Gradient Of Human Disturbance Research Articles

Habituation reverses fear‐based ecological effects in brown bears (Ursus arctos)

AbstractFear induced by human activity is increasingly becoming recognized to influence both behavior and population biology of wildlife. Exposure to human activity can cause animals to avoid human‐dominated areas or shift temporal activity patterns, but repeated, benign exposure can also result in habituation of individuals. Habituation is typically viewed as a negative potential consequence of human interactions with wildlife, with effects such as increased vulnerability of habituated animals to predation. Concurrently, the advancement of the understanding of the ecology of fear has shown reduced fitness in species because of behavioral changes in responses to fear of predators—including humans. Here, we test how habituation and fear drive the foraging ecology of brown bears (Ursus arctos) feeding on Pacific salmon (Oncorhynchus spp.) in Southeast Alaska, USA. We used motion‐detecting trail cameras at salmon spawning areas across a gradient of human disturbance to record human and bear activity at fine spatial and extended temporal scales. Higher human activity was associated with increased nocturnality of non‐habituated bears, likely leading to suboptimal foraging, but had no effect on habituated individuals. For the top 20% of sites for which human activity was greatest, an average of 78.7% of the activity of non‐habituated bears was nocturnal, compared with an average of only 10.2% of the activity of habituated individuals. Habituation of brown bears in this system alleviated perceived risk and avoidance of human activity, allowing habituated individuals to overcome their fear of human presence and maximize foraging opportunities. While habituation may lessen some of the deleterious effects of human activity on large carnivores, the long‐term effects of habituation may be negative, as habituated individuals may be at greater risk of depredation. Future research should examine whether habituated bears and their lower perceived risk of human activity ultimately experience smaller population‐level effects of human disturbance than non‐habituated individuals.

Biodiversity investigation on forest communities in lantau, HongKong

Biodiversity investigation on forest community structures were conducted under different gradients of human disturbance in Lantau, Hong Kong. The results show that species diversity of forest community decreases along the disturbance gradient of different intensity, diversity of forest community of natural growing vegetation (hill) diversity of light disturbed (Ngong Ping) diversity of heavy disturbed (Tung Chung). The species compositions and dominance also vary with the intensity of human-induced disturbance. Exotic species are introduced into the communities purposedly by human activities, and therefore build up new community structures. The ecolgical impact of exotic species should be investigated from several respects in more details.

Seasonality and human disturbance alter brown bear activity patterns: implications for circumpolar carnivore conservation?

Wildlife may adapt activity patterns to daily and seasonal variations in environmental factors and human activity. At the daily scale, diurnal or nocturnal activity can be a response to variations in food availability and/or human avoidance. At the seasonal scale, variation in prey vulnerability underlies the influence of predators on prey population dynamics, which is of management concern when predation affects domestic species. We analyzed the movement patterns of 133 GPS-collared brown bears in three study areas in Sweden in spring, when bears prey on the calves of domestic reindeer and moose, and in summer–early fall, when bears rely mostly on berries, in three areas with a gradient of human disturbance. In spring, the bears' daily movement patterns and time of predation on ungulates overlapped. In summer–early fall, when bears are hyperphagic to store fat for hibernation and reproduction, variation in the degree of nocturnal behavior among study areas likely reflected behavioral adjustments to reduce the risk of encountering people. Flexibility in daily movement patterns by large carnivores may help them survive in human-dominated landscapes, but behavioral changes may also reflect environmental degradation, for example human disturbance influencing foraging opportunities. Diurnal human activity disturbs the carnivores, but that does not hinder depredation on reindeer, because it occurs mostly at night. Thus, ideally carnivores and reindeer should be separated spatially to reduce depredations. A zoning system prioritizing carnivore conservation and reindeer herding in different areas might help reduce a long-lasting conflict.

Effects of different N sources on riverine DIN export and retention in a subtropical high-standing island, Taiwan.

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities have substantially altered the N cycle, both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind of the most rapidly industrializing eastern coast of China, can be a demonstration site for extremely high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds with similar climatic and landscape settings but classified into low, moderate, and highly disturbed categories based on population density to illustrate their differences in nitrogen inputs (through atmospheric N deposition, synthetic fertilizers, and human emission) and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ~ 3800 kg N km-2 yr-1, approximately 18 times the global average. The average riverine DIN export ratios are 0.30-0.51, which are much higher than the averages of 0.20-0.25 of large rivers around the world, indicating excessive N input relative to ecosystem demand or retention capacity. The low disturbed watersheds have a high N retention capacity and DIN export ratios of 0.06-0.18 in spite of the high N input (~ 4900 kg N km-2 yr-1). The high retention capacity is likely due to effective uptake by secondary forests in the watersheds. The moderately disturbed watersheds show a linear increase in DIN export with increases in total N inputs and mean DIN export ratios of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watersheds is the greater proportion of agricultural land cover in the moderately disturbed watersheds. Thus, their greater DIN export could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have a lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratios of the highly disturbed watersheds are very high, 0.42-0.53, suggesting that much of the N input is transported downstream directly, and urges the need to increase the proportion of households connected to a sewage system and improve the effectiveness of wastewater treatment systems. The increases in the riverine DIN export ratio along the gradient of human disturbance also suggest a gradient in N saturation in subtropical Taiwan. Our results help to improve our understanding of factors controlling riverine DIN export and provide empirical evidence that calls for sound N emission/pollution control measures.

Does habitat disturbance affect stress, body condition and parasitism in two sympatric lemurs?

Understanding how animals react to human-induced changes in their environment is a key question in conservation biology. Owing to their potential correlation with fitness, several physiological parameters are commonly used to assess the effect of habitat disturbance on animals’ general health status. Here, we studied how two lemur species, the fat-tailed dwarf lemur (Cheirogaleus medius) and the grey mouse lemur (Microcebus murinus), respond to changing environmental conditions by comparing their stress levels (measured as hair cortisol concentration), parasitism and general body condition across four habitats ordered along a gradient of human disturbance at Kirindy Forest, Western Madagascar. These two species previously revealed contrasting responses to human disturbance; whereas M. murinus is known as a resilient species, C. medius is rarely encountered in highly disturbed habitats. However, neither hair cortisol concentrations nor parasitism patterns (prevalence, parasite species richness and rate of multiple infections) and body condition varied across the gradient of anthropogenic disturbance. Our results indicate that the effect of anthropogenic activities at Kirindy Forest is not reflected in the general health status of both species, which may have developed a range of behavioural adaptations to deal with suboptimal conditions. Nonetheless, a difference in relative density among sites suggests that the carrying capacity of disturbed habitat is lower, and both species respond differently to environmental changes, with C. medius being more negatively affected. Thus, even for behaviourally flexible species, extended habitat deterioration could hamper long-term viability of populations.

The ecological condition of geographically isolated wetlands in the southeastern United States: The relationship between landscape level assessments and macrophyte assemblages

Geographically isolated wetlands (GIWs) are common features of the Dougherty Plain physiographic region in southwestern Georgia. Due to lack of protection at the state and federal levels, these wetlands are threatened by intensive agricultural and silvicultural land uses common in the region. Recently, the ecological condition of such GIWs was assessed for the southeastern United States using the Landscape Development Intensity Index (LDI), a practical assessment tool that relies on remotely sensed land use and land cover (LULC) data surrounding isolated wetlands to rapidly predict wetland condition. However, no assessments have been attempted for GIWs in the Dougherty Plain specifically. Our goal was to develop a framework to guide and refine remote assessment of wetland condition within this agriculturally intense region of the southeastern USA. In this study, we characterized human disturbances associated with isolated wetlands in the Dougherty Plain, and paired the rapid assessment of GIWs using LDI with an intensive assessment of wetland plant communities. Specifically, we: (1) examined how macrophyte assemblages and vegetation metrics vary across a human disturbance gradient in the Dougherty Plain; (2) compared multiple condition assessment outcomes using variations of the LDI method that differed in spatial extent and resolution of LULC categories; and (3) determined the predicted condition of GIWs in the Dougherty Plain as indexed by LDI and compared with region-wide assessments of GIWs of the southeastern USA. Generally, the relationship between wetland plant communities and surrounding land use supported the assumptions of the LDI index in that wetlands surrounded by agricultural land use classes featured distinct plant communities relative to those surrounded by forested land use classes. Our results indicated that finer spatial resolution of LULC data improved the predictive ability of LDI. However, based on incongruence between wetland vegetation composition and LDI scores in some forested landscapes, this study identified limitations of the LDI assessment method, particularly when applied in regions in which prescribed fire is an important ecological driver of vegetation and habitat. Thus, we conclude that LDI may be biased toward an overestimation of reference condition GIWs, even though the habitat may be functionally degraded by the absence of natural processes such as fire. Regardless, relative to the assessment of the entire southeastern US, a greater proportion of total GIWs of the Dougherty Plain were identified as impaired due to the intensity of irrigated agricultural land use.

Do human disturbance variables influence more on fish community structure and function than natural variables in the Wei River basin, China?

Quantifying how human disturbance affects biotic communities in the context of other natural and spatial factors is a vital precursor to develop environmental management strategies to effectively conserve and restore ecosystem. This is particularly so for freshwater ecosystems in heavily populated and increasingly disturbed regions such as the Wei River basin in north-west China. In this paper, we employed both species’ abundance and functional metrics (displaying species diversity, habitat, trophic level, tolerance and abundance) to quantify the effect of human disturbance using canonical correspondence analysis. The results showed that spatial, natural and human disturbance variables can explain 40.1% and 33.7% of the total variation in fish abundance without rare species and with all species, respectively. 37.1% and 37.9% variation can be explained in fish metrics without rare species and with all species. Human disturbance variables explained most of the total variations in the four fish matrices. Inclusion or exclusion of rare species will influence the total explained variation from three factors in fish metrics, but little in fish abundance. Rare species will highlight this relationship with human disturbance gradient. For fish metrics, removing rare species will reflect some wrong information for human disturbance gradient. We recommend to include rare species for fish metrics to assess the impact of environment.

Aggressive behavior by Western Bluebirds (Sialia mexicana) varies with anthropogenic disturbance to breeding habitat

Human population growth has resulted in more frequent interactions between humans and wildlife, making it increasingly important to understand how anthropogenic disturbance affects animal populations. A number of recent studies on birds have shown that individuals experiencing high levels of disturbance are frequently more aggressive than conspecifics living in less disturbed areas. Our study asked whether heterospecific aggression varied in Western Bluebirds (Sialia mexicana) breeding in artificial nest boxes over a gradient of human disturbance in the Okanagan Valley of British Columbia, Canada. Unlike most previous studies, which have investigated effects of high disturbance (urbanization), our study focused on sites with lower rates of human disturbance, including ranch lands, vineyards, and recreational trails. Using decoys and playback, we measured the response of bluebird pairs to a simulated territory intrusion by one of two heterospecifics: a competing cavity nester, the House Wren (Troglodytes aedon), and a non-competing species, the American Goldfinch (Spinus tristus). We asked whether this response varied with the level of human disturbance experienced by the pair, and also whether aggression was correlated with female flight initiation distance (FID; a measure of boldness), local density of boxes in a territory, and presence of neighboring cavity-nesters. Overall, aggression was significantly higher towards the competitor stimulus (wren) than the non-competitor (goldfinch). Aggression towards the wren model did not change with disturbance level; however, aggression towards the goldfinch model increased significantly in more disturbed areas. Female FID did not vary across disturbance categories, but was correlated with aggression towards the wren, where individuals that responded more aggressively had marginally larger FIDs (i.e., behaved less boldly). Female FID was not correlated with aggression towards the goldfinch. Birds nesting in territories with more boxes tended to be more aggressive towards the wren, and birds nesting in territories with one or more box-nesting neighbors were significantly more aggressive towards the wren than birds without neighbors. Neither of these factors was correlated with aggression towards the goldfinch. Thus, the predicted association between disturbance and aggression was detected only in response to the non-competitor species (goldfinch), whereas aggression towards the competitor species (wren) varied with territory quality and number of competitors. Our study shows that variation in low levels of anthropogenic disturbance may be associated with behavioral effects in bird populations, and serves as a reminder that different factors may influence the expression of aggression in different contexts.

Sensitivity of breeding birds to the “human footprint” in western Great Lakes forest landscapes

Breeding birds in forest ecosystems are generally diverse, habitat selective, and easily sampled. Because they must integrate environmental variables over space and time, local populations of forest birds (like other animal and plant taxa) may provide meaningful signals of local forest health or degradation. We evaluated 949 breeding bird surveys in areas ranging from degraded urban/suburban forest remnants to relatively pristine old growth forests in the western Laurentian Great Lakes region of North America. The “human footprint” across this landscape was represented by a one‐dimensional numeric gradient derived from land cover variables, forest fragmentation metrics, and publicly available data on housing density and transportation corridors. We used an iterative, maximum likelihood approach to quantify species‐specific responses to this human disturbance gradient. Many species showed significant directional responses, consistent with known life history attributes. Other species were most commonly detected at intermediate levels of anthropogenic disturbance, yielding unimodal responses. Relationships between the “human footprint” and occurrences of 38 bird species were illustrated by general Gaussian functions that represented both unidirectional and unimodal patterns. These biotic response (BR) functions were combined into a bird‐based index of ecological condition (IEC) ranging from 0 (maximally degraded) to 10 (minimally degraded). We described a successful application of the IEC method at the Wild Rivers Legacy Forest (WRLF), a >260 km2 conservation landscape in northeastern Wisconsin, USA, managed primarily under a working forest conservation easement established in 2006. In general, areas within the WRLF yielded high IEC values (7.0–9.0), but nearby forest areas not under the conservation easement were characterized by significantly lower IEC values based on breeding bird assemblages.

Do squirrels in human disturbed areas become habituated to humans? A measure of flight initiation distance across disturbance gradients

Human population growth results in destruction of natural habitats, although some animals are adapting to living in areas with human disturbance. North American red squirrels (Tamiasciurus hudsonicus) may be one such species that is successfully adapting to living alongside humans. Flight initiation distance, the distance at which an animal flees from an approaching predator, may act as an indicator of habituation to humans. I predicted that if North American red squirrels were habituating to humans, their flight initiation distance would decrease along a gradient of increasing human disturbance. To examine this, I measured flight initiation distances of 39 North American red squirrels across eight sites, classified as low, medium or high human disturbance areas. No significant difference was found in mean flight initiation distances between disturbance levels, indicating that squirrel flight initiation distance may not be sensitive to small scales of human disturbance gradients.

Diversity, composition and phenology of araneid orb-weavers (Araneae, Araneidae) associated with riparian forests in southern Brazil

The Araneidae is a speciose family including web-spinning spiders that are very abundant in various terrestrial ecosystems. Several studies demonstrate that changes in vegetation surrounding rivers, streams and brooks affect the associated araneofauna. The aim of this research was to compare differences found in diversity (abundance and richness), composition and phenology of Araneidae spiders sampled in different habitats in four riparian forest catchments in southern Brazil. Samples were taken from riparian forests in four rivers of Rio Grande do Sul State: Piratini, Camaquã, Sinos and Maquiné rivers, each in a different hydrographic basin. Samples were taken twice seasonally on each basin during two years, sampling the araneofauna of the tree-shrub strata with beating tray. Six transects were employed on each basin, two per habitat: edge with grassland, forest interior and river edge. Araneids totalled 20 genera and 65 species. Comparing riparian forests significant differences are found. Spider abundance differed among riparian forests as well as species richness. Overall, Piratini river riparian forest had the higher abundance and richness for Araneidae; the lower values were in Sinos river forest. The stronger degradation and fragmentation of the riparian forests of Sinos river probably influenced the results, with human disturbance gradients associated negatively to web building. We present data on the diversity of these spiders, which were very abundant in the riparian forest interior and very rich in species in the grassland/riparian forest edge. Species composition also differs among the studied habitats (the above plus river/riparian forest edge). For the most abundant species the phenological pattern across the seasons was also analysed.

Spatial variation in plant species richness and diversity along human disturbance and environmental gradients in a tropical wetland

Human disturbance, natural environmental conditions and seed dispersal are often inferred as important drivers of plant community richness and diversity in wetland ecosystems. However, plant functional groups within a plant community have different environmental requirements and may respond differently to human disturbance. Therefore, the understanding of the relative importance of these variables in determining community and functional groups richness and diversity is important for improved management and wise use of wetland resources. We collected data on vegetation and environmental conditions, human disturbance and seed dispersal from 60 plots of 20 × 50 m, to identify variables that potentially affect total species richness and Shannon-Wiener diversity of the grassland plant community at the Kilombero Valley wetland, Tanzania. We further tested whether important predictor variables for species richness and Shannon-Wiener diversity differ among graminoid, forb and shrub functional groups. Overall, our results suggest that environmental conditions, human disturbance and seed dispersal determine spatial variation in species richness and Shannon-Wiener diversity of the grassland vegetation. The total richness and Shannon-Wiener diversity and the richness of shrubs decreased with distance from the Kilombero River, whereas the total Shannon-Wiener diversity and the Shannon-Wiener diversity of graminoids decreased with the increase in grazing intensity. Shrub species richness was related to the spatial position of plots and decreased with total organic carbon of soil. Current increase in human disturbances through cattle husbandry and changes in natural environmental conditions (e.g. through water diversion and drainage) should be discouraged in order to restore and sustain biodiversity of the Kilombero wetland.

Functional importance of avian seed dispersers changes in response to human-induced forest edges in tropical seed-dispersal networks.

Although seed-dispersal networks are increasingly used to infer the functioning of ecosystems, few studies have investigated the link between the properties of these networks and the ecosystem function of seed dispersal by animals. We investigate how frugivore communities and seed dispersal change with habitat disturbance and test whether relationships between morphological traits and functional roles of seed dispersers change in response to human-induced forest edges. We recorded interaction frequencies between fleshy fruited plants and frugivorous bird species in tropical montane forests in the Bolivian Andes and recorded functional bird traits (body mass, gape width and wing tip length) associated with quantitative (seed-removal rate) and qualitative (seed-deposition pattern) components of seed-dispersal effectiveness. We found that the abundance and richness of frugivorous birds were higher at forest edges. More fruits were removed and dispersed seeds were less clustered at edges than in the interior. Additionally, functional and interaction diversity were higher at edges than in the interior, but functional and interaction evenness did not differ. Interaction strength of bird species increased with body mass, gape width and wing tip length in the forest interior, but was not related to bird morphologies at forest edges. Our study suggests that increases in functional and interaction diversity and an even distribution of interaction strength across bird morphologies lead to enhanced quantity and tentatively enhanced quality of seed dispersal. It also suggests that the effects of species traits on ecosystem functions can vary along small-scale gradients of human disturbance.

Spatial Accounting of Environmental Pressure and Resource Consumption Using Night-light Satellite Imagery

Modern societies and economies are highly dependent on fossil energy for their survival. Unfortunately fossil energy resources and minerals are non-renewable and represent finite stocks. Consequently, societies and economies (production, trade and consumption modes) should be reorganized according to the awareness of less resource availability in the future. “Degrowth” and “prosperous way down patterns” have been suggested in order to avoid economic collapse and global societal turmoil and conflicts. This work assesses the dependence of a regional economy (Campania Region, Southern Italy) on non-renewable resources, by means of joint use of spatial modeling and Emergy Accounting. The Emergy method takes into account all the free environmental inputs (such as sunlight, wind, rain, geothermal heat) as well as the input flows of mineral and fossil energy resources, expressed in terms of their solar energy equivalents. Nonrenewable resources used within the regional economy were correlated to nighttime satellite images via GIS (Geographic Information System) methodology, to explore the load of human activities on landscape and ecological communities and to define a human disturbance gradient throughout the Region. This gradient was expressed by means of an emergy-based indicator, the Landscape Development Intensity index (LDI). Results show a high dependence of Campania Region economy from imported resources (about 85% of the total emergy used, U) and a high concentration of non-renewable flows in Napoli and Caserta Provinces. These two regional areas have much higher LDI indices, 44 and 36 respectively, suggesting the need for appropriate land use management actions capable to lower the environmental pressure to more sustainable levels. © 2013 L&H Scientific Publishing, LLC. All rights reserved. Keywords

Application of the landscape development intensity (LDI) index in wetland mitigation banking

The landscape development intensity (LDI) index, which can be used as a human disturbance gradient, is an effective tool in assessing location of wetland mitigation banks where large tracts of land are managed to protect wetland function by offsetting wetland losses from off-site land development. As part of a larger study to determine the effectiveness of mitigation banking in Florida, this article focuses on characterizing the landscape intensity of wetland mitigation banks in the state. Two scales of the LDI index were calculated: wetland assessment area scale LDI index (n=58), which characterizes the landscape surrounding a small parcel of land within a mitigation bank boundary, and mitigation bank scale LDI index (n=26), which characterizes the lands surrounding the entire boundary of the wetland mitigation bank. Approximately two-thirds of the wetland assessment areas (n=38) had LDI index scores less than 2.0 (where 0.0 represents no human development), with a mean LDI index score of 3.2 (σ=4.9). LDI index scores were calculated such that all lands within the 100m zone surrounding a wetland assessment area designated as restoration, enhancement, creation, or preservation were assigned LDI index scores reflecting natural lands. In this application, the LDI index score was considered a tool to predict potential wetland condition based on successful restoration. Bank scale LDI index scores, based on land use within the 100m zone surrounding the entire mitigation bank, were generally higher than assessment area scores, with a mean bank scale LDI index score of 7.8 (σ=5.4) and a median of 6.5. At the wetland scale, evaluation of landscape condition using the LDI index presented a quantitative analysis tool to determine potential ecological lift (i.e. expected gain in ecological condition) with successful wetland restoration practices within the mitigation bank. Whereas at the bank scale, LDI index calculations suggested the expected impacts from human land use activities outside of the control of the bank property. We propose using the LDI index to facilitate calculation of wetland mitigation potential and credit awards for mitigation banks, and that regardless of the tool used consideration of potential wetland functional lift should incorporate a landscape perspective.

Golden eagle Aquila chrysaetos in Xinjiang: Nest-site selection in different reproductive areas

The reports about the geographical distribution, reproductive ecology and population dynamics of the golden eagle Aquila chrysaetos were mostly descriptive in China, and lack quantified studies for the nest-site selection of this species. We carried out our investigations by direct observations in the northern Xinjiang during 2004–2011, attempting to reveal the main factors that affected on the nest-site selection and the differences of ecological variables of reproductive areas in the species (Mts. Tian Shan spurs and Mt. Kalamaili). We measured 38 nests totally belonging to the 16 home ranges. The average number of nests in each home range was 2.38±0.41, and with no significant difference (P>0.05) between different reproductive areas. In all cases golden eagles nested on cliffs (n=38) in our study area. The average external diameter of nests was (198.4±8.2) cm × (159.3±14.2) cm (Mean±SE, n=9), and inner diameter was (91.1±4.4) cm. The nest-site selection was extremely significant difference (P<0.01) for the different reproductive areas, i.e. elevation, hill height, nest-site height, cliff height, gradient, the distance to water resource, and the distance to residential area. The distance from the cliff bottom and from the cliff top were significant difference (P<0.05). However, the slope position, nest position, distance to unpaved and paved road were not significant difference (P>0.05). In Mts. Tian Shan spurs, the elevation was obviously selective (χ2=13.99, df=4, P<0.01), and mainly nested in altitude of 1 932–2 197m, where the main aspects were SW (36.4%, n=22) or SE (31.8%), and the slope gradient was above 85°. In Mt. Kalamaili, also it was found the significant differences for elevations (χ2=11.44, df=3, P<0.01), the eagle mainly nested in altitude of 1 112–1 423m, with aspects of NW (68.8%, n=16), and the gradient was relatively flat. In reproductive areas, eagles nested in the mid-slope parts and higher slope position (92.1%, n=38). Eagles nested far from the seriously disturbed places by human, especially roads, residential area, mineral mines, etc. The principal component method of the factor analysis indicated that there were four main factors affecting on the nest-site selection by golden eagle in Mts. Tian Shan spurs: human disturbance factor (eigenvalue is 4.800, Ratio of contribution is 34.28%), nest position factor (3.002%, 21.44%), prey factor (2.601%, 18.58%), and terrain factor (1.305%, 9.32%). In Mt. Kalamaili, there are five main factors as following: terrain factor (eigenvalue is 5.110, Ratio of contribution is 34.07%), nest position factor (3.747%, 24.98%), human disturbance factor (2.123%, 14.16%), prey factor (1.584%, 10.56%), and gradient factor (1.111%, 7.41%). To conclude, human disturbance and landscape are the two main factors affecting on the nest-site selection of the eagle. The nest-site selection is a result of trade-off among the human disturbance, landscape and prey amount. Eagles take corresponding strategy of nest-site selection for adaptation to the various environments, having different conditions for the eagle reproductive. So, we recommended the improvement of the habitat fitness for the increasing of the reproductive success of the golden eagle.

不同人为干扰下纳帕海湖滨湿地植被及土壤退化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 不同人为干扰下纳帕海湖滨湿地植被及土壤退化特征 DOI: 10.5846/stxb201305211134 作者: 作者单位: 同济大学环境科学与工程学院污染控制与资源化国家重点实验室,同济大学环境科学与工程学院污染控制与资源化国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41171074,U0933601,40771013) Analysis of vegetation and soil degradation characteristics under different human disturbance in lakeside wetland, Napahai Author: Affiliation: Key Laboratory of Yangtze River Water Environment,Ministry of Education,State Key Laboratory of Pollution Control and Resources Reuse,College of Environmental Science and Engineering,Tongji University,Key Laboratory of Yangtze River Water Environment,Ministry of Education,State Key Laboratory of Pollution Control and Resources Reuse,College of Environmental Science and Engineering,Tongji University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以滇西北高原纳帕海湖滨退化湿地为研究对象,对比分析了人为隔断水源补给、牛羊过度放牧和家猪拱地3种人为干扰下湿地植被和土壤退化特征。结果表明:3种干扰方式下,纳帕海湖滨湿地植物群落类型多样性、物种丰富度、物种数、Shannon-Wiener指数、沼生植物重要值以及土壤有机质、全氮、速效氮、含水率、毛管孔隙度变化规律为:人为隔断水源补给>牛羊过度放牧>家猪拱地,而土壤容重和全钾含量变化规律完全相反。Pearson相关性分析表明,不同人为干扰下相同土壤指标之间相关性质和相关强度不同;CCA分析表明植物群落种类组成和分布与土壤含水率和全磷含量显著相关。以原生湿地样点为对照,人为隔断水源补给、牛羊过度放牧和家猪拱地样带土壤退化指数分别为-7.40%、-14.53%、-45.01%。认为纳帕海湖滨湿地退化是三种干扰协同作用结果,但作用程度不同,其顺序为家猪拱地>牛羊过度放牧>人为隔断水源补给。 Abstract:Wetland degradation is the core issue of wetland science field. In lakeside wetland Napahai of northwest Yunnan Plateau, wetlands degradation was mainly caused by three types of human disturbance, including cutting off water supply, overgrazing and hogging. Based on the field survey of wetland ecological characteristics and environmental quality, eighteen degraded wetland plots were set up along the three human disturbance gradients on Napahai wetland area in 2011. The degradation characteristics of wetland vegetation and soil as well as the associated key ecological factors were investigated in the present paper. Among the three types human disturbance, the number of wetland plant community diversity, richness, number of species, Shannon-Wiener index, important value (IV) of helophyte plant and soil characteristics including organic matter, total nitrogen, available nitrogen, water content and porosity were highest in cutting off water supply, followed by overgrazing and lowest in hogging, whereas the order was opposite for soil bulk density, total potassium. The lowest community height was observed in hogging disturbance. The eighteen typical wetland plots were classified into five types by TWINSPAN, including primary wetland, lightly degraded wetland, moderately degraded wetland,severely degraded wetland and extremely degraded wetland. Pearson correlation analysis showed that water content was significantly and negatively correlated to bulk density and organic matter was positively correlated to total nitrogen among these three transects. The rest of indexes correlation varied greatly under different human disturbance among transects, which means human disturbance has seriously changed the soil physicochemical properties, especially hogging. CCA analysis was employed to test the effect of soil physicochemical factors on Ⅳ of plant species, which involved thirty-eight species variables and eleven soil variables. The correlation coefficient between vegetation characteristics and soil physicochemical properties was above 0.950, with the first two axis eigenvalue 0.811 and 0.613, respectively. The CCA results showed that plant community composition of Napahai lakeside degraded wetland was positively correlated to soil water content and negatively correlated to soil total phosphorus content. The soil degradation index was used to reflect the degree of soil degradation, with the primary wetland plot as reference. Then soil degradation index was-7.40%,-14.53%,-45.01% for cutting off water supply, overgrazing and hogging transects, respectively. This suggests that the soil was seriously degraded under human disturbance, especially hogging disturbance. Through analyses of TWINSPAN classification, soil degradation index, the change of plant community characteristic and soil physicochemical properties, degradation of wetland vegetation and soil in Napahai lakeside wetland were simultaneously dominated by three types disturbance, the order of human disturbance degree was hogging, overgrazing, cutting off water supply. Soil water content and total phosphorus content were the driven forces that caused the wetland degradation in Napahai lakeside wetland. Understanding driving factors of wetland degradation is a key step towards wetland ecosystems restoration and biodiversity conservation. Different intensity and type of human disturbance have different ecological influences on plant community characteristic, soil physicochemical properties and their interrelation. Therefore, comparing the effects among different human disturbances on the wetland plant community characteristics and soil properties can provide a theoretical basis for reasonable utilization and restoration of Napahai wetland. 参考文献 相似文献 引证文献

Do alien plant species profit more from high resource supply than natives? A trait-based analysis

Aim Previous studies comparing conditions of high- versus low-resource environments have pointed at differences in key traits that would allow aliens to perform better than natives under high-resource conditions. We generalize and test the robustness of this idea by exploring how trait differentiation between aliens and natives changes along continuous resource gradients. Location Global. Methods We constructed a database of three leaf traits (specific leaf area, SLA; photosynthetic capacity, Amass; leaf nitrogen content, Nmass) that are important for carbon capturing strategies in plants. The database includes 2448 native and 961 alien species over 88 locations world-wide. Using rank correlations and mixed-effect linear models, we assessed the relations between plant traits and climatic, edaphic and human disturbance gradients. Then we determined how the differences in traits between natives and aliens changed along the same gradients. Results Across all environments, aliens were found to have higher SLA, Nmass and Amass than natives. These differences were observed both globally and when controlling for co-occurrence. Also, higher average trait values were found in higher resource supply environments. However, trait differences between natives and aliens remained constant along the evaluated environmental and disturbance gradients. When compared in a multidimensional trait space defined by the leaf economics spectrum, co-occurring aliens and natives showed no between-group differences and no relation with any of the evaluated gradients. Main conclusions We suggest that although increased resource availability is positively related to higher carbon capture strategies (determined via higher plant leaf trait values), these benefits remain the same for aliens and natives. Therefore, we conclude that high-resource environments do not specifically cause aliens to outperform natives with respect to carbon capture, or at least not more than in other environments.

Co-Occurrence Patterns of Common and Rare Leaf-Litter Frogs, Epiphytic Ferns and Dung Beetles across a Gradient of Human Disturbance

Indicator taxa are commonly used to identify priority areas for conservation or to measure biological responses to environmental change. Despite their widespread use, there is no general consensus about the ability of indicator taxa to predict wider trends in biodiversity. Many studies have focused on large-scale patterns of species co-occurrence to identify areas of high biodiversity, threat or endemism, but there is much less information about patterns of species co-occurrence at local scales. In this study, we assess fine-scale co-occurrence patterns of three indicator taxa (epiphytic ferns, leaf litter frogs and dung beetles) across a remotely sensed gradient of human disturbance in the Ecuadorian Amazon. We measure the relative contribution of rare and common species to patterns of total richness in each taxon and determine the ability of common and rare species to act as surrogate measures of human disturbance and each other. We find that the species richness of indicator taxa changed across the human disturbance gradient but that the response differed among taxa, and between rare and common species. Although we find several patterns of co-occurrence, these patterns differed between common and rare species. Despite showing complex patterns of species co-occurrence, our results suggest that species or taxa can act as reliable indicators of each other but that this relationship must be established and not assumed.

Great Lakes coastal wetland habitat use by seven turtle species: influences of wetland type, vegetation, and abiotic conditions

Great Lakes coastal wetlands are important habitats for turtles but few studies have looked at factors driving community structure in these systems. We evaluated the effects of wetland type, vegetation, and abiotic conditions on turtle communities for 56 wetlands in Lakes Huron, Michigan, and Superior with data collected during the summers of 2000–2008. Overall, 1,366 turtles representing seven species were captured using fyke nets. For the majority of species, catches were highest in drowned river mouth wetlands In addition, turtles tended to be more abundant in water lilies, submersed aquatic vegetation, and cattails compared to bulrush. We also found positive correlations between catches of four of the species as well as total turtle catch and turtle species richness with a human disturbance gradient. These correlations suggest that turtles may be able to utilize coastal wetland areas that are inhospitable to fish because of hypoxic conditions. Our results show the importance Great Lakes coastal wetlands to turtles, and stress the need for managers to take into account turtle populations when preparing conservation and restoration strategies.