Synthesis of existing datasets to explore the implications of altered precipitation for carbon and water dynamics in desert ecosystems of the southwestern US

Principle Investigator: Kiona Ogle, University of Wyoming

Co-Investigators: Travis Huxman, University of Arizona
Michael Loik, University of California, Santa Cruz
Stan Smith, University of Nevada, Las Vegas
David Tissue, Texas Tech University

Abstract: This study is motivated by the potential for altered precipitation regimes (an element of climate change) to greatly impact water-limited ecosystems of the Southwest. Existing field studies exploring the effects of variation in precipitation on C (carbon) and H2O (water) dynamics in deserts of the Southwest have produced large datasets. However, no syntheses have been conducted with respect to these datasets to explore the broader implications of altered precipitation for arid and semiarid ecosystems.

Objectives. Our objective is to synthesize existing data related to C and H2O fluxes, spanning leaves to ecosystems, across four major deserts in the Southwest. A second objective is to use the synthesis results to identify novel questions/hypotheses and to help direct future, cross-site experiments.

Location(s). The datasets are derived from five extensively-studied sites: Santa Rita Experimental Range and San Pedro River Basin, AZ (Sonoran Desert), Big Bend NP, TX (Chihuahuan Desert), Nevada Test Site, NV (Mojave Desert), and Valentine Eastern Sierra Reserve, CA (Great Basin Desert). The Big Bend site occurs in the NICCR Southeastern Region, and the others are in the Western Region.

Questions. The synthesis results will be used to address a series of questions, including: How are C and H2O cycles affected by changes in pulse, seasonal, and annual precipitation? What ecological components appear critical to ecosystem C and H2O exchange, and which are most sensitive to precipitation changes? With respect to C and H2O, how do the four deserts differ in their responses to altered precipitation? What environmental variables (e.g., nitrogen, temperature) interact with precipitation to strongly affect C and H2O dynamics in these systems?

Approach. We will synthesis data from these sites within a Bayesian hierarchical framework that facilitates simultaneous coupling of diverse data sources and mechanistic models; the models contain ecologically-meaningful parameters that, when parameterized with field data, provide important insights into the factors controlling C and H2O dynamics at different scales.
Outcomes. Annual workshops involving key personnel will focus on developing a unified database and modeling framework that can be applied to multiple sites, made accessible to all investigators, and used to guide future experiments. Feedback to field studies is central to designing experiments that explore effects of multiple global change factors on deserts of the Southwest, and terrestrial ecosystems in general. Products from the study will contribute to building a better understanding of how arid lands may be affected by environmental changes such as altered precipitation.

last updated: 28 August 2006 PLH