Seasonal dynamics in soil microbial biomass C, N and P in a mixed-oak forest ecosystem of Manipur, North-east India
Introduction
Soil microbial biomass is an important parameter linking the plants to soil. Soil microbial biomass comprises about 2–3% of total organic carbon in the soil and has been recognized as an important source of nutrients to plants because of its fast turnover (Jenkinson and Ladd, 1981). Influence of environmental factors to microbial population and microbial biomass plays an important role in nutrients cycling in an ecosystem. Soil physico-chemical characteristics also has a great impact on microbial biomass and microbial activity and can be used to measure soil quality (Parr and Papendick, 1997) but it may take years for these parameters to make significant changes in soil. Soil biological and biochemical changes are very sensitive to small changes in soil conditions (degradation, erosion) and thereby gives more accurate and immediate information in soil quality because soil microbial activity has a direct influence in ecosystem stability and fertility (Smith and Papendick, 1993). Insam et al. (1989) also proposed that the ratio of microbial biomass to total organic carbon in a soil might serve as a quantitative indicator of carbon dynamics in the soil.
Information on soil microbial biomass in different forest ecosystems have been reported by several workers (Srivastava and Singh, 1991, Billore et al., 1995, Joergensen et al., 1995, Arunachalam et al., 1996, Mendham et al., 2002, Lee and Jose, 2003) but information on seasonal changes in the microbial biomass in an annual cycle in forest ecosystem is limited (Diaz-Ravina et al., 1995, Arunachalam and Arunachalam, 2000). Therefore, the present study was undertaken to assess the seasonal fluctuation in the microbial C, N and P and the influence of abiotic variables on the microbial biomass (C, N and P) in a sub-tropical mixed-oak secondary forest of Manipur, North-east India.
Section snippets
Materials and methods
The study site is located at 24°45′N latitude and 93°55′E longitude in Langol hills a distance of 7 km from Imphal city at an altitude ranging from 780 to 910 m above sea level. The climate of the area is monsoonic with warm moist summer and cool dry winter. There are three distinct seasons comprising of summer (March–May), rainy season (June–October) and winter (November–February). However, March is the transition month between winter and summer and November between rainy and winter seasons. The
Soil characteristics
The soil was sandy loamy with 51.6–61.4% sand, 13.3–14.8% clay and 22.7–30.7% silt in both the stands. The soil moisture ranges from 24.74 to 28.34%, soil temperature ranged from 16.83 to 17.08 °C, soil pH 4.2–6.1, soil organic carbon 2.6–4.4%, soil total N 0.33–0.54%, total P 0.042–0.082% and bulk density 1.38–1.46 g cm−3, C/N ratio varied from 7.0 to 8.7 across the two stands (Table 1).
Microbial C, N and P
In forest stand I, the microbial C, N and P ranged from 71.1 to 1412.6 μg g−1, from 32.1 to 115.7 μg g−1 and from
Discussion
The microbial C, N and P was significantly higher during the rainy season (P < 0.01) and lower in winter season in both the stands with the exception of microbial N exhibiting lowest value in summer season (Table 2). This may be due to higher immobilization of nutrients by the microbes from the decomposing litters as decomposition rate of litters and microbial activities are at peak during this period. Further, the growth of fungi also increased during this season due to high relative humidity
Conclusion
Thus, it may be concluded that the soil microbial biomass exhibits strong seasonality and is highly influenced by the abiotic variables. However, soil moisture has a strong influence on the microbial biomass. The microbial C:N ratio indicates that soil fertility is influenced by the species composition of the forest stands. High microbial N during the rainy season may be considered as a nutrient conservation strategy. Further, the proportion of microbial C and N to soil C and N indicates that C
Acknowledgement
Financial support received from UGC-SAP is thankfully acknowledged.
References (37)
- et al.
Principal components analysis of the soil microbial populations of humid zone of Galicia (Spain)
Soil Biol. Biochem.
(1990) - et al.
The impact of disturbance on detrital dynamics and soil microbial biomass of Pinus kesiya forest in North east India
Forest Ecol. Manage.
(1996) - et al.
Phosphorus in soil microbial biomass
Soil Biol. Biochem.
(1982) - et al.
Phosphorus in the soil microbial biomass
Soil Biol. Biochem.
(1984) - et al.
Chloroform fumigation and release of soil nitrogen: the effect of fumigation time and temperature
Soil Biol. Biochem.
(1985) - et al.
Microbial biomass and metabolic activity in four acid soils
Soil Biol. Biochem.
(1988) - et al.
Microbial N and biomass respiration and N mineralization in soil beneath two chaparral species along a fire-induced age gradient
Soil Biol. Biochem.
(1993) - et al.
Vegetation removal in two soils of the humid tropics: effect on microbial biomass
Soil Biol. Biochem.
(1994) - et al.
Influence of macroclimate on soil microbial biomass
Soil Biol. Biochem.
(1989) - et al.
Evaluation of the fumigation extraction method for the determination of microbial C and N in a range of forest soils
Soil Biol. Biochem.
(1990)
Microbial biomass, activity and soil respiration in relation to secondary succession
Pedobiologia
Microbial C N and P in dry tropical forest soils. Effects of alternate land uses and nutrient flux
Soil Biol. Biochem.
Microbial biomass measurements in forest soils: the use of the chloroform fumigation incubation method for strongly acid soils
Soil Biol. Biochem.
Controls of temporal variability of the soil microbial biomass: a global scale synthesis
Soil Biol. Biochem.
Tropical soil biology and fertility
A Handbook of Methods
Influence of gap size and soil properties on microbial biomass in a subtropical humid forest of North-east India
Plant Soil
Microbial biomass Nitrogen pools in soils from a warm temperate grassland and from deciduous and evergreen forests in Chiba, Central Japan
Biol. Fertil. Soils
Nitrogen total
Cited by (184)
Influence of forest types on soil physicochemical and biological characteristics of associated agroecosystems in the central Himalaya
2024, Science of the Total EnvironmentToward the tree-based ecosystems for carbon sequestration
2023, Agricultural Soil Sustainability and Carbon Management