Research on natural forest

Compilation of the past and present studies on the mixed deciduous forest with teak at Mae Huad, Lampang province. 21 species of tree over 4.5 cm in DBH with the density of 314 trunks per hectare. Age class distribution was discontinuous. The canopy layer was a mosaic of patches (85-563 square m patch area) which had different mean age. The maximum and mean size of gaps in 1 ha plot was 300 and 120 square m, respectively. Gap area was about 21.30 % of the total land area. The time-scale of the forest growth cycle took about 0-60, 60-110 and 225 years for the gap, building and mature phases, respectively. The correlation between tree biomass as representing the site quality and organic matter and total nitrogen contents in A and B-horizons were obtained. The site quality could be indicated as poor, medium and good site by using the amount of tree biomass, 50, 50-100 and 100 ton/acre, respectively. The establishment period of teak ranged from 4 to 30 years. Strong root growth and development of teak seedling occurs in the mid establishment period (12-18 years). Stems of teak regeneration greater than 2 m high can withstand a fire. The surface runoff of 139.19 cubic m/ha carried 4.79, 8.71, 8.19, 1.33, 0.23 and 0.42 kg/ha of Na, K, Ca, Mg, Fe and P, respectively. The sediment of 263.53 kg/ha brough out 0.01, 0.06, 0.66, 0.07, 0.02 and 0.81 kg/ha of Na, K, Ca, Mg, Mn and N, respectively. The combination of the two transporting media accounted for 14.09, 49.27, 38.60, 42.55, 65.71, 20.00 and 9.32 percent of Na, K, Ca, Mg, Fe, Mn and P in comparision to the amount of each nutrient obtaining by rainfall. Teak harvested in Northern Thailand in 1985 was only one-tenth of that harvested in 1971. The dramatic decrease has been attributed by some authors to loss of trees through shifting cultivation and intensification of modern agriculture. This report examined the possibility that previous removal of large trees during selective logging is also a reason for present low yield of teak. After selection cutting, most of the remaining teak was concentrated in diameter size classes less than 50 cm.