Midday transpiration rates and daily pan evaporation from a Melia volkensii plantation during the rainy season in a semi-arid area in Kenya

Midday transpiration rates and daily pan evaporation from forest floor and open area were measured to determine an effective way of controlling water loss from a Melia volkensii plantation. The research was conducted at an M. volkensii plantation in Tiva Pilot Forest, Kenya, during April and May 2014. A leaf porometer (LI-1600) was used to measure midday transpiration rates per unit leaf area (Ta) from 11:00 h to 13:00 h for four trees at three different leaf heights: top (A), middle (B), and bottom (C) layers of a crown. Midday transpiration rate per layer (Tl) and midday transpiration rate per tree (Tt) were estimated based on Ta and leaf area (LA) of layers. Daily pan evaporation from forest floor and open area were measured using 25 and two evaporation pans, respectively. Ta values for layer A were not significantly different among sample trees, while Tl values for layer A were significantly different, indicating the influence of LA on water loss through transpiration. Since Tl from layers B and C accounted for half of Tt, pruning of these layers could cause a 50 % reduction in water loss through transpiration. Daily pan evaporation in the plantation was approximately 70 % lower than that in the open area. Therefore, the layer A left after pruning should keep water loss through evaporation from the forest floor lower than that from the open area. Further research is required to determine the effect of pruning on reduction of water loss from the plantation.