Print PageThe availability of essential elements--N, P, K, and metals--varies in time and space and at different spatial grains. Ecological Stoichiometry Theory (EST) uses these gradients in availability to predict the distribution of functional traits, species composition, and ecological work like decomposition. Scaling Theory (ST) predicts the magnitude of dynamics as a function of the size of the players relative to the size of the ecological arena, or grain. Here we explore how 10 common invertebrate taxa from a tropical brown (decomposer) food web respond to fertilization by N, P, K, and micronutrients at two spatio-temporal scales: over 9 years on 40x40 m plots, and over 16 days after one nutrient pulse is applied to 0.25m2 plots.
Results/Conclusions
The large-scale phosphorus fertilization, sampled four times over nine years, promoted overall microbivore abundance by 50%. How these taxa increased, however, was a function of life history. Collembola, rapidly growing, high metabolism taxa, increased in number, but not body size; oribatid mites, slow growing, low metabolism taxa, increased in body size, but not abundance. We found little evidence of an increase in the next trophic level (e.g., gamasids, ants, and spiders), suggesting bottom up forces dominated at large spatial scales. In contrast, at the 0.25m2 pulse scale, predators initially increased simultaneously with microbivores, and decreased the magnitude of increase of prey. Moreover, these nutrient pulses generated semi-cyclical dynamics suggesting interactions between microbes, microbivores, and their predators over the 16 days.
