Moderately Disturbed Research Articles

The effects of disturbance on woody species composition, structure and regeneration status in the ura natural forest, Guangua district, Awi Zone, Ethiopia

Ethiopia Province has diverse forest resources. However, it has decreased over time, leaving the country's forest with only remnant patches. Therefore, the present study was conducted to examine the species composition, structure and regeneration status of woody plant species along disturbance gradients. To collect the data, the forests were first stratified into low disturbed (LD), moderately disturbed (MD) and heavily disturbed (HD) groups based on information from reconnaissance site visits and consultations with key informants. Three transect lines were laid systematically 200 m apart, and rectangular plots 10 m∗20 m (200 m2) in length were laid at 50 m intervals along each transect, for a total of 27 plots. The DBH and height of all woody individuals with ≥5 cm and ≥2 m were measured. Seedling and sapling data were recorded in four subplots of 2 m∗5 m (10 m2) respectevly in the opposite corner of the main plot. Woody species density, richness, evenness, diversity, frequency and IVI were determined for each disturbance class, and one-way ANOVA and mean comparison tests were used to examine significant differences among disturbance classes. A total of 37 woody species and 27 families were recorded. Based on structural analysis, only Croton macrostachyus exhibited an inverted J shape. It is concluded that woody species composition was affected by human disturbance. Therefore, a concentrated form of forest conservation should be established to protect against excessive human disturbance.

Anthropogenic disturbance produces divergent effects in the community structure and composition of tropical semi-evergreen forests in the Eastern Himalaya

Studies documenting anthropogenic disturbance-driven changes in forest communities of the Eastern Himalaya, a global biodiversity hot spot, are largely lacking. We studied six forest sites of tropical semi-evergreen forests in Arunachal Pradesh in the Eastern Himalaya to understand the effects of varying disturbance intensities on the forest community structure and composition. Based on the magnitude of disturbance, forest sites were classified as experiencing low, moderate and high disturbance. Mean species richness (SR) of trees and shrubs decreased from low disturbance to high disturbance. Mean SR of herbs was maximum in moderately disturbed forest sites. Maximum values of the Shannon-Wiener Diversity Index (SD) were recorded for trees at sites with low disturbance, for shrubs at sites with high disturbance and for herbs in moderately disturbed forests. Pilelou Evenness Index (EI) values were maximum for trees at sites with high disturbance, while maximum EI values for shrubs and herbs were recorded in the forest sites with low disturbance. The number of tree families decreased from 18 to 13 in the forests with low and high disturbance, respectively. Moderate disturbance led to increased herb species richness and diversity, while increasing disturbance produced contrasting effects on trees. High anthropogenic disturbance led to low species richness, but high diversity amongst shrubs. Our investigations suggest that the magnitude of disturbance elicits differential responses in different physiognomic classes in the forest ecosystems and further our understanding of the effects of disturbance in tropical forest ecosystems of a global biodiversity hotspot.

Macroinvertebrate assemblages along a gradient of physicochemical characteristics in four riverine wetlands, Upper Blue Nile basin, Northwestern Ethiopia

This study aims to examine the physicochemical variables that influence macroinvertebrate assemblages in wetlands of the Fetam River watershed. Macroinvertebrates and water quality samples were collected from 20 sampling stations across four wetlands between February and May 2022. Principal component analysis (PCA) was used to elucidate the physicochemical gradients among datasets and canonical correspondence analysis (CCA) was applied to explore the relationship between taxon assemblages and physicochemical variables. Aquatic insects such as Dytiscidae (Coleoptera), Chironomidae (Diptera), and Coenagrionidae (Odonata) were the most abundant families, and they comprised 20-80% of the macroinvertebrate communities. As demonstrated by cluster analysis, three site groups including slightly disturbed (SD), moderately disturbed (MD), and heavily disturbed (HD) sites were identified. PCA showed a clear separation of slightly disturbed sites from moderately and highly impacted sites. Differences in physicochemical variables, taxon richness and abundance, and Margalef diversity indices were observed along the SD to HD gradient. Phosphate concentration was an important predictor that influenced richness and diversity. The extracted two CCA axes of physicochemical variables accounted for 44% of the variability in macroinvertebrate assemblages. Nutrient concentration (nitrate, phosphate, and total phosphorus), conductivity, and turbidity were the main drivers of this variation. This suggested the need for sustainable wetland management intervention at the watershed level, ultimately benefiting invertebrate biodiversity.

Tree community structure, carbon stocks and regeneration status of disturbed lowland tropical rain forests of Assam, India

Tropical rain forests are global hotspots of biodiversity and key climate change regulators. Despite the decades of conservation efforts, tropical forests are increasingly under continuous threat from human activities. Therefore, understanding the impact of anthropogenic disturbances on biodiversity is necessary for better conservation and management. This study focused on a tropical rainforest located in Kakoi reserve, Assam, in the northeastern Himalayas, aiming to compare tree species composition, diversity, carbon stocks, and regenerating status in two forest sites experiencing disturbance regimes. A total of 55 tree species representing 36 genera and 26 families were recorded in the study area. The tree species richness was slightly higher in moderately disturbed (MD) Dirgha than in the highly disturbed (HD) Kakoi-Rajgarh forest. Tree density and basal area were 582 and 446 individuals ha−1, 38.43, and 32.63 m2 ha−1, respectively, in MD-Dirgha and HD-Kakoi-Rajgarh. Forest stand structure followed a typical reverse J-shaped trend in both sites, with a lesser density of large girth-class (>330 cm girth at breast height) individuals in HD-Kakoi-Rajgarh, reflecting the influence of past onsite disturbances. The analysis of the regeneration strata depicted that seedling and sapling density was 1.8 and 1.4 times lower in HD-Kakoi-Rajgarh compared to MD-Dirgha. Above-ground biomass and total carbon stocks were maximum in MD-Dirgha, followed by HD-Kakoi-Rajgarh. About 63.64% of the recorded tree species, including Critically Endangered Vatica lanceifolia are under IUCN Red List Categories, thus stressing the need for conservation. Our findings suggest that conserving species diversity and carbon reserves in tropical forests would principally depend on minimizing forest loss and degradation.

Tree Species Diversity and Regenerating Potential along Disturbance Gradient in Chandragiri Hill, Kathmandu, Central Nepal

Tress species regeneration is greatly influenced by climatic, topographic, and anthropogenic activities. Present study was designed to examine the tree species diversity and their regeneration patterns along the anthropogenic disturbance gradient in the temperate forest of Chandragiri Hill, Central Nepal. Data were obtained from 90 sample plots ranging between 1560 to 2290 m asl after randomly sampling along three disturbance classes classified based on canopy coverage and degrees of disturbance activities in 2021. Circumference at breast height (1.37 m height above the ground) of each tree individual was measured and classified into tree, sapling, and seedling. A total of 47 tree species belonging to 42 genera and 26 families were obtained by this study. The highest species richness for seedlings and saplings was obtained in severely disturbed areas and tree species richness in the moderately disturbed area. The tree stands density varied between 350 to 1017 individuals ha-1 with the total basal area between 12.7 to 72.78 m2 ha-1 with the least value in a highly disturbed area and highest in the least disturbed area. The seedling and sapling densities were found increased from lower to more disturbed forests indicating that the forest fragmentation negatively affected the regeneration. The highest values of the Shannon Weiner index, Pielou Index, and the lowest value of the Simpson index were observed at moderate disturbance areas. About 36 to 60% of species were found regenerating in the less disturbed and moderately disturbed forests and no regeneration in severely disturbed areas. Elevation, canopy cover, landslide, and slopes were found to be the most influential variables in forest regeneration as significantly represented by CCA1. The present study has found a moderate level of disturbance to become beneficial for better regeneration of tree species. So, the reduction of excessive disturbance from local people would be a better option for the adequate regeneration of tree species.

Comparison of Woody Species Diversity and Population Structure Along Disturbance Gradient in Babile Elephant Sanctuary, Ethiopia

Abstract The study was conducted at Babile Elephant Sanctuary (BES), to identify and document the list of woody species, and to analyze the diversity, richness, evenness, and population structural status of woody species. The diversity of plant species and population structure of woody species were analyzed from 60 quadrats, each with 20 m x 20 m for trees and 5 m x 5 m for shrubs and climbers, using systematic sampling methods with three levels of disturbances regime, namely, low disturbed (LD), moderately disturbed (MD) and heavily disturbed (HD) sites. Vegetation parameters such as diameter at breast height (DBH), richness, evenness, and density of woody species were recorded. Shannon Weiner Diversity Index was used to analysis vegetation diversity and evenness. A total of 61 woody species were identified in the study area that falls within 29 families and 38 genera of which 50.8 % were shrubs, 39.3 % were trees and the rest 9.83 % were climbers. Fabaceae was represented by the highest number of species (14 species = 22.90). The highest plant species richness was recorded from the low disturbed sites, followed by moderately disturbed and heavily disturbed sites respectively. The population density of vegetation was significantly higher in the MD site, followed by the LD site. The total basal area of LD, MD, and HD were 27.2, 19.8, and 11.2 m2/ha, respectively. LD site had significantly (P= 0.04) highest Shannon’s diversity index value (3.21) than the others two disturbance levels. This result suggests that the consequence of human-induced disturbance on woody species diversity and population structure appeared to be negative depending on the type and intensities of the disturbances.

Occupancy of wild southern pig-tailed macaques in intact and degraded forests in Peninsular Malaysia.

Deforestation is a major threat to terrestrial tropical ecosystems, particularly in Southeast Asia where human activities have dramatic consequences for the survival of many species. However, responses of species to anthropogenic impact are highly variable. In order to establish effective conservation strategies, it is critical to determine a species’ ability to persist in degraded habitats. Here, we used camera trapping data to provide the first insights into the temporal and spatial distribution of southern pig-tailed macaques (Macaca nemestrina, listed as ‘Vulnerable’ by the IUCN) across intact and degraded forest habitats in Peninsular Malaysia, with a particular focus on the effects of clear-cutting and selective logging on macaque occupancy. Specifically, we found a 10% decline in macaque site occupancy in the highly degraded Pasoh Forest Reserve from 2013 to 2017. This may be strongly linked to the macaques’ sensitivity to intensive disturbance through clear-cutting, which significantly increased the probability that M. nemestrina became locally extinct at a previously occupied site. However, we found no clear relationship between moderate disturbance, i.e., selective logging, and the macaques’ local extinction probability or site occupancy in the Pasoh Forest Reserve and Belum-Temengor Forest Complex. Further, an identical age and sex structure of macaques in selectively logged and completely undisturbed habitat types within the Belum-Temengor Forest Complex indicated that the macaques did not show increased mortality or declining birth rates when exposed to selective logging. Overall, this suggests that low to moderately disturbed forests may still constitute valuable habitats that support viable populations of M. nemestrina, and thus need to be protected against further degradation. Our results emphasize the significance of population monitoring through camera trapping for understanding the ability of threatened species to cope with anthropogenic disturbance. This can inform species management plans and facilitate the development of effective conservation measures to protect biodiversity.

Low- to Moderate-Level Forest Disturbance Effects on Plant Functional Traits and Associated Soil Microbial Diversity in Western Himalaya

This study quantifies the effect of low- to moderate-intensity anthropogenic activities and natural activities affecting less than 40% of the canopy cover on major plant functional traits and associated soil microbial diversity in western Himalayan temperate forests. Plots of 0.1 ha were placed in the temperate forests along disturbance gradient and were categorized based on lopping intensity, deadwood counts, grazing, and litter removal. Plots were classified into three classes, i.e., low disturbance intensity (LDI) and moderate disturbance intensities (MDI1 and MDI2) based on lopping activities and canopy cover. The study was conducted on functional traits related to growth and survival strategies of a species in a complex forest ecosystem. Furthermore, DNA was extracted and metagenome of soil samples was performed using Illumina MiSeq platform from three disturbance classes to study the effect of disturbance and plant traits on microbial diversity. Tree basal area was found to be most significantly affected by disturbance intensity. Total density was found to be greater for the LDI site. Specific leaf area (SLA) and crown cover (CC) were the most affected traits in the moderately disturbed sites, whereas maximum plant height (HT) and seed mass (SM) were least affected by disturbance. Soil microbial diversity was found to be negatively associated with disturbance index. Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were found to be significantly higher in LDI sites. Disturbance level elicited variation in microbial community composition.Proteobacteriawas the most abundant phylum andPhenylobacterium,DA101, andCandidatus solibacterwere mainly abundant at the genus level. A decreasing level of disturbance due to the absence of human residences in the LDI site led to the dominance ofPhenylobacterium(27%) which reduced to 18% in MDI1 site. Shannon alpha bacterial diversity and plant species diversity (H′) were found to be greatest for MDI2 site. In forests with varying levels of management, treefall gaps due to low levels of logging intensity might have a similar effect to those of reduced lopping intensities and deadwood count (due to natural disturbances) in the study sites. The study concludes that moderate disturbance is important for promoting species diversity and species richness (SR), but species having conservative ecological strategies would be more prone to continued disturbance intensity. Therefore, low- to moderate-level disturbance in such forests can be used as a model for natural treefall gaps, and moderate-level disturbance intensity plays a powerful role in buffering ecosystem processes.

Spatial pattern and interspecific association of tree species in coniferous and deciduous broad-leaved mixed forest under different disturbance intensities

We explored the effects of disturbance densities on the spatial pattern and the association of tree species in the coniferous broadleaved mixed forest in Pangquangou Nature Reserve of Guandi Mountain. Using three factors including canopy density, stand density and number of stumps, we classified the disturbance intensities of different forest stands into three levels, non-disturbance, moderate disturbance, and severe disturbance. The spatial distribution pattern and the association of different tree species were analyzed by spatial point pattern K2 function. The results showed that the diameter distribution of trees in undisturbed plots was inverted 'J' type, while that of moderate disturbance and serious disturbance plots was under bimodal curve distribution. The stand distribution pattern showed a small-scale aggregated distribution under undisturbed and moderately distur-bance, and a random distribution under heavy disturbance. At the small scale, the coniferous and broadleaved species showed no correlation in undisturbed stands, were positively correlated in moderately disturbed stands, and negatively correlated in seriously disturbed stands. At large scale, they were no correlated in both moderately and seriously disturbed stands. The results suggested that abundance of trees with small diameter in the forests was negatively with disturbance intensity, which led to the lower degree of intraspecific aggregation at small scale. Meanwhile, appropriate levels of disturbance would benefit the collaborative use of environmental resources for trees. Our results revealed the impacts of disturbance density on forest community structure and could provide theoretical basis for forest management.

Structure and composition of tree species in tropical moist deciduous forests of Eastern Ghats of Odisha, India, in response to human-induced disturbances

The changes in plant species diversity and community structure in response to human induced disturbances were studied in 12 ha of tropical moist deciduous forest stands of Eastern Ghats of Odisha, India. The forest stands were classified as undisturbed (UD), moderately disturbed (MD) and highly disturbed (HD) categories based on the types and levels of human-induced disturbance. Twenty four transects, each measuring 0.5 ha (5 m × 1000 m) were laid for enumeration of trees with ≥ 30 cm GBH. In total, 5451 trees under 101 species, 78 genera and 37 families were found to occur in the study site. The density of trees and basal area decreased with the increase in the level of disturbance. While the stand density varied in the range of 185.50 in HD stands to 744 stems ha−1 in UD stands, basal area ranged between 12.54 in HD to 36.95 m2 ha−1in UD stands. The number of individuals and number of species per unit area showed a declining trend with increase in girth class. Maximum number of species and density was recorded for trees of low girth class (30–60 cm) in all three stands. Shannon, Simpson, Fisher’s alpha and Margaleff’s indices varied greatly across the three stands experiencing different levels of disturbance. Shannon’s Index varied between 3.20 and 3.42 and Simpson Index ranged from 0.09 to 0.12. The range of variation in Evenness index, Fisher’s alpha index and Margaleff’s index were recorded between 0.75–0.79, 14.45–16.10 and 29.65–34.83, respectively. The diversity of shrub, liana and herb species and regeneration potential of tree species were assessed from two 5 m × 5 m sub-plots located within each transect. Dominance of trees in undisturbed forests, shrubs and lianas in moderately disturbed and herbs in highly disturbed forests were observed. The data generated in the present investigation may prove useful for formulation of appropriate forest management strategies.

Effect of disturbance on population structure, regeneration and conservation of Moghania chappar in sal forests of Gorakhpur, India

Non-seed regeneration is essentially a vagrant strategy of woody plants causing assemblage of homozygous populations in disturbed forests. We tried to understand how such hardy species like Moghania chappar produce close groups of individuals at different level of disturbance. The hypothesis of trade-off between ramet proliferation and disturbance level, and between growth pattern and resource conservation was tested. The three 1-ha sample plots of sal forest, facing low, moderate or high level of disturbance were observed within Sohagibarwa Wildlife Sanctuary. A total of 40 quadrats per 1-ha plot were sampled to record the age structure of genet and ramet populations of M. chappar. The architecture and foraging of the root-stock was mapped, the biomass of root and shoot was measured and the soil conserved by the root-complex was estimated at each disturbance level. The growth characteristics suggest that M. chappar conforms to Stone’s model of tree architecture. At moderate disturbance, the root-shoot junction sent many more sprouts, garnered much biomass and became flat and curved. The insurrection of ramets caused fragmentation of the root-complex. This clonal growth strategy, however, was neither clearly ‘phalanx’ nor ‘guerrilla’ type. It resulted in intermittent shallow cavities within fragmented root-stock that got filled with soil rich in organic matter. The growth strategy of the species showed potential to restore the soil system and to conserve the diversity of minor biota. In moderately disturbed sal forest, the understorey paved way to prolific non-seed regeneration of this fugitive mid-successional species. At moderate heat stress, the number of individuals as well as the proportion of seedlings per population was highest. The species rapidly increased the understorey foliage by producing a metapopulation of usable sprouts/ramets that facilitated retention of soil and nutrients within their root traps. The total extractible shoot biomass per plant was quite large as a ~ 6 year old individual weighed 473.5 ± 27.4 g. This study of clonal plant ecology may provide new impetus to the conservation of degraded forest ecosystems.

English

Transformation of natural landscapes is the leading cause of global biodiversity decline. This is often exacerbated through anthropogenic activities that result in the alteration of natural ecosystem. Displacement of local species is characteristics of this process and this is of negative consequence especially for species in mutualism. In this study, how grazing and mowing activities influence flower-insect interactions and communities of interacting partners was assessed. Insect-flower interactions were sampled in four replicates, each of grazed and mowed grasslands in a moderately disturbed ecosystem. Mean distance to natural areas was determined during the study to assess the buffering effect of these natural areas on insect-flower interactions in the local habitats. Flower visiting insect species richness and abundance were not significantly different between grazed and mowed grasslands; however, flowering plants richness and abundance were higher in grazed grasslands. Mean number of interactions was also higher in grazed grassland as compared to mowed. Furthermore, mean number of interactions reduced with increase in distance from the forest. This study showed the importance of natural habitat as a refuge for displaced flower-visiting insects from disturbed areas in a transformed landscape. Mutualistic partners in interaction tend to be resilient to moderate disturbance such as grazing in this study; however, an increase in the intensity of disturbance above the moderate threshold may result in a breakdown of interaction networks. Key words: Network metrics, grazing, landscape disturbance, flower-visiting insects, natural habitat.

Population collapse dynamics in Acropora downingi, an Arabian/Persian Gulf ecosystem-engineering coral, linked to rising temperature.

As in the tropical Atlantic, Acropora populations in the southern Persian/Arabian Gulf plummeted within two decades after having been ecosystem engineers on most wave-exposed reefs since the Pleistocene. Since 1996/1998 live coral cover in the Gulf declined by over 90% in many areas, primarily due to bleaching and diseases caused by rising temperatures. In the formerly dominant table-coral species A.downingi, population dynamics corresponding to disturbance regimes was quantified in three transition matrices (lower disturbance pre-1996; moderate disturbance from 1998 to 2010 and 2013 to 2017, disturbed in 1996/1998, 2010/11/12, 2017). Increased disturbance frequency and severity caused progressive reduction in coral size, cover, and population fecundity. Small size-classes were bolstered more by partial colony mortality than sexual recruitment. Some large corals had a size refuge and resisted die-back but were also lost with increasing disturbance. Matrix and biophysical larval flow models suggested one metapopulation. Southern, Arabian, populations could be connected to northern, Iranian, populations but this connectivity was lost under assumptions of pelagic larval duration at rising temperatures shortened to a third. Then, the metapopulation disintegrated into isolated populations. Connectivity required to avoid extinctions increased exponentially with disturbance frequency and correlation of disturbances across the metapopulation. Populations became unsustainable at eight disturbances in 15years, when even highest theoretical recruitment no longer compensated mortality. This lethal disturbance frequency was 3-fold that of the moderately disturbed monitoring period and 4-fold of the preceding low-disturbance period-suggesting ongoing shortening of the disturbance-free period. Observed population collapse and environmental changes in the Gulf suggest that A.downingi is heading toward at least functional extinction mainly due to increasingly frequent temperature-induced mortality events, clearly linked to climate change.

Effects of anthropogenic disturbance on tree population structure and diversity of a rain forest biosphere reserve in Ghana, West Africa

AbstractWe evaluated the impacts of anthropogenic disturbance on community structure and diversity along three management zones of the Bia biosphere reserve in Ghana. Sixty sample plots were distributed among the core, buffer and transition zones. We estimated the degree of disturbances from discernible indicators on the field and satellite images. All tree species ≥10 cm dbh (diameter at breast height) were identified and enumerated. Inventory data were compared across the zones and related to intensity of disturbances. A total of 1176 individual trees from 108 species and 33 families were encountered. Number of species varied from 27 in the highly disturbed (HD) to 61 in the least disturbed (LD) zone. Mean basal area (BA) varied from 11.71 in the HD to 28.26 in the LD. Both Margalef's species richness and Shannon‐Weiner's α‐diversity were highest in the moderately disturbed (MD) than either the least and most disturbed zones. Our study revealed significant differences in tree abundance, stem density, BA and species diversity, attributable to differences in degree of anthropogenic disturbances among zones. Given the different levels of anthropogenic disturbance and corresponding impacts across the reserve, we recommend an integrated management strategy for the conservation of biodiversity in the Bia biosphere reserve.

Composition, structure, and intra-stand spatial patterns along a disturbance severity gradient in a Quercus stand

Natural forest disturbances, which drive succession and development, differ in extent, severity, and return interval and range from frequent, gap-scale disturbances, to infrequent stand-replacing events. Most studies have focused on natural disturbances near the ends of the disturbance severity gradient and relatively little quantitative information is available on intermediate-severity disturbance. On 20 April 2011, an EF1 tornado tracked 5kmthrough the Sipsey Wilderness in Alabama and resulted in a patchwork mosaic of disturbed areas. To analyze the effects of the intermediate-severity wind event on composition, structure, and intra-stand spatial patterns, we established a 100×200m (2ha) rectangular plot perpendicular to the path of the storm within an affected Quercus alba stand. Based on the basal area removed (i.e. basal area of snags, snapped stems, or uprooted stems in decay class 1) by the wind event, we divided the plot into disturbance classes (minimal, light, and moderate) to compare compositional and structural attributes along a disturbance severity gradient. Composition varied little across the disturbance gradient, but diversity was highest in the moderately disturbed neighborhoods. Stems were relatively intermingled by species (i.e. each tree neighbored by trees of different species) in each disturbance severity class. However, some species, such as Fagus grandifolia and Ostrya virginiana exhibited less intermingling than Quercus spp. and stems classed in the “other spp.” taxonomic group. Large stems were disproportionately removed by the storm in the light and moderate disturbance categories. In the light disturbance class, O. virginiana was significantly less likely to experience mortality from the storm, which may in part explain the relatively high density of O. virginiana stems in the plot.

Anthropogenic disturbances and their impact on vegetation in Western Himalaya, India

The present study assesses anthropogenic disturbances and their impacts on the vegetation in Western Himalaya, India on the basis of various disturbance parameters such as density, Total Basal Cover (TBC) of cut stumps, lopping percentage and grazing intensities. On the basis of canopy cover and frequency of disturbances (%), the studied forests were divided into highly disturbed (HD), moderately disturbed (MD) and least disturbed (LD) categories. The HD forests had the lowest canopy cover, lowest density and lowest TBC and the LD had the highest canopy cover, highest density and highest TBC. The MD forests occupied the intermediate position with respect to these parameters. Species richness was least in HD forests, highest in one of the MD forests while LD forest occupied an intermediate position. The percentage of regenerating species was lowest (54%) in HD and highest (72%) in MD. The density of seedlings and saplings was higher in one of the MD forests as compared to HD and LD. We concluded that the moderate disturbances do not affect the vegetation adversely; however the increased degree of disturbance causes loss in plant diversity; affects regeneration and changes community characteristics. Construction of hydroelectric projects at various places in the study area was found to be one of the most important sources of anthropogenic disturbances in addition to the routine anthropogenic disturbances like grazing, fuelwood collection and fodder extraction. If all proposed dams in the Indian Himalaya are constructed combined with weak national environmental impact assessment and implementation, it will result in a significant loss of species. Therefore, various agents of disturbances should be evaluated in cumulative manner and any developmental activities such as hydropower projects, which trigger various natural and anthropogenic disturbances, should be combined with proper cumulative environmental impact assessment and effective implementation to minimise the anticipated loss of vegetation.

Coarse woody debris and the carbon balance of a moderately disturbed forest

Forested landscapes are shaped by disturbances varying in severity and source. Moderate disturbance from weather, pathogens, insects, and age-related senescence that kills only a subset of canopy trees may increase standing woody debris and alter the contribution of coarse woody debris (CWD) to total ecosystem respiration (RE). However, woody debris carbon (C) dynamics are rarely examined following moderate disturbances that increase standing dead wood pools. We used an experimental manipulation of moderate disturbance in an upper Great Lakes forest to: (1) examine multi-year changes in CWD mass through a moderate disturbance; (2) quantify in situ CWD respiration during different stages of decay for downed and standing woody debris and; (3) estimate the annual contribution of CWD respiration to the ecosystem C balance through comparison with RE and net ecosystem production (NEP). Six years following disturbance, we found that the standing dead wood mass of 24.5MgCha−1 was an order of magnitude greater than downed woody debris mass and a large source of ecosystem C flux. Instantaneous in situ respiration rates from standing and minimally decayed downed woody debris were not significantly different from one another. Separate estimates of ecosystem CWD respiration of 1.1–2.1MgCha−1yr−1 six years following disturbance were comparable in magnitude to NEP and 12.5–23.8% of RE, representing a substantial increase relative to pre-disturbance levels. Ecosystem respiration and NEP were stable following moderate disturbance even though ecosystem CWD respiration increased substantially, suggesting a reduction in the respiratory C contribution from other sources. We conclude that standing and downed CWD can be essential components of the ecosystem C balance following moderate severity disturbance.

Responses of tropical forest herpetofauna to moderate anthropogenic disturbance and effects of natural habitat variation in Sulawesi, Indonesia

Tropical forest destruction is a major contributor to global biodiversity loss, with much of remaining forests subject to extensive subsistence use. Compared to forest clear-felling and conversion, the impacts of these less intense but complex disturbance regimes on biodiversity remain poorly understood. Given the challenges of protecting pristine tropical forests for conservation in developing regions, there is a strong imperative to understand the role of altered forests with a range of low to moderate disturbance regimes in long term biodiversity conservation. We sampled tropical rainforest reptile and amphibian diversity over a nine year period along a gradient of moderate anthropogenic disturbance to intact primary rainforest in Sulawesi, Indonesia. We evaluated the relative influences of anthropogenic disturbance proxies and natural habitat variability on species richness and assemblage composition. Reptile and amphibian species richness were affected by natural variability in a range of habitat characteristics, but not by moderate anthropogenic disturbance. In contrast, species composition varied with both natural and anthropogenic disturbance metrics. Our results indicate that even low to moderate levels of anthropogenic disturbance have measurable, pervasive, impacts on tropical herpetofaunal diversity. However, moderately disturbed and altered forests that retain relatively high canopy cover and habitat complexity still retained most species associated with primary forest, indicating that they provide a significant contribution to herpetofaunal biodiversity conservation. Management implications from these findings complement those for birds and large mammals in tropical Asia, in that sustainable biodiversity conservation is likely to be best achieved by maintaining larger forest areas of variable disturbance and usage regimes around more remote, minimally disturbed core areas.

Seasonal dynamics of dissolved organic carbon, nitrogen and other nutrients in soil of Pinus massoniana stands after pine wilt disease disturbance

To understand changes in soil nutrients in Pinus massoniana forests affected by pine wilt disease (PWD), we examined the seasonal variation in dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and soil nutrients in Hefei, East China. The results showed a considerable decline in the population density and basal area in both highly disturbed (HD) and moderately disturbed (MD) forest stands and an increase in dead pine trees, causing pronounced changes in the stand structure and soil nutrient status. The concentrations of DOC and NO3-- N were significantly (p < 0.05) higher in every season in the disturbed forests compared to the undisturbed (UD) forest stand. However, during spring and summer, the variation in the DON and NH4+-N values was significantly (p < 0.05) lower in the HD forest stand than in the UD stand; total N concentrations were higher in the disturbed forests in every season. During spring and autumn, the variation in total P values was significantly (p < 0.05) lower in the MD forest stand than in the UD stand, whereas the total P values were significantly (p < 0.05) lower in every season in the HD stand than in the UD stand. In this study, disturbance resulted in a considerable increase in DOC, N and NO3-- N when compared to the UD stand and a pronounced increase in soil nitrate in the HD stand, which may lead to soil acidification, thereby increasing the possibility of soil nutrient leaching.

Non-great-circle propagation modes on the high-latitude HF radio path

We consider characteristics of the non-great-circle signals on the Murmansk—St. Petersburg oblique sounding path with a distance of 1050 km. The path crosses the main ionospheric trough and is highly influenced by the trough’s polar wall and the boundary of diffuse precipitations. Field-aligned ionospheric irregularities and ionization gradients are often observed in this area. The data analysis was performed for quiet, moderately disturbed, and strongly disturbed conditions and for different local times. The main results are as follows. Non-great-circle signals in the form of scattered waves mostly occur in the nighttime hours. The nighttime non-great-circle signals always appear under both quiet and disturbed conditions, while the signals reflected from the ionization gradients appear at any local time during the disturbed periods (storms, substorms). Non-great-circle signals with intense reflections from the ionization gradients are most often observed during a moderate disturbance, especially in the nighttime hours. The ray-tracing model of non-great-circle propagation shows that the calculated oblique sounding ionograms generally coincide with the experimental ones.