Forest recovery on abandoned farms of the Añasco river watershed of western Puerto Rico

Background/Question/Methods A shift in macroeconomic strategies, from an agricultural to a light industrial economy led to farm abandonment in the Añasco Valley of western Puerto Rico. These developing secondary forests in Añasco Valley offer important ecosystem services, such as decreased runoff, help restore soil microfauna and soil nutrient pools. The forest strucure and species composition has never been studied. These secondary forests are sinks of native plant. Species composition and forest structure were described for abandoned farmlands in the Añasco River Watershed. Prior to abandonment, coffee was cultivated on the slopes surrounding the valley while sugar cane and coconut palms were cultivated in the valley. Plots were randomly chosen from an age class map produced from aerial images taken in 1936, 1963, 1994, 2001 and vegetation data collected in 1978. Vegetation was sampled in 500 m2 circular plots, individuals with diameter at breast height (dbh) greater than 2.5 cm were measured and identified. Basal area, species richness and Shannon-Weiner diversity index were calculated to assess forest structure Results/Conclusions Significant differences were determined in structural characteristics between plot of the same age on the valley and on the mountains. Non-metric multidimensional scaling (NMS) determined distinct plant communities on abandoned coffee plantations and palm plantation but not for abandoned sugar plantations. From the NMS results present it can be inferred a seed dispersal pattern from the higher elevation sites to the lower elevation. Species composition at the abandoned coffee plantations resembles the composition of species at the Luquillo Experimental Forest and Central Cordillera Forest of Puerto Rico. Forest structure for some plots on the Añasco River Watershed reached levels comparable to that of mature forests after 80 years of vegetation succession.