Predictors of tree growth in a Dipterocarp-based agroforest: a critical assessment

Growth records from three 1 ha plots of old-growth agroforest that have been monitored for 3-7 years in Sumatra are analysed. These plots of damar agroforest show typical multi-species composition. Tree species were grouped into five sets according to species ecology and average growth rate. Variables used in the multiple linear regression to predict average annual increment were crown form index. crown position (CP) index and initial girth. Crown form (CF) index is indicative both of photosynthetic capacity and of general vigour of the tree. Crown position index is indicative of the amount of light available to a tree. Results show that crown form is the most effective predictor of growth and that initial girth, and crown position only marginally increase the percentage of variance accounted for in most cases. About 40-50% of the variance is explained by using the above mentioned variables depending on the sites. The significance of these results is discussed and some methodological improvements to the monitoring techniques currently in use are suggested. (C) 2002 Elsevier Science B.V. All rights reserved.