Nutrient cycling in secondary forests in the Blue Mountains of Jamaica

Secondary forests in the Blue Mountains of Jamaica, subject to human disturbance as well as hurricanes, are coming under increasing land-use pressure with a rising population density and the remaining primary forest becoming more remote from settlements. The practice of slash-and-burn agriculture is commonly carried out by local communities. This study reports on estimates of how the secondary forests have recovered to, or close to, the functioning of undisturbed forest, in terms of key soil and nutrient cycling variables. Nutrient conservation was assessed by measuring inputs in throughfall and litterfall, which were compared to site nutrient capital and losses in surface runoff and erosion. Litterfall, litter standing crop and the growth of bioassay plants were measured in paired plots of primary and secondary forests. The results were compared with data already published for key nutrient cycling variables in primary forests of the Blue Mountains to determine the extent to which nutrient cycling and soil fertility in the secondary forest has recovered to primary forest levels. Rates of nutrient loss in runoff and eroded sediment in the secondary forest were low, basal area had recovered to 81% of primary forest levels, and rates of Litterfall were high. Litterfall nutrient concentrations were high, particularly for P, and nutrient cycling was rapid as judged by the high ratio of litterfall to litter standing crop. Soil fertility had recovered well in the secondary forests as judged both by chemical analyses and the growth of the bioassay plants. The results indicate that, for forests in the middle of steep slopes, following the cessation of agriculture, tight nutrient cycling and soil condition and fertility are effectively restored during ca. 20 years of secondary succession. This results in the re-establishment of a forest with effective nutrient conservation which offers a high degree of protection of catchment soil and water resources, and the potential to sustain another cycle of agricultural production. (C) 2000 Elsevier Science B.V. All rights reserved.