Comparative enumeration for dominant species in selected natural forests, North Central Province, Sri Lanka to be used in assessment of Carbon sequestration

Abstract

With the increasing attention placed on climate change as the prime environmental hazard, more and more attention is on the forest ecosystems as sinks of carbon dioxide. At the International Convention on Climate Change in 1992 and subsequently the Kytoto Protocol Clean Development Mechanisms were introduced and one of its clauses was the trading of carbon between developing and developed countries. Despite the recognized potential of forests as an important sink to sequester carbon, accurate estimates of the carbon sequestration potential of different ecosystems or their component species are lacking especially in Sri Lanka. Out of the natural forests, the work done in this area on the dry zone forests is minimal.

Monteith (1972 & 1977) showed that the rate of biomass production is directly proportional to the amount of radiation intercepted by the foliage canopy. The above relationship can be given as: W = e RI , Where, W is the amount of total biomass (above and belowground biomass) produced and RI is the amount of radiation intercepted by canopy. The proportionality constant, e is termed as Radiation Use Efficiency (RUE). In order to find the carbon sequestration of particular ecosystem it is imperative to find the radiation use efficiency of dominant species which is being taken as the Important Value Index. This study reports the findings of the comparative assessment of  3 forest ecosystems ie Padawiya Proposed Reserve, Weddakanda Proposed Reserve  (PR) and Nagalakanda Proposed Reserve (PR) which are located in DL 1 a, DL 1 b and DL 1 c agro-ecological regions respectively for their dominant species. Padewiya PR lay on almost flat land and others are on isolated mountains. Elevation levels distributed between 55m to 210m from Mean Sea Level (MSL). Circular shape sample plots were located representing whole area and low, mid and high elevations.

No of species and no of families were resulted as Padawiya PR 30, 17, Weddakanda PR 37, 18 and Nagalakanda PR 40, 25 respectively. Stem density (for all species) of Padawiya, Weddakanda PR, and Nagalakanda PR were recorded as 526, 1800 and 2038 stems ha-1. Basal area of the selected forest (for all species) was 35.0, 45.2 and 51.8 m2ha-1 respectivly. Relative density, relative basal area and relative frequency were calculated for each species. According to   Important Value Index (IVI) dominant species are ranked as higher values are most dominant. Most dominant five species for Padawiya PR are Drypetes sepiaria, Syzygiyum cordifolium, Terminalia arjuna, Diospyros ovalifolia, and Wrightia angustifolia. Most dominant five species for Weddakanda PR are Drypetes sepiaria, Diospyros ebenum, Croton officinalis, Diospyros ovalifolia and Pterospermum suberifolium. As well as Mallotus walkerae, Drypetes sepiaria, Ficus tinctoria, Pterospermum suberifolium, and Glycosmis angustifolia are the most dominant species for Nagalakanda PR.