DISSERTATION RESEARCH: Temporal Dynamics of Alternative Stables States in a Desert Stream

Arizona State University, Scottsdale AZ

Investigators

Abstract

Understanding the response of ecological systems to disturbance is a central problem in ecology, and is of fundamental importance to management of ecosystems from local to global scales. Two major theories of disturbance are stability theory, which describes the rate of return of ecosystems to pre-disturbance conditions, and multiple state theory, which describes the transition of ecosystems between alternative equilibrium conditions (e.g., grassland vs. shrubland, etc.). Because desert streams are subject to frequent and severe disturbance in the form of both flood and drying, these ecosystems provide excellent models for understanding the response of ecosystems to disturbance more generally. Prior to the end of the 19th century, wetlands (cienegas) were a common feature of the Southwestern U.S. Erosion of these wetlands left most arid streams as bare, gravelbed channels (arroyos) that represent an alternative equilibrium. Recent observations of wetland re-establishment at a long-term ecological study site (Sycamore Creek, AZ) provides an opportunity to evaluate how the alternative configurations of desert streams respond to disturbances using the context of stability theory. Following flash flood disturbance, we will measure primary production and ecosystem respiration in both wetland and gravelbed sites to determine whether these alternative stable states differ in their response to disturbance. The Intellectual Merit of this proposal lies in this integration of single- and multiple-equilibrium theories of ecosystem response to disturbance. The Broader Impact of this research will be to improve conservation and restoration efforts of this formerly-widespread and now-rare wetland ecosystem, and to provide opportunities for training of graduate students in the design, execution, and analysis of ecological studies.