Influence of anthropogenic disturbance on bird communities in a tropical dry forest: role of vegetation structure

A study was carried out in Sariska Tiger Reserve in India to investigate the effects of anthropogenic disturbance caused by biomass extraction on the bird communities of tropical dry forests. The study was based on comparisons of the avifaunal community as well as vegetation structure between strictly protected ('undisturbed') and intensively used ('disturbed') sites that were demarcated a priori on the basis of disturbance indicators. There was no significant difference in the number of recorded species and bird abundance between disturbed and undisturbed sites. However, bird species diversity was significantly lower in disturbed sites. Bird species composition was found to differ significantly between disturbed and undisturbed sites and was associated with the measured disturbance indicators. Changes in bird species composition occurred because of seven of 26 locally abundant bird species (26.9%) responding significantly to the disturbance regime. All the affected bird species are primarily insectivorous. Bird species composition was significantly related to six vegetation structural variables, including two that were significantly altered by disturbance. Changes in vegetation structure accounted for all the changes in bird species composition caused by disturbance. However, vegetation structure had additional effects on bird species composition besides those caused simply by disturbance. Thus, our study indicates that forest use in the form of chronic biomass extraction can have significant effects upon bird diversity and species composition of tropical dry forest. There is a need to retain a proportion of natural ecosystems as inviolate if the full complement of biodiversity is to be conserved.     

Seasonal wetlands on the Lake Wales Ridge, Florida: does a relict seed bank persist despite long term disturbance?

Wetlands maintain biodiversity and provide numerous ecosystem services, so the pressure to perform successful restoration consequently is high. However, restoration projects rarely include an in-depth assessment of wetland potential for recovery, and restoration techniques may not be tailored to site-specific concerns. This study examined the seed bank of disturbed wetlands slotted for hydrologic, but not vegetation, restoration to determine if a seed bank comparable to that of nearby undisturbed wetlands persisted despite long-term anthropogenic disturbance. We compared the aboveground vegetation and seed bank compositions under drained, drawdown, and flooded conditions between undisturbed and historically ditched (“disturbed”) wetlands. Disturbed and undisturbed wetlands shared fewer than 30 % of total aboveground species. While undisturbed wetlands were dominated by graminoids, disturbed wetlands had greater cover of forbs. The seed banks of disturbed wetlands had high species diversity, but their composition was dissimilar to that of nearby undisturbed wetlands. In total, the seed banks of both disturbance histories germinated 56 species; drained conditions had the fewest germinants while flooded conditions had the most. Germinant richness was significantly affected by disturbance, moisture, and their interaction; evenness was significantly affected by moisture, and Shannon diversity by disturbance. Because the seed bank of disturbed wetlands included many fast-growing wetland plants, passive vegetation restoration and active hydrologic restoration may result in wetlands overgrown with weedy species and with fewer conservative wetland plants. An understanding of the capacity for seed banks to re-vegetate wetlands post-restoration and approximate undisturbed wetlands is crucial to the overall success of restoration projects.     

茂县土地岭植被恢复过程中物种多样性动态特征

植被恢复是退化生态系统重建的重要途径,植被恢复过程物种多样性的变化反映了植被的恢复程度.通过群落调查和多样性分析,研究了岷江上游土地岭植被恢复过程中群落物种多样性特征.结果表明： 恢复过程中6类不同类型群落分别表现其对于不同环境特征、干扰及更新方式等的响应;森林是较灌丛更适合当地环境状况的植被类型;人工恢复无干扰和轻度干扰群落的多样性相对较高,是较好的恢复模式.重度干扰使得1年生植物与地下芽植物比例增加,其它口食性较好的多年生草本减少.较强的干扰是群落无法更新、长期处于灌丛阶段且多样性较低的重要原因.本地区人工恢复群落在更新进程和多样性维持上优于自然更新群落,种植华山松加速了本地区植被演替进程.建议以适合恢复区域的多种恢复配置方式进行造林,并避免较强干扰,可以加速群落演替进程并保持恢复群落较高的物种丰富度与多样性.     

Disturbance Winners or Losers? Plants Bearing Extrafloral Nectaries in Brazilian Caatinga

Plants bearing extrafloral nectaries (EFNs) often have traits typical of pioneer species, and may be expected to proliferate in disturbed habitats. However, a negative effect of disturbance on visitation by attendant ants could prevent EFN‐bearing plants from acting as disturbance winners. Here, we address the effects of chronic anthropogenic disturbance on the abundance of EFN‐bearing plants and their interactions with attendant ants in Caatinga vegetation of northeastern Brazil. We recorded the abundance of EFN‐bearing plants, proportion of plants visited by ants and composition of ant attendant species at 24 sites varying in levels of disturbance. EFN‐bearing plants as a whole did not behave as a disturbance winner group. The responses of the 13 species to increasing disturbance were highly variable, with three species declining in abundance (loser species). The richness of ant species attending EFNs did not vary with disturbance, but species composition did. The overall proportion of EFN‐bearing plants attended by ants per 5‐min period was not affected by disturbance. However, for the three loser species, attendance decreased from about 50 percent with low and moderate disturbance to half that with very high disturbance. We hypothesize that disturbed sites are more stressful for loser species compared with other EFN‐bearing plants, with physiological stress resulting in lower production of EFN secretions and reduced attraction of ants. This would make such species double losers, with physiological stress at disturbed sites not only directly influencing their performance but also indirectly affecting it through the disruption of a key mutualism.     

Patterns of Rodent Species Diversity and Abundance in a Kenyan Relict Tropical Rainforest

Patterns of rodent species abundance and diversity were examined over a 5 months period in two areas of a Kenyan relict tropical rainforest. The two areas are subjected to different administrations which lead to various levels of anthropogenic disturbance: one can be considered relatively disturbed and one relatively undisturbed. Anthropogenic disturbance causes a reduction in woody stem density between 0 and 1.5 m and reduced understory tree canopy cover. Rodent abundance was estimated using the program CAPTURE and compared with the number of individuals actually captured. Density was estimated with three different methods, two of these utilised a boundary strip to estimate effective size of the area trapped. Density resulted in being relatively high in both areas, so population might have been at a peak. Species richness was higher in the disturbed forest, while species diversity and evenness was higher in the undisturbed forest. We suggest that in the disturbed forest the increase in number of species might be due to sporadical entrance in the forest by non-forest species, while the decrease in diversity might be due to the decrease of lower strata vegetation that occurs in the disturbed forest, hence this factor might affect species equitability. Bibliographic data supports this hypothesis as rodent species diversity and ground vegetation cover have been found to be correlated.     

Development of microtopography in a semi-arid grassland: Effects of disturbance size and soil texture

Our objective was to evaluate effects of disturbance size and soil texture on the development of microtopography for a shortgrass plant community in north central Colorado USA. Disturbances, defined as the death of individual plants, were created in 1984 and 1985 to evaluate development through time of the small-scale pattern of perennial bunchgrasses and bare soil openings that characterize this semiarid grassland. Disturbed plots of three sizes (50, 100, 150 cm-diameter) comparable in size to naturally-occurring disturbances were produced by killing plants at two sites differing in soil texture (sandy loam, clay loam). Disturbed plots were not manipulated after being created. In 1993, a laser surveying instrument was used to measure heights of crowns of individual plants of the dominant species, the perennial bunchgrass Bouteloua gracilis ([H.B.K.] Lag. ex Griffiths), and bare soil openings between plants for two locations: within each disturbance and in the surrounding undisturbed landscape.Differences between crown heights of plants and bare soil openings were comparable for both the undisturbed landscape and inside disturbances indicating that small-scale microtopography had recovered within nine years after disturbance occurred. However, complete recovery to the undisturbed state had not occurred since crown heights of plants relative to bare soil openings were significantly less on disturbed than undisturbed locations. Differences in height between plant crowns and bare soil openings on disturbed plots increased as disturbance size increased, indicating greater soil redistribution with increasing plot size. Larger differences in height were also found on plots on the fine- than the coarse-textured soil, indicating the importance of soil particle size and plant cover type to the development of microtopography. Differences in height between microsites on disturbed plots were positively related to total plant cover and negatively related to cover of B. gracilis indicating the importance of this species to reducing erosion on disturbed areas.In this semiarid grassland, patterns in microtopography were heterogeneous, likely as a result of the small-scale redistribution of soil between bare soil openings and B. gracilis plants through time. Our results indicate that this redistribution of soil is affected by disturbance size, soil texture, and patchy plant cover. The major effect of small-scale disturbances on patterns in microtopography of the shortgrass steppe are causing plant death and exposing soil to erosional and depositional processes.     

Spatio-Temporal Variation in Contrasting Effects of Resident Vegetation on Establishment,Growth and Reproduction of Dry Grassland Plants: Implications for Seed Addition Experiments

Successful establishment of plants is limited by both biotic and abiotic conditions and their interactions. Seedling establishment is also used as a direct measure of habitat suitability, but transient changes in vegetation might provide windows of opportunity allowing plant species to colonize sites which otherwise appear unsuitable. We aimed to study spatio-temporal variability in the effects of resident vegetation on establishment, growth and reproduction of dry grassland species in abandoned arable fields representing potentially suitable habitats. Seeds were sown in disturbed (bare of vegetation and roots) and undisturbed plots in three fields abandoned in the last 20 years. To assess the effects of temporal variation on plant establishment, we initiated our experiments in two years (2007 and 2008). Seventeen out of the 35 sown species flowered within two years after sowing, while three species completely failed to become established. The vegetation in the undisturbed plots facilitated seedling establishment only in the year with low spring precipitation, and the effect did not hold for all species. In contrast, growth and flowering rate were consistently much greater in the disturbed plots, but the effect size differed between the fields and years of sowing. We show that colonization is more successful when site opening by disturbance coincide with other suitable conditions such as weather or soil characteristics. Seasonal variability involved in our study emphasizes the necessity of temporal replication of sowing experiments. Studies assessing habitat suitability by seed sowing should either involve both vegetation removal treatments and untreated plots or follow the gradient of vegetation cover. We strongly recommend following the numbers of established individuals, their sizes and reproductive success when assessing habitat suitability by seed sowing since one can gain completely different results in different phases of plant life cycle.     

Forest Modification Affects Diversity (But Not Dynamics) of Speciose Tropical Pyraloid Moth Communities

We studied temporal and spatial dynamics of extremely diverse moth ensembles (Lepidoptera: Pyraloidea) along a gradient of forest disturbance ranging from undisturbed primary tropical rain forest to different kinds of modified forest and open cultivated land at the margin of Mount Kinabalu National Park (Sabah, East Malaysia). We sampled moths by light trapping during two periods (March‐May and August‐September 1997). We collected a total of 7724 individuals representing 680 species during 78 light‐trapping nights at six study sites. Species diversity (Fisher's α) of ensembles in undisturbed primary forest was distinctly higher than in disturbed or secondary forest. More pyraloid moths were attracted in undisturbed primary forest. Samples from disturbed primary or old‐growth secondary forest were statistically indistinguishable from the undisturbed primary forest ensemble in regard to species composition. Thus, pyraloid ensembles from disturbed forest with tall trees remaining appeared to represent impoverished subsets of the undisturbed primary forest community. The more heavily disturbed sites had a distinct fauna and showed a stronger faunal differentiation among each other. Four species of the genus Eoophyla, in which aquatic larvae feed on algae in fast‐running streams benefited prominently from forest disturbance. Temporal variation of ensembles was remarkably concordant across the disturbance gradient. Relative abundance variation of the commonest species was identical at all sites. Overall, pyraloid moths responded more sensitively to anthropogenic habitat alteration than most other moth taxa studied thus far in tropical regions and allowed for an analysis of diversity patterns at a high temporal resolution.     

Effects of anthropogenic disturbance on indri (Indri indri) health in Madagascar

Anthropogenic habitat disturbance impairs ecosystem health by fragmenting forested areas, introducing environmental contamination, and reducing the quality of habitat resources. The effect of this disturbance on wildlife health is of particular concern in Madagascar, one of the world's biodiversity hotspots, where anthropogenic pressures on the environment remain high. Despite the conservation importance of threatened lemur populations in Madagascar, few data exist on the effects of anthropogenic disturbance on lemur health. To examine these impacts, indri (Indri indri) populations were evaluated from two forest reserves that differ in their exposure to anthropogenic disturbance. We compared the health status of 36 indri individuals from two sites: one population from a protected, undisturbed area of lowland evergreen humid forest and the other population from a reserve exposed to frequent tourism and forest degradation. Comparison of indri health parameters between sites suggests an impact of anthropogenic disturbance, including significant differences in leukocyte count and differential, 12 serum parameters, 6 trace minerals, and a higher diversity of parasites, with a significant difference in the presence of the louse, Trichophilopterus babakotophilus. These data suggest that indri living in disturbed forests may experience physiological changes and increased susceptibility to parasitism, which may ultimately impair reproductive success and survival.     

Local‐ and landscape‐level effects of land use change on bird diversity in Abiata‐Shalla Lakes National Park,Ethiopia

Understanding the effects of anthropogenic disturbances on biodiversity is important for conservation prioritization. This study examined the effects of vegetation degradation on bird diversity in Abiata‐Shalla Lakes National Park, Ethiopia. We surveyed birds and vegetation structure between January and March 2015 in disturbed (impacted by settlement and agriculture) and undisturbed (not impacted) transects of two vegetation types (savannah woodland and gallery forest). We compared between disturbed and undisturbed transects at local (within vegetation types) and landscape (across vegetation types) levels: (a) avian species richness of the entire assemblage and feeding guilds and (b) species assemblage composition. We found significantly greater mean and total bird species richness of the entire assemblage and insectivore and granivore feeding guilds in the undisturbed transects, while the nectarivore guild was totally absent in the disturbed transects. We also found significant differences in bird species assemblage composition between the disturbed and undisturbed transects both within and across the vegetation types, and bird species assemblage composition at the landscape level was positively correlated with tree abundance and understorey vegetation height. In conclusion, our results demonstrate and add to the increasing body of evidence concerning the adverse effects of human‐induced vegetation change on bird diversity.     

Does Invasion of Exotic Plants Promote Invasion of Exotic Flower Visitors? A Case Study from the Temperate Forests of the Southern Andes

Habitat disturbance, particularly of human origin, promotes the invasion of exotic plants, which in turn might foster the invasion of alien-interacting animals. Here we assess whether the invasion of exotic plants – mostly mediated by habitat disturbance – facilitates the invasion of exotic flower visitors in temperate forests of the southern Andes, Argentina. We recorded visit frequencies and the identity of visitors to the flowers of 15 native and 15 exotic plant species occurring in different highly disturbed and less disturbed habitats. We identified three alien flower visitors, the hymenopterans Apis mellifera, Bombus ruderatus, and Vespula germanica. We found significantly more visitation by exotic insects in disturbed habitats. This pattern was explained, at least in part, by the association between alien flower visitors and flowers of exotic plants, which occurred more frequently in disturbed habitats. However, this general pattern masked different responses between the two main alien flower visitors. Apis mellifera exploited almost exclusively the flowers of a subset of herbaceous exotic plants that thrive under disturbance, whereas B. ruderatus visited equally flowers of both exotic and native plants in both disturbed and undisturbed habitats. We did not find any strong evidence that flowers of exotic plants were more generalist than those of native plants, or that exotic flower visitors were more generalist than their native counterparts. Our results suggest that alien plant species could facilitate the invasion of at least some exotic flower visitors to disturbed habitats. Because flowering plants as well as flower visitors benefit from this mutualism, this association may enhance, through a positive feedback, successful establishment of both exotic partners.     

Species turnover of monkey beetles (Scarabaeidae: Hopliini) along environmental and disturbance gradients in the Namaqualand region of the succulent Karoo, South Africa

Species turnover of monkey beetle (Scarabaeidae: Hopliini) assemblages along disturbance and environmental gradients was examined at three sites within the arid, winter rainfall Namaqualand region of the succulent Karoo, South Africa. At each site two study plots with comparable vegetation and soils but contrasting management (grazing) histories were chosen, the disturbed sites having fewer perennial shrubs and generally more annuals and bare ground. Beetles collected using coloured pan-traps showed a consistently higher abundance in disturbed sites. Lepithrix, Denticnema and Heterochelus had higher numbers in disturbed plots, while Peritrichia numbers were lower in disturbed areas. Measures of species richness and diversity were consistently higher in the undisturbed sites. Distinctive assemblages of monkey beetles and plants occurred at each site. A high compositional turnover ( diversity) was recorded for both monkey beetles and plants along a rainfall gradient; between-site diversity values ranged from 0.7 to 0.8 (out of a maximum of 1.0). Species turnover of beetles was higher between the disturbed sites along the environmental gradient than the corresponding undisturbed sites. The high monkey beetle species turnover is probably linked to the high plant species turnover, a distinctive feature of succulent Karoo landscapes. Monkey beetles are useful indicators of overgrazing disturbance in Namaqualand, as their pollinator guilds are apparently disrupted by overgrazing. A shift away from perennial and bulb pollinator guilds towards those favouring weedy annuals was observed in disturbed areas. The consequences to ecosystem processes due to the effects of disturbance on monkey beetle communities and the role of monkey beetles as indicators of disturbance is discussed, as well as the implications of disturbance on monkey beetle pollination guilds.     

Feral pigs in a temperate rainforest ecosystem: disturbance and ecological impacts

Feral pigs (Sus scrofa) are a widespread invasive species, and cause biotic disturbance. This study evaluated the impacts associated with ground disturbance by feral pigs in the North Island of New Zealand. Exclosure cages were erected over feral pig-disturbed ground and visually undisturbed ground (the latter as controls). Buried resin bags and litter bags were located in these plots to examine differences in soil nutrients and decomposition rates and seedling/sapling recruitment (abundance, species composition and richness) was monitored over 21 months. No difference was found in the litter decomposition between the disturbed and visually undisturbed plots. Significantly more nitrate (NO₃-N/NO₂-N) was found in the disturbed exclosures. Seedling density was not significantly affected by feral pig disturbance. However, seedling/sapling species richness was lower in disturbed areas. Species composition changes occurred at disturbed sites with species increasing and decreasing in density after feral pig disturbance. However, no pattern was observed between species that were negatively affected by feral pig disturbance. This study shows that feral pig disturbance affects vegetation through direct removal, but also indirectly through increased nitrate, potentially leading to seedling and sapling species composition changes. Feral pigs are known to return to previously disturbed areas to re-disturb. These areas may remain in a re-disturbed state if not protected, and through continued disturbance and increased nitrate, ecosystem changes may occur, especially in characteristically nutrient poor environments.     

Effects of human disturbance on composition and structure of Brachystegia woodland in Arabuko-Sokoke Forest, Kenya

We examined tree species diversity, density, dispersion patterns and size class distributions in Brachystegia woodland of Arabuko-Sokoke Forest, Kenya. The metrics varied with human disturbance (disturbed versus relatively undisturbed areas). Julbernardia magnistipulata Harms occurred only in the undisturbed site. Brachystegia spiciformis Benth. had the highest importance value (IV) at both study sites, whereas the IVs for the other tree species were greater within the undisturbed than the disturbed sites. Simpson's Diversity Index and tree densities were greater in the undisturbed site than in the disturbed site. All seven tree species exhibited random dispersions in the disturbed site, but three species were clumped in the undisturbed areas. Smaller individuals of B. spiciformis were over-represented in the disturbed habitat relative to the undisturbed habitat. In contrast, J. magnistipulata , Lannea schweinfurthii Engl. and Mimusops obtusifolia Wall. exhibited a greater proportion of smaller trees in the undisturbed site. The tree size class distributions may provide an index of regeneration for these four tree species in the disturbed and undisturbed sites respectively. Active management and restoration may be desirable for J. magnistipulata but appears unnecessary for the remaining common tree species. Illegal logging has persisted in the forest despite its conservation status over many decades. If logging activities cease, it would be instructive to document changes in vegetation composition and structure over time.     

Terrestrial wildlife responses to logging and fire in a Bolivian tropical humid forest

Logging and wildfire are significant anthropogenic disturbance agents in tropical forests. We compared the abundance and species richness of selected terrestrial wildlife taxa including small mammals, amphibians, reptiles, and terrestrial invertebrates in areas burned by wildfire and then logged and in adjacent undisturbed areas of a tropical humid forest in Bolivia. Disturbed areas had 24% less canopy cover than undisturbed areas but had 2.6 times the cover of large woody debris. Understory cover did not differ between disturbed and undisturbed areas. Small mammal abundance and species richness in disturbed areas were 43 and 70% higher, respectively, than in adjacent undisturbed areas. Herpetofaunal abundance did not differ significantly among disturbed and undisturbed areas, but trends for higher abundance were observed for both reptiles and amphibians in disturbed areas. Herpetofaunal species richness was significantly higher in disturbed compared to undisturbed areas. Total terrestrial invertebrate abundance, as estimated by pitfall traps, was significantly higher in undisturbed compared to disturbed areas mostly due to higher abundances of Formicidae and Blattidae. However, two invertebrate groups, Orthoptera and Lepidoptera (larvae) were more abundant in disturbed areas. Wildlife conservation strategies for areas where logging or wildfire occur should take into account species- or guild-specific responses to these disturbance agents.     

The effects of human disturbance on the species composition,species diversity and functional diversity of a Miombo woodland in northern Malawi

Anthropogenic disturbances have serious impacts on ecosystems across the world. Understanding the effects of disturbance on woodlands, especially in regions where local people depend on these natural resources, is essential for sustainable natural resource management and biodiversity conservation. In this study, we evaluated the effects of anthropogenic disturbance, specifically selective logging of Brachystegia floribunda, on woodlands by comparing species composition, species diversity and functional diversity of woody plants between disturbed and undisturbed woodlands. We combined species data and functional trait data for leaves, fruits and other traits related to resource and disturbance responses to calculate functional indices (functional richness, evenness and divergence) and community‐weighted means of each trait. Shifts in taxonomic species composition were analysed using nonmetric multi‐dimensional scaling. Species composition differed significantly between disturbed and undisturbed woodlands. Tree density was greater in disturbed woodlands, whereas evenness, functional evenness and functional divergence were greater in undisturbed woodlands. In terms of forest cover, selective logging of B. floribunda appeared to have little impact on Miombo woodlands, but some shifts in functional traits, such as the shift from a deciduous to evergreen phenology, may increase the vulnerability of these ecosystems to environmental change, especially drought.     

青藏高原多年冻土区不同草地生态系统恢复能力评价

草地生态系统恢复能力是评价人类工程活动对青藏高原多年冻土生态系统影响的重要组分.分析了不同草地生态系统干扰带和非干扰带群落特征、植物多样性、草地初级生产力和经济类群,综合评价了青藏高原多年冻土区地上植被在受工程活动干扰后的综合恢复能力.结果表明:经过近20多年的自然恢复,青藏苔草草原、紫花针茅草原、扇穗茅草原、高山嵩草草甸、矮蒿草草甸和藏蒿草沼泽化草甸6种草地的盖度和物种组成均有一定程度的恢复,且草原群落的恢复程度好于草甸群落,但干扰群落仍低于未干扰群落;紫花针茅草原分布区物种多样性恢复好于其他草地类型分布区;干扰带由最初的地上植物生物量全部为0恢复到148.8～489.6 g·m^-2,其中藏嵩草沼泽化草甸干扰带恢复最好,生物量达489.6 g·m^-2;除藏嵩草恢复群落的饲用植物类群组成相对稳定外,干扰后的其他5种草地类型饲用价值降低.高寒草原生态系统的植被综合恢复能力显著高于草甸生态系统.     

Community and population dynamics of serpentine grassland annuals in relation to gopher disturbance

Summary This study examines the effects of soil disturbance by gophers on patterns of species abundance in an annual grassland community on serpentine soil. We assessed production, dispersal and storage of seed, germination, survivorship and growth of the most abundant species in undisturbed vegetation and on gopher mounds. Fewer seeds of the dominant species were dispersed onto gopher mounds due to the limited movement of seeds from within the closed vegetation. Species with taller flowering stalks were more likely to colonise gopher mounds. The timing of gopher disturbance in relation to the timing of seed fall determined which species could colonise mounds. Lower numbers of seeds falling onto gopher mounds resulted in lower seedling densities of several species compared with undisturbed areas. Survivorship of the commonest species differed between undisturbed areas and gopher mounds formed at different times of year. This resulted in characteristic spectra of species abundance on the different microhabitats, giving rise to distinct spatial patterning in the community. Plants growing on gopher mounds were generally larger and produced more seed than plants in undisturbed vegetation. We suggest that continued gopher disturbance is a factor allowing several species, including perennial grasses, to persist in this community.     

Acridids as indicators of disturbance in dry deciduous forest of West Bengal in India

Acridid communities are sensitive to anthropogenic disturbance and the community structure of acridids plays vital role in functioning the forest ecosystem. They are potentially useful bioindicators for conservation planning and habitat disturbances. Acridid assemblages of three different habitat types based on degree of disturbance as follows five natural sites, five moderately disturbed sites and five highly disturbed sites in Chaupahari forest, West Bengal, India were studied. Diversity, abundance, equitability and species richness of acridid were observed in respect to undisturbed and disturbed habitats. The species richness and diversity of the sites tracked the intensity of disturbance, the greatest value being associated with the natural site followed by the moderately disturbed site and highly disturbed site. The highest species richness and diversity index indicate the suitable habitat for acridid population. Statistical analysis infers that different species show different behavior and the sites are also different in relation to different habitat types.     

Disturbances by human trampling alter the performance,sexual reproduction and genetic diversity in a clonal woodland herb

Disturbances play a major role in structuring the community composition in a variety of ecosystems. The potential impact of disturbances on sexual reproduction and genetic diversity of plants has so far received little attention. We examined the effects of disturbance by human trampling on the performance, sexual reproduction and clonal diversity in the woodland herb Anemone nemorosa in six sites disturbed by intensive recreational activities and in six undisturbed sites in suburban forests in Switzerland. Disturbance by human trampling decreased shoot height of A. nemorosa and altered the size-dependent flowering probability function. Furthermore, in disturbed sites an increased percentage of aborted seeds was found, resulting in a reduced sexual reproductive potential of A. nemorosa populations. Both clonal and genetic diversity of A. nemorosa were reduced in disturbed sites. Our study shows for the first time that disturbance by human trampling can decrease the genetic diversity in a clonal woodland plant. This suggests that genetic aspects of woodland plants should be considered in restoring degenerated forest sites.