Rainfall drives leaf traits and leaf nutrient resorption in a tropical dry forest in Mexico

Core leaf traits, such as leaf mass per area (LMA) and leaf nitrogen (N) and phosphorus (P) concentrations in green and senesced leaves, are currently used to discern patterns of variation, constraints, and relations to nutrient availability and climate among plant species up to the biomes and global scale. These traits and nutrient resorption were measured in 21 woody species in three phenological groups of the Chamela tropical dry forest (TDF) during a 3-year study period under conditions of contrasting rainfall. The LMA was similar among years and showed negative relationships with green-leaf N and P concentrations, in agreement with the global assessments. Community-level mean N concentrations in green and senesced leaves did not change among years, but P concentrations decreased with lower water availability in dry years. Both mean and minimum foliar N:P mass ratios increased with diminishing rainfall, suggesting that leaf stoichiometry reflects a water control on soil P limitation in this forest. In the wet year, green-leaf N and P concentrations were not correlated, and there were high coefficients of variation among species in leaf P and N:P ratios, indicating that species variability and physiological constraints are expressed in leaf stoichiometry upon the removal of water limitation. The resorption efficiency and proficiency of P, but not N, increased in years with low rainfall, suggesting that the costs of nutrient resorption relative to acquisition from soil differ between N and P and that P conservation increases when rainfall decreases in the Chamela TDF. Our results support the proposal that water availability controls P dynamics in this ecosystem.