and heterogeneity.
Pickett, Steward*,1, Cadenasso, M.1, 1 Institute of Ecosystem Studies, Millbrook, NY
ABSTRACT- We introduce the three key factors — resource availability, disturbance, and spatial heterogeneity — that will help evaluate how understanding urban soils can contribute to ecological theory. These factors suggest the causes of similarities and differences between urban soils to those in non-urban ecosystems. Although these factors are familiar to ecologists, the forms they take in urban systems may differ from their expression in non-urban ecosystems. Urban resources relevant to soil formation and dynamics include terrestrial nutrient dynamics and runoff, modified groundwater and stream flow, and atmospheric deposition of nitrogen and base cations. Disturbance can be conceptualized the same way in urban as in wild ecosystems. However, in addition to biophysical disturbances of streams, vegetation, and soils, demographically- and socially-mediated changes in ecosystem structure must be considered in urban systems. Sociologically based disturbances may include human migration, dynamics of human population structure, institutional shifts, differential economic investment and disinvestment, and the effects of human health and morbidity. Finally, spatial heterogeneity integrates the effects of resources and disturbance, and influences subsequent resource levels and susceptibility to disturbance. Layers of heterogeneity include not only the geomorphic template, but modified urban climate and biotic composition, and the new layers of buildings, infrastructure, and demographic-social patterns. The complex layering of natural and social factors that constitute urban heterogeneity permits the continuation of some important ecological processes, and modifies other ecological fluxes important to soils.
Key words: disturbance, ecosystem, urban, heterogeneity