Litterfall in Montane Rain Forests of Jamaica and its Relation to Climate

Abstract

(1) Litterfall at four sites in impoverished Montane Rain forest at c. 1550 m in the Blue Mountains in Jamaica was studied, as a preliminary to the investigation of mineral cycling, during two separate periods-January 1974 to March 1975 and March 1977 to April 1978. Temperature, rainfall, throughfall, relative humidity, litterfall and water content of the trapped litter were studied for varying lengths of time. (2) Mean monthly maximum temperatures were 18 5-20-5 ?C, absolute maxima 21.5-24-0 ?C, mean monthly minima 11 -0-12.0 ?C and extreme minima 8-5-100 0C. Rainfall in the area was c. 2500 mm yr-1. Relative humidity in the forest was usually above 90% as a result of persistent low cloud and fog. Rainfall was markedly seasonal; 5 months (four consecutive) each had less than 200 mm, but the effects were mollified by the high humidity. (3) Litterfall (t ha-' yr-1) was 6-6 (total) and 4-9 (leaves) in Mor Ridge forest; 5.5 (total) and 5 3 (leaves) in Mull Ridge forest; 5.6 (total) and 4 4 (leaves) in Wet Slope forest; and 6-5 (total) and 5 5 (leaves) in Gap forest. The rate of litterfall in the drier part of the year (January to August) was approximately twice the rate in the wetter part of the year for all four forests. (4) Mean leaf-life was estimated as c. 18 months in Mor Ridge forest and c. 13 months in well-developed Mull Ridge forest. (5) The biomass of leaves and the amount of leaf litterfall in the upper Montane Rain forests were similar to published values for Lower Montane and Lowland forests, but above-ground net primary production was lower in Upper Montane Rain forests than in Lowland Rain forests (c. 7 compared with c. 16 t ha-' yr-1). (6) The relative impoverishment of the Jamaican forests is discussed in relation to examples of well-developed Lower Montane and Lowland Rain forest.