Resource Islands: Their Role in the Stability of Desert Ecosystems

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This proposal addresses the role of resource islands in the desertification of the Jornada basin of southern New Mexico. Resource islands represent small-scale patches or "hot spots" of biological activity distributed across a heterogeneous desert landscape. They can be characterized by the functional and structural properties of the shrubs that occupy and form the island, along with the interactions of the shrubs with their immediate abiotic and biotic environment. The significance of these islands to the function and persistence of desert ecosystems in response to disturbances and environmental change is poorly understood. This project, conducted by Drs. Virginia and Reynolds, seeks to understand how desert shrubs acquire resources to form these islands. The investigators are also interested in understanding how the degree of island formation is related to the stability of individual islands, and the role of resource island formation in determining the stability of desert grasslands and shrublands. These tasks will be accomplished by an integrated field and modeling research effort that will: 1) examine the degree of resource island formation associated with the two most successful shrubs (Prosopis glandulosa ımesquite!, Larrea tridentata ıcreosotebush!) in the recently desertified Jornada landscape; 2) determine if structural changes accompanying island formation (e.g. plant architecture) result in a positive feedback system of island self-augmentation; 3) determine if the magnitude and pattern of response of Larrea and Prosopis to an extreme environmental change (e.g. induced summer drought) is a function of the degree of island formation; and 4) develop landscape models that can increase our understanding of the stability of grassland-shrubland systems in a changing environment. Drs. Virginia and Reynolds are leading ecosystem ecologists and have outstanding institutional support for this research.