Methods

Study sites —

The case study pertains to Devaravattikan (14^o 18′ 23"N lat ,74^o 52′ 14"E long), a 1.8 ha sized sacred grove in the Mattigar village of Siddapur taluk in the Uttara Kannada district of central Western Ghats region of Karnataka. The grove is surrounded by agricultural fields towards one side and Acacia plantation and village settlement on other sides. The region receives south-west monsoon during June to October with an average annual rainfall 3000-4500 mm. and temperature ranges between 15^o – 38^o C. Geologically, this area is mostly made up of large out crops of granites and soil is sandy-loamy type (Forest Working plan 2003).

Vegetation analysis —

Tree species (>30 cm in girth) of the grove were enumerated in 1991 and in 2009. Tree height and girth at breast height (GBH) were recorded. Transect cum quadrat method was used for shrub and herb layers . Quadrats measuring 5 m X 5 m were laid for shrub layer and within the shrub quadrat smaller sub-quadrats of 1 m X 1 m were laid for herb study.

Species diversity, dominance and richness were calculated following Shanon-Weiner index (Shanon and Wiener 1963), Simpson dominance index (Simpson 1949) and species richness index (Margaleaf 1958). Woody species were arranged into several girth class categories to understand the population structure.

Carbon estimation  —

Species level above ground biomass was calculated through basal area equations and an indirect estimation was done for calculating below ground biomass (Murali et al. 2005; Ravindranath and Ostwald 2008).

Above Ground Biomass (AGB) (t/ha) =   -2.81 + 6.78 (BA), r² = 0.53, BA = Basal area in m²/ha.
Below Ground Biomass (t/ha) = 0.26 * AGB

The resultant biomass was multiplied by 0.5 for estimating carbon storage. Changes in the biomass and carbon stock in the fragment after 18 years were computed by deducting the benchmark year values from the final year values. The annual average gain or loss of carbon was calculated by dividing the net change for the study period, i.e., 18 years.