Assessment of Level of Human Disturbance in Village-adjacent Natural Forest Plots in the Kerala Part of Nilgiri Biosphere Reserve

U.M. Chandrashekara


The structure and composition of tree community was analysed in ten forest plots, adjacent to villages, in the Kerala part of Nilgiri Biosphere Reserve (NBR), and the level of disturbance in each plot was determined. These plots represent secondary forest, generally dominated by evergreen light demanding, late and early successional species and deciduous species such as Xylia xylocarpa, Terminalia paniculata, Macaranga peltata, Aglaia malabarica, Alseodaphne semecarpifolia, Bischofia javanica, Wrightia tinctoria etc. In all the plots, a distorted girth class distribution, with a drastic decline in the number of individuals of girth ranging from 20 cm to 60 cm, was noticed. The litter removal from the forest floor depicted a three-fold adverse effect on species richness; by way of physical removal of tree propagules along with other litter materials, run-off of tree propagules in the absence of litter layer and seedling mortality consequent to soil dryness and desiccation. However, in the forest plots adjacent to villages  Kadasseri and Manikunnmala, the species number increased due to invasion of exotic species from the adjoining landuse systems. In order to assess the level of disturbance in these plots, three forest quality indicators namely Ramakrishnan Index of Stand Quality (RISQ), Index of Ecological Quality (IEQ) and Index of Human disturbance (IHD) were measured. The high value for RISQ (more than 3) is an indicative of the fact that majority of the forest plots are under different stages of succession and need more time for their recovery from the anthropogenic disturbances. A positive correlation between any two forest quality indicators suggested that they are complementary to each other and helpful to accurately assess ecological and human factors responsible for the status of the forest stand and identify site-specific suitable conservation and management strategies.


Chronic Disturbance; Disturbance Variables; Biomass Harvest; Tree Community; Tree Girth Class Distribution; Successional Status; Forest Quality Indicators


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