Kan plianplaeng sombat khong din nai pa thammachat tam laksana kan chai prayot thi din thi Sakaerat, Pakthongchai, Nakhonratchasima.

This study was designed to investigate the changes in soil properties under the natural forest, the tranformation type of different land use as well as distribution of biomass and the total nutrients within plant and soil sub-systems at Sakaerat Environmental Research Station. Some physical properties of soil under the cultivating fields and abandoned fields differ markedly from primary forest. Bulk density and particle density of surface soils under MF, OC1 and OC2 sites increased 7-9% and 5-10% respectively as compared to the forest sites but those at lower depth decreased. Both bulk and particle densities of CF increased 5-9% in all layers. Soil porosity in the cultivating fields and abandoned fields at the depth of 20 cm. and in the deeper layers show an increasing trend about 3-15% as compared to the forest areas. Chemical properties of soils also show the same patterns as the physical properties. Chemical properties that suggest some increasing trends in the cultivating fields and abandoned fields are pH, K, Ca, Mg and C.E.C. but they are demonstrated in different soil layers. The amount and distribution of biomass and total nutrient are high in natural forest areas. Biomass of Dry Evergreen Forest and Dry Diptrocarp Forest are accounted for 242.32 and 94.82 ton/ha. respectively. The amount of plant nutrient contained in living and litter layers are about 20% while the other 80% is in the soil. In the abandoned fields which possess the biomass content between 21.12-31.49 ton/ha. contain 5.7% of plant nutrient within plant sub-system while 94.3% of nutrient is in the soil. In the maize and cassava fields, living plant is between 3.47-4.00 ton/ha. but the nutrient is only 1-2%. The remaining 98-99% of nutrients is in the soil.