Modelling landscape effects on density-contact rate relationships of deer in eastern Alberta: Implications for chronic wasting disease

Managing wildlife diseases requires an understanding of disease transmission, which may be strongly affected by host population density and landscape features. Transmission models are typically fit from time-series disease prevalence data and modelled based on how the contact rate among hosts is affected by density, which is often assumed to be a linear (density-dependent transmission) or constant (frequency-dependent transmission) relationship. However, long-term time-series data is unavailable for emerging diseases, and this approach cannot account for independent effects of landscape. We developed a mechanistic model based on ecological data to empirically derive the contact rate-density relationship in white-tailed and mule deer in an enzootic region of chronic wasting disease (CWD) in Alberta, Canada and to determine whether it was affected by landscape. Using data collected from aerial surveys and GPS-telemetry, we developed empirical relationships predicting deer group size, home range size, and habitat selection to iteratively simulate deer distributions across a range of densities and landscapes. We calculated a relative measure of total per-capita contact rate, which is proportional to the number of other deer contacted per individual per unit time, for each distribution as the sum of pairwise contact rates between a target deer and all other individuals. Each pairwise contact rate was estimated from an empirical relationship developed from GPS-telemetry data predicting pairwise contact rates as a function of home range overlap and landscape structure. Total per-capita contact rates increased as a saturating function of density, supporting a transmission model intermediate between density- and frequency-dependent transmission. This pattern resulted from group sizes that reached an asymptote with increasing deer density, although this relationship was mediated by tree and shrub coverage in the landscape, such that in heavily wooded areas, the contact rate saturated at much lower densities. These results suggest that CWD management based on herd reductions, which require a density-dependent contact rate to be effective, may have variable effects on disease across a single management region. The novel mechanistic approach we employed for estimating effects of density and landscape on transmission is a powerful complement to typical data-fitting approaches for modelling disease transmission.     

Preface to the selected papers on spatially explicit landscape modelling: Current practices and challenges

In the past 30 years, the notion of landscape has emerged in ecology as a result of both theoretical strategies and practical aspects of land use. This has generated a variety of computerized models addressing both objectives and techniques. Scientists model landscapes for at least two reasons: to better understand the landscape dynamics themselves (called intrinsic needs) and to offer a realistic frame to support other ecological processes (extrinsic needs). This special issue concerns both needs and illustrates the way socioeconomic and/or ecological mechanisms of various landscapes have been understood through modelling approaches. It outlines the links between landscape and model concepts, focusing on one hand on several landscape types (agricultural, forested and aquatic) and on the other hand on several landscape model characteristics (explicit or neutral, dynamic or static, patchy or continuous and multi- or mono-scale). The patterns and processes of each landscape model presented in this issue, in particular, should be analysed in order to highlight the way they are contributing to the landscape ecology discipline. We finally argue that the discipline can now offer a theoretical dimension to landscape dynamics, aiming at understanding the possible mechanism unity underlying this complex object.     

Assessment of the contribution of land use pattern and intensity to landscape quality: use of a landscape indicator

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’ (I_land) allows to take into account the objective as well as the subjective approach of landscape. I_land 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.     

Meso-scale landscape analysis based on landscape balance investigations: problems and hierarchical approaches for their resolution

Varied utilization demands of society to the landscape are leading to an overlay of interests and thus to land use conflicts. Thereby, essential landscape functions like the regulation function (i.e. run-off regulation, groundwater recharge, groundwater protection, buffer functions of the soil, etc.) may be affected, and result in stresses to our natural resources like soil and water. The land use conflicts become especially obvious in a regional context. The diminution of such land use conflicts in terms of a regional management of environment and natural resources requires the knowledge of the response of the landscape balance to land use changes. The results of integrated landscape analysis enable the calculation of scenarios that allow the derivation of site-suitable land use variants with positive effects (decrease) to material out-wash from landscape parts and material inputs into surface water and groundwater. Numerous and complex methodological problems arise with such analysis, as well as with the investigation and assessment of the landscape water balance and water-bound material fluxes on the mesoscale.As a contribution for the resolution of these problems, the authors present a hierarchical nested approach that interlinks scale-specific methods. Due to the complexity and difficult implementation from purely system-oriented approaches in both applied landscape research and planning, the connection to more pragmatic approaches is herewith striked. Thus, information about the impact of land use changes on the landscape balance, as well as the assessment of landscape functions for both watersheds and administrative units should be enabled. Beside the check of the scale-specific applicability of models (i.e. E2D/3D, ABIMO, ASGi, SWAT, modifications of the USLE), the transferability of parameter- and indicator systems for the assessment of the landscape balance on the concerned scale levels is also investigated. An important objective is thereby the optimization of the validity of landscape information for the spatio-temporal levels of the mesoscale.     

The role of local and landscape level measures of greenness in modelling boreal plant species richness

Measurements of primary productivity and its heterogeneity based on satellite images can provide useful estimates of species richness and distribution patterns. However, species richness at a given site may depend not only on local habitat quality and productivity but also on the characteristics of the surrounding landscape. In this study we investigated whether the predictions of species richness of plant families in northern boreal landscape in Finland can be improved by incorporating greenness information from the surrounding landscape, as derived from remotely sensed data (mean, maximum, standard deviation and range values of NDVI derived from Landsat ETM), into local greenness models. Using plant species richness data of 28 plant families from 440 grid cells of 25 ha in size, generalized additive models (GAMs) were fitted into three different sets of explanatory variables: (1) local greenness only, (2) landscape greenness only, and (3) combined local and landscape greenness. The derived richness–greenness relationships were mainly unimodal or positively increasing but varied between different plant families, and depended also on whether greenness was measured as mean or maximum greenness. Incorporation of landscape level greenness variables improved significantly both the explanatory power and cross-validation statistics of the models including only local greenness variables. Landscape greenness information derived from remote sensing data integrated with local information has thus the potentiality to improve predictive assessments of species richness over extensive and inaccessible areas, especially in high-latitude landscapes. Overall, the significant relationship between plants and surrounding landscape quality detected here suggests that landscape factors should be considered in preserving species richness of boreal environments, as well as in conservation planning for biodiversity in other environments.     

Minimum area requirements for an at‐risk butterfly based on movement and demography

Determining the minimum area required to sustain populations has a long history in theoretical and conservation biology. Correlative approaches are often used to estimate minimum area requirements (MARs) based on relationships between area and the population size required for persistence or between species’ traits and distribution patterns across landscapes. Mechanistic approaches to estimating MAR facilitate prediction across space and time but are few. We used a mechanistic MAR model to determine the critical minimum patch size (CMP) for the Baltimore checkerspot butterfly (Euphydryas phaeton), a locally abundant species in decline along its southern range, and sister to several federally listed species. Our CMP is based on principles of diffusion, where individuals in smaller patches encounter edges and leave with higher probability than those in larger patches, potentially before reproducing. We estimated a CMP for the Baltimore checkerspot of 0.7–1.5 ha, in accordance with trait‐based MAR estimates. The diffusion rate on which we based this CMP was broadly similar when estimated at the landscape scale (comparing flight path vs. capture‐mark‐recapture data), and the estimated population growth rate was consistent with observed site trends. Our mechanistic approach to estimating MAR is appropriate for species whose movement follows a correlated random walk and may be useful where landscape‐scale distributions are difficult to assess, but demographic and movement data are obtainable from a single site or the literature. Just as simple estimates of lambda are often used to assess population viability, the principles of diffusion and CMP could provide a starting place for estimating MAR for conservation.     

基于景观格局的辽河三角洲湿地生态安全分析

以1990年和2005年遥感影像为基本信息源,在GIS技术支持下,在对辽河三角洲湿地景观格局分析的基础上,采用破碎度、分离度、优势度等景观格局指数和景观类型脆弱度为评价指标研究辽河三角洲湿地景观生态安全。20世纪90年代以来大规模的资源开发,加剧了辽河三角洲湿地景观的破碎化程度,使景观优势度增高,多样性下降。从1990-2005年,研究区主要湿地景观类型水稻田、苇田、滩涂的干扰程度有所增加,生态安全度均有所下降,表明人类对自然湿地生态系统的干扰越来越明显。总体来说,15年来研究区整体景观生态安全度呈现下降趋势。以往湿地生态安全的研究主要集中在环境脆弱性和保护策略方面,研究层次着重在生态系统层面,而从景观格局角度对湿地景观生态安全的研究涉及较少,文章涉及的是景观生态学可持续发展研究的一个新领域,所提出的内容实质上是景观生态安全定量表征的方法探讨。应用景观生态学方法研究生态安全,揭示景观结构与功能关系并进一步分析区域生态环境的变化趋势及其内在因素,不但为辽河三角洲湿地及其生物多样性的保护和资源开发提供了科学依据,而且丰富和发展了我国生态安全研究的理论与方法。     

Ranking individual habitat patches as connectivity providers: Integrating network analysis and patch removal experiments

Here we propose an integrated framework for modeling connectivity that can help ecologists, conservation planners and managers to identify patches that, more than others, contribute to uphold species dispersal and other ecological flows in a landscape context. We elaborate, extend and partly integrate recent network-based approaches for modeling and supporting the management of fragmented landscapes. In doing so, experimental patch removal techniques and network analytical approaches are merged into one integrated modeling framework for assessing the role of individual patches as connectivity providers. In particular, we focus the analyses on the habitat availability metrics PC and IIC and on the network metric Betweenness Centrality. The combination and extension of these metrics jointly assess both the immediate connectivity impacts of the loss of a particular patch and the resulting increased vulnerability of the network to subsequent disruptions. In using the framework to analyze the connectivity of two real landscapes in Madagascar and Catalonia (NE Spain), we suggest a procedure that can be used to rank individual habitat patches and show that the combined metrics reveal relevant and non-redundant information valuable to assert and quantify distinctive connectivity aspects of any given patch in the landscape. Hence, we argue that the proposed framework could facilitate more ecologically informed decision-making in managing fragmented landscapes. Finally, we discuss and highlight some of the advantages, limitations and key differences between the considered metrics.     

Translating land-use science to a museum exhibit

For land-use science to engage the general public it must successfully translate its concepts and conclusions and make them public outside of traditional scientific venues. Here we explore science-art exhibits, which blend artistic presentations with specific scientific data or themes, as a possible effective way of communicating scientific information and disrupting misconceptions. We describe the process of producing a science-art exhibit on remote sensing and Puerto Rican landscape history from 1937 to the present, sited at a rural Puerto Rican community museum, and examine the visitor experience and educational outcomes of the museum exhibit through analysis of survey data. The exhibit project engaged undergraduate students from a variety of academic backgrounds, introduced land-use science concepts to the public in an engaging format, and was effective at reshaping visitors’ misconceptions of Puerto Rico’s landscape change history.     

Potential impact model to assess agricultural pressure to landscape ecological functions

Conservation and protection of soil and water resources and visual aspects of landscape, as well as the promotion of biodiversity, are some of the central tasks of environmental policy development and social politics in the future. One of the main questions is: ‘which agricultural systems are able to guarantee sustained resource-conserving land use?’ Based on the ecological risk concepts of the 1970s and 1980s, a potential impact model was developed using a universal assessment algorithm derived from fuzzy logic. The model estimated the potential impact of agricultural land use on ecosystem function using a few resource indicators. Intervention intensities of agricultural land-use are set in relation to site conditions and aggregated for each of several defined potential impact categories. The interpretation with respect to risk and the calculation of potential impact values are explained.     

Challenges of simulating complex environmental systems at the landscape scale: A controversial dialogue between two cups of espresso

With the advancement of computational systems and the development of model integration concepts, complexity of environmental model systems increased. In contrast to that, theory and knowledge about > environmental systems as well as the capability for environmental systems analyses remained, to a large extent, unchanged. As a consequence, model conceptualization, data gathering, and validation, have faced new challenges that hardly can be tackled by modellers alone. In this discourse-like review, we argue that modelling with reliable simulations of human-environmental interactions necessitate linking modelling and simulation research much stronger to science fields such as landscape ecology, community ecology, eco-hydrology, etc. It thus becomes more and more important to identify the adequate degree of complexity in environmental models (which is not only a technical or methodological question), to ensure data availability, and to test model performance. Even equally important, providing problem specific answers to environmental problems using simulation tools requires addressing end-user and stakeholder requirements during early stages of problem development. In doing so, we avoid modelling and simulation as an end of its own.     

Aphid population response to agricultural landscape change: A spatially explicit,individual-based model

A spatially explicit individual-based simulation model has been developed to represent aphid population dynamics in agricultural landscapes. The application of the model to Rhopalosiphum padi (L.) population dynamics is detailed, including an outline of the construction of the model, its parameterisation and validation. Over time, the aphids interact with the landscape and with one another. The landscape is modified by varying a simple pesticide regime, and the multi-scale spatial and temporal implications for a population of aphids is analysed. The results show that a spatial modelling approach that considers the effects on the individual of landscape properties and factors such as wind speed and wind direction provides novel insight into aphid population dynamics both spatially and temporally. This forms the basis for the development of further simulation models that can be used to analyse how changes in landscape structure impact upon important species distributions and population dynamics.     

深圳市盐田区植被格局分析

运用景观生态学的方法 ,选取斑块形状指数、斑块形状破碎化指数、分维数、景观多样性指数、均匀度、相对丰富度、优势度等指标 ,对深圳盐田区的植被格局进行分析。结果显示 :在城乡发展过程中 ,盐田区植被景观保存较好 ,类型丰富 ;植被景观总体上呈现出符合其生境特征的规则分布 ;群落景观异质性较高 ,拥有南亚热带的沟谷雨林、山地常绿阔叶林、红树林等特色植被景观 ;沟谷雨林和季风常绿林是本区较脆弱的生态系统 ,应积极加以保护和发展     

Wildfire, landscape diversity and the Drossel-Schwabl model

How simple can a model be that still captures essential aspects of wildfire ecosystems at large spatial and temporal scales? The Drossel-Schwabl model (DSM) is a metaphorical forest-fire model developed to reproduce only one pattern of real systems: a frequency distribution of fire sizes resembling a power law. Consequently, and because it appears oversimplified, it remains unclear what bearings the DSM has in reality. Here, we test whether the DSM is capable of reproducing a pattern that was not considered in its design, the hump-shaped relation between the diversity of succession stages and average annual area burnt. We found that the model, once reformulated to represent succession, produces realistic landscape diversity patterns. We investigated four succession scenarios of forest-fire ecosystems in the USA and Canada. In all scenarios, landscape diversity is highest at an intermediate average annual area burnt as predicted by the intermediate disturbance hypothesis. These results show that a model based solely on the dynamics of the fuel mosaic has surprisingly high predictive power with regard to observed statistical properties of wildfire systems at large spatial scales. Parsimonious models, such as the DSM can be used as starting points for systematic development of more structurally realistic but tractable wildfire models. Due to their simplicity they allow analytical approaches that further our understanding under increasing complexity.     

Evaluating the ecological benefits of wildfire by integrating fire and ecosystem simulation models

Fire managers are now realizing that wildfires can be beneficial because they can reduce hazardous fuels and restore fire-dominated ecosystems. A software tool that assesses potential beneficial and detrimental ecological effects from wildfire would be helpful to fire management. This paper presents a simulation platform called FLEAT (Fire and Landscape Ecology Assessment Tool) that integrates several existing landscape- and stand-level simulation models to compute an ecologically based measure that describes if a wildfire is moving the burning landscape towards or away from the historical range and variation of vegetation composition. FLEAT uses a fire effects model to simulate fire severity, which is then used to predict vegetation development for 1, 10, and 100 years into the future using a landscape simulation model. The landscape is then simulated for 5000 years using parameters derived from historical data to create an historical time series that is compared to the predicted landscape composition at year 1, 10, and 100 to compute a metric that describes their similarity to the simulated historical conditions. This tool is designed to be used in operational wildfire management using the LANDFIRE spatial database so that fire managers can decide how aggressively to suppress wildfires. Validation of fire severity predictions using field data from six wildfires revealed that while accuracy is moderate (30-60%), it is mostly dictated by the quality of GIS layers input to FLEAT. Predicted 1-year landscape compositions were only 8% accurate but this was because the LANDFIRE mapped pre-fire composition accuracy was low (21%). This platform can be integrated into current readily available software products to produce an operational tool for balancing benefits of wildfire with potential dangers.     

Probabilistische Modelle der Expositionsabschätzung

Probabilistic exposure and risk assessment can show and help to explicate the uncertainties of deterministic single-point estimates. Heterogeneity in population and exposure parameters (variability) is a part of probabilistic models which makes use of distributions for the main influential factors. The distributions of the target variables are calculated as a model-based combination of all influence factors by Monte Carlo-simulation methods. The differences between classical and probabilistic exposure assessment are demonstrated using a residential area with soil contamination as an example. The estimated arsenic exposure due to soil and dust is calculated by deterministic single-point estimates and probabilistic exposure assessment. The results are compared to the biomonitoring results of an epidemiological study. A criteria catalogue for exposure model validation is given and discussed for this example. In this scenario, the probabilistic exposure prognosis fits the empirical data better than that of a deterministic, single-point assessment. Both approaches seem to overestimate exposure with respect to empirical data.     

珠江三角洲典型区景观生态聚类分析

珠海是珠江三角洲地区一个海陆交互作用与人类干扰活动频繁的典型区域。文章以2000年TM数据为基础数据源，编制珠海地区景观类型图，并以镇(区)为基本空间单元将珠海划分为20个景观生态子区，在GIS与景观斑块分析软件Patch Analyst 2．0支持下计算各子区的景观特征指数。通过各子区的景观指数对比分析，探讨研究区范围内景观格局的空间差异，揭示人类活动、自然干扰等各种景观生态机制对区域景观生态的影响。根据各指数反映的景观特征信息，选择平均斑块大小(MPS)、斑块大小变异系数(PSCOV)、边缘密度(ED)、面积加权分维数(AWMPFD)、破碎度指数(F)、多样性指数(SDI)及人为干扰指数(DT)进行珠海景观生态聚类分析，根据聚类分析结果可多层次客观地对珠海地区进行景观生态类型区划分。     

Effects of Habitat Fragmentation on Effective Dispersal of Florida Scrub‐Jays

Abstract: Studies comparing dispersal in fragmented versus unfragmented landscapes show that habitat fragmentation alters the dispersal behavior of many species. We used two complementary approaches to explore Florida Scrub‐Jay (Aphelocoma c?rulescens) dispersal in relation to landscape fragmentation. First, we compared dispersal distances of color‐marked individuals in intensively monitored continuous and fragmented landscapes. Second, we estimated effective dispersal relative to the degree of fragmentation (as inferred from two landscape indexes: proportion of study site covered with Florida Scrub‐Jay habitat and mean distance to nearest habitat patch within each study site) by comparing genetic isolation‐by‐distance regressions among 13 study sites having a range of landscape structures. Among color‐banded individuals, dispersal distances were greater in fragmented versus continuous landscapes, a result consistent with other studies. Nevertheless, genetic analyses revealed that effective dispersal decreases as the proportion of habitat in the landscape decreases. These results suggest that although individual Florida Scrub‐Jays may disperse farther as fragmentation increases, those that do so are less successful as breeders than those that disperse short distances. Our study highlights the importance of combining observational data with genetic inferences when evaluating the complex biological and life‐history implications of dispersal.     

Hotspot detection and clustering: ways and means

This paper reviews the development of methods for the analysis of hotspots and clustering. Discussion focusses on different data types and the usefulness of density estimation, scan testing and model-based approaches to clustering. Various application areas are considered ranging from ecology, over health mapping to genomics and landscape analysis. A discussion of software availability is also provided.