Print PageCompetition is often presented as a negative interaction between two or more organsims struggling for the same scarce resource. Competition is not thought of as a negative interaction between an organism and its environment contending for a scarce resource. Perhaps because gas exchange may be the only case in which an organism might compete with its environment. For example, the atmosphere is a strong contender for water vapor and evaporation fills that sink. In order to survive, plants must balance water use (i.e. transpiration) with evaporation. These two competing processes are often lumped into one process called evapotranspiration; we strongly believe in order to better understand the interactions between organisms and their environment scientists should partition evapotranspiration into its two competing components evaporation and transpiration. Here we present data from a controlled study done in the glasshouse at Biosphere 2. Tanglehead and buffelgrass are two important grasses of the semiarid southwestern United States. Buffelgrass being exotic is important because of its dominance on the landscape and tanglehead because of its native status and co-evolution with other native species. We studied the interactions and feedbacks of: an ambient environment, a +4 °C hotter environment, buffelgrass, and tanglehead on transpiration and evaporation.
Results/Conclusions
Results of transpiration and evaporation of water as two dominate water loss processes are key to understanding interactions and feedbacks that lie at the heart of ecology, hydrology, ecohydrology, and global change. Initial results of our controlled experiment suggest that water loss is dominated by evaporation in a warmer climate but transpiration dominates in a cooler climate. These shifts in dominance are further controlled by the amount of plant available water, the individual species associated with transpiration and their interaction with each other in a competitive situation. Furthermore, our result suggest that some species such as the native tanglehead grass may be very sensitive to these shifts in dominance. Understanding shifts in transpiration dominated systems to evaporation dominated systems when native and exotic species are involved will be key to sustaining plant biodiversity and soil water in a warmer and drier climate that many global change models predict will occur in semiarid environments such as the American southwest.
