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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: PAR conversion efficiencies of a tropical rain forest | 523s Ann. Sci. For. 1989 46 suppl. 523s-525s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA PAR conversion efficiencies of a tropical rain forest R.J. Luxmoore1 and J.G. Saldarriaga2 1 Environmental Sciences Division Oak Ridge National Laboratory Oak Ridge TN U.S.A. and 2 Tropenbos Program Bogotá Colombia Introduction The mean annual quantities of photosynthetically active radiation PAR absorbed during various stages of regeneration of a tropical rain forest in the upper Rio Negro region of Colombia and Venezuela were estimated for the intervals between clearcut and 1 3 10 20 35 60 80 and 200 yr of growth. The forest phytomass and litterfall at each stage were obtained from previous studies and the data were used to calculate the mean annual quantity of net dry matter production per unit of absorbed PAR the PAR conversion efficiency. Methods The basic equation for the calculation is given by Total dry matter PAR conversion X Absorbed 1 production efficiency PAR gm-2-yr1 g-MJ-1 MJm-2-yr-i Saldarriaga et al. 1986 investigated forest succession at 23 sites representing a chronosequence ranging from recently abandoned areas after slash-and-burn agriculture to mature rain forest. Aboveground and belowground living phytomass litter and root production standing dead mass and leaf area indices were estimat ed with allometric regression relationships using diameter height dry weight and wood density data from each of the 23 sites. Recently available data for 1 and 3 yr regrowth forest stands were also included in this analysis. Regression equations for converting leaf phytomass to leaf area were used with number of trees per hectare Saldarriaga et al. 1986 to derive leaf area index LAI values for the forest stands. The value of LAI for the 1-3 yr period was 3.9 and this increased up to a mean value of 6.7 for the oldest stand 80-200 yr . Results The annual quantities of PAR absorbed by the forest stands Table I were calculated from the Bouguer-Lambert Beers Law
