EFFECT OF COMMUNAL USE OF DRY ZONE FOREST LAND ON SOIL EROSION

Abstract

A broad spectrum of successions in natural vegetation from abandoned chena lands to primary forest is found in the dry zone with a wide diversity in plant composition. Man's interference with the natural vegetation here is mainly the complete removal of forest for cultivation, but most of the remaining forest lands also have been exploited by selective removal. A study was carried out to understand the soil erosion and surface hydrology in three different vegetation types formed due to human activities. The types of vegetation considered are selectively logged forest, scrub vegetation and chena lands under cultivation.

The study was conducted during the period from November 1988 to May 1990 at Paindikulama in Anuradhapura District. Plant composition was surveyed in selectively logged forest and scrub lands. Runoff plots of 22 m x 4 m were constructed in lands under each vegetation type. Two plots were used for each treatment, and runoff and soil loss were measured.

The survey indicated that 49 plant species are found in the study site. Although about 45% of these are available in selectively logged forest almost all tree species have been used by villagers for various purposes. Consequently, some trees have not survived and have been replaced by others. However, soil loss measurements show that the protection given by selectively logged canopy and scrub vegetation is adequate to prevent serious soil erosion. Relatively high runoff (40%) and soil loss (12 t/ha) values were observed from cultivated chena lands. If can thus be concluded that communal use of forest land by selective logging has no serious effect on soil erosion.