Estimation of carbon stocks in the forest plantations of Sri Lanka

W A J M De Costa,H.R Suranga

doi:10.4038/jnsfsr.v40i1.4166

Abstract

Forest plantations have the ability to sequester carbon in their biomass and reduce the rate of increase of atmospheric carbon dioxide. Therefore, plantation forestry forms an important option for mitigating global warming and consequent climate change. The objective of the present study was to estimate the biomass and carbon stocks of the existing forest plantations in Sri Lanka. Height and diameter measurements of the trees at breast height from 22 monocultures and 51 mixed-cultures, established and maintained by the Forest Department, were obtained from the FORDATA data base and used to calculate the existing carbon stocks using allometric relationships. The total estimated monoculture C stock in 2008 amounted to 4.23 million metric tons in an area of 57618.8 ha. Around 89% of this total C stock in monocultures is contributed by five tree species, namely, Pinus caribaea (44%), Tectona grandis (21%), Eucalyptus grandis (11%), Eucalyptus camaldulensis (7%) and Swietenia macrophylla (6%), occupying 92% of the area. Total C stock in mixed cultures in 2008 amounted to 0.681 million tons in 5949.6 ha. Five mixed cultures, i.e. Eucalyptus robusta and E. grandis (17%), Pinus mixed (13%), E. grandis and E. microcorys (12.5%), Eucalyptus mixed (7%) and Acacia mangium and A . auriculiformis (5%), contributed to 55% of this C stock. Monocultures, which showed the highest per ha C stocks were Pinus caribaea in Badulla (205 t ha-1) and Nuwara Eliya (164 t ha-1) and Eucalyptus grandis in Ratnapura (197 t ha-1) and Nuwara Eliya (168 t ha-1). Mixed plantations of Acacia decurrens and different species of Eucalyptus grown in Nuwara Eliya showed the highest combined per ha C stocks ranging from 226 – 279 t ha-1. The maximum per ha C stock in some of the Sri Lankan forest plantations in different climatic zones were either on par or above the benchmark average C stock values specified by the IPCC for the respective climatic zones. Age distribution of the monoculture C stocks showed that the highest percentage (i.e. 39%) was in the 21-30 year plantations, followed by the 31-40 year plantations (32%). Keywords: Carbon sequestration, climate change mitigation, forest biomass, tropical forests. DOI: http://dx.doi.org/10.4038/jnsfsr.v40i1.4166 J.Natn.Sci.Foundation Sri Lanka 2012 40 (1): 9-41

Highlights

In Sri Lanka, forest plantations have been established since 1880s to meet the increasing demand for timber and fuelwood, with soil conservation in important watersheds being an additional benefit (Pushparajah, 1987; Sahajananthan, 1987)
Around 89% of this total C stock in monocultures is contributed by five tree species, namely, Pinus caribaea (44%), Tectona grandis (21%), Eucalyptus grandis (11%), Eucalyptus camaldulensis (7%) and Swietenia macrophylla (6%), occupying 92% of the area
Carbon stock values calculated in the present study can be considered as the first overall estimates of carbon stocks in the Sri Lankan forest plantations

Summary

Introduction

In Sri Lanka, forest plantations have been established since 1880s to meet the increasing demand for timber and fuelwood, with soil conservation in important watersheds being an additional benefit (Pushparajah, 1987; Sahajananthan, 1987). Almost all the existing plantations have been established after the 1950s and consist of fast-growing exotic trees such as species of Eucalyptus, Pinus and Acacia along with teak and mahogany (Vivekanandan, 1987). In addition to their industrial timber products, the importance of forest plantations has increased substantially during the last two decades, in view of the increased awareness on global climate change and the role of forests in regulating the global carbon cycle (Dixon et al, 1994; Clark et al, 2003; Clark, 2004a; Houghton, 2005). Plantation forestry forms an important option for climate change mitigation (IPCC, 2007; Nabuurs et al, 2007)

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