Abstract

Several exotic species have been used for afforestation in Kerala as a part of the Social Forestry Programme, mainly funded by the World Bank. Among them, the most widely planted species is Acacia auriculiformis which has met with great success in survivial and yield. However, the tree has been the subject of discussion and criticism from some members of the public who have alleged several environmental problems associated with its large scale introduction. Among them, its excessive consumption of water is the most serious one. This report is an attempt to study the water use of A. auriculiformis by evapotranspiration. To determine how far the evapotranspiration is comparable to other trees, two other species, namely Anacardium occidentale (cashew)and Tectona grandis(teak) have been also studied. To determine the water use of the three species three pure plantations belonging to the above species in Palghat and Trichur Districts of Kerala have been selected. Intensive monitoring of rainfall interception, soil moisture, leaf water potentials microclimate above the canopy and leaf area index were done in all the three plantations round the year on selected sampling dates. Stomatal resistence and net photosynthesis were also measured simultaneously.Cashew shows less respose to vapour pressure deficit when compared to acasia. It has not been possible to understand the exact correlations in teak. However, teak prevents a lot of water loss during dry periods by shedding its leaves. The water use efficiency of the trees have been also compared. Cashew and acacia are certainly more efficient in their water use when compared to that of teak. At the same time, a cashew tree can consume more than 400 liter of water a day during peak summer. Several observations related to reainfall interception, microclimate, water potentials etc. are presented in this report