Physico-chemical, biochemical and microbial characteristics of soils of mangroves of South Andaman: impacts of anthropogenic disturbances.

摘要

The impacts of anthropogenic disturbances like cutting of mangrove for fuelwood, making poles and fencing purposes and also illegal encroachment of mangrove area on the physico-chemical, biochemical and microbial characteristics of soils (0-30 cm) of major mangroves of South Andamans, India, viz., Rhizophora mucronata, R. apiculata, Bruguiera gymnorrhiza, Xylocarpus granatum, Ceriops tagal and Nypa fruticans were the focus of this study. For this purpose we included soils from the inter-tidal areas of 10 disturbed and undisturbed mangrove forest sites of South Andaman. Soil pH, clay, cation exchange capacity, Al2O3 and Fe2O3 levels exhibited minimum variation between the disturbed and undisturbed sites. In contrast, organic C, total N, Bray P and K levels exhibited marked variation between the sites and were considerably lower at the disturbed sites. In comparison to the undisturbed sites, the levels of all the general and specific biochemical parameters were considerably lower at the disturbed sites due mainly to significant reductions in organic matter/substrate levels. The study also indicated the low N availability and the possibility of fungi dominating over bacteria at both the mangrove sites. Overall, the study suggested that the number and activity of soil microorganisms depend mainly on the quantity of mineralizable substrate and the availability of nutrients in these mangrove soils..