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National Science Foundation (USA) 1995

Effects of Elevated CO2 on a Mojave Desert Ecosystem

Elevated CO2 - Mojave Desert


Titre : Effects of Elevated CO2 on a Mojave Desert Ecosystem

Organismes NSF : Division Of Integrative Organismal Systems (IOS)

Durée : September 1, 1995 — August 31, 1999

Current atmospheric carbon dioxide levels are more than 25% higher than pre-industrial levels. Projections based upon the present rate of carbon input into the atmosphere indicates that the atmospheric carbon dioxide content will double in less than a century. Although there is debate as to whether this increase will result in significant global warming, there is little doubt that this increase will have potentially dramatic effects on plant production and will possibly result in changes in plant composition of major world ecosystems. There is a need to understand the spectrum of responses that will occur over the major ecosystem types of the world as a consequence of rising atmospheric greenhouse gas concentrations, most notably carbon dioxide, and it is critical that these experiments be conducted in intact ecosystems, not in artificial conditions such as greenhouses or growth chambers. Deserts account for the largest percentage of the earth’s land surface area, and through the process of global desertification, are showing the most rapid increase in surface area. Deserts are also the ecosystem type that are predicted to be the most sensitive to global change because elevated carbon dioxide relaxes the effects of water stress in plants. Elevated carbon dioxide may significantly impact the productivity and biodiversity of desert ecosystems and result in a substantial change in the function and land-use patterns of this prevalent ecosystem type. However, there have yet to be any large-scale studies of the effects of global change on desert ecosystems. The Mojave Desert is one of the most arid deserts in North America and most resembles true deserts in other parts of the world, giving the potential to serve as a model system for the study of the response of desert vegetation to elevated carbon dioxide. A Free Air carbon dioxide Enrichment (FACE) system is currently being constructed on the Nevada Test Site within the Mojave Desert of southern Nevada. This technology entails a series of experimental "rings" in which elevated carbon dioxide is constantly supplied to an intact ecosystem within each ring, and does not otherwise alter the climate of the site with artificial enclosures. Specific experiments to be conducted in this study include analysis of the responses of plant production, reproduction and survival, and landscape water balance to elevated carbon dioxide. These specific experiments will be integrated through a series of ecosystem based models that will be developed specifically for the Mojave Desert site. The modeling effort will particularly emphasize two integrating concepts : (1) under the extremely dry and infertile soils of deserts, intense competition between plants controls the function of the ecosystem, and elevated carbon dioxide may change the competitive balance that currently exists ; and (2) recruitment and survival of plants in deserts are determined by episodic conditions (droughts and abnormal wet cycles), and elevated carbon dioxide may change plant responses to these episodic conditions. Desert ecosystems may become more productive and will use water more efficiently under elevated carbon dioxide, but complex ecosystem feedback processes may limit this response over the long term. Experiments like this will provide the data we need to predict how these changes will affect arid lands.

Partenaires : Stanley Smith ssmith (Principal Investigator) Jeffrey Seemann (Co-Principal Investigator) John Ball (Co-Principal Investigator) Robert Nowak (Co-Principal Investigator) Yiqi Luo (Co-Principal Investigator)

Financement : $415,000.00

Présentation (National Science Foundation)

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