Báo cáo lâm nghiệp: PAR conversion efficiencies of a tropical rain forest

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..
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Báo cáo lâm nghiệp: "PAR conversion efficiencies of a tropical rain forest"PAR conversion efficiencies of rain forest tropical aR.J. Luxmoore 1 J.G. 2 Saldarriaga1 Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A., andEnvironmental2 Tropenbos Program, Bogoti, Colombia ed with allometricIntroduction regression relationships using diameter, height, dry weight and wood density data from each of the 23 sites. Recently avail-The mean annual quantities of photosyn- able data for 1 and 3 yr regrowth forest standsthetically active radiation (PAR) absorbed also included in this analysis. wereduring various stages of regeneration of a Regression equations for converting leaf phy-tropical rain forest in the upper Rio Negro tomass to leaf area were used with number ofregion of Colombia and Venezuela were trees per hectare (Saldarriaga et aL, 1986) to derive leaf area index (LAI) values for the forestestimated for the intervals between clear- stands. The value of LAI for the 1-3 yr periodcut and 1, 3, 10, 20, 35, 60, 80, and 200 yr was 3.9, and this increased up to a mean valueof growth. The forest phytomass and litter- of 6.7 for the oldest stand (80-200 yr).fall at each stage were obtained from pre-vious studies, and the data were used tocalculate the mean annual quantity of netdry matter production per unit of absorbed ResultsPAR, the PAR conversion efficiency. The annual quantities of PAR absorbed by the forest stands (Table I) were calculated from the Bouguer-Lambert (Beers) LawMethods using appropriate LAI values with an extinction coefficient for PAR of 0.74 andThe basic for the calculation is equation given an annual net incoming PAR of 2.75by: GJ-m-2!yrl. This latter value was ob-Total dry matter PAR conversion Absorbed (1 ) x = tained from the mean annual solar radia- PAR production efficiency tion (5.2 GJ measured in the ) 1 yr 2 m- ’ ) 1 yr 2 m- ’ (g ) 1 MJ- ’ (g ) 1 yr 2 m- ’ (MJ area since 1971, by using a factor of 0.55 et al. (1986) investigated forestSaldarriaga for the proportion of PAR (Stigter andsuccession at 23 sites representing a chronose- Musabilha, 1982) and a PAR albedo ofquence ranging from recently abandoned areas 0.04 (Dickinson, 1983).after slash-and-burn agriculture to mature rain Dry mat ...