Loss of natural forests by forest clearcutting has been identified as a critical conservation challenge worldwide. This study addressed forest fragmentation and loss in the context of the establishment of a functional green infrastructure as a spatiotemporally connected landscape-scale network of habitats enhancing biodiversity, favorable conservation status, and ecosystem services. Through retrospective analysis of satellite images, we assessed a 50- to 60-year spatiotemporal clearcutting impact trajectory on natural and near-natural boreal forests across a sizable and representative region from the Gulf of Bothnia to the Scandinavian Mountain Range in northern Fennoscandia. This period broadly covers the whole forest clearcutting period; thus, our approach and results can be applied to comprehensive impact assessment of industrial forest management. The entire study region covers close to 46,000 km2 of forest-dominated landscape in a late phase of transition from a natural or near-natural to a land-use modified state. We found a substantial loss of intact forest, in particular of large, contiguous areas, a spatial polarization of remaining forest on regional scale where the inland has been more severely affected than the mountain and coastal zones, and a pronounced impact on interior forest core areas. Salient results were a decrease in area of the largest intact forest patch from 225,853 to 68,714 ha in the mountain zone and from 257,715 to 38,668 ha in the foothills zone, a decrease from 75% to 38% intact forest in the inland zones, a decrease in largest patch core area (assessed by considering 100-m patch edge disturbance) from 6114 to 351 ha in the coastal zone, and a geographic imbalance in protected forest with an evident predominance in the mountain zone. These results demonstrate profound disturbance of configuration of the natural forest landscape and disrupted connectivity, which challenges the establishment of functional green infrastructure. Our approach supports the identification of forests for expanded protection and conservation-oriented forest landscape restoration. 相似文献
Accurate estimations of the abundance of threatened animal populations are required for assessment of species’ status and vulnerability and conservation planning. However, density estimation is usually difficult and resource demanding, so researchers often collect data at local scales. However, anthropogenic pressures most often have landscape-level effects, for example, through habitat loss and fragmentation. We applied hierarchical distance sampling (HDS) to transect count data to determine the effect of habitat and anthropogenic factors on the density of 3 arboreal primate species inhabiting 5 distinct tropical forests across a landscape of 19,000 km2 in the Udzungwa Mountains of Tanzania. We developed a novel, multiregion extension of HDS that allowed us to model density and detectability jointly across forests without losing site-specific information. For all species, the effect of anthropogenic disturbance on density was overwhelmingly negative among metapopulations: −0.63 Angolan colobus (Colobus angolensis palliatus) (95% Bayesian CI −1.03 to −0.27), −0.54 Udzungwa red colobus (Procolobus gordonorum) (−0.89 to −0.22), and −0.33 Sykes' monkey (Cercopithecus mitis monoides) (−0.63 to −0.07). Some responses to habitat factors were shared, notably the negative effect of elevation and the positive effect of climber coverage. These results are important for conservation science and practice because: the among-populations negative responses to anthropogenic disturbance provides a foundation for development of conservation plans that hold at the landscape scale, which is a comprehensive and cost-efficient approach; the among-species consistency in responses suggests conservation measures may be generalized at the guild level, which is especially relevant given the functional importance of primates in tropical rainforests; and the greater primate densities in areas at low elevation, which are closer to human settlements, point to specific management recommendations, such as the creation of buffer zones and prioritization of areas for protection. 相似文献
Abstract: Our understanding of fire and grazing is largely based on small-scale experimental studies in which treatments are uniformly applied to experimental units that are considered homogenous. Any discussion of an interaction between fire and grazing is usually based on a statistical approach that ignores the spatial and temporal interactions on complex landscapes. We propose a new focus on the ecological interaction of fire and grazing in which each disturbance is spatially and temporally dependent on the other and results in a landscape where disturbance is best described as a shifting mosaic (a landscape with patches that vary with time since disturbance) that is critical to ecological structure and function of many ecosystems. We call this spatiotemporal interaction pyric herbivory (literal interpretation means grazing driven by fire). Pyric herbivory is the spatial and temporal interaction of fire and grazing, where positive and negative feedbacks promote a shifting pattern of disturbance across the landscape. We present data we collected from the Tallgrass Prairie Preserve in the southern Great Plains of North America that demonstrates that the interaction between free-roaming bison ( Bison bison ) and random fires promotes heterogeneity and provides the foundation for biological diversity and ecosystem function of North American and African grasslands. This study is different from other studies of fire and grazing because the fires we examined were random and grazing animals were free to roam and select from burned and unburned patches. For ecosystems across the globe with a long history of fire and grazing, pyric herbivory with any grazing herbivore is likely more effective at restoring evolutionary disturbance patterns than a focus on restoring any large vertebrate while ignoring the interaction with fire and other disturbances . 相似文献
Total forest carbon (C) storage is determined by succession, disturbances, climate, and the edaphic properties of a site or region. Forest harvesting substantially affects C dynamics; these effects may be amplified if forest harvesting is intensified to provide biofuel feedstock. We tested the effects of harvest intensity on landscape C using a simulation modeling approach that included C dynamics, multiple disturbances, and successional changes in composition. We developed a new extension for the LANDIS-II forest landscape disturbance and succession model that incorporates belowground soil C dynamics derived from the CENTURY soil model. The extension was parameterized and calibrated using data from an experimental forest in northeastern Wisconsin, USA. We simulated a 9800 ha forested landscape over 400 years with wind disturbance combined with no harvesting, harvesting with residual slash left on site (‘standard harvest’), and whole-tree harvesting. We also simulated landscapes without wind disturbance and without eastern hemlock (Tsuga canadensis) to examine the effects of detrital quantity and quality on C dynamics. We estimated changes in live C, detrital C, soil organic C, total C, and forest composition. Overall, the simulations without harvesting had substantially greater total C and continued to sequester C. Standard harvest simulations had more C than the whole tree harvest simulations. Under both harvest regimes, C accrual was not evident after 150 years. Without hemlock, SOC was reduced due to a decline in detritus and a shift in detrital chemistry. In conclusion, if the intensity of harvesting increases we can expect a corresponding reduction in potential C storage. Compositional changes due to historic circumstances (loss of hemlock) may also affect forest C although to a lesser degree than harvesting. The modeling approach presented enabled us to consider multiple, interacting drivers of landscape change and the subsequent changes in forest C. 相似文献
Unpredictable or variable ecosystem recovery from disturbance presents a challenge to conservation, particularly as the scale of human disturbance continues to increase. Theory suggests land-cover and disturbance characteristics affect recovery, but individual studies of disturbance and recovery frequently struggle to uncover generalizable patterns because of high levels of site-specific variation. To understand how land-cover, disturbance type, and disturbance duration influence ecosystem recovery, we used studies documenting recovery of 50 streams to perform a global meta-analysis of stream recovery from disturbances that affect water quality (e.g., oil spill, fire, wastewater). We extracted upstream natural and urban land-cover percentages for each site and performed model selection and averaging to identify influences on recovery completeness. Most streams improved following the end of a disturbance (median 240% of disturbed condition) but did not recover fully to baseline predisturbance condition within the studied period (median study period 2 years; median recovery 60% of baseline). Scale of disturbance in time and space did not predict recovery, but sites with higher percentages of upstream natural land cover had less complete recovery relative to sites with more urban or agricultural cover, possibly due to higher baseline conditions in these streams. Our findings suggest impacts to systems with low anthropogenic stress may be more irreversible than impacts to already modified systems. We call for more long-term evaluations of ecosystem response to disturbance and the inclusion of regional references and predisturbance reference conditions for comparison. A more thorough understanding of the role of the surrounding landscape in shaping stream response to disturbance can help managers calibrate expectations for recovery and prioritize protection. 相似文献
Understanding how human modification of the landscape shapes vertebrate community composition is vital to understanding the current status and future trajectory of wildlife. Using a participatory approach, we deployed the largest camera-trap network in Mesoamerica to date to investigate how anthropogenic disturbance shapes the occupancy and co-occurrence of terrestrial vertebrate species in a tropical biodiversity hotspot: the Osa Peninsula, Costa Rica. We estimated species richness in different categories of land protection with rarefaction analysis and estimated the expected occupancy with a joint species distribution model that included covariates for anthropogenic disturbance, land protection, habitat quality, and habitat availability. Areas with the most stringent land-use protections (e.g., Corcovado National Park, 24 species [95% CI 23–25]) harbored significantly more species than unprotected areas (20 species [19.7–20.3]), mainly due to a reduced presence of large-bodied species of conservation concern in unprotected areas (e.g., jaguar Panthera onca and white-lipped peccary Tayassu pecari). Small-bodied generalist species, such as opossums (Didelphidae) and armadillos (Dasypus novemcinctus), in contrast, were more common at disturbed sites, resulting in a significant difference in vertebrate community composition between sites with low and high disturbance. Co-occurrence of species was also mainly associated with response to disturbance. Similar responses to disturbance create two groups of species, those whose site-level occupancy usually increased as anthropogenic disturbance increased and those whose estimated occupancy decreased. The absence of large-bodied species entails an important loss of ecological function in disturbed areas and can hinder forest development and maintenance. Efforts to protect and restore forested landscapes are likely having a positive effect on the abundance of some threatened species. These efforts, however, must be sustained and expanded to increase connectivity and ensure the long-term viability of the wildlife community. 相似文献
Low-impact development (LID) technologies, such as bioretention areas, rooftop rainwater harvesting, and xeriscaping can control stormwater runoff, supply non-potable water, and landscape open space. This study examines a hybrid system (HS) that combines LID technologies with a centralized water system to lessen the burden on a conventional system (CS). CS is defined as the stormwater collection and water supply infrastructure, and the conventional landscaping choices in the City of Atlanta. The study scope is limited to five single-family residential zones (SFZs), classified R-1 through R-5, and four multi-family residential zones (MFZs), classified RG-2 through RG-5. Population density increases from 0.4 (R-1) to 62.2 (RG-5) persons per 1,000 m2. We performed a life cycle assessment (LCA) comparison of CS and HS using TRACI 2.1 to simulate impacts on the ecosystem, human health, and natural resources.We quantified the impact of freshwater consumption using the freshwater ecosystem impact (FEI) indicator. Test results indicate that HS has a higher LCA single score than CS in zones with a low population density; however, the difference becomes negligible as population density increases. Incorporating LID in SFZs and MFZs can reduce potable water use by an average of 50% and 25%, respectively; however, water savings are negligible in zones with high population density (i.e., RG-5) due to the diminished surface area per capita available for LID technologies. The results demonstrate that LID technologies effectively reduce outdoor water demand and therefore would be a good choice to decrease the water consumption impact in the City of Atlanta.
Water column production measurements were made during a bloom of the marine dinoflagellate Gyrodinium cf. aureolum in the Western English Channel in July 1987. The bloom was sampled over a period of 5 d, and primary production was measured using the oxygen light and dark bottle method and the 14C technique. The photosynthetic quotient (PQ) varied between 1.2 and 3.7. During the period sampled, the proportion of phaeopigments significantly increased (from <5 to >50%) and mixed layer dissolved oxygen saturation decreased from 133 to 114%. A model was used to determine gross water column productivity in the surface mixed layer on two days, and net production values were shown to be close to zero or slightly negative. Comparisons of production values are made with other published G. cf. aureolum bloom data. 相似文献
The distribution of vascular plant species richness along an altitudinal gradient and their relationships with environmental variables, including slope, aspect, bank (flooding) height, and river width of the Xiangxi River, Hubei Province, were examined. Total vascular plant species richness changed with elevation: it increased at lower elevations, reached a maximum in the midreaches and decreased thereafter. In particular, tree and herbaceous species richness were related to altitude. Correlation analysis (Kendall's τ) between species richness and environmental variables indicated that the change in species richness in the riparian zone was determined by riparian environmental factors and characteristics of regional vegetation distribution along the altitudinal gradient. The low species richness at lower elevations resulted from seasonal flooding and human activities – agriculture and fuel collection – and the higher species richness in the midreaches reflected transitional zones in natural vegetation types that had had little disturbance. These results on species distribution in the riparian community could be utilized as a reference for restoration efforts to improve water quality of the emerging reservoir resulting from the Three Gorges Hydroelectric Dam project. 相似文献
The objective of this research work is the evaluation of the impact of landuse pattern and intensity on landscape by means of an indicator. The method used to calculate a ‘landscape indicator’ (Iland) allows to take into account the objective as well as the subjective approach of landscape. Iland corresponds to the degree of agreement between landscape supply by farmers and landscape demand by the social groups. The supply and the demand are evaluated through four criteria: ‘diversity’, ‘upkeep’, ‘openness’ and ‘heritage’. The landscape supply is calculated from data of landscape objects (punctual, linear and spatial) for each criterion recorded at the field level. The values of the four criteria for the landscape demand are allocated by the user(s) of the indicator (decision makers, regional council, social groups…) into five classes (0–4). The value of the landscape indicator is the least favourable difference between supply and demand for the four criteria. An example of calculation of the ‘landscape indicator’ for an arable farm is given. The collection of data needs 2 h with the farmer and 2 h for a survey of the farm land. 相似文献
Health risks associated with excessive intake of fluoride through drinking water are one of the geoenvironmental health problems observed in many parts of the world, mainly in countries of the humid tropical belt, including Sri Lanka. Fluoride-related health problems are widespread in the dry climatic region compared to the wet climatic zone of Sri Lanka. The potential health risks of fluoride for communities in a river basin which drains through two climatic zones, viz. wet and dry zones, were investigated in this study. Sixty-three groundwater samples were collected from wells in the Walawe river basin during pre- and post-monsoon periods. From collected samples, ten selected samples were analyzed for their tritium (3H) levels to find out the approximate resident time of groundwater. In the river basin, the dry zone segment is characterized by elevated levels of fluoride (>?1.0 mg/L) in groundwater. Groundwater fluoride in the region was primarily of geogenic origin. The tritium values showed older groundwater contained higher fluoride levels, showing a increased dissolution of fluoride-bearing minerals. The hazard quotient (HQfluoride) showed that about 45% of pre- and 55% of post-monsoon groundwater samples in the dry zone area were unsuitable for drinking purposes for school children who are vulnerable to non-carcinogenic risks and dental fluorosis. This study emphasizes the need for continuous water quality monitoring and mitigation measures to ensure the health of residents.
In marine systems, the occurrence and implications of disturbance-recovery cycles have been revealed at the landscape level, but only in demographically open or closed systems where landscape-level dynamics are assumed to have no feedback effect on regional dynamics. We present a mussel metapopulation model to elucidate the role of landscape-level disturbance cycles for regional response of mussel populations to onshore productivity and larval transport. Landscape dynamics are generated through spatially explicit rules, and each landscape is connected to its neighbor through unidirectional larval dispersal. The role of landscape disturbance cycles in the regional system behavior is elucidated (1) in demographically open vs. demographically coupled systems, in relation to (2) onshore reproductive output and (3) the temporal scale of landscape disturbance dynamics. By controlling for spatial structure at the landscape and metapopulation levels, we first demonstrate the interaction between landscape and oceanographic connectivity. The temporal scale of disturbance cycles, as controlled by mussel colonization rate, plays a critical role in the regional behavior of the system. Indeed, fast disturbance cycles are responsible for regional synchrony in relation to onshore reproductive output. Slow disturbance cycles, however, lead to increased robustness to changes in productivity and to demographic coupling. These testable predictions indicate that the occurrence and temporal scale of local disturbance-recovery dynamics can drive large-scale variability in demographically open systems, and the response of metapopulations to changes in nearshore productivity. 相似文献
Coastal zones experience increased rates of coastal erosion, due to rising sea levels, increased storm surge frequencies, reduced sediment delivery and anthropogenic transformations. Yet, coastal zones host ecosystems that provide associated services which, therefore, may be lost due to coastal erosion. In this paper we assess to what extent past and future coastal erosion patterns lead to losses in land cover types and associated ecosystem service values. Hence, historical (based on CORINE land cover information) and projected (based on Dynamic and Interactive Vulnerability Assessment - DIVA - simulations) coastal erosion patterns are used in combination with a benefits transfer approach. DIVA projections are based on regionalized IPCC scenarios. Relative to the period 1975–2050, a case study is provided for selected European coastal country member states. For historical (1975–2006) coastal erosion trends, we observe territory losses in coastal agricultural, water body and forest & semi-natural areas – total coastal erosion equaling over 4,500 km2. Corresponding coastal ecosystem service values decrease from about €22.3 billion per year in 1975 to about €21.6 billion per year in 2006. For future (2006–2050) coastal erosion projections, total territory losses equal between ~3,700 km2 and ~5,800 km2 – coastal wetland areas being affected most severely. Corresponding coastal ecosystem service values decrease to between €20.1 and €19.4 billion per year by 2050. Hence, we argue that the response strategy of EU member states to deal with coastal erosion and climate change impacts should be based on the economic as well as the ecological importance of their coastal zones. 相似文献
To maintain healthy ecosystems, natural-disturbance-based management aims to minimize differences between unmanaged and managed landscapes. Two related approaches may help accomplish this goal, either applied together or in isolation: (1) concentrating anthropogenic disturbance through zoning (with protected areas and intensive management); and (2) emulating natural disturbances. The purpose of this paper is to examine the effects of these two approaches, applied both in isolation and in combination, on the structure of the forest landscape. To do so, we use a spatially explicit landscape simulation model on a large fire-dominated landscape in eastern Canada. Specifically, we examine the effects of (1) increasing the maximum size of logged stands (cutblocks) to better emulate the full range of fire sizes in a fire-dominated landscape, (2) increasing protected areas, and (3) adding aggregated or dispersed intensive wood production areas to the landscape in addition to protected areas (triad management). We focus on maximizing the amount and minimizing the fragmentation of old-growth forest and on reducing road construction. Increasing maximum cutblock size and adding protected areas led to reduced road construction, while the latter also resulted in less fragmentation and more old growth. Although protected areas led to reduced harvest volume, the addition of an intensive production zone (triad management) counterbalanced this loss and resulted in more old growth than equivalent scenarios with protected areas but no intensive production zone. However, we found no differences between aggregated and dispersed intensive wood production. Our results imply that differences between unmanaged and managed landscapes can be reduced by concentrating logging efforts through a combination of protected areas and intensive wood production, and by creating some larger cutblocks. We conclude that the forest industry and regulators should therefore seek to increase protected areas through triad management and consider increasing maximum cutblock size. These results add to a growing body of literature indicating that intensive management on a small part of the landscape may be better than less intensive management spread out over a much larger part of the landscape, whether this is in the context of forestry, agriculture, or urban development. 相似文献
Disturbance regimes are changing rapidly, and the consequences of such changes for ecosystems and linked social-ecological systems will be profound. This paper synthesizes current understanding of disturbance with an emphasis on fundamental contributions to contemporary landscape and ecosystem ecology, then identifies future research priorities. Studies of disturbance led to insights about heterogeneity, scale, and thresholds in space and time and catalyzed new paradigms in ecology. Because they create vegetation patterns, disturbances also establish spatial patterns of many ecosystem processes on the landscape. Drivers of global change will produce new spatial patterns, altered disturbance regimes, novel trajectories of change, and surprises. Future disturbances will continue to provide valuable opportunities for studying pattern-process interactions. Changing disturbance regimes will produce acute changes in ecosystems and ecosystem services over the short (years to decades) and long-term (centuries and beyond). Future research should address questions related to (1) disturbances as catalysts of rapid ecological change, (2) interactions among disturbances, (3) relationships between disturbance and society, especially the intersection of land use and disturbance, and (4) feedbacks from disturbance to other global drivers. Ecologists should make a renewed and concerted effort to understand and anticipate the causes and consequences of changing disturbance regimes. 相似文献
Juvenile bivalves may be dispersed by entering a bysso-pelagic phase where they drift through the water mass aided by a long
thread. The ability to resuspend and control the specific weight in two bivalve species, the cockle Cerastoderma edule (L.) and the Japanese clam Ruditapes philippinarum (Adams and Reeves), was documented with juveniles through flume and still-water experiments. Cockle juveniles initially placed
on an unsuitable substratum were exposed to two shear velocities (u*). At the end of the experiment, 42 (±15)% (for u*=0.51 cm s−1) and 79 (±9)% (for u*=0.99 cm s−1) of individuals were retrieved from the sand area which represents only 8% of the total flume surface. Most juveniles (70.5%)
with shell lengths <2.5 mm migrated from the unsuitable Plexiglas substratum to the sand array by resuspension in the water
column. The percentage was lower (21.5%) for larger individuals. The same experimental design was applied to clams, which
immediately adhered to the Plexiglas substratum and remained attach to it. Sinking rates of live and dead specimens of both
species were measured in a 1 m long transparent PVC tube. Cockle fall velocities showed severe deceleration, probably due
to byssus secretion (up to 15-fold slower than dead cockles), sometimes interrupted by brutal acceleration probably due to
byssal rupture. Cockles were able to reduce their sinking rate for shell lengths up to 4.25 mm. By contrast, clam sinking
rates were constant, and similar to dead clam sinking rates. Specific weights of all experimental juveniles were calculated
in relation to their lengths, and their passive motion into the boundary layer was theoretically assessed with Shields curve.
In short, C. edule and R. philippinarum can both exhibit dense populations in the field with a good capacity to colonize, although juveniles display different abilities
to resuspend in the water column.
Received: 27 January 1997 / Accepted: 13 February 1997 相似文献
Organisms can be affected by processes in the surrounding landscape outside the boundary of habitat areas and by local vegetation characteristics. There is substantial interest in understanding how these processes affect populations of grassland birds, which have experienced substantial population declines. Much of our knowledge regarding patterns of occupancy and density stem from prairie systems, whereas relatively little is known regarding how occurrence and abundance of grassland birds vary in reclaimed surface mine grasslands. Using distance sampling and single‐season occupancy models, we investigated how the occupancy probability of Grasshopper (Ammodramus savannarum) and Henslow's Sparrows (A. henslowii) on 61 surface mine grasslands (1591 ha) in Pennsylvania changed from 2002 through 2011 in response to landscape, grassland, and local vegetation characteristics . A subset (n = 23; 784 ha) of those grasslands were surveyed in 2002, and we estimated changes in sparrow density and vegetation across 10 years. Grasshopper and Henslow's Sparrow populations declined 72% and 49%, respectively from 2002 to 2011, whereas overall woody vegetation density increased 2.6 fold. Henslow's Sparrows avoided grasslands with perimeter–area ratios ≥0.141 km/ha and woody shrub densities ≥0.04 shrubs/m2. Both species occupied grasslands ≤13 ha, but occupancy probability declined with increasing grassland perimeter–area ratio and woody shrub density. Grassland size, proximity to nearest neighboring grassland ( = 0.2 km), and surrounding landscape composition at 0.5, 1.5, and 3.0 km were not parsimonious predictors of occupancy probability for either species. Our results suggest that reclaimed surface mine grasslands, without management intervention, are ephemeral habitats for Grasshopper and Henslow's Sparrows. Given the forecasted decline in surface coal production for Pennsylvania, it is likely that both species will continue to decline in our study region for the foreseeable future. Patrones de Ocupación de Poblaciones Regionalmente Declinantes de Gorriones de Pastizales en un Paisaje Boscoso de Pennsylvania 相似文献