NITROGEN AND PHOSPHORUS REABSORPTION EFFICIENCY AND STOICHIOMETRIC RELATIONSHIPS DURING SENESCENCE IN SPECIES OF THE SONORAN DESERT

Background: Nitrogen (N) and Phosphorus (P) are the most limiting nutrients in plants and their resorption efficiency suggest conservation strategies. Resorption also change litter stoichiometry and affect ecological interactions and biogeochemical cycles along aridity gradients. Species nutrient resorption efficiency will be higher in sites at the arid extreme, such that resorption proficiency and stoichiometry for C:N and C:P will be higher in senescent leaves. Studied species: Ipomoea arborescens, Fouquieria macdougalii, Cercidium microphyllum, Encelia farinosa, Mimosa laxiflora, Jatropha cardiophylla, Olneya tesota, Prosopis velutina, Cercidiurn floridum, Fouquieria splendens, Brongniarlia minutifolia, Jatropha cordata, Colubrina viridis, Larrea tridentata and Cercidium praecox. Study site and years of study: Three sites along an aridity gradient in the Sonoran Desert, Central Region in Sonora. August to November 2017 and 2018. Methods: We obtained N and P reabsorption efficiency, as well as stoichiometric proportions for C:N y N:P from green and senescent leaves to compare species, functional types and sites. Results: N and P reabsorption efficiency decreased with aridity and C:N and C:P stoichiometry of senescent leaves, as well as N:P for legumes. Conclusions: Reabsorption efficiency does not suggest a resource conservation strategy, however different functional types allowed us to differentiate ecological and stoichiometric strategies, in particular legumes, that help enhance their role in the biogeochemistry of Sonoran and Mexican and lands.