Global changes include greater climate variability, increased nutrient availability and desertification, and the invasion of woody species into grasslands. Although each of these factors affects biological systems, it is not known how these factors will interact to affect ecosystems in the future. Furthermore, although arid and semi-arid lands cover approximately one third of the earth's surface, few experimental warming studies have been conducted in these systems. This research involves a multiple-factor global change experiment in an arid area at the boundary between shortgrass prairie and desert grassland, which is undergoing shrub encroachment. Specifically, the investigators will experimentally simulate predicted future environmental conditions of increased nighttime temperatures, nitrogen deposition, and El Nino frequency (which increases winter precipitation by 50% at our field site). This study focuses on species that are near the edge of their ranges, and thus may be particularly responsive to the effects of climate change. In addition, this study will measure how these global changes interact; this interaction is the largest source of uncertainty in global change research.
Broader Impact: This study addresses several issues with important policy and economic consequences. Specifically, this research will investigate the effect of climate change on two dominant and economically important forage grasses and their susceptibility to competition from shrubs. The invasion of creosote into grasslands is associated with a decrease in forage value, and increases in carbon sequestration and nitrogen leaching, with implications for ranching, climate change feedbacks, and water quality. The investigators conduct research at a minority-serving institution and the research will include members of underrepresented groups via an ongoing undergraduate mentoring program associated with the Sevilleta LTER. Resulting data will be made available via the web and will be used in K-12 curriculum activities. The field site will include an interactive demonstration of the experimental warming protocols and signage to inform school groups and other visitors of the goals of the research.
