Ecosystem Patterns and Processes

This article begins with a discussion of nutrient limitation from an ecosystem perspective. In terrestrial ecosystems, global patterns in relative availability of soil nutrients suggest that N limitation is most pronounced in recently glaciated temperate areas P-poor soils most frequently found in highly weathered tropical regions. A similar assessment indicates that phosphorus tends to limit gross primary production in freshwater ecosystems, whereas nitrogen tends to limit production in marine environments though many exceptions exist. Unlike nutrient limitation, nutrient use efficiency (NUE) reflects the relative influence of nutrient availability on net production. Variation in NUE reflects plasticity in nutrient use. Several studies indicate that NUE decreases with increasing nutrient availability and that carbon use efficiency (CUE) decreases with increasing food C:nutrient ratio. Next, we explore the trend for higher body nitrogen and phosphorus concentrations in first-order consumers relative to their diet and its implications for ecosystem processes. Additional stoichiometric patterns in herbivory and first-order detritivory are also presented. Finally, this article examines global implications of ecological stoichiometry using an existing framework for linking organism biochemical properties to global ecological patterns and processes. This section also discusses A. C. Redfield’s classic work on nutrient ratios in the world’s ocean and their implications for coupling global patterns in carbon, nitrogen, and phosphorus cycling.