Project Number: 5409-22660-002-00
Project Type: Appropriated

Start Date: Jan 20, 2005
End Date: Feb 29, 2008

Objective:
I. Increase the accuracy and utility of state-and-transition models by more fully characterizing their ability to classify and predict vegetation change, and learn how grazing (intensity and season of use), plant resources (N and water), and exclusion of plant enemies (insects and pathogens) influence vegetation change in northern mixed-grass prairie and shortgrass steppe. II. Develop very large-scale aerial (VLSA) photography and ground photography methods to accurately monitor bare ground, plant cover, and plant communities in sagebrush and shortgrass steppe and northern mixed-grass prairie.

Approach:
Because semi-arid rangeland ecosystems often exhibit nonlinear dynamics, we will use the state-and-transition model theory as a conceptual underpinning to study plant community attributes and key ecological processes involving C, N and water. C, N and water processes will be studied to provide insight into potential mechanisms that govern changes between states of vegetation and may be used in a predictive manner to clarify how and when transitions occur. Enemy exclusion and resource manipulation experiments will target mechanisms underlying the increase of invasive weeds in these systems. Experiments will address the utility of very large-scale aerial (VLSA) photography to assess landscape scale patterns of weed invasions, and to determine the correlation in changes in bare ground and plant cover from VLSA photography to net ecosystem production, and water and energy fluxes.