Forest stressors and roadside vegetation management in an exurban landscape

As part of the forest landscape, roadside trees are susceptible to multiple stressors that increase potential for tree damage during storm events and contribute to power outages. In exurban areas, decision-making related to the roadside forest is divided among many land ownerships and management entities with diverse objectives. Our objectives were to (1) identify general forest and roadside vegetation management objectives and challenges, (2) identify forest stressors and assess perceived severity and level of concern for forest stressor impacts to the roadside forest, and (3) evaluate manager interrelationships based on management objectives and challenges. We conducted semi-structured interviews with thirty-nine members of the forest management community who manage non-residential and non-industrial tracts of forest land in Connecticut, USA. Improving overall forest health and resilience, wildlife habitat, and forest products were the three most common general forest objectives. The two most frequently identified roadside objectives were public safety and mitigating hazardous conditions. The most common general forest management challenges included workforce limitations, financial constraints, and public perceptions. Support and satisfaction among the public and other stakeholders was the most frequently mentioned roadside forest management challenge. Although participants recognized the importance of roadside vegetation management, many avoided active management along roadsides. Immediate roadside vegetation issues such as public safety were prioritized rather than long-term planning. Stakeholders are constantly orchestrating a balance of numerous objectives as they integrate roadside vegetation considerations into broader forest management.     

Modeling exurban development near Washington, DC, USA: comparison of a pattern-based model and a spatially-explicit econometric model

The development of private rural lands can significantly fragment landscapes, with potentially negative consequences on ecosystem services. Models of land-use trends beyond the urban fringe are therefore useful for developing policy to manage these environmental effects. However, land-use change models have been primarily applied in urban environments, and it is unclear whether they can adequately predict exurban growth. This study compared the ability of two urban growth models to project exurban development in north-central Virginia and western Maryland over a 24-year period. Pattern-based urban growth models (such as SLEUTH) are widely used, but largely mimic patterns that emerge from historic conditions rather than allowing landowner decision-making to project change. In contrast, spatially-explicit econometric models (such as the complementary log?Clog hazard assessed in this study) model landowner choices as profit-maximizing behavior subject to market and regulatory constraints. We evaluated the two raster-based models by comparing model predictions to observed exurban conversion at pixel and county scales. The SLEUTH model was more successful at matching the total amount of new growth at the county scale than it was at the pixel scale, suggesting its most appropriate use in exurban areas is as a blunt instrument to forewarn potential coarse-scale losses of natural resources. The econometric model performed significantly better than SLEUTH at both scales, although it was not completely successful in fulfilling its promise of projecting changes that were sensitive to policy. The lack of significance of some policy variables may have resulted from insufficient variation in drivers over our study area or time period, but also suggests that drivers of land use change in exurban environments may differ from those identified for urban areas.     

Evolving core-periphery interactions in a rapidly expanding urban landscape: The case of Beijing

We characterized and analyzed the dynamics of a rapidly expanding urban landscape of Beijing Municipality, based on the Hierarchical Regional Space (HRS) model. We focused on ecological processes such as flows of energy, materials and population between the urban core and its periphery, and how these processes co-evolved with urbanization. We treated the HRS as an alternative to the cellular automata (CA) approach to characterizing and modeling of landscape dynamics. With LANDSAT data, we showed that the urban area of Beijing expanded from 269 km² to 901 km² in the period from 1975 to 1997, an increase of 2.35 times in 22 years. Meanwhile, a number of secondary urban centers formed on areas that used to be sparsely populated around the city. These secondary centers quickly expanded and ultimately merged with each other and with the urban core. The changes in spatial pattern and organization were accompanied by evolution of urban functions and particularly the interactions between the urban core and its periphery. We demonstrated a dramatic increase in dependence of the urban core on the periphery as well as the cores influence on the periphery with a case analysis of the vegetable supply to Beijing. The tightening link between the city and its periphery reinforces the urbanization process and further drives the transformation of the regions landscape. We conclude that the HRS model is capable of characterizing the patterns and processes of complex and dynamic landscapes such as the case of Beijing, and this model has great potential for quantitative modeling of human dominated landscapes as well.This revised version was published online in May 2005 with corrections to the Cover Date.     

Effects of habitat fragmentation on four rodent species in a Polish farm landscape

Bank vole, striped field mouse, wood mouse, and yellow-necked mouse populations were studied in a mosaic of field and forest habitats. Live-trapping was carried out in 8 woodlots of different sizes (1.5–9.5 ha), situated 5 to 900 m from each other and surrounded by agricultural fields. Near the study area a dense, several hundred hectare forest complex was situated. It was found that the densities of all the studied species' populations in the woodlots were positively correlated with woodlot quality. For local bank vole populations a positive correlation of density with the surface area and circumference of woodlots, as well as with the area/circumference ratio was found. A negative correlation was found for population density and the distance between a given woodlot and the forest complex. For the yellow-necked mouse a positive correlation occurred between the density of local populations and the distance to the nearest neighboring woodlot. For the striped field mouse a positive correlation was found only between the population density in each woodlot and the distance to the forest complex. The wood mouse was insensitive to the variations in woodlot features present except for woodlot quality, and hence was probably responding in density to some other factors. Four rodent species, coexisting in the field-forest habitat mosaic demonstrated different reactions to its spatial characteristics, which were mainly related to different habitat preferences, spatial behavior, and mobility of individuals of the studied species.     

Making molehills out of mountains: landscape genetics of the Mojave desert tortoise

Heterogeneity in habitat often influences how organisms traverse the landscape matrix that connects populations. Understanding landscape connectivity is important to determine the ecological processes that influence those movements, which lead to evolutionary change due to gene flow. Here, we used landscape genetics and statistical models to evaluate hypotheses that could explain isolation among locations of the threatened Mojave desert tortoise (Gopherus agassizii). Within a causal modeling framework, we investigated three factors that can influence landscape connectivity: geographic distance, barriers to dispersal, and landscape friction. A statistical model of habitat suitability for the Mojave desert tortoise, based on topography, vegetation, and climate variables, was used as a proxy for landscape friction and barriers to dispersal. We quantified landscape friction with least-cost distances and with resistance distances among sampling locations. A set of diagnostic partial Mantel tests statistically separated the hypotheses of potential causes of genetic isolation. The best-supported model varied depending upon how landscape friction was quantified. Patterns of genetic structure were related to a combination of geographic distance and barriers as defined by least-cost distances, suggesting that mountain ranges and extremely low-elevation valleys influence connectivity at the regional scale beyond the tortoises’ ability to disperse. However, geographic distance was the only influence detected using resistance distances, which we attributed to fundamental differences between the two ways of quantifying friction. Landscape friction, as we measured it, did not influence the observed patterns of genetic distances using either quantification. Barriers and distance may be more valuable predictors of observed population structure for species like the desert tortoise, which has high dispersal capability and a long generation time.     

Effects of interactive scale-dependent variables on beetle diversity patterns in a semi-arid agricultural landscape

Understanding species-diversity patterns in heterogeneous landscapes invites comprehensive research on how scale-dependent processes interact across scales. We used two common beetle families (Tenebrionidae, detrivores; Carabidae, predators) to conduct such a study in the heterogeneous semi-arid landscape of the Southern Judean Lowland (SJL) of Israel, currently undergoing intensive fragmentation. Beetles were censused in 25 different-sized patches (500–40,000 m²). We used Fisher’s α and non-parametric extrapolators to estimate species diversity from 11,125 individuals belonging to 56 species. Patch characteristics (plant species diversity and cover, soil cover and degree of stoniness) were measured by field transects. Spatial variables (patch size, shape, physiognomy and connectivity) and landscape characteristics were analyzed by GIS and remote-sensing applications. Both patch-scale and landscape-scale variables affected beetle species diversity. Path-analysis models showed that landscape-scale variables had the strongest effect on carabid diversity in all patches. The tenebrionids responded differently: both patch-scale and landscape-scale variables affected species diversity in small patches, while mainly patch-scale variables affected species diversity in large patches. Most of the paths affected species diversity both directly and indirectly, combining the effects of both patch-scale and landscape-scale variables. These results match the biology of the two beetle families: Tenebrionidae, the less mobile and more site-attached family, responded to the environment in a fine-grained manner, while the highly dispersed Carabidae responded to the environment in a coarse-grained manner. We suggest that understanding abiotic and biotic variable interactions across scales has important consequences for our knowledge of community structure and species diversity patterns at large spatial scales.     

Effects of landscape urbanization on magpie occupancy dynamics in France

Responses of species to landscape modifications are generally documented through their distribution at a given time along an intensity gradient of land transformation. By focusing on patterns, we are limited to infer ecological processes occurring within a system and its response to environmental disturbances which can further change over time. Using diachronic datasets at the scale of France, we analyzed the spatial responses of the black-billed magpie, which has recently colonized cities, to landscape urbanization. This study applied recently developed statistical approaches incorporating detection uncertainty of the magpie, based on the capture-recapture statistical framework. We tested whether, and how, extinction and colonization mechanisms influenced variations of magpie occupancy from 2001 to 2005. In addition, we assessed the importance of the recent urbanization of the French countryside in determining population dynamics. Overall, our analysis proved that the proportion of urban areas and recent urbanization in France led to an increase in the probability of magpie occupancy. Unexpectedly, the species is concomitantly disappearing from the countryside, leading to a rapid change in the distribution of the species. This study stressed the importance of incorporating detection uncertainty in inference process about spatial dynamics. Overall, we show how useful it is to account for the dynamic evolution of the landscape in ecological studies.     

Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis

Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal.     

Effects of landscape structure on avian-mediated insect pest control services: a review

Context

Despite increasing evidence that landscape composition and configuration strongly influence the community structure of potential pest-regulators, landscape structure has seldom been explicitly linked with the rate and magnitude of pest-control services.

Objectives and methods

We conducted a systematic literature review evaluating 158 relevant studies to: (1) characterize our existing understanding of the empirical relationships between landscape structure and avian-mediated insect pest control services in agricultural systems, (2) identify gaps in our current understanding, and (3) develop a conceptual model of landscape structural influences on avian-mediated pest control.

Results and discussion

We found on-farm pest suppression by birds was often higher in landscapes with higher native habitat cover, higher compositional heterogeneity, and in agricultural patches in closer proximity to native habitats. We identified more than 200 bird species that provide pest control services across both temperate and tropical regions. While most avian predators are habitat-generalist species, a substantial fraction of pest control services in tropical regions was mediated by habitat-dependent species, suggesting a link between conservation management and maintenance of pest control services. We identified a three-part research agenda for future investigations of the relationships between landscape structure and avian-mediated pest control, focusing on an improved understanding of mechanisms related to: (1) predator–prey interactions and landscape modulation of trophic relationships, (2) bird dispersal ability and landscape connectivity, and (3) cross-habitat spillover of habitat-dependent avian predators.

Implications

These findings can be applied to efforts to manage and design landscapes capable of supporting both biodiversity and ecosystem services.

     

塞罕坝机械林场生态景观林空间结构对夏季景观质量的影响

林内景观质量评价对林场的经营和管理有重要意义,而林分空间结构的研究对生态景观林景观质量有重要影响。以塞罕坝机械林场落叶松纯林与落叶松-白桦混交林为研究对象,选取了16张最具代表性的照片,采用美景度评价（SBE）法以美景度作为景观质量指标,通过探究林分空间结构对林分夏季近景的景观质量影响,进而为塞罕坝生态景观林夏季景观经营技术提供依据。结果表明：（1）林内垂直结构越完整,林下整齐度越高,人们的喜好频数越高,美景度越高。（2）林内透视距离与美景度值存在明显的二项式关系;林内透视距离高于1倍树高时,美景度值随透视距离增加而增加。（3）林分枝下高与株高比值和美景度值存在二项式关系,林分枝下高与株高比值在0.5～0.6之时,美景度值存在1个峰值,此时人们接受程度最高。人们对林内垂直结构、透视距离、林下整齐度、树干形态与枝下高等指标偏好程度为打造更美好的生态景观林提供科学指导,对林场的转型和森林景观旅游事业有促进作用。     

Landscape services as a bridge between landscape ecology and sustainable development

Landscape ecology is in a position to become the scientific basis for sustainable landscape development. When spatial planning policy is decentralised, local actors need to collaborate to decide on the changes that have to be made in the landscape to better accommodate their perceptions of value. This paper addresses two prerequisites that landscape ecological science has to meet for it to be effective in producing appropriate knowledge for such bottom-up landscape-development processes—it must include a valuation component, and it must be suitable for use in collaborative decision-making on a local scale. We argue that landscape ecological research needs to focus more on these issues and propose the concept of landscape services as a unifying common ground where scientists from various disciplines are encouraged to cooperate in producing a common knowledge base that can be integrated into multifunctional, actor-led landscape development. We elaborate this concept into a knowledge framework, the structure–function–value chain, and expand the current pattern–process paradigm in landscape ecology with value in this way. Subsequently, we analyse how the framework could be applied and facilitate interdisciplinary research that is applicable in transdisciplinary landscape-development processes.     

Effects of forest regeneration on songbird movements in a managed forest landscape of Alberta,Canada

Recent studies have shown that barrier effects exist even in relatively vagile species such as forest songbirds. The objectives of this study were to determine whether a 560 × 100 m riparian buffer strip of mature forest was used as a movement corridor by forest songbirds and, if so, to what extent corridor effects persisted as woody vegetation regenerated in the adjacent clearcut. Over a 4-yr period, juvenile movement rates decreased in the riparian buffer strip and increased in the regenerating clearcut. Adult movement rates increased in the riparian buffer strip in the first year after logging, then gradually decreased, while still increasing in the regenerating clearcut. However, both juvenile and adult movement rates were higher in the buffer strip than in an undisturbed control site. Results suggest that most adults we captured held territories in the vicinity of the net lanes,and that most of the juveniles captured were dispersing away from their natal territory. Four years after harvest, juvenile movement rates were higher in the regenerating clearcut than in the riparian buffer strip, but several species had not yet been captured or detected in the regeneration. Our results suggest that the use of the riparian buffer strip as a movement corridor decreased with forest regeneration for both adults and juveniles. However, the buffer strip still acted as a movement corridor for the following species: Philadelphia and Red-eyed Vireos, Red-breasted Nuthatch, and Ovenbird. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of viewing forest landscape on middle-aged hypertensive men

With increasing attention on the health benefits of a forest environment, evidence-based research is required. This study aims to provide scientific evidence concerning the physiological and psychological effects of exposure to the forest environment on middle-aged hypertensive men. Twenty participants (58.0 ± 10.6 years) were instructed to sit on chairs and view the landscapes of forest and urban (as control) environments for 10 min. Heart rate variability (HRV) and heart rate were used to quantify physiological responses. The modified semantic differential method was used to determine psychological responses. Consequently, the high-frequency component of HRV, a marker of parasympathetic nervous activity that is enhanced in relaxing situations, was significantly higher and heart rate was significantly lower in participants viewing the forest area than in those viewing the urban area. The questionnaire results indicated that viewing the forest environment increased “comfortable,” “relaxed,” and “natural” feelings than viewing the urban environment. In conclusion, viewing forest landscape produces physiological and psychological relaxation effects on middle-aged hypertensive men.     

Effects of sensor spatial resolution on landscape structure parameters

We examined the effects of increasing grain size from 20 m to 1100 m on landscape parameters characterizing spatial structure in the northern Wisconsin lake district. We examined whether structural parameters remain relatively constant over this range and whether aggregation algorithms permit extrapolation within this range. Images from three different satellite sensors were employed in this study: (1) the SPOT multispectral high resolution visible (HRV), (2) the Landsat Thematic Mapper (TM), and (3) the NOAA Advanced Very High Resolution Radiometer (AVHRR). Each scene was classified as patches of water in a matrix of land. Spatial structure was quantified using several landscape parameters: percent water, number of lakes (patches), average lake area and perimeter, fractal dimension, and three measures of texture (homogeneity, contrast, and entropy). Results indicate that most measures were sensitive to changes in grain size. As grain size increased from 20 m using HRV image data to 1100 m (AVHRR), the percent water and the number of lakes decreased while the average lake area, perimeter, the fractal dimension, and contrast increased. The other two texture measures were relatively invariant with grain size. Although examination of texture at various angles of adjacency was performed to investigate features which vary systematically with angle, the angle did not have an important effect on the texture parameter values. An aggregation algorithm was used to simulate additional grain sizes. Grain was increased successively by a factor of two from 20 m (the HRV image) to 1280 m. We then calculated landscape parameter values at each grain size. Extrapolated values closely approximated the actual sensor values. Because the grain size has an important effect on most landscape parameters, the choice of satellite sensor must be appropriate for the research question asked. Interpolation between the grain sizes of different satellite sensors is possible with an approach involving aggregation of pixels.     

Effects of habitat fragmentation on Eurasian red squirrel (Sciurus vulgaris) in a forest landscape

We studied the effects of habitat fragmentation, measured as forest stand size and isolation, on the distribution of Eurasian red squirrels (Sciurus vulgaris). Squirrel density was surveyed during four years in 46 forest stands (0.1–500 ha) in a forest landscape in south-central Sweden. The only factor that significantly influenced a density index was the proportion of spruce within a habitat fragment. Neither fragment size nor degree of isolation were significant. Furthermore, none of the interactions with year were significant, suggesting the same pattern in all four years. Thus, the effect of habitat fragmentation in this study seems to be only pure habitat loss, i.e. halving the proportion of preferred habitat in the landscape should result in a halving of the red squirrel population. Therefore, the landscape can be viewed as functionally continuous for the squirrels, although the preferred habitat was divided into fragments. The most likely explanation for the difference between this study and other studies on squirrels that found effects due to habitat fragmentation is a combination of shorter distances and less hostile surroundings in our study area. To identify landscape effects requires multiple studies because single studies usually consider only one landscape.     

Effects of landscape composition on spread of an herbicide-resistant weed

Widespread adoption of genetically modified glyphosate-resistant (GR) crops in the US has dramatically changed the agricultural landscape to one that selects for establishment and spread of weedy species resistant to glyphosate, a commonly applied herbicide. Weed species that possess the means to readily spread across the landscape will be contained by weed management strategies that limit weed establishment and prevent seed set. An empirically-derived simulation model was developed to explore GR Conyza canadensis spread in relation to characteristics of the agricultural landscape. C. canadensis seeds are carried in the wind and move among fields and therefore, access high quality habitat (GR crops) at long distances. The baseline scenario was the current GR adoption levels in many US agricultural landscapes with corn and soybean rotated annually. Alternate scenarios examined the interacting effects of management uniformity (GR crop adoption) and increased landscape richness (three crops: corn, soybean, alfalfa, instead of two), over a 10 year simulation period. When landscape uniformity increased (increased GR corn adoption), 3× more fields would be infested with the resistant biotype and a specific field would have up to 24% greater likelihood of being infested compared to the current GR crop adoption levels. Increased landscape richness (adding alfalfa as a third crop) slightly decreased GR C. canadensis abundance. Reduced GR management uniformity by way of reducing GR soybeans to half their current adoption levels had the greatest impact on spread and prevented GR C. canadensis from reaching high abundance. Large-scale reliance on glyphosate for weed management has increased high-fitness habitat and will result in rapid spread of glyphosate-resistant weeds. Without significant reductions of glyphosate use and without spatial coordination of weed and crop management practices, GR weeds will continue to spread rapidly and impact agricultural practices in areas reliant on glyphosate.     

Effects of landscape configuration on mapping ecosystem service capacity: a review of evidence and a case study in Scotland

Context

Humans structure landscapes for the production of food, fibre and fuel, commonly resulting in declines of non-provisioning ecosystem services (ESs). Heterogeneous landscapes are capable of providing multiple ESs, and landscape configuration—spatial arrangement of land cover in the landscape—is expected to affect ES capacity. However, the majority of ES mapping studies have not accounted for landscape configuration.

Objectives

Our objective is to assess and quantify the relevance of configuration for mapping ES capacity. A review of empirical evidence for configuration effects on the capacity of ten ESs reveals that for four ESs configuration is relevant but typically ignored in ES quantification. For four ESs we quantify the relevance of configuration for mapping ESs using Scotland as a case study.

Methods

Each ES was quantified through modelling, respectively ignoring or accounting for configuration. The difference in ES capacity between the two ES models was determined at multiple spatial scales.

Results

Configuration affected the capacity of all four ESs mapped, particularly at the cell and watershed scale. At the scale of Scotland most local effects averaged out. Flood control and sediment retention responded strongest to configuration. ESs were affected by different aspects of configuration, thus requiring specific methods for mapping each ES.

Conclusions

Accounting for configuration is important for the assessment of certain ESs at the cell and watershed scale. Incorporating configuration in landscape management provides opportunities for spatial optimization of ES capacity, but the diverging response of ESs to configuration suggests that accounting for configuration involves trade-offs between ESs.