Impacts of Soil Microbial Population on Enzyme Activities under Tropical Dry Evergreen Forest Soil, Coromandel Coast, India ABSTRACT Sudhakaran M. 1, Ramamoorthy D. 2 and Swamynathan B. 3 1Ph.D Scholars, Department of Ecology and Environmental Sciences, Pondicherry University, Puducherry 605014 2Associate Professor, Department of Ecology and Environmental Sciences, Pondicherry University, Puducherry 605014 3Ph.D Scholars, Department of Ecology and Environmental Sciences, Pondicherry University, Puducherry 605014 E-mail: 2 d.ramamoorthy01@gmail.com The present study was conducted in six tropical dry evergreen forest sites such as Oorani, Puthupet and Vadaagram located near Puducherry. Kotthatai, Sendrakillai and Palvathunnan located near cuddalore. The result showed that urease, L-glutaminase, arylsulphatase, saccharase, amidase and L-asparaginase were significantly correlated with selected soil microbial population. Our investigation indicated that soil enzymes in tropical dry evergreen forest mainly are influenced by soil microbial population. Consequently, the soil enzymes are very essential for maintaining soil health as they play a vital role in decomposition of organic matter, converting plant unavailable nutrient to available plant nutrient form (N, C, S& P) thus facilitating nutrient cycling in tropical dry evergreen forest. Such studies on soil enzyme activity can be used as an important indicator of soil microbial diversity. Keywords: Soil Enzymes, Soil Microbes and Tropical Dry Evergreen Forest INTRODUCTION Soil microorganism and soil enzymes are the most important component of forest because they are responsible for biogeochemical cycling. Presence of microorganisms shows the evidence of increasing microbial properties (enzymes and soil respiration) which could be potential indicators of soil fertility and land-use changes in forest ecosystem (Doran et al. 1996). The tropical dry evergreen forests are located in the Coromandel Coast of India. Litter production is higher in the tropical dry evergreen forests because they are climatically located in drier region and receives dew as a source of moisture for about six months in a year (Arul Pragasan and Parthasarathy 2005). So we selected six sites in TDEF of along the Coromandel Coast of Peninsular India for analysis of soil enzyme activities and microbial populations. Our aims are: (1) to evaluate the soil microbial populations and soil enzyme activities in tropical dry evergreen forest. (3) Analyzing the impacts of soil microbial populations on soil enzyme activities in tropical dry evergreen forest.
Impacts of Soil Microbial Population on Enzyme Activities under Tropical Dry Evergreen 353 STUDY AREA The present study was conducted in six tropical dry evergreen forests in the Coromandel coasts of Tamil Nadu, southern India. Name of the sites are Oorani (12 0 09 N 79 0 55 S), Puthupet (12 0 04 N 79 0 53 E), and Vadaagram (12 0 04 N 79 0 55 E) forest are located 28 km north of Pondicherry. Site Kotthatai (11 0 28 N 70 0 42 E), Sendrakillai (11 0 29 N 79 0 41 E), Palvathunnan((11 0 29 N 79 0 43 E) are located 39 Km south of Pondicherry.The aerial extent of TDEF sites studied ranged from 0.5 ha to ~15 ha. METHODOLOGY The numbers of bacteria, fungi and actinomycetes were determined by serial dilution plate count method (Germida 1993). Selected Soil enzyme (Urease, Amidase, L Asparaginase, L Glutaminase, L Histidine ammonia, Acid phosphatase, Alkaline phosphatase, Cellulose, β Glucosidase, Saccharase, Xylananase and Aryl sulphatase ) activities were determined as described by Alef and Nannpieri (1995). SOIL SAMPLING AND DATA ANALYSIS In each site, three 20 20 m plots were randomly established to collect the data of site environment parameter, community structure characteristics and soil profile description. A total of 18 samples were collected (6 sites 3 plots) at the depth of 20 cm samples were taken to the laboratory and stored at 4 0 for Soil enzyme and microbial population analysis. All analyses were carried out in triplicate. All the experimental data were analyzed with SPSS/16. The relationship among soil microbial population and soil enzyme activities were analyzed by person correlation. RESULTS AND DISCUSSION Based on the soil microbial population analysis the number of bacterial population was highest, which was more than other selected soil microbial population. The phosphobacterial population was in the next place. The fungi and actinomycetes population were in third place and the least were Beijerinckia, Azotobacter, bacillus and rhizobacterial populations in number. Bacteria, fungi andactinomycetes population were higher in soil from Palvathunan forest. Beijerinckia population was higher in Puthupet. Azotobacter and bacillus population were higher in Sendrakillai forest soil. Similarly rhizobacteria population was higher in soil from Sendrakillai and Puthupet. Phosphobacteria population was higher in Kothattai forest soil (Fig. 1). In the present study Puthupet forest site soil shows highest amount of amidase, acid phosphatase alkaline phosphatase and aryl sulphatase activities. L-aspariginase, L-glutaminase and saccharase activities were highest in Palvathunnan forest soil. Urease activity was higher in Sendrakillai forest soil (Fig. 2). Cellulose and β Glucosidase activities were showed highest in Vadaagaram forest soil. Oorani forest soil showed highest level of L-histidineammonia activity. Xylanase activity was highest in Kothattai forest
354 Green India: Strategic Knowledge for Combating Climate Change: Prospects & Challenges soil (Fig. 2). Among the six tropical dry every green forests, Urease activity was positively correlated with all selected microbial populations (Table 1). Fig. 1: Soil Microbial Population in Six Tropical Dry Evergreen Forest Sites Tropical dry evergreen forest soil microbes are the main sources of urease activity. Urease activity was significantly higher than all selected enzyme activities, it's indicated that tropical dry evergreen forest has a better effect in improving soil urease activity and soil nitrogen condition. L-glutaminase and L-asparaginase activities in tropical dry evergreen forest soil significantly
Impacts of Soil Microbial Population on Enzyme Activities under Tropical Dry Evergreen 355 correlated with actinomycetes population (Table 1). Urease, amidase, L-asparaginase and L-glutaminase activities are positively correlated with azotobacter population. These enzymes are widely distributed in nature and it has an important role in nitrogen mineralization of soils (Tabatabi, 1977). Mycorrhizal colonization was the main sources of Acid and Alkaline phosphatase in the forest soil, it s indirectly indicated mychorrhizal population was higher in Puthupet forest soil (Tisserant et al., 1993). Table 1: Pearson Correlation Among Soil Enzymes and Selected Soil Microbial Populations Bacteria Fungi Actinomycetes Beijerinckia Azotobacter Rhizobium Bacillus Phoshobacteria Urease 0.734 0.440 Ns 0.339 0.538 0.222 0.697 0.129 Amidase 0.489 Ns Ns 0.738 0.151 NS 0.170 NS L Asparaginase Ns 0.128 0.901* NS 0.126 0.350 NS NS L-Glutaminase Ns 0.127 0.902* NS 0.126 0.349 NS NS L-Histidine Ns Ns Ns 0.005 NS NS 0.011 0.274 ammonia Acid phosphatase 0.673 0.149 Ns 0.661 0.403 NS 0.499 0.013 Alkaline Ns Ns 0.107 0.280 NS NS NS 0.070 phosphatase Cellulose Ns Ns 0.282 NS NS NS NS NS β Glucosidase Ns Ns Ns 0.078 NS NS NS NS Saccharase 0.271 0.433 0.863* NS 0.538 0.325 0.256 NS Xylananase Ns 0.007 0.346 NS NS 0.462 NS 0.322 Aryl sulphatase Ns Ns Ns 0.573 NS NS NS 0.458 *correlation is significant at the 0.05 level of interval, **correlation is significant at the 0.01 level of interval
356 Green India: Strategic Knowledge for Combating Climate Change: Prospects & Challenges Fig. 2: Soil Enzyme Activities in Six Tropical Dry Evergreen Forest Sites Actinomycetes population was significantly correlated with saccharase activity and positively correlated with xylanase activity (Table 1). These enzymes are controlling factor for organic matter decomposition and mineralization in tropical dry evergreen forest soils (Ajwa and Tabatabai, 1994). Actinomycetes microbes are the primary source for organic matter decomposing in forest soil. Saccarase activities in tropical dry evergreen forest soil are mainly influenced by Actinomycetes population (Wriston, 1971). Major activities of cellulases and β Glucosidase in forest soils were derived by plant debris incorporated to the soil and that a limited amount may also originate from microbial biota (Deng and Tabatabai, 1994; Ndiaye et al., 2000). More amount of plant litter fall and fine root biomass were the initial sources of cellulases and β Glucosidase activities in six tropical dry evergreen forest soils
Impacts of Soil Microbial Population on Enzyme Activities under Tropical Dry Evergreen 357 (Visalakshi, 1994; Mani and Parthasarathy, 2007). Beijerinckia and phoshobacteral population were positively correlated with aryl sulphatase activities. It is responsible for the hydrolysis of sulphate esters in the soil and secreted by bacteria into the external environment as a response to sulphur limitation (Acosta-Martı nez and Tabatabai, 2000). CONCLUSION From the above study it was concluded that most of the soil enzyme activities have a positive correlation with selected soil microbial populations. Soil microbial population and plant litter were important sources for soil enzyme activities. Our investigation indicated that soil enzymes in tropical dry evergreen forest mainly influenced by soil microbial populations. Consequently, The soil enzymes are very essential for maintaining soil health as they play a vital role in decomposition of organic matter, converting plant unavailable nutrient to plant liable nutrient form and nutrients (N, C, S & P) cycling in tropical dry evergreen forest. REFERENCES [1] Acosta-Martı nez V, Tabatabai MA (2000).Enzyme activities in a limed agricultural soil. BiolFertil Soils 31:85 91. [2] Alef and Nannpieri (1995). Methods in soil microbiology and biochemistry. Academic press ltd. ISBN 0-12-513840-7. [3] Arul Pragasan L, Parthasarathy N. (2005). Litter production in tropical dry evergreen forests of south India in relation to season, plant life-forms and physiognomic groups. Current Science, vol. 88, no. 8. [4] Deng SP, Tabatabai MA (1994). Cellulase activity of soils. Soil BiolBiochem 26:1347 1354. [5] Dick, R.P. (1994): Soil enzyme activities as indicator of soil quality. In: Doran, J.W., Coleman, D.C., Bezdicek, D.F., Stewart, B.A. (Eds.): Defining soil quality for sustainable environment. Soil Sci. Soc. Am. Spec. Pub. 35, Madison, WI: 107 124. [6] Germida, J.J. 1993. Cultural methods for soil microorganisms. In M.R. Carter, Ed. Soil Sampling and Methods of Analysis. A Special Publication of the Canadian Society of Soil Science. Lewis Publishers, Boca Raton, FL, pp. 263 275. [7] Ndiaye EL, Sandeno JM, McGrath D, Dick RP (2000) Integrative biological indicators for detecting change in soil quality. Am J AlternAgric 15:26 36. [8] Tisserant B, Gianinazzi-Pearson V, Gianinazzi S, Gollotte A (1993).In plantahistochemical staining of fungal alkaline phosphatase activity for analysis of efficient arbuscularmycorrhizal infections. Mycol Res 97:245 250.