Microbial Biomass C, N and P in Disturbed Dry Tropical Forest Soils, India

Variations in microbial biomass C (MB-C), N (MB-N) and P (MB-P) along a gradient of different dominant vegetation covers (natural forest, mixed deciduous forest, disturbed savanna and grassland ecosystems) in dry tropical soils of Vindhyan Plateau, India were studied from January 2005 to December 2005. The water holding capacity, organic C, total N, total P and soil moisture content were comparatively higher in forest soils than in the savanna and grassland sites. Across different study sites the mean annual MB-C, MB-N and MB-P at 0–15 cm soil depth varied from 312.05 ± 4.22 to 653.40 ± 3.17, 32.16 ± 6.25 to 75.66 ± 7.21 and 18.94 ± 2.94 to 30.83 ± 23.08 μg g−1 dry soil, respectively. At all the investigated sites, the maximum MB-C, MB-N and MB-P occurred during the dry period (summer season) and the minimum in wet period (rainy season). In the present study, soil MB-C, MB-N and MB-P were higher at the forest sites compared to savanna and grassland sites. The differences in MB-C, MB-N and MB-P were significant (P < 0.001) among sites and seasons. The MB-C (P < 0.0001), MB-N (P < 0.001) and MB-P (P < 0.0001) were positively correlated with organic C, while the relationship between soil moisture and MB-C, MB-N and MB-P (P < 0.001, P < 0.01 and P < 0.0001, respectively) was negative. The decreasing order of MB-C, MB-N and MB-P along study ecosystems was natural forest > mixed deciduous forest > savanna > grassland. The results suggested that deforestation and land use practices (conversion of forest into savanna and grassland) caused the alterations in soil properties, which as a consequence, led to reduction in soil nutrients and MB-C, MB-N and MB-P in the soil of disturbed sites (grassland and savanna) compared to undisturbed forest ecosystems.