Nitrogen and Phosphorus Allocation Strategies in a Chronosequence of Tropical Dry Forests: Plant Coordination and Environmental Drivers

Abstract

Identifying how limited resources, such as nutrients, are allocated across plant organs can provide new insights into ecophysiological strategies, as well as ecosystem nutrient cycles. Plants may allocate different nutrients within a specific organ or the same nutrient among different organs. In this study, we explored the allocation strategies of nitrogen (N) and phosphorus (P) in the leaves, stems, and roots of nine dominant tree species in secondary tropical dry forests using scaling analysis. The results showing that N and P have different scaling relationships within and among plant organs. The scaling relationships of P versus N concentrations in non-leaf organs were isometric across secondary succession and shifted in leaves from allometric (P concentration increased faster than N concentration) to isometric. The scaling relationships of N or P concentrations between metabolic (leaves vs. fine roots) or between structural (stems vs. coarse roots) plant organs tended to be isometric along succession. Whilst the scaling relationships of the same nutrient between metabolic versus structural plant organs tended to be allometric (N and P concentrations increased faster in woody organs than in metabolic organs) across succession. A principal component analysis suggests associations of nutrient allocation to woody organs with soil pH over the chronosequence and with vegetation structure and soil nutrient availability in the case of metabolic organs. These findings on the sensitivity in plant nutrient allocation to changes in soil and vegetation properties during secondary succession may have practical implications for carbon sequestration management and models and restoration of this threatened ecosystem.