PARENT SESSION
Oral Session # 16: Ecological Modeling I.
Presiding: C Ray
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.
The relationship between biodiversity and ecosystem productivity: Extending our spatial and temporal scales of inference.
Cardinale, Bradley1, Ives, Anthony1, Inchausti, Pablo2, 1 Department of Zoology, Madison, WI, USA2 Laboratoire d'Ecologie, Paris, France
ABSTRACT- Research examining how species diversity influences ecosystem productivity has increased greatly in the past decade as concern about global loss of biodiversity has intensified. Studies to date have very much improved our understanding; yet, because most experiments have been performed at limited spatial and temporal scales, it is unclear whether conclusions can be readily extrapolated to the scales at which natural communities exist. We develop a simple patch-dynamics model to examine some of the scale dependent and independent qualities of the diversity-productivity relationship. We first simulate a typical diversity-productivity experiment and show that the influence of species richness on productivity is temporally dynamic, growing stronger through successional time. This holds true whether resource partitioning or a sampling effect is the underlying mechanism of the diversity-productivity relationship. We then increase the spatial scale of our experiment from individual patches to a region of many patch types. The diversity-productivity relationship is not influenced by spatial scale per se, but the mechanism producing the relationship changes from sampling effects within individual patches to resource partitioning across patch types composing the region. This occurs even though model dynamics are the same at both scales, suggesting that sampling effects and resource partitioning are descriptions of the same process operating concurrently at different scales of observation. Lastly, we incorporate regional processes of dispersal and disturbance into the model and show that these processes can amplify the effects of species richness on productivity leading to patterns not easily anticipated from experiments. We conclude that the relative control of community structure by local verses regional processes may be a primary determinant of the diversity-productivity relationship. Therefore, past experiments may not reflect patterns and processes giving rise to diversity-productivity relationships in natural communities where disturbance and dispersal play a major role in determining the biomass of species.
Key words: ecosystem functioning, theory, species richness, dispersal and disturbance