STUDY OF HIGH SHADE TREES (Gravillea robusta) ON MICRO CLIMATE OF A TEA FIELD
Shade trees are widely grown in tea plantations in Sri Lanka to provide physical shade fortea during the dry weather. It also enriches the soil fertility by leal" Iall. An investigation wascarried out to quantify the radiation and canopy temperature around an eight year old 'high'shade tree Gravillea robusta. The measurements were made at hourly intervals [rom 9.15am to 3.15 prn on January lSth. 1999. In addition. relative humidity was measured in theshaded and unshaded area.
The radiation was measured by a tube solari meter and the canopy temperature wasmeasured by infra red thermometer. The organic carbon content of the topsoil between twoshade trees were measured at north-south and cast-west directions at 2m intervals.
On a clear day the shaded area ranged from 12-15%, highest during the early morning andlowest during the noon. The canopy temperature under shade was 4-6oC less than theunshaded area. There was a marginal difference in relative humidity between shaded andunshadcd area. The relative humidity of the shaded area was marginally higher than theunshadcd area in the afternoon. The organic carbon content ranged from 3-49'<" A high valuewas round near the base of the tree and a low value was found midway in between the shadetrees. The mean leaf area index of the Grevillea canopy was 6.9 and the canopy extinctioncoefficient was 0.21.