HIGH CONTRIBUTION OF BIOMASS INCREMENT TO ABOVEGROUND NET PRIMARY PRODUCTION IN AN ACACIA PLANTATION

To understand carbon cycling in a forest ecosystem, estimating net primary production (NPP) becomes important. In this study, aboveground NPP in an Acacia auriculiformis plantation was estimated based on established allometry for aboveground biomass increment (ΔAGB) and litter trap technique for litterfall (Li). The experiment was conducted in a plot of 300 m2 (15×20 m), established in a 21-month old plantation. Data were collected five times at 3-month intervals. The results indicated that Li and ΔAGB were seasonally dependent. Litterfall was highest (2.85 g m-2 day-1) during Sep-Jan (winter) and lowest (0.41 g m-2 day-1) during Mar-Jun (early summer). While ΔAGB was highest (7.11 g m-2 day-1) during Jun-Sep (summer) and lowest (2.5 g m-2 day-1) during Jan-Mar (winter). Total Li was 6.29 tons ha-1 year-1 and ΔAGB was 18.28 tons ha-1 year-1. Total aboveground NPP of the present study plantation was 24.57 tons ha-1 year-1. It is concluded that acacia plantation plays an important role in soil nutrient cycling through high litterfall and carbon sequestration by high ΔAGB.