Role of fine roots and soil microbes in C, N & P dynamics in a humid tropical forest ecosystem of Northeast India

Doctoral Thesis / Dissertation from the year 2006 in the subject Biology - Botany, grade: none, North-Eastern Hill University, language: English, abstract: The tropical rainforests are dense, evergreen vegetation characterized by highdiversity of plant and animal species. They are one of the most fragile and complexterrestrial ecosystems on Earth, presently occupying less than 7% area of Earth's surfacein America, Southeast Asia and Africa (Richards 1952; Whitmore 1998). Withincontinental Asia, patches of tropical rainforests are found in Indo-China, South China andnortheast India (Whitmore 1998). The tropical wet evergreen forest patches also occur inthe Western Ghats of India. In northeast India, tropical rainforests are restricted to the fareastern part of the region, particularly in Tirap and Changlang districts of ArunachalPradesh and Tinsukia and Dibrugarh districts of Assam. Although a major portion ofthese forests has been brought under protected area management, they are still threatenedby anthropogenic activities.Tropical forests worldwide are exposed to a variety of disturbances ranging fromfrequent localized events to less frequent, landscape level or multiple disturbance events.Natural disturbances and concomitant recovery are integral aspects of normal ecosystembehaviour (White 1979). Human disturbances, on the other hand, differ in kind, scale,intensity and frequency and sometimes they may be more severe and extensive than thenatural disturbances. Shifting cultivation and extraction of timber and NTFP's species aremajor causes of disturbance in the humid tropics (Reiners 1980), which have destroyedvast tracts of the humid tropical forest ecosystem. Logging and timber removal or conversion of forest to other land uses has long-term consequences on secondaryvegetation, nutrient cycles and water balance (Turner et al. 1997).Several workers have reported that removal or loss of forest cover alters physicochemicalcharacteristics of soil (Joergensen and Raubuch 2002) and adversely affects thesoil hydrological regime, microclimate, energy balance and enhances soil erodibility(Fenn et al. 1993). Input of organic matter and nutrients to soil through litter and rootmass help improve nutrient availability by favourably altering the hydrology andphysico-chemical and biological properties of the soil. The periodicity, extent and patternof litter fall and litter decomposition are important in this respect (Ambasht 1985).[...]