International Journal of A griculture and Forestry 2013, 3(6): 240-243 DOI: 10.5923/j.ijaf.20130306.06 Organic Carbon in Soil and Biomass of an Alnus nepalensis Forest in Kathmandu, Nepal Khila Nath Dahal 1 , Gandhiv Kafle 2,* 1 Institute of Forestry, Hetauda, Nepal 2 Faculty of Forestry, Agriculture and Forestry University, Hetauda, Nepal Abstract This article reports the results of measuring organic carbon contents in biomass and soil of an Alnus nepalensis forest in Kathmandu. The aboveground and belowground biomass of A. nepalensis were 62.21 t/ha and 12.44 t/ha respectively in the forest. The aboveground and belowground carbon stock in the forest were 29.24 t/ha and 5.85 t/ha respectively. Average organic carbon stock in soil depths 0-10 cm and 10-20 cm were found 19.78 t/ha and 10.61 t/ha respectively. The mean organic soil carbon stock in 0-20 cm soil depth was found 15.20 t/ha and in living biomass was found 35.09 t/ha. The organic carbon stock in 0-10cm soil depth was found 1.86 times more than in soil depth of 10-20 cm. Carbon stored in living vegetation biomass is 2.31 times more than soil organic carbon in the forest upto 20cm soil depth. Soil bulk density in 0-10 cm and 10-20cm soil depths were found 0.69 g/cm 3 and 1.14 g/cm 3 respectively. Keywords Carbon, Soil, Biomass, Alnus nepalensis 1. Introduction The exchange of carbon between the atmosphere and terrestrial ecosystems (soil and vegetation) is critical to the patterns of carbon dioxide concentration in the atmosphere [1][2][3][4]. The carbon pool in a terrestrial ecosystem can be broadly categorized into biotic (vegetative carbon) and pedologic (soil carbon) components. Forests are the largest carbon stock in terrestrial ecosystems[5][6][7][8][9] and estimated to be about 1150 Gg, of which 49% is in boreal forests, 37% in tropical forests and 14% in temperate forests[10]. Soils are viable sinks of atmospheric carbon (C) and may significantly contribute to mitigation of global climate change[11][12] [13][14]. Soil organic carbon (SOC) stocks in forest soils fluctuate from 50 to more than 200 Mg/ha, depending upon the climate and soil conditions, the age and type of the tree stand, and management practices[15]. A study by FAO[16] showed that 496 million metric tons of organic carbon is stored in soils at forest and shrub land of Nepal. Bajracharya et al.[17] estimated soil organic carbon storage in Nepal's middle hills to be around 423.7 mt C. By depth, forest and shrub land have higher amount of soil organic carbon (2.0% and 2.3% respectively) than the cultivated soils in the top layer between 1 and 30 cm. Vertical patterns of Soil Organic Carbon (SOC) can * Corresponding author: gkafle@scientist.com (Gandhiv Kafle) Published online at http://journal.sapub.org/ijaf Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved contribute as an input or as an independent validation for biogeochemical models and thus provide valuable information for examining the responses of terrestrial ecosystems to global change[18][19][20]. Thus, improved knowledge of distribution of SOC across different soil depth is essential to determine whether carbon in deep soil layers will react to global change and accelerate the increase in atmospheric carbon dioxide (CO 2 ) concentration [21]. In this context, this research was carried out to quantify levels of organic carbon in soil at two depths and biomass of an Alnus nepalensis Forest in Kathmandu, Nepal. 2. Materials and Methods The study was conducted in Rajat Uddhyan Community Forest, located in Mulpani-6, in Kathmandu District of Nepal. It is about 3 km away from Chabahil Chowk. The forest is a community managed forest with 1.5 hectares area. Alnus nepalensis is dominant species with more than 90 percent coverage. The A. nepalensis in the forest are only of pole sizes. Vegetation Measurement The area of forest was 1.5 hectares, so all the poles of A. nepalensis were measured for diameter and height. Diameter at breast height (Dbh) was measured using diameter tape. The distance between the A. nepalensis pole and measurer was measured using Linear Tape. Ground slope, and top and bottom angle to the pole of A. nepalensis was measured using Clinometer. The information thus taken was used to