Abstract

The Nilgiri Biosphere Reserve (NBR), the first Biosphere Reserve of India constituted under the Biosphere Reserve Programme has an area of 5520 km2, encompassing parts of the states of Kerala, Karnataka and Tamil Nadu Western Ghats. The Kerala part of NBR covering an area of 1455 km2 is rich in biological diversity due to the presence of a wide range of biophysical and climatic conditions. Like most other protected areas, the NBR is also facing the threat of forest degradation and natural resource depletion at a landscape level, particularly in village-fringe forests. A study to analyse the vegetation structure and composition in village-adjacent forests and in the relatively undisturbed forests of the Biosphere Reserve and also to determine the causes and level of disturbance in the village-adjacent forests was made. Changes in cropping pattern in the villages and their impact on forest resource flow into the village landscape units was also attempted as part of the study to identify the forest rehabilitation strategies. A comparative study of the relatively undisturbed forests village-adjacent forest plots indicated the difference in species composition and structural features such as girth class distribution of tree community, regeneration. Stand Quality intedex values also (RISQ) indicated the nature of disturbance regime. The village-adjacent forest plots were secondary forests and experiencing different levels of disturbance. In these forest plots, litter collection and other anthropogenic disturbances have reduced the number of species in the seedling community. The litter removal from the forest floor depicted a tri-fold 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 like Kadasseri and Manikunnmala, the species number increased due to invasion of exotic species from the adjoining landuse systems. In general, the tree density in village-adjacent forest plots was significantly lesser than that in the undisturbed forest plots. Collection of poles and fuel wood has been identified as the major causative for such a decline in tree density in the forest plots. Invariably the village-adjacent forests are found to be in disturbed status and the current challenge is to quantify the rate and degree of disturbance and habitat change to enable the stakeholders and managers of forest to plan rationally on appropriate measures of conservation and management. The high value for RISQ (more than 3) is 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.

Landuse and land-cover in the villages adjacent to 10 forest plots were analysed with a view to understand their impact on the forest plots. The area under agriculture ranged from 65 to 81 per cent of the total village area, dominated by farms of coconut, arecanut and rubber. Paddy cultivation, once prevalent in all ten villages is now seen in six villages only consequent to transformation of paddy fields into other landuse types. In all ten villages, fuel wood is the major source of energy for cooking. Quantity of fuel wood collected from the adjacent forest plot ranged from 3.9 to 18.9 kg ha-1 of forest area. The litter collection from the forest floor recorded in the plot at Pattakarimba was found to be responsible for about 60% reduction in the standing litter biomass. The estimated quantity of fresh litter removed from the plot ranged from 4,440 kg to 12,316 kg ha-1 month-1, which was significantly more during February-March, coinciding with the summer mulching in crop lands. On an average, about 1,000 kg of free seeds/fruits ha-1 were also removed from the forest floor in four months period and thus the tree seedling abundance in the litter collected plots was significantly low. The farming community in the village Punchavayal harvested green foliage from the adjacent forest plot with an estimated quantity of 11,720 kg ha-1 yr-1. In all the ten villages, livestock is an integral part of agriculture and grazing in forest plots is common with the number of Adult Cattle Units (ACUs) ranging from 3 to 78 individuals day-1 km-1. The forest plots at Pattakarimba and Punchavayal, where the grazing pressure by domestic animals is intense, also form the elephant corridors of the region. Therefore, low plant biomass in these plots reduces the fodder availability to elephants and other wild herbivores.

The above data indicated that despite prohibition, the resource collection in different forms, magnitude and frequency is continuing in the village-adjacent forest plots. The resultant ecological changes have profound effects on the forest species composition and structure. The precarious status of vegetation in the forest plots due to unsustainable harvest and utilisation of bioresources warrants strategic management plans on a site-by-site basis. Certain strategies and activities, i.e., reducing the forest dependence by the forest-adjacent communities, protecting forest lands and bioresources, improving human resources for managing forest plots and research and monitoring for improving forest quality have been put forth for conserving biodiversity in the village adjacent forest plots. For accelerating progressive succession in the forest plots, silvicultural practices such as, assisted natural regeneration and enrichment planting are to be adopted. Species suitable for such programmes are also listed. The need for a Village-Forest Committee, comprising of the representatives of all stakeholder groups, to each village-adjacent forest plot and a Village-Forest Committee Fund as a long-term measure to ensure continuous support for sustainable management of village-adjacent forests in the Nilgiri Biosphere Reserve has been highlighted here.