Report on an erosion and revegetation investigation at Wan Chuk Yuen, Pat Heung and K.A.R.C., New Territories, Hong Kong

Abstract

This report first sets out the objectives, methods and the first year of results of a study of surface erosion at a grass- and fern - land site in the New Territories H.K., as well as directions that the experiment will take in future. The study covers only erosion by surface wash, since this is more or less continuous. Three separate methods, erosion-pin meansurement, splash-trap (near-ground) collection to measure sediment mobilization, sediment-trap (ground-level) collection were employed to compare estimated levels of erosion, on four 6 x 20 m paired plots. In each pair, on slopes matched for soils, slope-angle, shape and orientation, one plot was maintained uncut and the other was cut annually. Towards the end of the first year a pair of burnt plots, also 6 x 20 m, was added to the experiment. Results suggest that on uncut plots only small amounts of sediment are mobilized and that rapid regeneration of the vegetation on the cut plots, following a 'burst' of sediment after cutting, results in similarly low levels of sediment mobilization and movement.

The second part of this Report details the objectives, methods and results of an experimental oversowing of rough grassland at the Kadoorie Agricultural Research Centre with the tropical legume Stylosanthes scabra. Since native grasslands produce dry matter of generally low quality, especially in protein and fat, oversowing was attempted using low-cost methods involving no or minimal tillage in order to minimize soil disturbance on sloping sites. Sowings were into grassland either undisturbed, initially slashed before sowing and initial slashing combined with maintenance slashing. Since none of these treatments proved successful, high-rate sowing in contour furrows followed by maintenance slashing was employed and this proved successful in establishing Stylosanthes stands.