The Role of Trees in Countering Land Degradation in Cultivated Fields in Northeast Thailand

Abstract

The paper describes characteristics of trees in cultivated fields, a familiar feature of Northeast Thailand; their origin in connection with land-use development; their ecological roles, with emphasis on soil fertility, that can restore degraded land; and ways to increase their number. Farmers make concious decision leading to the existence of these trees. They have useful functions for farmers from socio-economic and ecological viewpoints. When forest is changed to agriculture fields, soil fertility declines rapidly and soil erosion is accelerated. Much work in the Northeast has shown conclusively the soil fertility increases in the presence of trees. Leaf litter has been shown to be an important agent for nutrient cycling in tree-soil system. Leaf litter of different tree species plays different roles in improving soil fertility depending on their "quality" or chemical compositions. Trees also play important roles in nutrient capture through roots. This is particularly useful for sandy and prone-to-leaching soils of the Northeast. There are many constraints in integrating more trees into farming systems including small land holding at household level; negative impact of trees on yields of agricultural crops; and loss or damage of planted trees. Despite such constraints, some farmers have been integrating more trees into their fields. More research should be done on how to effectively integrate trees into farms.