Collaborative Research: Exploration of the mechanistic basis and biogeochemical implications of differential nutrient limitation among trophic levels

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The structure and function of ecosystems is governed by patterns of nutrient limitation of plants and those organisms that consume plant remains, such as soil microbes. Often, plants and consumers are limited by the same nutrient. However, increasing evidence indicates that different nutrients can be limiters in some ecosystems, a situation known as differential nutrient limitation. This study examines why differential nutrient limitation occurs in some ecosystems but not others, and what the consequences are with respect to the utilization and storage of carbon. These questions will be tested using a network of fertilized plots in four wetlands from Rhode Island to Georgia, including both freshwater and saline systems. Standardized sampling at all sites will ensure comparable measurements of plant and microbial productivity, phosphorus cycling and ecosystem metabolism. It is expected that differential nutrient limitation will occur in ecosystems with higher rates of phosphorus mineralization and will yield less carbon storage. This study has implications for ecosystem management and provides a conceptual framework to integrate ecological studies at multiple scales by understanding how nutrient ratios affects the biogeochemical cycles that govern ecosystem energetics. It includes a commitment to students from under-represented groups, including American Indians and African Americans, through a research mentoring program.