Abstract:
Dry zone forest systems in Sri Lanka provide essential
environmental services,
including carbon sequestration, biodiversity conservation, and water cycle regulation,
critical for sustaining the region's ecological balance. The Katupotha Forest, with its
diverse vegetation and unique ecological dynamics, exemplifies the complex interaction
between human activity and natural habitats in the dry zone. Soil Microbial Biomass
Carbon (MBC), a vital indicator of soil health and fertility, plays a key role in or ganic
matter decomposition and nutrient cycling. Numerous studies have been conducted on
MBC and soil available macronutrients in Sri Lanka s wet zone forests, but research on
the dry zone forests remains limited. Therefore, this study has aimed to assess the
current status of MBC and soil available macronutrients (available phosphate, nitrate
and ammonium) in the soils of the Katupotha tropical dry zone forest systems in
Mihintale, Sri Lanka and to investigate the interrelationships among them. Soil sample s
were obtained from the above ground level (0 15 cm) of the Katupotha forest using the
Stratified Random Sampling technique. The Soil MBC and available macronutrients
were analysed using standard protocols. Pearson Correlation analysis was used for
analysing the results. The results revealed that the MBC varied from 0.045% t o 0.283%
with a mean value of 0.1695%. Soil available phosphate ranged from 0.244 µg/g soil to
5.166 µg/g soil, having a mean value of 1.791 µg/g soil. While the soil available nitrate
varied from 0.781 µg/g soil to 16.629 µg/g soil with a mean value of 7. 432 µg/g soil,
and the soil available ammonium ranged from 4.122 µg/g soil to 51.047 µg/g soil with
a mean of 14.230 µg/g soil. Accordingly, MBC was positively correlated with the soil
available ammonium (p= 0.012) and MBC had a negative correlation with s oil available
phosphate (p= 0.047). According to similar studies done on the Knuckles Forest Range
which belongs to the wet zone, the Sub Montane Forests showed MBC of 0.053%,
Montane Forests had 0.035% and Open Sparse Forests with an MBC of 0.048%. It i s
noticeable that even though the minimum MBC recorded in Katupotha dry zone forest
is lower than that of the Sub Montane Forests and Open Sparse Forests, the Montane
Forests exhibit a comparatively lower MBC than that of the Katupotha tropical dry zone
fo rest systems. The findings of this study underscore the significant role of soil
microbial biomass carbon in providing valuable implications for maintaining ecological
health and future forest conservation and projects on combating climate change.
