Estimation of carbon stock in Kandyan Homegardens located in Kandy and Matale

Abstract

Increasing levels of atmospheric greenhouse gases due to fossil fuel use, deforestation and other anthropogenic sources have changed the global climate. Global warming is the most widespread problem of the new millennium. Carbon dioxide (CO2) is the most important greenhouse gas released as a result of human activities. “Stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” is the main objective of the UNFCCC. To help achieve this, the Protocol allows developed nations to credit removals of greenhouse gas emissions by natural sinks that store carbon. Forest based land use systems such as natural forests, forest plantations and agroforestry systems sequester CO2, through the C stored in their biomass. Management of forests and agroforestry systems is identified as the most promising option to mitigate atmospheric Carbon dioxide (CO2). The objective of the present study was to investigate the carbon sequestration potential of Kandyan Homegarden in Sri Lanka located in Kandy and Matale District.

Two representative gardens were selected from each District in Kandy and Matale. After conducting a comprehensive vegetation survey done in 16, 10 x 10m plots in each garden in a 1 ha area located to capture the maximum variability in terms of tree density, topographic and edaphic differences. All the trees were measured for dbh and height and from the results dominant tree species which contribute to the long term carbon sequestration were selected using Important Value Index. Trees were then categorized into diameter classes and a tree each from each diameter class was selected for detailed measurements including stem and canopy volume. Representative number of trees per diameter class was destructively sampled to get the weight measurements and these were used to extrapolate the weight of the rest of the trees according to the volumes estimated. In this way the total aboveground biomass and carbon lodged in these gardens were arrived at. The potential to sequester carbon dioxide without being emitted to the atmosphere was also calculated for the individual gardens and extrapolated to all the Homegardens in the particular district.

According to the results, average total aboveground carbon content that could be lodged in the Homegardens and total carbon dioxide that can be stored as carbon without being emitted to the atmosphere in Kandy District (Agro ecological zone WM3a) are 89.98 t C/ha and 330.23 t C/ha and are 103.89 t C/ha and 381.27 t C/ha in Matale District (Agro ecological zone IUI) respectively. According to the Forestry Sector Master Plan (1995) the total extent of the Homegardens in Kandy District is 61,029 ha and 20,258 ha in Matale District. Therefore total aboveground carbon content and carbon dioxide stored in the form of carbon in the Homegardens in Kandy District vary between 5,397,404 t C (5 x 106) – 5,585,374 (5 x 10 6) t C and 19,888,182 t C (19.89 x 106 ) – 20,499,030 t C (20.45 x 106 ) respectively. In Matale District the total aboveground carbon content and carbon dioxide stored as carbon in homegardens vary between 2,455,674 t C (2.45 x 10 6 ) – 1,753,532 t C (1.75 x 10 6) and 9,012,176 t C (9.00 x 10 6 ) – 6,435,358 t C (6.44 x 10 6 ) respectively. Annual litterfall rate of selected Homegarden system in Kandy District is 8.16 t/ha and 9.38 t/ha in selected Homegarden in Matale District. Mean annual litterfall rate in Kandyan Homegarden system is equal to 8.77 tons ha-1 year-1.