Comparison of biomass production, tree allometry and nutrient use efficiency of multipurpose trees grown in woodlot and silvopastoral experiments in Kerala, India

In woodlot and silvopasture experiments involving a total of three age-sequences, the rates of biomass accumulation and nutrient accumulation by multipurpose trees were evaluated. The woodlot experiment included nine multipurpose trees ( Acacia auriculiformis, Ailanthus triphysa, Artocarpus heterophyllus, Artocarpus hirsutus, Casuarina equisetifolia, Emblica officinalis, Leucaena leucocephala cv. K8, Paraserianthes falcataria and Pterocarpus marsupium) and the silvopastoral experiment involved a subset of four trees ( Acacia auriculiformis, Ailanthus triphysa, Casuarina equisetifolia and Leucaena leucocephala cv. K8). Both plantings were maintained at Thiruvazhamkunnu, Kerala, India. Trees in the woodlot experiment were felled (partially) at 8.8 years of age and that of the silvopastoral experiment both at 5 years and 7 years of age. Rate of biomass accumulation and nutrient accumulation was highest for Acacia and the least for Leucaena. Allometric relationships linking above ground biomass with DBH and/or total height gave reasonable predictions. A comparison between species and among tissue types within species indicated that nutrient use efficiency for N, P and K varied widely. Implications for nutrient export from the site through whole tree harvesting systems involving fast growing multipurpose tree species are discussed.