Holland et al. showed how physiological responses to herbivory provide feedbacks to nutrient availability by controlling carbon and nitrogen supply to soil heterographs. The analysis focused on three physiological differences between two populations that vary in grazing tolerance: changes in net primary production in response to defoliation, changes in carbon allocation in response to defoliation, and changes in nitrogen allocation in response to defoliation. Holland et al. used meteorological driving variables from, and parameterized the CENTURY model, a nutrient-cycling simulation model, for Wind Cave National Park, South Dakota. The simulations demonstrate that nitrogen limitation may have a substantial effect on plant response to grazing. Simulations further demonstrated that modifying plant production and belowground: aboveground ratios affected nitrogen mineralization and immobilization. Differences in physiological responses between on- and off-colony plant productions had significant ecosystem consequences and controlled nitrogen losses from the system. Furthermore, the demonstrated link between plant physiological adaptations and nitrogen cycling via production and immobilization provides a framework for understanding how plant populations may influence ecosystem processes. The demonstrated model sensitivity to subtle changes in plant response to herbivory suggests that understanding the variability of individual populations may help us better understand the behavior of ecosystems.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.