Biomass production and nutrient accumulation in an age series of caesalpinia sappan Linn. plantations

Abstract

The present study was conducted at College of Forestry, Kerala Agricultural University, Vellanikkara on biomass production and nutrient accumulation in an age series (5, 6 and 7) of Caesalpinia sappan plantations in three districts of Kerala. The study reveals that diameter, height, biomass, productivity and volume increased with increasing age. The above ground biomass and biomass components also increased with increasing ages. The above ground biomass produced was 23.81 t ha-1 at 5 year, 37.80 t ha-1 at 6 year and 44.36 t ha-1 at 7 year. The productivity at age 5 year was 4.77 t ha-1yr-1, at age 6 year 6.30 t ha-1 yr-1 and at age 7 year was 6.34 t ha-1 yr-1. The increase of the productivity between 6 and 7 years were very low (0.04 t ha-1yr-1), which indicated that no further increase in the productivity of the trees. It highlights that a levelling off the productivity beyond 6 year. This consideration suggests 6 year as the optimum harvesting period of C. sappan. The percentage contribution of various components to above ground biomass was in the order: bole > branch > twig > fruit > leaves> bark. The biomass components were also showed an increasing trend. The prediction equations were prepared for above ground biomass as well as biomass components with respect to dbh and height. Even though some equations were proved more fit with combination of dbh and height, R2 value and Furnival index were relatively similar to equations with dbh alone could not be selected, it is difficult to measure height of the standing trees with definite accuracy. Hence, equations with dbh alone were selected for predicting the biomass. With respect to the dbh alone as independent variable, the total above ground biomass, the best fit equation was W = b0 +b1 D+ b2 D2. In leaves also this model proves as best fit. The components like bole, bark, branch and fruit, the best fitted equation was ln W =b0 + b1 ln D. But in twig, it was W=b0 + b1 D2. Weight table prepared for bole (UB) and total above ground biomass based on the best fit equation using diameter at breast height The nutrient concentration was increased with increasing age except in bole and branches. Concentration in bole and branches increased from 5 to 6 year and decreased from 6 to 7 year. Leaves had the maximum concentration of the nutrients and bole the lowest. The nutrient accumulation of the above ground biomass as well as biomass components increased with the increasing age of plantation. The maximum nutrients accumulated in bole and minimum in bark. Among the nutrients, N accumulated maximum followed by K and P. Nutrient use efficiency increased with increasing ages. The maximum nutrient use efficiency observed for P followed by K and N. It was found to be maximum in bole and minimum in leaf.