Vegetation Diversity, Biomass, and Conservation Status of Agricultural Buffer Zones in the Tukad Ayung Watershed, Bali

Abstract

The Tukad Ayung Watershed, the longest in Bali Province, functions as a vital buffer zone for food production areas. However, variation in vegetation composition across its upstream, midstream, and downstream regions has not been adequately examined in relation to ecosystem service capacity. This study aims to (1) analyze tree vegetation diversity, (2) assess its variation based on species origin (native/exotic) and growth status (planted/naturally grown), and (3) analyze aboveground tree biomass contribution to support sustainable food production. Vegetation diversity was evaluated using the Shannon–Wiener index, and basal area calculations were used to estimate aboveground tree biomass and carbon sequestration. Statistical significance in the distribution of tree origin, tree status, and biomass among the three villages (Belancan, Kerta, and Abiansemal) was tested using Pearson’s Chi-square test, while data visualization was performed with the ggplot2 package in R software version 4.3.3. The results showed Shannon–Wiener diversity indices (H') of 3.01 in Belancan Village, 2.79 in Abiansemal Village, and 2.67 in Kerta Village. Vegetation composition varied spatially, with endemic dominance in Belancan and Abiansemal and exotic dominance in Kerta driven by human cultivation. Aboveground tree biomass was highest in Abiansemal (704.81 kg/ha) and lowest in Kerta (380.37 kg/ha). The chi-square test indicated significant differences in biomass (χ2 = 582.76, df = 538, p = 0.089) among locations. These findings demonstrate that the Tukad Ayung Watershed has high vegetation diversity and biomass potential, emphasizing the importance of site-specific conservation and mixed-garden management strategies to maintain ecosystem stability and food security.