Issue (Who cares and why?)
Current global models predict that carbon dioxide (CO2) levels in the atmosphere will double pre-industrial levels by the year 2050. Increasing atmospheric CO2 may lead to global warming and other climate changes. By the processes of photosynthesis and respiration, CO2 is exchanged between the atmosphere and the land where it is sequestered as wood and other organic forms in the soil. Elevated CO2 also increases productivity particularly in desert ecosystems.
Information is needed on the exchange process in order to predict climate change. Will there be changes in the rate at which plants grow over the next hundred years? Will the storage of carbon in the desert ecosystem change? Will water balance change in this arid environment? Will species composition of desert plant communities change?
What has been done?
To examine responses of arid ecosystems to elevated atmospheric CO2, a host of contributors established the Nevada Desert FACE (Free Air CO2 Enrichment) Facility in the Mojave Desert of southern Nevada, which is the driest area of North America.
Over the past ten years, University of Nevada, Reno’s investigation team have determined the effect of elevated CO2 on key physiological processes that affect primary production in an intact Mojave Desert ecosystem. They have determined the effect of elevated CO2 on seasonal and inter-annual variations in climate constraints on primary production in an intact Mojave Desert ecosystem. They have established how elevated CO2 may impact ecosystem water balance, and therefore the water limitation to primary production, in this water-limited system. They have ascertained the effects of elevated CO2 on nitrogen dynamics, including N-fixation, volatization and nitrification rates, and litter decomposition. They have established the effect of elevated CO2 on total belowground respiration in a Mojave Desert ecosystem.
The team evaluated the impacts of elevated CO2 on plant reproductive patterns in an intact Mojave Desert ecosystem to provide the link between species performance and population reaction to elevated CO2, while also, assessing the impacts of elevated CO2 on fine roots: their occurrence, length, area density, population dynamics and biomass production.
Increases in atmospheric CO2 concentration during the last 250 years are unequivocal, and CO2 will continue to increase at least for the next several decades. Arid ecosystems are some of the most important biomes globally on a land surface area basis, are increasing in area at an alarming pace, and have a strong coupling with regional climate. These water-limited ecosystems also are predicted to be the most sensitive to elevated CO2, in part because they are stressful environments where plant responses to elevated CO2 may be amplified.
Results from the University’s work at the Nevada Desert FACE Facility have provided significant insight into the complex responses of an intact desert ecosystem to elevated CO2. This project is helping land managers and ecologists: (1) understand the structure and function of desert ecosystems; (2) how elevated atmospheric CO2 will affect the structure and function of desert ecosystems; and (3) is providing guidance to land managers and users on actions that will adversely affect deserts in the short- and long-term.