ESTIMATION OF SOIL LOSS BY USING EROSION BRIDGE : A GUIDE TO SUSTAINABLE FOREST MANAGEMENT

Abstract

Soil loss estimation by using erosion bridge to be used as a guide to sustainable forest management was conducted in Huai Nam Gud, Khunkong Watershed Research Station, Chiangmai. The extimation of soil loss in each landused type was done, including, shifting cultivation, natural pine forest, pine forest plantation, filled side-slope and forest road to indicate sustainable forest management. The results indicated that shifting cultivation have the highest monthly soil surface change of 34.018 millimeters. Forest road, pine forest plantation, natural pine forest and filled side-slope had monthly soil surface change of 21.134, 11.371, 4.741 and 4.326 millimeters respectively. Sediment delivery ratio of Huai Nam Gud Watershed was 0.263. On site erosion was 9.441 tonnes/rai/month and off site erosion was 2.481 tonnes/rai/month. Shifting cultivation produced the most annual soil loss of 58.674 tonnes/rai/year. Forest road, pine forest plantation and natural pine forest had annual soil loss of 29.216, 15.992 and 9.406 tonnes/rai/year. Reforestation in bare land and degenerated forest can reduce soil loss and eventually recovered to natural forest. Agro-forestry system is an option which could be applied in soil and water conservation practices in order to promote the forest plantations in combination with agricultural crops.