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

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 high
diversity of plant and animal species. They are one of the most fragile and complex
terrestrial ecosystems on Earth, presently occupying less than 7% area of Earth's surface
in America, Southeast Asia and Africa (Richards 1952; Whitmore 1998). Within
continental Asia, patches of tropical rainforests are found in Indo-China, South China and
northeast India (Whitmore 1998). The tropical wet evergreen forest patches also occur in
the Western Ghats of India. In northeast India, tropical rainforests are restricted to the far
eastern part of the region, particularly in Tirap and Changlang districts of Arunachal
Pradesh and Tinsukia and Dibrugarh districts of Assam. Although a major portion of
these forests has been brought under protected area management, they are still threatened
by anthropogenic activities.
Tropical forests worldwide are exposed to a variety of disturbances ranging from
frequent localized events to less frequent, landscape level or multiple disturbance events.
Natural disturbances and concomitant recovery are integral aspects of normal ecosystem
behaviour (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 the
natural disturbances. Shifting cultivation and extraction of timber and NTFP's species are
major causes of disturbance in the humid tropics (Reiners 1980), which have destroyed
vast tracts of the humid tropical forest ecosystem. Logging and timber removal or conversion of forest to other land uses has long-term consequences on secondary
vegetation, nutrient cycles and water balance (Turner et al. 1997).
Several workers have reported that removal or loss of forest cover alters physicochemical
characteristics of soil (Joergensen and Raubuch 2002) and adversely affects the
soil hydrological regime, microclimate, energy balance and enhances soil erodibility
(Fenn et al. 1993). Input of organic matter and nutrients to soil through litter and root
mass help improve nutrient availability by favourably altering the hydrology and
physico-chemical and biological properties of the soil. The periodicity, extent and pattern
of litter fall and litter decomposition are important in this respect (Ambasht 1985).[...]