Within the last 100 years, many grasslands throughout the southwestern United States have been inadvertently converted to dense thickets of woody plants, including the thorny shrub mesquite. These conversions have had important impacts on human activities, biological diversity, nutrient cycling, and wildfire regimes. However, many mesquite-dominated grasslands have themselves been recently invaded by an African grass, Lehmann lovegrass. Invasions by this grass may change the availability of water and nutrients in the soil, and thus shift mesquite shrublands back towards grassland. However, these grasslands would be dominated by a non-native grass with arguably greater impacts on ecological systems than mesquite has had on former grasslands. When predicting how southwestern rangelands might respond to invasions by grasses and woody plants, one must also consider how soil characteristics (e.g., clay content) and potential changes in climate (e.g., changes in precipitation) affect the relative performance, and the ultimate ratio, of grasses to shrubs. By conducting a field experiment in southern Arizona, the investigators will test the hypothesis that grass invasions will interact with soil type and seasonal precipitation to affect the successful establishment of mesquite in this habitat. The response of mesquite introduced as seeds into experimental plots will be used to gauge the potential response of this species to different environments. Concurrent investigations of the cycling and storage of carbon dioxide and water within these plots will facilitate our understanding of interactions between water, soil type, and plant cover. This research explicitly considers both climate change and biological invasions, each of which will continue to affect natural ecological systems and the goods and services that they provide to human society. Research will foster collaborations between scientists, land managers, and students from several institutions, and will promote interdigitation of subdisciplines including soil science, modeling, ecology and atmospheric sciences. The project includes training opportunities for students, including those in teacher training programs and in underrepresented groups.

Agency
National Science Foundation (NSF)
Institute
Division of Environmental Biology (DEB)
Type
Standard Grant (Standard)
Application #
0417228
Program Officer
Alan James Tessier
Project Start
Project End
Budget Start
2004-09-01
Budget End
2007-08-31
Support Year
Fiscal Year
2004
Total Cost
$109,498
Indirect Cost
Name
University of Wyoming
Department
Type
DUNS #
City
Laramie
State
WY
Country
United States
Zip Code
82071