MICROCLIMATE AND WATER STATUS OF SAND TAILINGS AT AN EX-MINING SITE IN PENINSULAR MALAYSIA

Abstract

Experimental plots, each of size of 12 x 7.5m, were established on sand tailings at an ex-mining site in Peninsular Malaysia at 8m above the standing water-table level (a.s.w.l.) (open and shade plots) and at 2.5m a.s.w.l. (open plot only). The shade plot received about 45% irradiance while the open plot received full irradiance. Acacia mangium and A. auriculiformis seedlings were planted in both plots at 0.75 x 0.75 m spacing. Shading reduced air temperature, raised relative humidity (RH) and decreased air vapour pressure deficit (VPD_air). The results of 195 daily recordings of water-table levels in 3-m depth dipwells showed that ground water supply was limited at the site. The suction of sand at 0-15 cm depth at 1, 3 and 6 days after rainfall (> 37 mm per day) showed that the sand tailings at 8 m a.s.w.l dried rapidly from 3 to 6 days after rainfall. Days of available sand water (DAW) for A. mangium and A. auriculiformis were estimated based on root depths of each species and water release characteristics of the sand tailings. The DAW values for 9-month-old A. mangium and A. auriculiformis were 6 and 11 days respectively.