The data reported here are only for tabonuco forest at El Verde. Following plot setup and one year of pre-treatment measurements, Hurricane Hugo struck before the first planned fertilization. Because a year and a half of annual above ground litter inputs of phosphorus were dropped onto the forest floor in the form of leaf litter, we added a debris removal treatment to the original two, fertilized & control.
These data were used to determine the pools of readily available nitrogen in soil solution in debris removal and fertilizer treatments applied to tabonuco forest at El Verde immediately after Hurricane Hugo struck in September 1989. The treatments (complete removal of litter and woody debris, total fertilization, and control). Both ammonium and nitrate were low in the May 1990 samples. All samples had more KCl extractable ammonium in September, but negligible nitrate. Increases in ammonium were greatest in the fertilized and debris removal plots as compared to the control treatment. These results were positively correlated with litterfall production and canopy closure, with faster rates of recovery in the fertilized and debris removal treatments as compared to the control. Soil extractable (readily available) N was negatively correlated with microbial N in the samples collected one year after Hurricane Hugo, indicating microbial immobilization of N. Century modeling results were consistent with our observations and indicated that woody debris increased the input of low-nutrient substrate to the soil thereby stimulating microbial uptake/immobilization. Thus the soil microbes in the control plots outcompeted the trees for limiting N, thereby slowing their recovery.