Estimation of Aboveground Carbon Stocks in Selected Homegardens in Five Agro Ecological Regions of the Low Country Intermediate Zone of Sri Lanka

Abstract

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. As a consequence,global average temperature is projected to increase by 1.4 to 5.8 0C over the period of 1990 to2100. Forest based land use systems such as natural forests, forest plantations and agroforestrysystems store carbon in their biomass leading to reduction of the atmospheric Carbon dioxidelevels. Management of forests and agroforestry systems is identified as the most promisingoption to mitigate atmospheric Carbon dioxide (CO2). The objective of the present study was toinvestigate the carbon storage of homegardens located in the dry intermediate zone of Sri Lanka.

Homegardens were selected based on the agro ecological regions and three homegardens eachwere taken for detailed studies in the 5 agro ecological regions (IL1), (IL2), (IL3), (IL1–L2),(IL1–L3) and the locations of the gardens were Kurunegala, Chilaw, Mahiyangana, Monergala,Wellawaya and Tangalle. In each garden transects were laid to capture the maximum diversityusing the Point Centre Quarter Method (PCQM) and a sampling intensity of around 60% wasobtained from each garden. Dbh and height were measured in each tree. Non woody trees andwoody trees having < 1cm dbh were excluded. Allometric regression equation AGB = 0.0509 xq D2H [AGB – abovegroud biomass (kg); D – dbh (cm) and H (height (m)] was used to estiamtethe aboveground biomass while Wc =W * 0.5 (Wc –carbon weight, W – above ground dryweight) was used to estimate the carbon content.

According to the results, 55 woody species were recorded from the homegardens. Theaboveground carbon stock was highest in the gardens in Chilaw (345.88 t/ha) followed bygardens in Wellawaya (287.41 t/ha), gardens in Kurunegala (274.66 t/ha), gardens in Tangalle(229.57 t/ha), gardens in Mahiyangana (191.32 t/ha). The gardens in Moneragala recorded thelowest 9149.58 t/ha).