Interactions between disturbance regimes and nutrient availability strongly influence forest ecosystem dynamics. Recent studies suggested that variation in tropical forest growth and mortality is explained by variation in soil properties that influence nutrient cycling. Uncertainty exists over the importance of soil fertility properties (i.e., total soil phosphorus-P concentration) in mediating forest ecosystem resistance to and recovery from tropical wind disturbances (e.g., cyclones). We hypothesized that forests growing on soils with low total P (e.g., developed on limited-P parent material) have a higher resistance to but a slower recovery from wind disturbances compared to forests on high P soils. To test this hypothesis, we investigated the impacts of wind disturbance on litterfall, which is a crucial conduit for nutrient recycling in forest ecosystems. We compiled site-level forest litterfall data from published studies and datasets associated with nineteen tropical cyclones and one simulated hurricane in four cyclone basins within the tropics. We quantified the effect of wind disturbance on litterfall mass and nutrient fluxes over the first five years following the disturbance, and assessed the effect of soil P and related soil properties on litterfall wind-disturbance responses.
Results/Conclusions
The overall effect sizes of wind disturbance on litterfall mass flux varied with time post-disturbance, from highest immediately after (1663%) to lowest ( Abstract48%) two and a half years after the disturbance. A large initial increase reflects the magnitude of the wind-derived plant material input to the forest floor, which is followed by a persistent reduction in litterfall production for years after the disturbance. The overall effect size variance, indicating variation among forest types and sites based on soil P, was highest immediately after the disturbance compared to the subsequent months of recovery. Over 60% of the variance in the immediate impact was explained by parent material, soil order, and forest type sensu Holdridge. Overall effect sizes of disturbance on leaf-fall P concentration remained positive (from 29% to 57%) over two years post-disturbance, possibly indicating plant uptake and allocation of wind-derived P to leaves. Results highlight the importance of understanding the interactions between disturbance and ecosystem nutrient cycling to understand forest responses to altered disturbance regimes expected under climate change. Ongoing work aims to enhance the coverage of our pan-tropical analysis to better understand how post-disturbance trajectories of litterfall mass and nutrient fluxes influence post-disturbance forest nutrient cycling and forest development