Accepted 19th September, 2016
An experiment was conducted in a semi arid ecosystem in south central Kenya to evaluate the impacts of tree clearing on the microclimate beneath Acacia tortilis trees that support a dense matrix of Panicum maximum Jacq. A randomized complete block design was set up to measure the effects of tree clearing on quantum flux, leaf temperature, transpiration rates and leaf water potential. Maximum values of quantum flux of the order of 1900µmol. m-2s-2 and 900 µmol. m-2s-2 were observed in the exposed and intact sites respectively. These quantum flux values in the contrasting sites were statistically significant at p≤ 0.05.The highest leaf temperature recorded for Panicum maximum in the exposed sites was 35C0 whereas that in the intact sites was 30C0. Leaf water potential values were lowest in the exposed sites (- 5bars) compared to -2bars in the intact sites. The leaf water potential values in the contrasting micro sites were not statistically significant at p≤ 0.05.The highest transpiration rates for Panicum maximum were recorded for the exposed sites (6.5µgm-2s-1) compared to 5.2 µmol. m-2s-2 for the intact sites. The findings suggest that long term shifts in micro climatic conditions in the exposed habitats are likely to negatively influence photosynthetic rates and primary productivity of Panicum maximum.
Keywords: Acacia tortilis, Panicum maximum, eco physiology, savanna, microclimate, productivity