Tree Species Growth Changes Over 16 Years in the Long-Term Dynamic Plots of Sakaerat Deciduous Dipterocarp Forest, Northeastern Thailand

บทคัดย่อ

A census was carried out annually for 16 years (1984-2000) in four permanent longterm dynamic plots in the Sakaerat deciduous dipterocarp forest (SDDF), northeastern Thailand. The diameter at breast height (DBH, defined as 1.3 m above ground from the stem base) was measured for all trees having a DBH greater than or equal to 4.5 cm and growth rates of all existing tree species in each period in these stands were estimated. The studies revealed that all tree species investigated in each stand had different growth in terms of the absolute growth rate of basal area (AGRBA) and the relative growth rate of basal area (RGRBA). Several common tree species (Albizia odoratissima, Cratoxylum formosum, Canarium subulatum, Lannea coromandelica, Pterocarpus macrocarpus, Shorea roxburghii, Shorea siamensis and Xylia xylocarpa var. kerrii) were among the relatively fast growing species in all stands, whilst Dillenia obovata, Diospyros mollis, Quercus kerrii and Shorea obtusa were slow growing species, and overall, these latter tree species showed a greater reduction in stocking due to high mortality rates. The RGRBA exhibited the same trend as the AGRBA, and based on this rate, common tree species in all four stands were classified into nine different groups having significantly different RGRBA values.

Keywords: absolute and relative growth rate, basal area growth, fast growing species, gain and loss in basal area, slow growing species, Sakaerat