Effects of Three Global Climate Change Factors on Soil Water and Sap Flow of Larrea Tridentata in the Mojave Desert

Larrea tridentata is one of the most abundant and widespread perennial plants in deserts of southwestern North America. Averaged over all treatments, L. tridentata exposed to summer irrigation treatments have significantly greater sap flow than plants in non-irrigated plots. This irrigation effect lasts approximately seven weeks after the last irrigation when a transition is made and plants in non-irrigated plots begin to have significantly greater sap flow until the irrigations of the following year. Not only is L. tridentata able to respond to an increase in soil water during the hot summer months, but evidence is also presented that suggests L. tridentata has an additional physiological response to the increase in soil water within a two week period. L. tridentata plants exposed to the highest nitrogen addition consistently had the greatest rates of sap flow. The effect of the biological soil crust treatment on sap flow of L. tridentata was variable and dependant on interactions with the irrigation and nitrogen treatments. These results demonstrate that predicted impacts of global changes have the potential to have important effects on the Mojave Desert by affecting the primary production of L. tridentata and the ecohydrology of the ecosystem.