RT Journal Article
SR Electronic
T1 Nonlinear Effects of Intraspecific Competition Alter Landscape-Wide Upscaling of Ecosystem Function
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 470591
DO 10.1101/470591
A1 Chelsea J. Little
A1 Emanuel A. Fronhofer
A1 Florian Altermatt
YR 2019
UL http://biorxiv.org/content/early/2019/04/15/470591.abstract
AB A major focus of ecology is to understand and predict ecosystem function across scales. Many ecosystem functions are only measured at local scales, while their effects occur at a landscape level. Here, we investigate how landscape-scale predictions of ecosystem function depend on intraspecific competition, a fine-scale process, by manipulating intraspecific density of shredding macroinvertebrates and examining effects on leaf litter decomposition, a key function in freshwater ecosystems. Across two species, we found that leaf processing rates declined with increasing density following a negative exponential function, likely due to interference competition. To demonstrate consequences of this nonlinearity, we upscaled estimates of leaf litter processing from shredder abundance surveys in 10 replicated headwater streams. In accordance with Jensen’s inequality, applying density-dependent consumption rates reduced estimates of catchment-scale leaf consumption up to 60-fold versus using density-independent rates. Density-dependent consumption estimates aligned closely with metabolic requirements in catchments with large, but not small, shredder populations. Importantly, shredder abundance was not limited by leaf litter availability and catchment-level leaf litter supply was much higher than estimated consumption, thus leaf litter processing was not limited by resource supply. Our work highlights the need for upscaling which accounts for intraspecific interactions.