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Anthropogenic pressures in a tropical forest ecosystem in Western Ghats, India: Are they sustainable?
No full textSever~l million of humans still thrive in the forest of tropics and use resources therein for their livelihood. Owing to the fact that they have been with, and depending upon the forest for several centuries, it is believed that their harvesting patterns could represent a good model for sustainable use of forest resources. As of yet however, there are no identified models of such sustainable use, though rigorously sought for (Uma Shanker, et al., 1996). In this paper we report the impact of one such indigenous community on the structure and composition of the forest ecosystem using indicator species birds, butterflies (Kremen, 1992, 1994) and vegetation of a wildlife sanctuary in South lndia
Distribution of forest birds in the Andaman islands: importance of key habitats
No full textThe aim of this study was to assess the influence of island area, distance to source pool, latitude, habitat diversity and habitat type on species richness of forest birds in the
Andaman islands
Genetic Diversity of Medicinal Plant Species in Deciduous Forest of South India: Impact of Harvesting and other Anthropogenic Pressures
No full textA rich repository of medicinal plants are used by various indigenous health care systems in the Indian subcontinent. Over the years, there has been an extensive extraction of the medicinal plants from their natural habitats rendering many of them rare, endangered or threatened . It is feared that unless urgent measures are taken to conserve the genetic resources of the medicinal plant species, the genetic variability of many of the species would be irreversibly lost. We examined the impact of anthropogenic pressures on the regeneration and genetic diversity of two medicinally important plant species, Termillalia bellirica and Terminalia chebula in the deciduous forest of south India . Three levels of disturbance namely control, mildly and highly disturbed regions were identified in the forest based on their proximity to human settlement, extent of fore st stand and the extent of harvesting. Our studies showed that populations close to human settlements had relatively less proportion of small size class individuals compared to populations away from the settlements. While there was no discernible pattern in the genetic diversity parameters of the various populations, there appeared to be significant differentiation of the populations in the two species across the disturbance levels, suggesting that extraction of the medicinal plants may have altered the genetic structure of the populations. We discuss the
results of our study in the context of the need to conserve and manage the genetic resources of medicinally important plant species in the country
Dispersal modes of tree species in the wet forests of southern Western Ghats
Get PDFDispersal modes of tree species in a wet evergreen forest
at Kakachi in the Kalakad–Mundanthurai Tiger Reserve, southern India are described here. Frugivore visitors to 82 tree species were observed. Biotic agents involved in seed dispersal and seed predation were six species of birds and five species of mammals. Birddispersed species were the most common species (59%), followed by mammal-dispersed species (26%). Primates were less important than bats and civets in seed dispersal. Fifteen per cent of the species had no apparent adaptation for abiotic dispersal (mechanically dispersed) except one wind-dispersed species. Many bird-dispersed species occurred at low density but the total density of bird-dispersed species compares with that of mammal and mechanically dispersed species. Edge or gap habitat species were less
abundant than the closed forest ones in all three types
of dispersal modes. Species level comparison with other wet forest sites indicates a high degree of similarity between Kakachi and La Selva in central America
Role of structural requirements in web-site selection in Cyrtophora cicatrosa Stoliczka (Araneae: Araneidae)
Get PDFCyrtophora cicatrosa weaves a three-dimensional dome web and is commonly found in thorny bushes and cacti. The factors that could be responsible for this selection were studied, both by field observations and laboratory experiments. Structural requirements in terms of space availability were found to be an important factor in the selection of the website, though other factors could be significant. The relationship between C. cicatrosa and its immediate environment is discussed
A new approach to conservation of genetic resources of forest trees: Promise and processes
No full textThe tropical forests are characterized by a great diversity of tree species. Because of the intense human pressures on these resources, many of the species, especially the economically important ones, are rendered either rare, endangered or threatened with incredibly low population sizes. Conventional approaches like ex situ and in situ methods, to conserve the genetic diversity of these populations, are not feasible. In fact in these small and frequently anthropogenically impacted
populations, conservation of populations in situ may lead to a loss of diversity through drift and other processes. Under these situations, newer approaches that integrate the genetic variability of the spatially disjunct or fragmented populations should be deployed to help avert the loss of the genetic diversity of the species. We propose an approach based on the establishment of ‘forest gene banks’ wherein the genetic diversity of a species is conserved in situ at a ‘sink’ population into which periodically genes from identified ‘source’ populations are infused. Through such a process, not only is the genetic diversity of the ‘sink’ population enriched and made representative of the others, but also the genetic diversity could be rescued from potentially moribund populations. We discuss the forest gene bank model in
the context of the conflicting views on the gene mixing strategies in conservation and argue that under the circumstances of threat to a large number of tropical forest tree species, such approach may have to be followed, albeit with precautions
Pollination and fruit dispersal in the wet forests of the southern Western Ghats
No full textPollination and seed dispersal can play an important role in the functioning of tropical ecosystems and the maintenance of diversity in them. Wet forests in tropics are known to have exceptionally high diversity of pollination and dispersal mechanisms that are complex and can vary across continents. Identifying modes of pollination and dispersal can, to some extent, delineate
this complexity and help in better understanding of these systems (TharraManriquez and Oyama, 1992). Only recently a detailed analysis of the pollination and dispersal modes of the wet forests of Western Ghats, a biodiversity hotspot, has been carried out (Ganesh and Davidar, 2001; Devy, 1998). This study documents the pollination and seed dispersal modes of tree species in a mid-elevation wet forest at Kakachi in the southern Western Ghats. A total of 89 flowering species and 82 fruiting species were observed. Flowers were watched for visitors from the commencement of an thesis. Similarly fruiting trees were watched for visitors during ripe fruit stage and also frugivore identity was inferred from fruits and seeds in droppings and scats. Nocturnal observations were also done for visitors of several species. The data were obtained over a span of seven years and are based on direct observations of visitors to flowers and fruits. Many of these observations were recorded by ascending the canopy of trees using tree ladders
Participatory resource monitoring for non-timber forest products in Biligiri Rangaswamy Temple wildlife sanctuary, Karnataka, India
No full textExtensive harvesting of plant and animal products from natural ecosystems is one of the principal causes of the loss of biodiversity and degradation of ecosystems. In India, as elsewhere, millions of people derive their
livelihoods by harvesting a wide variety of non-timber forest products (NTFPs) from the ecosystem. Although local communities had some sort of monitoring programs in place to estimate production and harvest levels, such systems are gradually breaking down with increasing
commercialization and the loss of local control over resources. We initiated a program of participatory resource monitoring (PRM) with the Soligas, the indigenous people of the Biligiri Rangaswamy Temple (BRT) Wildlife Sanctuary, as part of an effort to develop models of sustainable use of forest resources (Bawa, 1999). A detailed description of BRT is available in Ramesh (1989) and Hegde el al. (1996). The Soligas derive almost half their income from NTFPs (Lele el al., unpublished data). Of the various products that the
Soligas harvest, the most important are Phyllanlhus emblica and P. indojischeri (collectively known as 'amla'), and honey from Apis dorsala, or rock bees
Impact of human-induced disturbance on the diversity of dung beetles (Coleoptera: Scarabaeidae) and ants (Hymenoptera: Formicidae)
No full textDisturbance, whether natural or anthropogenic, is an important factor that aff~cts the ecosystem functions. Although insects contribute to the major share of biodiversity, impact of disturbance on its diversity is
poorly understood (Hamer and Hill, 1999). Insects are known to respond differently to disturbance dynamics (Schowalter, 1985). Some studies have shown that disturbance causes a reduction in diversity of insects (Daily and Ehrlich, 1995; Hill e/ ai., 1995) while others suggest that disturbance
results in an increase in diversity (Kremen, 1992; Hamer e/ ai., 1997). In this study we have attempted to assess the response of dung beetles and ants to disturbance in a wildlife sanctuary of South India
Spatial patterns of suspended sediment yields in a humid tropical watershed in Costa Rica
No full textHumid tropical regions are often characterized by extreme variability of fluvial processes. The Rio Terraba drains the largest river basin, covering 4767 km2, in Costa Rica. Mean annual rainfall is 3139±419sd mm and mean annual discharge is 2168±492sd mm (1971–88). Loss of forest cover, high rainfall erosivity and geomorphologic instability all have led to considerable degradation of soil and water resources at local to basin scales. Parametric and non-parametric statistical methods were used to estimate sediment yields.In the Terraba basin, sediment yields per unit area increase from the headwaters to the basin mouth, and the trend is generally robust towards choice of methods (parametric and LOESS) used. This is in contrast to a general view that deposition typically exceeds sediment delivery with increase in basin size. The specific sediment yield increases from 112±11·4sd t km−2 year−1 (at 317·9 km2 on a major headwater tributary) to 404±141·7sd t km−2 year−1 (at 4766·7 km2) at the basin mouth (1971–92). The analyses of relationships between sediment yields and basin parameters for the Terraba sub-basins and for a total of 29 basins all over Costa Rica indicate a strong land use effect related to intensive agriculture besides hydro-climatology. The best explanation for the observed pattern in the Terraba basin is a combined spatial pattern of land use and rainfall erosivity. These were integrated in a soil erosion index that is related to the observed patterns of sediment yield. Estimated sediment delivery ratios increase with basin area. Intensive agriculture in lower-lying alluvial fans exposed to highly erosive rainfall contributes a large part of the sediment load. The higher elevation regions, although steep in slope, largely remain under forest, pasture, or tree-crops. High rainfall erosivity (>7400 MJ mm ha−1 h−1 year −1) is associated with land uses that provide inadequate soil protection. It is also associated with steep, unstable slopes near the basin mouth. Improvements in land use and soil management in the lower-lying regions exposed to highly erosive rainfall are recommended, and are especially important to basins in which sediment delivery ratio increases downstream with increasing basin area. Copyright © 2001 John Wiley & Sons, Ltd