Impact assessment of exotic plantations of varied ages on edaphic properties of woodland habitat of Nilgiris Biosphere Reserve, Tamil Nadu

Abstract

The present investigation is aimed at to study the impact of plantations of exotic species of varied age groups on the edaphic properties in the Nilgiris Biosphere Reserve (NBR), Tamil Nadu. It is observed that the soils, under natural forest possess the high pool of energy contents, organic carbon (3.46% to 5.20%), available nitrogen (0.295% to 0.399%), available phosphorus (0.006%), water holding capacity (105.2% to 115.6%) with proportionate values of porosity and cation exchange capacity. Results further exhibit that the same soils, when brought under monocultures of exotic species belonging to the genera Eucalyptus, Acacia, Pinus, Casuarina, Araucaria and Tectona, etc., they lose their acquired characteristics rapidly. Such results are more apparent in matured (aged) species; however, in young stages these species in association with quickly renewable ground flora help the soils in their gradual recovery. Against soil’s acquired characteristics, their inherent characteristics are excessively loaded with silica contents, sesquioxides and iron oxide. Soils reactions are either slightly or moderately acidic but with aged monocultures pH becomes exceptionally acidic. The vital edaphic characteristics which get highly affected by such plantations are, soils energy materials, soil proteins, pH, water holding capacity, porosity, cation exchange capacity, exchangeable calcium and available phosphorus. Besides, the ecosystem loses its existing water regime permanently at its source. However, results again show that mixed plantation of Eucalyptus globulus + Casuarina equisetifolia + Acacia nilotica proved better in promoting desired edaphic properties.