Kunhamu, T KSuganya, SKAU2017-08-292017-08-292014http://krishikosh.egranth.ac.in/handle/1/5810029897A field study was carried out to evaluate the biomass production, carbon sequestration and nutrient dynamics in a 22-year-old Ailanthus triphysa stand managed at variable densities viz., 2360 trees ha-1, 1560 trees ha-1, 900 trees ha-1 and 560 trees ha-1. Total number of 80 trees (20 from each density regime) was destructively sampled for the biomass and carbon stock assessment. Also nutrient stocks (N, P and K) in various tissue types were assessed following standard procedures. The soil carbon and nutrient contents were assessed for one meter soil depth at regular depth intervals. The average stand height and bole height were 12.84 m and 8.19 m respectively which varied significantly with stand density with maximum value recorded for 1560 trees ha-1. The average dbh, mean tree volume and bole volume put in by the 22- yearold A. triphysa stand was 18.78 cm, 0.15 m3 and 0.16 m3 respectively which however could not yield a predictable trend with stand density. Despite this, the stand volume exhibited a proportional increase with stand density. The mean tree biomass production by the stand was 129.81 kg tree-1 that varied with stand density. Biomass production at stand level showed a consistent increase with increasing stand density with highest produced corresponding to 2360 trees ha-1 stand (384.67 Mg ha-1) and lowest for 560 trees ha-1 stand (93.86 Mg ha-1). Component wise biomass allocation was highest for stemwood (63 %) followed by roots (20 %) for all the density regimes while twig portion registered the least (0.97 %). The mean tree C stocks and corresponding MAI for A. triphysa at 22 years of stand age were 74.54 kg tree-1 and 3.38 kg tree-1 yr-1 respectively which was comparable with many fast growing MPT’s similar growth habit in humid tropics. Elemental carbon storage at stand level showed proportionate increase with density (177.00 Mg ha-1, 2360 tree ha-1; 140.47 Mg ha-1, 1560 tree ha-1; 49.06 Mg ha-1, 900 trees ha-1 and 43.33 Mg ha-1, 560 trees ha-1). Allometric models were developed for total aboveground biomass, bole biomass, aboveground carbon sequestration, total volume and bole volume using dbh and height as predictor variables. Among various models tried single variable (dbh) quadratic equations were best fitting with high R2 value. The nutrient concentration varied substantially among various biomass components with foliage registering highest N, P and K concentration (%). Tissue nutrient concentration followed the general order: leaves> twig> branch> root> stemwood. Biomass nutrient stocks at stand level varied considerably with stand density which was closely following biomass production trends. Nutrient storage followed the order N > P > K with highest stocks corresponding to stemwood followed by roots, branchwood, leaves and twigs. High nutrient accumulation in the stemwood suggests possible higher levels of nutrient export from the site through harvest. Transfer of nutrient rich leaf biomass into the soil at harvest would be a viable strategy in this context that replenish the nutrient loss through harvest. Carbon and nutrient contents in the soil were substantially higher in all sampled depths implying the dominant role of trees in improving the soil productivity in wooded systems. Study converges to the generalization that A. triphysa trees have a good potential for volume and biomass production under proper silvicultural management regimes.ennullThesis