A field experiment was conducted to compare the rapidity with which the shrubs Larrea tridentata and Prosopis glandulosa utilized water, CO₂ and nitrogen (N) following a simulated summer rainfall event. Selected plants growing in a roughly 50-m² area were assigned to treatment and control groups. Xylem water potential (Ø_x) and net assimilation rate (A_net) were evaluated one day before and one and three days after watering. To monitor short-term N uptake, soils around each plant were labeled with eight equally distant patches of enriched ¹⁵N before watering. Nitrogen uptake, measured as leaf ä¹⁵N, was evaluated at smaller time intervals and for a longer period than those used for Ø_x and A_net. Both Ø_x and A_net exhibited a significant recovery in watered vs. control Larrea plants within 3 days after the imposition of treatment, but no such recovery was observed in Prosopis in that period. Larrea also exhibited a greater capacity for N uptake following the rain. Leaf ä¹⁵N was 5-fold greater in watered compared to unwatered Larrea plants within 2 days after watering, while foliar ä¹⁵N was not significantly different between the watered and unwatered Prosopis plants during the same period. Lack of a significant change in root ¹⁵NO₃ uptake kinetics of Larrea, even 3 days after watering, indicated that the response of Larrea to a wetting pulse may have been due to a greater capacity to produce new roots. The differential ability of these potential competitors in rapidly acquiring pulses of improved soil resources following individual summer rainfall events may have significant implications for the dynamic nature of resource use in desert ecosystems.