Abstract
Aim of the study: The aim of the study was to assess the seasonal dynamics of microbial biomass and its contribution to soil system along a fragment size gradient in subtropical humid forest of Meghalaya. Area of study: The study was conducted in forest fragments located at Jarain and adjoining areas in Jaintia Hills of Meghalaya, northeast India.Material and Methods: Forest fragments of sizes ranging from 3.8 to 105 ha were selected for the study and grouped into Small (< 5 ha), Medium (> 5 and < 15 ha), Large (>15 and < 50 ha) and Very Large (105 ha) classes. Three experimental plots each of 20 x 20 m were established at the forest edge and at 50 m distance assigned as ‘interior’ microsite in each of the fragments for sampling of soil. Soil samples (0-10 cm depth) from each of the experimental plots were collected in replicates on seasonal interval and microbial biomass was estimated by the fumigation extraction method.Important findings: Microbial biomass- C, -N and -P varied significantly (p< 0.05) between the fragment sizes, microsites and seasons. The microbial biomass was higher in the interior as compared to the edge. It was also high during the winter season. Overall, soil microbial biomass -C, -N and -P ranged from 260 to 969; 25 to 95 and 8 to 67 µg g-1 respectively. The contribution of microbial biomass -C, -N and -P to soil organic carbon, total Kjeldahl nitrogen and phosphorus ranged from 1.48 to 1.81 %, 2.54 to 4.54 % and 3.41 to 5.22 % respectively. Fragmentation alters the microenvironmental conditions and soil properties that in turn affect the microbial biomass. Highlights: This interaction of plant, soil and microbial community would gradually degrade in the fragments due to change in vegetation composition and structure, microclimatic conditions and soil physical and chemical properties. Our results suggests that microbial mediated ecosystem processes such as nutrient cycling are more susceptible to variation at the edge which may become unstable and unpredictable in forest fragments exposed to various human disturbances.Keywords: fragment size, microbial biomass, microenvironment, subtropical forest.
Highlights
Fragmentation of forests has been identified as a major cause of biodiversity loss
Forest fragmentation leads to a shift in ecological traits of dominant species and reduces the buffering ca pacity of microclimate at the edge (Zhu et al, 2004)
The forest in the study area occurs in the form of patches and was once part of the same continuous forests that got fragmented over time due to human disturbances such as road construction, shifting cultivation and mining (Pao & Upadhaya, 2017)
Summary
Fragmentation of forests has been identified as a major cause of biodiversity loss It leads to edge creation and alter the microclimatic conditions that may have deleterious effect on ecosystem structure and function (Chen et al, 1999; Ibanez et al, 2014). Studies have shown that the litterfall increases in the forest edge with high nutrient concentration (Sizer et al, 2000) but often displays decrease decomposition rate (Moreno et al, 2014; Ruitta et al, 2012). Such changes may affect the soil nutrient balance in the edge (Bierregaard et al, 1992). In fragmented forests, changes in microbial population and invertebrate activity may lead to reduced decomposition rates and may affect nutrient cycling (Yeong et al, 2016)
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