The effect of canopy disturbance on species richness in a central Himalayan oak forest (original) (raw)
Related papers
Environmental Monitoring and Assessment, 2009
Changes in tree and understory plant diversity and community composition in two sites at different disturbance levels were studied on the Anaikatty hills, Western Ghats. Systematic sampling using small scale permanent quadrates (50 × 20 m for trees, 5 × 5 m for shrubs/saplings, 1 × 1 m for herbs/seedlings) enumerated 3,376 individuals of trees (106 species), 8,599 of individuals shrubs (122 species) and 16,659 individuals of herbs (145 species). Among the two sites, species richness and diversity were highest for low disturbed stand (98 and 3.9, respectively) compared to high disturbed site (45 and 2.71, respectively). Result of cluster analysis showed that two distinct clusters were formed on the basis of disturbance of the area in concordance with our field observation. A total of 37 species were common to both sites, sixty one species exclusively found in low disturbed site and eight species were pertained to highly disturbed site. Mann–Whitney test based on Monte Carlo approximation at 95% confidence levels indicated that both populations were not entirely different. The clear difference was only observed for average basal area of trees, density of seedlings, number of species, density and diversity for shrubs and number of species and diversity for herb. The species composition were different in two stand i.e., Nothopegia racemosa–Albizia amara–Maba neilghrrensis in low disturbed stand and Albizia amara–Pleiospermium alatum–Bauhinia racemosa in high disturbed stand. The major disturbance factors identification using spearman rank correlation indicated that the disturbance in low disturbed habitats were mostly from past logging followed by cutting and illicit felling and grazing, while in high disturbed habitats, it was human presence, past logging and lopping and fuel wood collection.
Biodiversity changes caused by anthropogenic disturbance through foliage removal (lopping) were studied in Quercus semecarpifolia Sm. (oak) dominated forests in Nepal. We studied the locations of Phulchoki (Kathmandu Valley) and Ghorepani (Annapurna Region). Alpha (α) diversity, gamma (γ ) diversity and different estimates of beta (β) diversity of vascular plant species were estimated in six disturbance classes characterized on the basis of lopping intensity. The effects of different levels of anthropogenic pressure on the diversity measures were analyzed by examining how β-diversity corresponds with the pattern of α-diversity. Alpha (α)-and γ -diversities show a unimodal response to disturbance gradient, but β-diversities do not follow a consistent pattern. However, the linear relationships between beta diversities (β SD and β A ) and the disturbance gradient indicate that all kinds of plant species diversity measures increase up to the level where forest disturbance is intermediate. Hence, we suggest the adoption of prescribed forest utilization systems as a management policy. Such a policy has two advantages: on the one hand, it contributes to sustainable livelihoods of the people depending on local forest resources, and on the other hand, it contributes to conservation of plant species diversity.
Tropical Ecology, 2001
More than two third tree species were in early succession and similarly, the higher number of shrubs and herbs were in early and mid-succession indicates the successional nature of the community. A comparatively higher number of trees and shrubs were recorded on the western aspect where low erosion and greater anthropogenic pressure were present. The total tree density was higher at hilltop of eastern aspect and hill slope of western aspect. Total tree basal area varied from 4.5 m 2 ha -1 (hill base) to 11.9 m 2 ha -1 (hilltop) on the eastern aspect and from 9.3 m 2 ha -1 (hilltop) to 16.8 m 2 ha -1 (hill base) on the western aspect. The sapling and seedling density was lower on western aspect because higher anthropogenic disturbances may lead the removal of seedlings of most of the tree species. The shrub and herb diversity was higher on both the aspects as compared to tree diversity because opening of canopy provides greater opportunity for the recruitment of shrubs and herbs. There were few individuals of important species in older girth classes and higher numbers in younger girths indicate the forest is regenerating. The significant presence of Coriaria nepalensis, nonleguminous nitrogen fixing species, at all the sites seems to help in the restoration of the ecosystem.
Vegetation diversity and vertical structure as indicators of forest disturbance
Forest Ecology and Management, 2004
Plant species composition and vertical structure of oak-mixed Atlantic woodlands differing on disturbance regime were studied in the Basque Country, northern Spain. Four different disturbance groups were considered depending on the time since last thinning and the presence/absence of grazers. Plant species cover varied among disturbance groups for 17 out of the total 47 species present in the study area. In general, disturbance by clear-cutting favoured the cover of Betula alba, Castanea sativa and Quercus robur. The shrub species most affected by disturbance were heathers. Among these, the most drastic effect was found for Calluna vulgaris, Daboecia cantabrica and Erica vagans which disappeared in those woodlands subjected to grazing. Several nemoral species, such as Vaccinium myrtillus, Blechnum spicant and Lamiastrum galeobdolon, were absent in these same grazed forests. By contrast, generalist species, such as Ruscus aculeatus, Geranium robertianum and Veronica officinalis, were mostly present in the grazed woodlands.
Patch implications in the maintenance of species richness in an isolated forest site
Biological Conservation, 2001
Plant species richness as a function of patchiness of three different management types, viz. clear-felled, selective-cut and protected, was evaluated in an abandoned urban forest in central Japan. One-hundred and thirty-seven vascular species were recorded at the understory in this 3.2 ha planted forest stand of indigenous conifer — Cryptomeria japonica and Chamaecyparis obtusa. These species included 52.5% herb, 13.9% climber, 15.3% shrub and 18.2% tree species. This species diversity was sustained by dynamic attributes of the patches which were generated and modified by disturbances originating from human activities and natural processes. Past management practices contributed largely to the variation of canopy openings, and continued human activities such as trampling added heterogeneity by soil compaction. These anthropogenic and natural disturbances interacted to effect the pattern of plant species diversity and composition.
Biodiversity and …, 2004
This study analyses the effects of anthropogenic disturbance on plant diversity and community attributes of a sacred grove (montane subtropical forest) at Swer in the East Khasi Hills district of Meghalaya in northeast India. The undisturbed, moderately disturbed and highly disturbed stands were identified within the sacred grove on the basis of canopy cover, light interception and tree (cbh $ 15 cm) density. The undisturbed forest stand had .40% canopy cover, .50% light interception and a density of 2103 trees per hectare, whereas the highly disturbed stand had ,10% canopy cover, ,10% light interception and 852 trees per hectare. The moderately disturbed stand occupied the intermediate position with respect to these parameters. The study revealed that the mild disturbance favoured species richness, but with increased degree of disturbance, as was the case in the highly disturbed stand, the species richness markedly decreased. The number of families of angiosperms was highest (63) in the undisturbed stand, followed by the moderately (60) and highly disturbed (46) stands. The families Rubiaceae, Asteraceae and Poaceae were the dominant families in the sacred forest. Rubiaceae was represented by 11, 14 and 10 species in the undisturbed, moderately disturbed and highly disturbed stands, respectively, whilst the family Asteraceae had 16 species in the moderately disturbed stand and 14 species in the highly disturbed stand. The number of families represented by a single species was reduced significantly from 33 in the undisturbed stand to 23 in the moderately and 21 in the highly disturbed stand. The similarity index was maximum (71%) between the undisturbed and moderately disturbed stand and minimum (33%) between the undisturbed and highly disturbed stands. The Margalef index, Shannon diversity index and evenness index exhibited a similar trend, with highest values in the moderately disturbed stand. In contrast, the Simpson dominance index was highest in the highly disturbed stand. There was a sharp 21 2 21 decline in tree density and basal area from the undisturbed (2103 trees ha and 26.9 m ha) to the 21 2 21 moderately disturbed (1268 trees ha and 18.6 m ha) and finally to the highly disturbed (852 trees 21 2 21 ha and 7.1 m ha) stand. Density-girth curves depicted a successive reduction in number of trees in higher girth classes from the undisturbed to the moderately and highly disturbed stands. The log-normal dominance-distribution curve in the undisturbed and moderately disturbed stands indicated the complex and stable nature of the community. However, the short-hooked curve obtained for the highly disturbed stand denoted its simple and unstable nature.
Himalayan vegetation is subjected to various types of disturbances and most of them are either geological or anthropogenic or both. Biodiversity at all hierarchical levels is impacted upon by disturbance of an ecosystem in terms of maintenance and restoration. Protected Areas are forests that have as their primary function the protection of people or assets against the impacts of natural hazards. The main 'product' of these forests are standing trees which act as obstacles to down slope mass movements such as rock falls, snow avalanches, erosion, landslides, debris flows, and floods. The study area is located between 29 0 24' and 29 0 27' N latitude and 78 0 52' and 78 0 59' E longitude between 280 and 370 m elevation in Uttarakhand Himalaya. In this study, an attempt was made to study the vegetational parameters of floral biodiversity under different disturbance regimes of protected area i.e Corbett National Park (CNP). Overall species richness of the study ...
Journal of Ecology, 2014
1. Disturbance can function to maintain diversity within forest communities; however, specific mechanisms and the relationship to productivity are not well understood. 2. We examined these linkages in forest ground-layer plant communities using a replicated, manipulative field experiment. Treatments included a range of gap sizes and untreated controls. We assessed spatial and temporal responses over the first three years following gap creation. 3. Light transmittance and soil water content increased with gap size, while rates of colonization and species richness increased after a critical threshold. Subsequent increases in productivity were associated with declines in species richness, increased rates of local extirpation and a unimodal relationship between species richness and productivity at the individual quadrat scale (4 m 2 ). 4. The richness and productivity of vines, shrubs and especially graminoids, increased within 200-380 m 2 gaps treatments. However, the productivity of forbs and tree seedlings did not, showing possible drought sensitivity overriding treatments. Spatial and temporal partitioning of gaps occurred as a result of interactions between species traits and environmental conditions. Significantly, productivity and richness showed complex relationships with canopy structure. 5. Synthesis. Our results show that richness increases to an asymptote after a critical threshold in disturbance severity initially. Decreases in species richness over time associated with increases in productivity may eventually result in the unimodal relationship predicted by the intermediate disturbance hypothesis. However, species composition continues to differ with canopy gap size, suggesting a range of canopy gap sizes is required to maintain the greatest diversity of plant species over broader spatial and temporal scales.