AUTHOR: Tshering Dorji, Tsheten Dorji, Sangita Pradhan, Dawa Tashi, Karma Dema Dorji
Soil organic carbon (SOC) plays an integral part in improving soil security, water security, food security, energy security, climate change abatement, biodiversity protection, and ecosystem services. It is important to understand its stock and spatial distribution for better management. However, not many countries have managed to map their national SOC stock and Bhutan is no exception. There is paucity of SOC information to clearly formulate plans and programs to increase Carbon (C) sequestration and enhance SOC storage in the country. A preliminary mapping of SOC stock of Bhutan for the top 30 cm depth was carried out to establish a baseline and contribute to global SOC mapping. A total of 993 data points was used for mapping SOC stock using regression kriging (RK). Regression tree model and ordinary kriging were used to perform the RK with elevation, land use land cover (LULC), slope, aspect, profile and plan curvatures, normalized difference vegetation index, SAGA wetness index, mean precipitation, mean temperature, geology, and terrain ruggedness index as environmental covariates. The model validation was done by repeated data splitting method. Preliminary results show that for the top 30 cm depth, Bhutan stores about 0.4 giga tonne carbon (GtC) with SOC density ranging from 0.5 to 315.3 ton ha-1. Among the environmental covariates, LULC, topography, and climatic factors had significant influence on SOC stock and its spatial distribution. SOC stock was relatively low in the southern and eastern regions as opposed to the western and northern parts of the country. Under different LULC types, the SOC stock was lowest under agriculture land and highest under forest. These results are based on a small set of soil data and must be used with caution. However, for better SOC stock estimation and mapping, more and well distributed soil data will be necessary.
Soil Organic Carbon, Mapping, Land use land cover
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ASRIS. (2011). ASRIS – Australian Soil Resource Information System. http://.asris.csrio.au. Accessed November 7, 2012.
Baillie, I. C., Tshering, K., Dorji, T., Tamang, H. B., Dorji, T., Norbu, C. (2004). Regolith and soils in Bhutan, Eastern Himalayas. European Journal of Soil Science, 55(1), 9-27. doi:10.1046/j.1365-2389.2003.00579.x
Baldock, J. A., Wheeler, I., McKenzie, N., & McBrateny, A. (2012). Soils and climate change: potential impacts on carbon stocks and greenhouse gas emissions, and future research for Australian agriculture. Crop and Pasture Science, 63(3), 269-283. doi:http://dx.doi.org/10.1071/CP11170
Bishop, T. F. A., McBratney, A. B., & Laslett, G. M. (1999). Modelling soil attribute depth functions with equal-area quadratic smoothing splines. Geoderma, 91(1–2), 27-45. doi:http://dx.doi.org/10.1016/S0016-7061(99)00003-8
Blake, G. R., Hartge, K. H., & Klute, A. (1986). Bulk density. Methods of soil analysis. Part 1. Physical and mineralogical methods. SSSA Book Series, 363-375.
Caspari, T., Bäumler, R., Norbu, C., Tshering, K., & Baillie, I. (2006). Geochemical investigation of soils developed in different lithologies in Bhutan, Eastern Himalayas. Geoderma, 136(1–2), 436-458. doi:10.1016/j.geoderma.2006.04.017
Dorji, T., Caspari, T., Bäumler, R., Veldkamp, A., Jongmans, A., Tshering, K. (2009). Soil development on Late Quaternary river terraces in a high montane valley in Bhutan, Eastern Himalayas. CATENA, 78(1),48-59. doi:10.1016/j.catena.2009.02.018
Dorji, T., Odeh, I. O. A., Field, D. J., & Baillie, I. C. (2014). Digital soil mapping of soil organic carbon stocks under different land use and land cover types in montane ecosystems, Eastern Himalayas. Forest Ecology and Management, 318(0), 91-102. doi:http://dx.doi.org/10.1016/j.foreco.2014.01.003
FAO (Cartographer). (2017). Global Soil Organic Carbon Map
Jobbágy, E. G., & Jackson, R. B. (2000). The vertical distribution of soil organic carbon and its relation to climate and vegetation. Ecological Applications, 10(2), 423-436.
LCMP. (2010). Land cover mapping project. Technical Report. Ministry of Agriculture and Forests, Royal Government of Bhutan, Thimphu. http://www.nssc.gov.bt/bhutan-landcover-assessment-2010 (accessed on 29 September 2012).
McBratney, A., Field, D. J., & Koch, A. (2014). The dimensions of soil security. Geoderma, 213, 203-213.
McBratney, A. B., Mendonça Santos, M. L., & Minasny, B. (2003). On digital soil mapping. Geoderma, 117(1–2), 3-52. doi:10.1016/s0016-7061(03)00223-4
Minasny, B., & McBratney, A. B. (2007). Spatial prediction of soil properties using EBLUP with the Matérn covariance function. Geoderma, 140(4), 324-336. doi:http://dx.doi.org/10.1016/j.geoderma.2007.04.028
Minasny, B., & McBratney, A. B. (2008). Regression rules as a tool for predicting soil properties from infrared reflectance spectroscopy. Chemometrics and Intelligent Laboratory Systems, 94(1), 72-79. doi:http://dx.doi.org/10.1016/j.chemolab.2008.06.003
Minasny, B., McBratney, A. B., Mendonça-Santos, M. L., Odeh, I. O. A., & Guyon, B. (2006). Prediction and digital mapping of soil carbon storage in the Lower Namoi Valley. Soil Research, 44(3), 233-244. doi:http://dx.doi.org/10.1071/SR05136
Minasny, B., McBratney, A. B., & Whelan, B. M. (2005). VESPER version 1.62. Australian Centre for Precision Agriculture, McMillan Building A05, The University of Sydney, NSW 2006. http://www.usyd.edu.au/su/agric/acpa (accessed on 1st July 2012).
Odeh, I. O. A., McBratney, A. B., & Chittleborough, D. J. (1995). Further results on prediction of soil properties from terrain attributes: heterotopic cokriging and regression-kriging. Geoderma, 67(3–4), 215-226. doi:10.1016/0016-7061(95)00007-b
Singh, S. P., Singh, V., & Skutsch, M. (2010). Rapid warming in the Himalayas: ecosystem responses and development options. Climate and Development, 2(3), 221(212).
Walkley, A., & Black, I. A. (1934). An examination of the Degtjareff method for determining soil organic matter, and a proposed modification of the chromic acid titration method. Soil Science, 37(1), 29-38. doi:10.1097/00010694-193401000-00003