Impact Of Human Disturbance Research Articles

Impact of human disturbance on the thermoregulatory behaviour of the endangered ringed sawback turtle (Graptemys oculifera)

Abstract Human recreational disturbance of riverine environments may be contributing to population declines of aquatic organisms worldwide. Aquatic turtles that are heavily dependent on basking in sunlight to maintain an optimal body temperature may abandon basking perches because they perceive humans as potential predators. The impact of boat traffic, the availability of basking structures, and various environmental factors on the basking behaviour of the ringed sawback turtle (Graptemys oculifera) was assessed at two sites on the Pearl River, Mississippi, USA. This information was used to model the likely effects of human disturbance on the body temperature of large female turtles. Both the duration of basking and the percentage of turtles in a basking group that abandoned their basking perch were influenced by the availability of alternative basking sites, frequency of boat traffic, boat speed enforcement zones (‘wake’ or ‘no wake’), boat type, air temperature, weather conditions, and Julian day. A simulation model of anthropogenically disturbed and undisturbed adult female ringed sawbacks showed that disturbance probably decreases the mean daily body temperature, especially at higher disturbance probabilities and in May, when the air temperature is low. Management recommendations are provided that minimize the adverse effects of unintentional human disturbance of the ringed sawback to enable more effective conservation of this endangered, endemic species. Such methods are likely to be useful elsewhere as recreational disturbance becomes a greater conservation issue worldwide.

Impacts of human disturbance on ghost crab burrow morphology and distribution on sandy shores.

Ghost crabs have been widely used as a bio-indicator species of human impacts on sandy beaches to obtain reliable biological data for management and conservation purposes. Ghost crab population densities and individual sizes decline dramatically under human pressure. However, distribution within a beach and the factors that determine this distribution of ghost crabs is still an open question. These factors may provide valuable information for understanding human impacts on sandy beaches. Here we examine ghost crab burrows on 20 sandy beaches of South Carolina, USA under various levels of human impacts to understand the response in terms of spatial distribution of this species to human impacts. We also examine the burrow characteristics and environmental properties of the burrows to determine whether these factors alter burrow characteristics. We show that crabs on heavily impacted beaches altered their spatial distribution to mostly occupy the edges of impacted beaches. Further, this change in spatial distribution was influenced by the size distribution of the population on a beach (i.e. larger individuals occupy upper parts on the beaches). We also found that ghost crabs altered the morphology of their burrows on heavily impacted beaches. Ghost crabs create deeper, steeper and smaller burrows under human impacts. These patterns were also influenced by physical characteristics of the beach. Our results suggest that human impacts can directly influence the spatial distribution of ghost crab populations within a beach and therefore sampling at upper parts of the beaches overestimates the population density and individual sizes. Our results support the use of ghost crabs as indicator species in effective beach management, but suggest that assessments would benefit from examining the morphology and distribution of burrows as opposed to simply using burrow counts to assess the health of sandy shores.

Comparison of a recent elm decline with the mid-Holocene Elm Decline

The threat of devastating pathogens on a range of tree species has increased recently, which justifies the investigation of the temporal dynamics of tree declines caused by disease. The mid-Holocene Elm Decline was a widespread and synchronous event recorded in pollen diagrams across northwest Europe. The probable drivers of this event have been debated for over 80 years but the role of disease has gathered greatest support in recent decades. Here we report pollen data at sub-decadal resolution from a closely sampled sediment core from eastern Ireland covering the last 160 years. This provides data on the structure and dynamics of the surrounding woodland before, during and after the outbreak of Dutch elm disease in the 1970s. A decline in elm was also recorded in the 1940s associated with an earlier, less virulent, outbreak of elm disease. The elm population recovered from the 1940s outbreak after 20 years but did not recover from the 1970s pandemic. The pollen data also facilitate the comparison of this disease-mediated decline with the mid-Holocene Elm Decline; the impact of human disturbance and disease resulted in different woodland compositions and the adjustment of the woodland in response to these factors was rapid. The impact of Dutch elm disease on this elm 1970s population was very similar to that recorded in the mid-Holocene Elm Decline in Britain and Ireland.

Chemical composition and trophic state of shallow saline steppe lakes in central Asia (North Kazakhstan).

The purpose of this study was to identify the prevailing chemical composition and trophic state of the shallow saline steppe lakes of North Kazakhstan along a wide size range (<1-454km2) and salinity gradient (2-322gL-1) on a large spatial scale (1000km), taking into account the potential effects of human disturbances. Water depth, Secchi disk transparency, temperature, pH, electric conductivity, major ions, total dissolved solids, total organic carbon, total nitrogen and phosphorus, nitrate, soluble reactive phosphorus, and chlorophyll a were measured. The equivalent percentage of major ions, Spearman rank correlation, multivariate analyses, equilibrium state of lakes, and spatial GIS autocorrelation were calculated. The impact of human disturbances (settlements, farms, and mines) on total organic carbon, nitrogen, phosphorus, and chlorophyll a were tested by Kruskal-Wallis ANOVA. The most common combinations of dominant ions were Na-Cl>SO4 and Na-Cl (n=16; 64%); the Ca, Mg, HCO3, and SO4 ions precipitate with increasing salinity (2-322gL-1); and ion composition shifts from Na>Mg-Cl>SO4 to Na-Cl. The most of the chemical variables positively, but chlorophyll a negatively, correlated with total dissolved solids, and the total phosphorus had no significant correlation with any variables. The trophic state of these lakes in most cases exceeded the hypertrophic level. The increase in salinity causes change in chemical composition and effects on the phytoplankton development independently from the size of water surface, and the human disturbances had negligible effect on the trophic state of shallow saline lakes in this region of Kazakhstan.

Impacts of human disturbance in tropical dry forests increase with soil moisture stress

AbstractQuestions(1) Which disturbances (harvesting, browsing, drought and fire) are important for tree mortality in a tropical dry forest (TDF), and do these change with size class (juvenile, sapling, adult)? (2) How is mortality and recruitment in a TDF related to soil moisture content (SMC) and does the relationship change for different size classes? (3) Is disturbance‐related mortality selectively removing particular species from the TDF?LocationSonebhadra and Mirzapur districts, Uttar Pradesh, India.MethodsWe analysed the structure of a TDF in central India in terms of the tree composition of juveniles, saplings and adults at five distinct sites located along a gradient of SMC, and recorded the numbers of individuals in each size class killed by the four disturbance types over 2 yr. We also recorded total stem density and recruitment at each site. We compared annual mortality index (AMI) and its four disturbance components (harvesting, browsing, drought and fire) and annual recruitment index (ARI) against the mean SMC of each site using GLMM.ResultsThe impact of all disturbances on total AMI decreased as SMC increased whereas ARI increased as SMC increased. Mortality due to harvesting was substantially higher than other disturbances for adult and sapling trees, whereas both harvesting and browsing were important drivers of mortality for juveniles. There was little evidence that particular species were being deliberately selected for harvesting across sites.ConclusionsTree saplings and adults in this TDF were mainly killed by harvesting, indicating that anthropogenic impacts on tree mortality are more important than non‐anthropogenic impacts in the TDF, and impacts of all disturbances become more severe with increasing water stress. Thus changes in TDF structure due to harvesting are likely to be more rapid in more arid environments.

Meta-analysis of anthropogenic habitat disturbance effects on animal-mediated seed dispersal.

Anthropogenic habitat disturbance is a strong biodiversity change driver that compromises not only the species persistence but also the ecological interactions in which they are involved. Even though seed dispersal is a key interaction involved in the recruitment of many tree species and in consequence critical for biodiversity maintenance, studies assessing the effect of different anthropogenic disturbance drivers on this interaction have not been performed under a meta-analytical framework. We assessed the way habitat fragmentation and degradation processes affect species diversity (abundance and species richness) and interaction rates (i.e., fruit removal and visitation rates) of different groups of seed-disperser species at a global scale. We obtained 163 case studies from 37 articles. Results indicate that habitat degradation had a negative effect on seed-disperser animal diversity, whereas habitat fragmentation had a negative effect on interaction rates. Birds and insects were more sensitive in terms of their diversity, whereas mammals showed a negative effect on interaction rates. Regarding habitat, both fragmentation and degradation had a negative effect on seed-disperser animal diversity only in temperate habitats, and negative effects on interaction rates in tropical and temperate habitats. Our results indicate that the impact of human disturbance on seed-disperser species and interactions is not homogeneous. On the contrary, the magnitude of effects seems to be dependent on the type of disturbance, taxonomic group under assessment, and geographical region where the human impact occurs.

Human impact on tropical-alpine plant diversity in the northern Andes

Conserving paramo diversity and ecosystem services in the northern Andes is urgent, and understanding factors that control vegetation changes is therefore crucial. Although anthropogenic activities have been common in the Andean highlands for cen- turies, the role of human influence in shaping paramo vegetation remains unclear. To assess the relative importance of human disturbance associated with cattle farming and cultivation for plant species diversity and composition, we analyzed variables driven by both natural and human impact in the Santurbanp aramo, Colombia. Canonical corre- spondence analysis (CCA) showed that the main gradient in plant species composition is related to the gradient of human impact. Partial CCA showed that the pure effect of the variables driven by human impact on floristic composition is twice the size of the pure effect of the variables driven by natural impact. Forward selection procedure indicated that the impact of human disturbance on floristic composition is determined by the level of accessibility. Vegetation patterns are driven by a complex set of elevation-related envi- ronmental factors, and human disturbance plays a primary role. Strict protection should be granted to remote and upper sites of the paramo. Restriction of fire and agriculture along steep slopes may counteract negative effects of human disturbance on plant species diversity.

Difference Analysis of Different Land Use Types on Soil Organic Carbon in Loess Gullied-Hilly Region of China

The cycles of carbon in terrestrial ecosystems has received increasing attention worldwide. Because the balance between inputs and outputs of carbon to the soil has an important influences on the atmospheric CO2 and global climate. With the increasing deforestation and overgrazing, the impact of human disturbances on carbon storage and fluxes have exceeded the rate and extent of effects from natural variability, this could significantly raise the CO2 concentration in the atmosphere. Thus, accurate estimations of land use and land cover in soil ecosystem have become increasingly important for estimating the carbon balance of regions. One of the greatest uncertainties concerning the influence of human activities is changes in soil carbon stock. In this study, soil samples were collected form farmland, orchard, woodland, grassland, wasteland five different land use types. Each soil sample core was separated into 0-10, 10-20, 20-40 and 40-60 cm depth. The study revealed the difference of soil carbon pool storage and mass effect in different land use styles by the contrast analysis of total organic carbon, labile organic carbon and carbon management index in number, distribution and changes. The results showed that there were big differences for the density of Total Organic Carbon (TOC) among different land use types, which means soil organic carbon storages were different. The extent of variation of the mass fraction of TOC and LOC was increase with the increase of soil depth and 0-20 cm layer was significantly greater than 20-60 cm layer. Relative to wasteland, the density of LOC and NLOC, total organic carbon storage and carbon management index for other four land use types were higher, especial for woodland and grassland. The woodland use type and grassland use type were significantly increased the carbon management index and improved the quality of soil carbon pool. The change of soil organic carbon reserve is huge influenced by human land use.

Impact of human disturbance, density, and environmental conditions on the survival probabilities of pipistrelle bat (Pipistrellus pipistrellus)

AbstractNatural and anthropogenic disturbances can strongly impact population dynamics of species and are often responsible for zoonotic emerging infectious diseases. However, long‐term studies on the demographic consequences of human disturbances are unusual. We used 6 years (1995–2000) of mark‐recapture data to investigate how climatic conditions, human disturbance and density affect sex‐ and age‐specific apparent survival probabilities of the pipistrelle bat (Pipistrellus pipistrellus, Schreber 1774) in a maternity colony. Our study demonstrated that density played an important role in population dynamics of pipistrelle bat and that its effect differed with respect to age and sex. Notably, human disturbance caused a strong decline of adult female survival, suggesting that perturbations have important consequences in bat‐colony dynamics. Juvenile female survival was negatively influenced by density, being considerably lower in high densities. In contrast, juvenile and adult males were apparently not affected as they had constant survival probabilities. Although climatic factors can markedly affect population dynamics of temperate insectivorous bats, in this study, the weather conditions did not influence the survival rates of pipistrelle bats. We provide the first report that demonstrates the density‐dependent effect on bat survival. That is especially relevant to better understanding of the bat‐population dynamics and to evaluate the consequences of human disturbance and their potential changes in the maternity colony structure.

Endogenous knowledge and human disturbance impact on abundance of two underutilized wild edible tree species in southern Benin

This study assessed endogenous knowledge and impact of human disturbance on the abundance of two underutilized wild fruit tree species: Drypetes floribunda (Müll. Arg.) Hutch. (Euphorbiaceae) and Mimusops andongensis Hiern. (Sapotaceae) in the Lama Forest Reserve (LFR) in southern Benin. A survey was conducted with 145 randomly selected people amongst the surrounding communities of LFR in order to assess the endogenous knowledge of the species. One hundred square plots were established in the forest for characterizing species abundance in different habitats according to human disturbance degree. Results indicated that this species has multiple uses and either local knowledge on their uses or their organ plant uses depend on social factors. A densities assessment suggests a negative effect of human disturbance on the abundance of both species. Results support the need to envisage conservation and sustainable use strategies as perspective policies.

Impacts of human disturbance on the temporal stability of climate–growth relationships in a red spruce forest, southern Appalachian Mountains, USA

We used dendrochronological techniques to develop a tree-ring chronology (AD 1874–2009) from live trees and investigated the temporal stability of regional climate signals in the heavily disturbed red spruce (Picea rubens Sarg.) and Fraser fir [Abies fraseri (Pursh) Poir.] forest of Roan Mountain, Tennessee and North Carolina, USA. We performed bootstrapped correlation analyses in split data sets and moving intervals analyses to detect shifts in climatic sensitivity during periods of changing forest structure following disturbances. Most notably, a significant shift in red spruce temperature sensitivity occurred post-1930s, where positive growth responses to warm temperatures shifted to negative responses, and this shift coincided with a period of clearcut harvesting. As exogenous disturbances (i.e. ice storms, wind throw, and acidic deposition) are expected to continue altering the structure of this forest throughout the region, the climatic sensitivity of these species may become increasingly unstable.

Impacts of Human Disturbance on Large Prey Species: Do Behavioral Reactions Translate to Fitness Consequences?

Anthropogenic disturbances have been demonstrated to affect animal behavior, distribution, and abundance, but assessment of their impacts on fitness-related traits has received little attention. We hypothesized that human activities and infrastructure cause a decrease in the individual performance of preys because of anthropogenically enhanced predation risk. We evaluated the impacts of commercial logging and road networks on the fitness of a large herbivore known to be sensitive to human disturbance: the forest-dwelling woodland caribou (Rangifer tarandus caribou). For 8 consecutive years (2004–2011) we monitored 59 individuals using GPS telemetry in the Charlevoix region of Québec, Canada. We also used Very High Frequency telemetry locations collected on 28 individuals from 1999–2000. We related habitat selection of adult caribou at various spatio-temporal scales to their probability of dying from predation, and to indices of their reproductive success and energy expenditure. The probability that adult caribou died from predation increased with the proportion of recent disturbances (including cutblocks ≤5 years old) in their annual home range. The respective effects of increasing paved and forestry road densities depended upon the overall road density within the home range of caribou. At a finer scale of 10 to 15 days before their death, caribou that were killed by a predator selected for recent disturbances more than individuals that survived, and avoided old mature conifer stands. The home range area of caribou increased with road density. Finally, the composition of the home range of females had no effect on their reproductive success. We show that human activities and infrastructure may influence the individual performance of large prey species in highly managed regions. We outline the need to consider the full set of impacts that human development may have on threatened animal populations, with particular emphasis on predator-prey relationships and population dynamics.

Assessing the reliability of biologger techniques to measure activity in a free-ranging primate

Assessmentof animal activity patterns can shed lighton a rangeof behavioural and ecological processes. The timing of activity canhelp improve understanding of a species’ spatial ecology, chrono-biology, energetic demands, reproductive strategy and nutritionalrequirements (Halle & Stenseth 2000; Erkert 2003). Activity dataare also useful for the assessment of animal welfare and conser-vation planning (Kitchen & Martin 1996; Broom & Fraser 2007;Cooke 2008); Activity patterns allow us to measure the impact ofhuman disturbance on habitat viability and behaviour (Williamset al. 2006; Yang et al. 2007), and to predict the influence of localor global climate change on the survival and distribution of a spe-cies or population (Walther et al. 2002; Hetem et al. 2012). Reliablemeasures of activity are thus fundamental to furthering our un-derstanding of animal behaviour and ecology.Two main methodological approaches have been used to recordthe activity patterns of free-ranging animals: behavioural obser-vation and biologging (reviewed in Cooke et al. 2004; Nathan et al.2012; Ropert-Coudert et al. 2012). Instantaneous scan sampling(Altmann 1974) is the most commonly used method to record ac-tivity and behaviour data in traditional studies of animal behav-ioural ecology. Scan sampling involves human observers recordingthe activity state (i.e. resting, foraging, travelling or social) of studyanimals at predetermined time intervals, to provide a descriptivemeasure of an individual’s or group’s activity. Scan sampling allowsarangeofbehaviouralinformation(e.g.diet, posture andproximityto conspecifics), in addition to states of activity, to be recordedsimultaneously. However, scan sampling often requires studysubjects to be individually identifiable and habituated to thepresence of human observers, and data can, by definition, only becollected during those periods when human observers are present.These prerequisites for successful scan sampling mayconstrain thecollectionofactivitydata.Insomespeciesorpopulationsitmaynotbe feasible to follow animals regularly, for example, if they arenocturnal or live in an inaccessible habitat, or if the researcher’spresence disrupts normal activity patterns.Biologgers,eitherattachedexternallyorimplantedintheanimal’sbody, have become increasingly popular for recording activityremotely(Cookeetal.2004;Ropert-Coudertetal.2012).Thesedevices

An algorithmic and information-theoretic approach to multimetric index construction

The use of multimetric indices (MMIs), such as the widely used index of biological integrity (IBI), to measure, track, summarize and infer the overall impact of human disturbance on biological communities has been steadily growing in recent years. Initially, MMIs were developed for aquatic communities using pre-selected biological metrics as indicators of system integrity. As interest in these bioassessment tools has grown, so have the types of biological systems to which they are applied. For many ecosystem types the appropriate biological metrics to use as measures of biological integrity are not known a priori. As a result, a variety of ad hoc protocols for selecting metrics empirically has developed. However, the assumptions made by proposed protocols have not be explicitly described or justified, causing many investigators to call for a clear, repeatable methodology for developing empirically derived metrics and indices that can be applied to any biological system. An issue of particular importance that has not been sufficiently addressed is the way that individual metrics combine to produce an MMI that is a sensitive composite indicator of human disturbance. In this paper, we present and demonstrate an algorithm for constructing MMIs given a set of candidate metrics and a measure of human disturbance. The algorithm uses each metric to inform a candidate MMI, and then uses information-theoretic principles to select MMIs that capture the information in the multidimensional system response from among possible MMIs. Such an approach can be used to create purely empirical (data-based) MMIs or can, optionally, be influenced by expert opinion or biological theory through the use of a weighting vector to create value-weighted MMIs. We demonstrate the algorithm with simulated data to demonstrate the predictive capacity of the final MMIs and with real data from wetlands from Acadia and Rocky Mountain National Parks. For the Acadia wetland data, the algorithm identified 4 metrics that combined to produce a −0.88 correlation with the human disturbance index. When compared to other methods, we find this algorithmic approach resulted in MMIs that were more predictive and comprise fewer metrics.

村落文化林与非文化林多尺度物种多样性加性分配

Culturally protected forests,which are preserved and managed by local people on the basis of traditional cultural practices and beliefs,have certain social and ecological functions,and also show significant role in biodiversity conservation.The research worldwide nowadays mainly focuses on qualitative description of culturally protected forests and therefore lack quantitative comparison of biodiversity and difference in species composition between culturally protected forests and non-culturally protected forests,particularly diversity from different spatial scales.The tree layer,shrub layer,herb layer and vine layer of three culturally protected forests and non-culturally protected forests were investigated,using additive partition measured by species abundance to analyze diversity of multi-scale in subtropical region of China.Partitioning of total species diversity can be described as Alpha diversity(within grid diversity)+ Beta diversity= Gamma diversity(total diversity at landscape),among which Beta diversity could be divided into diversity between grids,diversity between plots,diversity between forest types.The results were:(1) Total 296 species belonging to 66 families and 163 genera were found in culturally protected forests,dominated by Castanopsis sclerophylla,Cinnamomum camphora and Castanopsis carlesii,while 189 species belonging to 67 families and 135 genera were found in non-culturally protected forests,dominated by Cunninghamia lanceolata,Pinus massoniana and Phyllostachys heterocycla cv.pubescens.Culturally protected forests had more species in tree layer and shrub layer although the differences of species composition were complex in herb and vine layer depending on human disturbance and locations,and most of species diversity was higher in culturally protected forests.(2) This model implied that Beta diversity was increasing at larger spatial scale,and which showed uniform results in different layers in both culturally protected forests and non-culturally protected forests.Additive partitioning of diversity between forest types was highest which was from 41.9% to 62.8% of total diversity at landscape level,followed by diversity between plots which was from 18.6% to 31.9%,the contribution of diversity within and between grids was only small proportion.(3)Culturally protected forests play dominant role in partitioning of diversity between forests types,and provided 54.4% to 81.0%,51.2% to 60.2%,42.9% to 64.1%,49.9% to 62.2% of total diversity in culturally protected forests and non-culturally protected forests in tree,shrub,herb and vine layers respectively.That means culturally protected forests act as species pool to the regional area,particularly in conservation of tree species.(4) Species accumulation curves of tree layer achieved smooth slower indicating larger number stands protected in culturally protected forests than non-culturally protected forests within the same sample area.Additive partitioning of species diversity offers an operational method for explaining species diversity and in terms of better understanding of how alpha and Beta diversity change across multiple spatial scales.The model suggests culturally protected forests could be key factor to make contribution for diversity at landscape level.Therefore,when making biodiversity protection and restoration strategies,it′s better to focus more on culturally protected forests.However,the impact of human disturbance to culturally protected forests still needs to be studied in depth.

Landscape disturbance causes small-scale functional homogenization, but limited taxonomic homogenization, in plant communities

Summary 1. Biotic homogenization (BH), a dominant process shaping the response of natural communities to human disturbance, reflects both the expansion of exotic species at large scales and other mechanisms that often operate at smaller scales. 2. Here, we examined the relationship between BH in plant communities and spatio-temporal landscape disturbance (habitat fragmentation and surrounding habitat conversion) at a local scale (1 km²), using data from a standardized monitoring programme in France. We quantified BH using both a spatial partitioning of taxonomic diversity and the average habitat specialization of communities, which informs on functional BH. 3. We observed a positive relationship between local taxonomic diversity and landscape fragmentation or instability. This increase in local taxonomic diversity was, however, paralleled by a decrease in average community specialization in more fragmented landscapes and in more unstable landscapes around forest sites. The decrease in average community specialization suggests that landscape disturbance causes functional BH, but there was limited evidence for concurrent taxonomic BH. 4. Synthesis. Our results show that landscape disturbance is partly responsible for functional BH at small scales via the extirpation of specialist species, with possible consequences for ecosystem functioning. However, this change in community composition is not systematically associated with taxonomic BH. This has direct relevance in designing biodiversity indicators: metrics incorporating species sensitivity to disturbance (such as species specialization to habitat) appear much more reliable than taxonomic diversity for documenting the response of communities to disturbance.

DISTRIBUIÇÃO DA BATUÍRA-DE-BANDO (Charadrius semipalmatus) AO LONGO DO ANO DE 1999 NA PRAIA DA ILHA COMPRIDA

The beach of Ilha Comprida is important site in the semipalmated plover (Charadrius semipalmatus) migration. This paper analyses the seasonal occurrence of the semipalmated plover at Ilha Comprida and the impact of human disturbance in order to avaluate the importance of the area as a stopover site. The sighted birds were counted and simultaneously they were registered the atmosphere where happened, activity type that they were accomplishing and the disturbance human if there was. The results show that Ilha Comprida areas seem to be an important stopover site during December, but not during winter (June, July and August), and the abundance of semipalmated plover may be reduced by 80% in July. The Ilha Comprida is stopover in the migration for the south and north and important area for foranging and rest, for the Charadrius semipalmatus.

Impact of human disturbance and beliefs on the tree agama Acanthocercus atricollis atricollis in a South African communal settlement

We investigated the effects of human disturbance and attitudes on the density of the tree agama Acanthocercus atricollis atricollis in a densely populated rural settlement in South Africa. In this environment agamas live on trees that are harvested for firewood or maintained for fruit production. We conducted visual encounter surveys of A. a. atricollis and interviewed local households to establish whether human attitudes and actions could affect tree agama populations. Although local residents viewed tree agamas negatively (50% of interviewees claimed to have killed an agama) and acted to exclude them from their environment, tree agama density in villages was higher than that of adjacent communal rangelands and than a previously reported density estimate in a nearby protected area. We suggest three major factors that could explain why tree agamas are favoured in this peri-urban landscape in the face of human persecution: firstly, predators such as snakes and raptors are likely to occur at a much lower density in peri-urban areas; secondly, their primary prey (insects) may be more abundant or accessible in this landscape; thirdly, they may experience less competition for resources.

Seedling establishment of vascular epiphytes on isolated and enclosed forest trees in an Andean landscape, Ecuador

The impact of human disturbance on colonisation dynamics of vascular epiphytes is poorly known. We studied abundance, diversity and floristic composition of epiphyte seedling establishing on isolated and adjacent forest trees in a tropical montane landscape. All vascular epiphytes were removed from plots on the trunk bases of Piptocoma discolor. Newly established epiphyte seedlings were recorded after 2 years, and their survival after another year. Seedling density, total richness at family and genus level, and the number of families and genera per plot were significantly reduced on isolated trees relative to forest trees. Seedling assemblages on trunks of forest trees were dominated by hygrophytic understorey ferns, those on isolated trees by xerotolerant canopy taxa. Colonisation probability on isolated trees was significantly higher for plots closer to forest but not for plots with greater canopy or bryophyte cover. Seedling mortality on isolated trees was significantly higher for mesophytic than for xerotolerant taxa. Our results show that altered recruitment can explain the long-term impoverishment of post-juvenile epiphyte assemblages on isolated remnant trees. We attribute these changes to a combination of dispersal constraints and the harsher microclimate documented by measurements of temperature and humidity. Although isolated trees in anthropogenic landscapes are considered key structures for the maintenance of forest biodiversity in many aspects, our results show that their value for the conservation of epiphytes can be limited. We suggest that abiotic seedling requirements will increasingly constitute a bottleneck for the persistence of vascular epiphytes in the face of ongoing habitat alteration and atmospheric warming.

Diversity and density of diurnal squirrels in a primary hill dipterocarp forest, Malaysia

Squirrels (Order Rodentia; Family Sciuridae) are among the group of small mammals that have high species diversity in the Malaysian tropical rain forests (Corbet &amp; Hill 1992). In Peninsular Malaysia alone a total of 14 diurnal and 11 nocturnal species has been recorded (Medway 1983). In Peninsular Malaysia, several studies on squirrels have been done which emphasized vertical stratification (Harrison 1962, Lim et al. 1977, MacKinnon 1978, Saiful et al. 2001a), diversity (Zubaid &amp; Ariffin 1997), home range sizes (Tamura 1993, Saiful et al. 2001b), social behaviour (Tamura &amp; Yong 1993) and impact of human disturbance on habitat (Johns 1987). These studies were conducted in lowland and hill forests that have been logged. There are, however, few studies on squirrel abundance in terms of their density in Peninsular Malaysia especially in primary ill forests. Therefore, the purpose of the present study is to provide baseline data and information on squirrel richness, diversity and abundance in the Malaysian primary hill forest.