INTERACTIVE EFFECTS OF QUANTUM FLUX, TRANSPIRATION RATES AND LEAF STOMATA CONDUCTANCE ON NET CO2 ASSIMILATION RATES OF SAVANNAH GRASSES IN KENYA

Abstract

The current study was conducted to investigate the interactive effects of quantum flux, transpiration rates, and leaf stomata conductance on net CO2 assimilation rates of Panicum maximum beneath Acacia tortilis canopies and disturbed micro sites where these trees were removed. A randomized complete block design was used to measure the treatment effects created by cutting Acacia tortilis trees on CO2 assimilation rates of Panicum maximum. The mean quantum fluxes for the canopy micro sites and disturbed micro sites were 694.8µmol m-2 s1 and 1184.5µmol m-2 s-1, respectively. The average leaf stomata conductance values for Panicum maximum in the exposed and canopy micro sites were 249.6 mmolm-2s-1 and 332.8mmol m-2 s-1 respectively. These average leaf stomata conductance values were significantly different at p≤ 0.05 Transpiration means for Panicum maximum in the exposed micro sites (4.0 mgcm-2s-1) and canopy micro sites (4.2mg cm-2s-1) were not significantly different at P≤ 0.05. Panicum maximum in the disturbed micro sites exhibited significantly lower (p≤0.05) net CO2 assimilation rates (mean of 1.4µmolCO2 m-2 s-1) than the rates measured for the same species (mean of 9µmolCO2 m-2 s-1) in the canopy micro sites. These findings suggest that induced disturbances created by clearing of Acacia tortilis trees in the long term will cause shifts in micro environmental fluxes of energy, water and CO2 exchange with significant implications on herbaceous under storey productivity.