International Journal of Agriculture and Forestry

p-ISSN: 2165-882X    e-ISSN: 2165-8846

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 Dahal1, Gandhiv Kafle2

1Institute of Forestry, Hetauda, Nepal

2Faculty of Forestry, Agriculture and Forestry University, Hetauda, Nepal

Correspondence to: Gandhiv Kafle, Faculty of Forestry, Agriculture and Forestry University, Hetauda, Nepal.

Email:

Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved.

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/cm3 and 1.14 g/cm3 respectively.

Keywords: Carbon, Soil, Biomass, Alnus nepalensis

Cite this paper: Khila Nath Dahal, Gandhiv Kafle, Organic Carbon in Soil and Biomass of an Alnus nepalensis Forest in Kathmandu, Nepal, International Journal of Agriculture and Forestry, Vol. 3 No. 6, 2013, pp. 240-243. doi: 10.5923/j.ijaf.20130306.06.

Article Outline

1. Introduction
2. Materials and Methods
3. Results and Discussion
4. Conclusions
ACKNOWLEDGEMENTS

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 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 (CO2) 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 calculate the height of the measured pole of A. nepalensis.
Soil Measurement
Ten pits of 40cm depth were dug for soil sample collection in the study area. For the purpose of estimating bulk density, three individual soil samples of approximately 200 cm3, one each from two depths (0-10 cm, and 10-20 cm) were collected with the help of a standardized 200 cm3 metal soil sampling corers. Similarly for the purpose of analysing organic carbon, three individual soil samples of approximately 100 gram, one each from two depths (0-10 cm, and 10-20 cm) were collected.
Soil samples were placed in sample bags, labelled and transported to the laboratory for further analysis.
The overall field measurement methods were guided by ANSAB[22].
Vegetation Data Analysis
The following biomass model was used to estimate aboveground pole biomass as per guidelines given in[23] on the basis of climate and forest stand type.
AGPB = 0.0509 *ρD2H
Where,
AGPB = above ground biomass of pole (kg),
D = Diameter at Breast Height (cm),
ρ = Wood Specfic Gravity (g/cm3)
H = Height of tree (m).
After taking the sum of all the individual weights (in kg) and dividing it by the forest area, the biomass stock density was attained in kg m-2. This value was converted to t ha-1 by multiplying it by 10. The biomass stock density was converted to carbon stock density after multiplication with the IPCC[24] default carbon fraction of 0.47. Belowground pole biomass was estimated as 20% of aboveground pole biomass using MacDicken[25] root-to-shoot ratio value of 1:5.
Soil Data Analysis
Soil bulk density was determined using the soil core samples[26]. The soil organic carbon (SOC) concentration was determined by dry combustion of oven-dry soil samples[27].
Bulk Density of Soil = (Oven dry weight of soil in gram) / (Volume of the soil in cm3)
Soil Organic Carbon (ton per hectare) = Organic carbon content% × soil bulk density (gram/cm3) × soil layer depth (cm).

3. Results and Discussion

Biomass of Alnus nepalensis
The aboveground biomass and belowground biomass of A. nepalensis forest was found to be 62.21 t/ha and 12.44 t/ha respectively. Mean living biomass of A. nepalensis was found 74.65 t/ha in the forest (table 1).
Table 1. Biomass of Alnus nepalensis
     
Ranabhat et al.[28] found 91.92 t/ha living biomass in A. nepalensis forest in Kaski district of Nepal at altitude range of 1200-1300 m. This study found 74.65t/ha living biomass in A. nepalensis forest, the slight fluctuation can be referred to the absence of tree size of the species in the area and altitudinal variation.
Organic Carbon in Biomass of Alnus nepalensis Forest
The organic carbon content in aboveground and belowground biomass of A. nepalensis forest was 29.24 t/ha and 5.85 t/ha respectively. Mean organic carbon content in living biomass of A. nepalensis was found 35.09 t/ha in the forest (table 2).
Table 2. Vegetation carbon content of Alnus nepalensis
     
Ranabhat et al.[28] found 39 t/ha organic carbon in living biomass of A. nepalensis forest in Kaski district of Nepal at altitude range 1200-1300 m. This study found 35.09 t/ha organic carbon in living biomass in A. nepalensis forest, the slight fluctuation can be referred to the absence of tree size of the species in the area and altitudinal variation.
Soil Bulk Density
Soil bulk densities in soil depths 0-10 cm and 10-20 cm were 0.69 g/cm3 and 1.14 g/cm3 respectively (table 3). The soil density was found increasing with depth.
Organic Carbon Content in Soil
Organic carbon content in soil depths 0-10 cm and 10-20cm in A. nepalensis forest were 2.91% and 0.99% respectively. The mean organic carbon content up to 20 cm soil depth was 1.95%. Mean organic carbon stock in soil depths 0-10cm and 10-20 cm were 19.78 t/ha and 10.61 t/ha respectively, which differs significantly at 0.5% level of significance in ANOVA test. The mean organic carbon stock upto 20cm soil depth was 15.20 t/ha (table 3).
Table 3. Organic carbon and density status of soils in Alnus nepalensis forest
     
The soil organic carbon was found decreasing with soil depth.
Ranabhat et al.[28] found 43.3 t/ha organic carbon in soil upto 20cm depth of A. nepalensis forest in Kaski district of Nepal at altitude range 1200-1300 m. The slight fluctuation can be referred to the absence of tree size of the species in the area, limited litter deposition, decomposition and altitudinal variation.
Total Carbon Stock Measurement
Total organic carbon content in aboveground and below ground biomass in A. nepalensis forest was 29.24 t/ha and 5.85 t/ha respectively. Soil organic carbon stock was found 15.19 t/ha in the forest. Total organic carbon stock in the A. nepalensis forest was found 50.28t/ha (table 4).
Ranabhat et al.[28] estimated the total carbon sequestration potential of A. nepalensis forest to be 186.05 t/ha. In that case, the soil organic carbon was estimated upto 1m soil depth. The variation of the total organic carbon stock in the forest can be attributed to the variation in the site conditions, vegetation maturity level, soil profile depth for carbon estimation and altitude,
Table 4. Carbon stock in Alnus nepalensis forest
     

4. Conclusions

A comparison of the organic carbon stock values in soils of A. nepalensis forest show that the carbon stock tonnes per hectare decrease with soil depth upto 20cm from the ground level. The organic carbon content in living biomass of A. nepalensis was found around double than the total soil organic carbon content upto 20cm depth. Total organic carbon stock in the A. nepalensis forest was found 50.28 t/ha. Further studies on soil organic carbon in deep soil layers and A. nepalensis forest of varying age class are highly recommended for generalization of the findings.

ACKNOWLEDGEMENTS

The authors are highly grateful to the ComForM project of Institute of Forestry for supporting this research. We got sincere support from the user group committee members of the Rajat Uddhyan Community Forest during field work and are highly grateful to their involvement.

References

[1]  Luo, Y., Zhou, X. 2006. Soil respiration and the environment. Elsevier, Amsterdam, 316 pp.
[2]  Houghton R.A. 2007. Balancing the global carbon budget. Annual Review of Earth and Planetary Sciences 35, 313−347.
[3]  IPCC. 2007. Climate change 2007. The Physical Science Basis. Contribution of working group I to the fourth assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK.
[4]  Lambers, H., Chapin III, F.S., and Pons, T.L. 2008. Plant Physiological Ecology, 2nd ed. Springer, New York, USA, 604 pp.
[5]  IPCC. 2000. Special report on land use, land-use change, and forestry.[Watson R.T., Noble I.R., Bolin B., Ravindranath N.H., Verardo D.J., Dokken D.J. (Eds.)]. IPCC, Cambridge University Press, Cambridge, UK. 377 pp.
[6]  Geider R.J., Delucia E.H., Falkowski P.G. 2001. Primary productivity of planet earth: biological determinants and physical constraints in terrestrial and aquatic habitats. Global Change Biology 7, 849−882.
[7]  Janzen, H.H. 2004. Carbon cycling in earth systems, a soil science perspective. Agriculture, Ecosystem and Environment 104, 399−417.
[8]  Roxburgh, S.H., Wood, S.W., Mackey, B.G., Woldendorp, G., and Gibbons, P. 2006. Assessing the carbon sequestration potential of forests: a case study from temperate Australia. Journal of Applied Ecology 43, 1149−1159.
[9]  Bonan G.B. 2008. Forests and climate change: forcings, feedbacks, and the climate benefits of forests. Science 320, 1444−1449.
[10]  Malhi, Y., Baldocchi, D.D., and Jarvis, P.G. 1999. The carbon balance of tropical, temperate and boreal forests. Plant, Cell and Environment 22, 715−740.
[11]  Bajracharya, R.M., Lal, R., and Kimble, J.M. 1998. Soil organic carbon distribution in aggregates and primary particle fractions as influenced by erosion phases and landscape po-sition. p. 353–367.
[12]  Phillips, O.L., Malhi, Y., Higuchi, N., Laurance, W.F., Nunez, P.V., Vasquez, R.M., Laurance, S.G., Ferreira, L.V., Stern, M., Brown, S., and Grace, J. 1998. Changes in the carbon balance of tropical forests: evidence from long-term plots. Science 282(5388):439–442
[13]  Lal, R. 2004. Soil Carbon Sequestration to Mitigate Climate Change. Geoderma 123:1-22.
[14]  Smith, P. 2004. Carbon sequestration in croplands: the potential in Europe and the global context. Eur J Agron 20(3): 229–236
[15]  Ostrowska, A., Porębska, G., Kanafa, M. 2010. Carbon Ac-cumulation and Distribution in Profiles of Forest Soils. Polish J. of Environ. Stud. Vol. 19, No. 6, 1307-1315.
[16]  FAO, 2006. Global Forest Resources Assessment 2005. FAO Forestry Paper 147. Rome: Food and Agriculture Organization.
[17]  Bajracharya, R.M., Sitaula, B.K., Shrestha, B.M., Awasthi, K.D., Balla, M.K. & Singh, B.R. 2004. Soil Organic Carbon Status and Dynamics in the Central Nepal Middle Mountains. Forestry, 12.
[18]  Jobb´agy, E. G. and Jackson, R. B.2000. The vertical distri-bution of soil organic carbon and its relation to climate and vegetation, Ecol. Appl., 10, 423–436.
[19]  Wang, S. Q., Huang, M., Shao, X. M., Mickler, R. A., Li, K. R., and Ji, J. J. 2004. Vertical distribution of soil organic carbon in China, Environ. Manage., 33(Suppl.1), S200–S209.
[20]  Mi, N., Wang, S. Q., Liu, J. Y., Yu, G. R., Zhang, W. J., and Jobb´agy, E. G. 2008. Soil inorganic carbon storage pattern in China, Global Change Biol., 14, 2380–2387.
[21]  Fontaine, S., Barot, S., Barre´ , P., Bdioui, N., Mary, B., and Rumpel, C. 2007. Stability of organic carbon in deep soil layers controlled by fresh carbon supply, Nature, 450, 277–280.
[22]  ANSAB. 2010. Forest Carbon Stock Measurement: Guide-lines for measuring carbon stocks in community- managed forests. ANSAB, Kathmandu, Nepal. 79pp.
[23]  Chave, J; Andalo, C; Brown, S; Cairns, MA; Chambers, JQ; Eamus, D (2005) Tree allometry and improved estimation of carbon stocks. Oecologia , 87-99
[24]  IPCC. 2006. Good practice guidelines for National Greenhouse gas inventories. Intergovernmental Panel on Climate Change, Switzerland.
[25]  MacDicken, K.G. 1997 A Guide to Monitoring Carbon Storage in Forestry and Agro-forestry Projects. Winrock International, Arlington, USA.
[26]  Blake, G.R. and Harte, K.H. 1986. Bulk Density, p. 363-375, In A. Klute, ed. Methods of Soil Analysis Part 1. Physical and Mineralogical Methods-Agronomy Monograph (2nd Edition). American society of agronomy-soil science society of America.
[27]  Nelson, D.W., and Sommers, L.E. 1982. Total Carbon, Organic Carbon and Organic Matter, p. 539-580, In A. L. Page, R. M. Miller and D. R. Keeney, eds. Methods of Soil Analysis Part 2. Chemical and Microbiological Properties, 2nd Ed. American Soc. Of Agron. Monograph No. 9, ASA-SSSA, Inc., Madison, WI, USA.
[28]  Ranabhat, S., Awasthi, K.D. and Malla, R. 2008. Carbon stock in Alder Forest in Kaski District of Nepal.