Legumes are essential plants in dryland ecosystems worldwide because they increase nitrogen availability, so their understanding is vital for improving knowledge and modeling in the face of climate change. This work studies the differences in resource use efficiency and their relationship with photosynthetic, photochemical, bioelemental, and stoichiometric traits of coexistent legumes and non-legumes in a Sonoran Desert ecosystem. We found that legumes had higher photosynthetic rates, intrinsic and seasonal water use efficiency (WUE), phosphorus use efficiency (PPUE), and higher light utilization mediated by chlorophyll content and active reaction centers, which may increase their photoprotection. Legumes can increase their WUE and PPUE with no changes in nitrogen use efficiency (PNUE). Consequently, observed trait relationships between studied traits in these legumes have significant differences with the non-legume species in the study. Stoichiometry is helpful, in some cases, as an indicator of nutrient use efficiency and enables functional group differentiation. Our results strongly relate legumes' higher resource use efficiency with their success in dryland ecosystems.

Field measurements and sampling were conducted on the most dominant shrub and tree species, three leguminous and five non-leguminous, which contributed to about 80% of the plant community's dominance. Physiological measurements were obtained from five (occasionally four) leaves from previously marked healthy adult individuals of each species within a plot of around 1000 m2. All measurements were performed after the onset of the North American Monsoon summer rains (between July and October) in 2021 and no official permits were required to perform the field work.

Funding provided by: Consejo Nacional de Humanidades, Ciencias y TecnologíasROR ID: https://ror.org/059ex5q34Award Number: CB-61865 Funding provided by: Consejo Nacional de Humanidades, Ciencias y TecnologíasROR ID: https://ror.org/059ex5q34Award Number: CB-223525 Funding provided by: Universidad de SonoraROR ID: https://ror.org/00c32gy34