Showing papers in "Landscape Ecology in 2002"

A gradient analysis of urban landscape pattern: a case study from the Phoenix metropolitan region, Arizona, USA

Abstract: Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and human life. Quantifying landscape pattern and its change is essential for the monitoring and assessment of ecological consequences of urbanization. Combining gradient analysis with landscape metrics, we attempted to quantify the spatial pattern of urbanization in the Phoenix metropolitan area, Arizona, USA. Several landscape metrics were computed along a 165 km long and 15 km wide transect with a moving window. The research was designed to address four research questions: How do different land use types change with distance away from the urban center? Do different land use types have their own unique spatial signatures? Can urbanization gradients be detected using landscape pattern analysis? How do the urban gradients differ among landscape metrics? The answers to these questions were generally affirmative and informative. The results showed that the spatial pattern of urbanization could be reliably quantified using landscape metrics with a gradient analysis approach, and the location of the urbanization center could be identified precisely and consistently with multiple indices. Different land use types exhibited distinctive, but not necessarily unique, spatial signatures that were dependent on specific landscape metrics. The changes in landscape pattern along the transect have important ecological implications, and quantifying the urbanization gradient, as illustrated in this paper, is an important first step to linking pattern with processes in urban ecological studies.

Key issues and research priorities in landscape ecology: An idiosyncratic synthesis

Abstract: Landscape ecology has made tremendous progress in recent decades, but as a rapidly developing discipline it is faced with new problems and challenges. To identify the key issues and research priorities in landscape ecology, a special session entitled “Top 10 List for Landscape Ecology in the 21st Century” was organized at the 16th Annual Symposium of the US Regional Association of International Association of Landscape Ecology, held at Arizona State University (Tempe, Arizona, USA) during April 25–29, 2001. A group of leading landscape ecologists were invited to present their views. This paper is intended to be a synthesis, but not necessarily a consensus, of the special session. We have organized the diverse and wide-ranging perspectives into six general key issues and 10 priority research topics. The key issues are: (1) interdisciplinarity or transdisciplinarity, (2) integration between basic research and applications,(3) Conceptual and theoretical development, (4) education and training, (5)international scholarly communication and collaborations, and (6) outreach and communication with the public and decision makers. The top 10 research topics are: (1) ecological flows in landscape mosaics, (2) causes, processes, and consequences of land use and land cover change, (3) nonlinear dynamics and landscape complexity, (4) scaling, (5) methodological development, (6) relating landscape metrics to ecological processes, (7) integrating humans and their activities into landscape ecology, (8) optimization of landscape pattern, (9)landscape sustainability, and (10) data acquisition and accuracy assessment. We emphasize that, although this synthesis was based on the presentations at the“Top 10 List” session, it is not a document that has been agreed upon by each and every participant. Rather, we believe that it is reflective of the broad-scale vision of the collective as to where landscape ecology is now and where it may be going in future.

Empirical patterns of the effects of changing scale on landscape metrics

Abstract: While ecologists are well aware that spatial heterogeneity is scale-dependent, a general understanding of scaling relationships of spatial pattern is still lacking. One way to improve this understanding is to systematically examine how pattern indices change with scale in real landscapes of different kinds. This study, therefore, was designed to investigate how a suite of commonly used landscape metrics respond to changing grain size, extent, and the direction of analysis (or sampling) using several different landscapes in North America. Our results showed that the responses of the 19 landscape metrics fell into three general categories: Type I metrics showed predictable responses with changing scale, and their scaling relations could be represented by simple scaling equations (linear, power-law, or logarithmic functions); Type II metrics exhibited staircase-like responses that were less predictable; and Type III metrics behaved erratically in response to changing scale, suggesting no consistent scaling relations. In general, the effect of changing grain size was more predictable than that of changing extent. Type I metrics represent those landscape features that can be readily and accurately extrapolated or interpolated across spatial scales, whereas Type II and III metrics represent those that require more explicit consideration of idiosyncratic details for successful scaling. To adequately quantify spatial heterogeneity, the metric-scalograms (the response curves of metrics to changing scale), instead of single-scale measures, seem necessary.

Bridging the gap between ecology and spatial planning in landscape ecology

Abstract: Landscapes are studied by pattern (the geographical approach) and by process (the ecological approach within landscape ecology). The future of landscape ecology depends on whether the two approaches can be integrated. We present an approach to bridge the gap between the many detailed process studies on species, and applied activities such as landscape evaluation and design, which require integrated knowledge. The approach consists of four components: 1) Empirical case studies of different scales, organisms and processes. 2) Modeling studies to extrapolate empirical studies across space and time. 3) Modeling studies to produce guidelines and standards for landscape conditions. 4) Methods and tools for integration to the landscape level, which can be built into multidisciplinary tools for design and evaluation. We conclude that in the landscape ecological literature, the steps 1 and 2 are well represented, whereas the steps 3 and 4 are mostly neglected. We challenge landscape ecologists to push landscape ecology to a higher level of maturation and to further develop its profile as a problem-oriented science.

Hierarchical, Multi-scale decomposition of species-environment relationships

Abstract: We present an adaptation of existing variance partitioning methods todecompose species-environment relationships in hierarchically-structured,multi-scaled data sets. The approach translates a hierarchical, multi-scaleconceptual model into a statistical decomposition of variance. It uses a seriesof partial canonical ordinations to divide the explained variance inspecies-environment relationships into its independent and confoundedcomponents, facilitating tests of the relative importance of factors atdifferent organizational levels in driving system behavior. We discuss themethod in the context of an empirical example based on forest bird communityresponses to multiple habitat scales in the Oregon Coast Range, USA. Theexamplepresents a two-tiered decomposition of the variation in the bird community thatis explainable by a series of habitat factors nested within three spatialscales(plot, patch, and landscape). This method is particularly suited for theproblems of hierarchically structured landscape data. The explicit multi-scaleapproach is a major step forward from conducting separate analyses at differentscale levels, as it allows comprehensive analysis of the interaction of factorsacross scales and facilitates ecological interpretation in theoretical terms.

Carabid beetle assemblages (Coleoptera, Carabidae) across urban-rural gradients: an international comparison

Abstract: We studied communities of carabid beetles in residual forest patchesalong urban-suburban-rural gradients in three cities (Helsinki, Finland; Sofia,Bulgaria and Edmonton, Canada) to examine their responses to urbanisation. OnlyFinnish carabids showed a marked division of community structure along thegradient. In Bulgaria and Canada, carabids did not separate into distincturban,suburban and rural communities. Our results provide some support for thepredictions that species richness will decrease, that opportunistic specieswillgain dominance, and that small-sized species will become more numerous underdisturbance such as that provided by urbanisation. The rather weak and variedresponse of carabids to this disturbance suggests that local factors and theirinteraction are of primary importance for community composition. Occurrence ofreasonably similar carabid communities across the gradient at each of the threelevels of urbanisation suggests that habitat changes commonly associated withurbanisation have not affected the ecological integrity of carabid assemblagesin residual urban forest patches.

Landscape patch shape complexity as an effective measure for plant species richness in rural landscapes

Abstract: The application of landscape patch shape complexity as a predictor ofvascularplant and bryophyte species richness is analysed. Several common complexityindices (shape index, fractal dimension, comparison to the area of the minimumbounding rectangle) are tested for their predictive power for plant speciesrichness. One new robust measure for shape complexity is presented whichovercomes some disadvantages of common complexity measures applied to highresolution analysis of agricultural landscapes based on aerial photographs. Thenew index is based on the number of shape characterising points along apolygon’s boundary. This new measure shows promising predictive capabilitiesforspecies richness of vascular plants and bryophytes (correlation coefficient:0.85 for vascular plants, 0.74 for bryophytes).

Wildfires and landscape patterns in the Eastern Iberian peninsula

Abstract: The relations between disturbance regime and landscape patterns have been developed from a theoretical perspective, but few studies have tested these relations when forces promoting opposing heterogeneity patterns are simultaneously operating on a landscape. This work provides quantitative evidence of these relations in areas dominated by human activity, showing that landscape heterogeneity decreases disturbance spread. In turn, disturbance introduces a source of landscape heterogeneity, but it is not enough to counterbalance the homogeneity trend due to agricultural abandonment. Land cover changes and wildfire occurrence (fires larger than 0.3 km2) have been monitored in the Tivissa municipality (208.4 km2) (Catalonia, NE Spain) from 1956 to 1993. Land cover maps were obtained from 1956, 1978 and 1993 and they were overlaid with fire occurrence maps obtained for the 1975–1995 period from 60 m resolution remote sensing images, which allow the identification of burned areas by sudden drops in Normalized Difference Vegetation Index (NDVI). Changes in landscape patterns in relation to fire regime have been analyzed considering several parameters: patch density, mean patch size, mean distance to the nearest neighbour of the same category, edge density, and the Shannon diversity index. In the 1956–1993 period there is a trend to increasing landscape homogenization due to the expansion of shrub­lands linked to a decrease in forest surface, and to the abandonment of agricultural lands. This trend, however, is not constant along all the period. Fires are more likely to occur in woody, homogenous areas, increasing landscape heterogeneity, as observed in the 1978–1993 period. This increase in heterogeneity does not counterbalance the general trend to landscape homogenization as a consequence of agricultural abandonment and the coalescence of natural vegetation patches.

The influence of management history and habitat on plant species richness in a rural hemiboreal landscape, Sweden

Abstract: We explored patterns of plant species richness at different spatial scales in 14 habitats in a Swedish rural landscape. Effects of physical conditions, and relationships between species richness and management history reaching back to the 17 (th) century were examined, using old cadastral maps and aerial photographs. The most species-rich habitats were dry open semi- natural grasslands, midfield islets and road verges. Alpha diversity (species richness within sites) was highest in habitats on dry substrates (excluding bedrock with sparse pines) and beta diversity (species richness among sites) was highest in moist to wet habitats. Alpha and beta components of species richness tended to be inversely related among habitats with similar species richness. Management history influenced diversity patterns. Areas managed as grasslands in the 17 th and 18 th century harboured more species than areas outside the villages. We also found significant relationships between species richness and soil type. Silt proved to be the most species- rich topsoil (10- 20 cm) in addition to thin soils top of on green- or limestone bedrock. The variation in species richness due to local relief or form of the site also showed significant relationships, where flat surfaces had the highest number of species. In contrast, no significant relationship was found between species richness and aspect. Our study suggests that present- day diversity patterns are much influenced by management history, and that small habitat, e. g., road verges and midfield islets, are important for maintaining species richness.

Changes in anthropogenic impervious surfaces, precipitation and daily streamflow discharge: a historical perspective in a mid-atlantic subwatershed

Abstract: Aerial photography provides a historical vehicle for determining long-term urban landscape change and, with concurrent daily streamflow and precipitation records, allows the historical relationship of anthropogenic impervious surfaces and streamflow to be explored. Anthropogenic impervious surface area in the upper Accotink Creek subwatershed (near Annandala, Virginia, USA) was mapped from six dates of rectified historical aerial photography ranging from 1949 to 1994. Results show that anthropogenic impervious surface area has grown from approximately 3% in 1949 to 33% in 1994. Coincident to this period, analysis of historical mean daily streamflow shows a statistically significant increase in the streamflow discharge response (per meter of precipitation) associated with “normal” and “extreme” daily precipitation levels. Significant changes were also observed in the frequency of daily streamflow discharge at given volumes above and below the historical daily mean. Simultaneously, the historical magnitude, frequency and pattern of precipitation values ≥ 0 mm, ≥ 6.0 mm and ≥ 35.0 mm show either no statistically significant change or influence on streamflow. Historical changes in streamflow in this basin appear to be related to increases in anthropogenic impervious surface cover. Historical aerial photography is a viable tool for revealing long-term landscape and ecosystem relationships, and allows landscape investigations to extend beyond the temporal and spatial constraints of historical satellite remote sensing data.

Gap-crossing decisions by forest birds: an empirical basis for parameterizing spatially-explicit, individual-based models

Abstract: Spatially-explicit, individual-based models are increasingly used to evaluate the effects of habitat loss and fragmentation on habitat use and population persistence. Yet, they are criticized on the basis that they rely on little empirical data, especially regarding decision rules of moving individuals. Here we report the results of an experiment measuring the gap-crossing decisions of forest birds attracted to a recording of chickadee(Poecile atricapillus) mobbing calls, and provided with options to travel to the speaker by either crossing an open area (short cut) or taking a longer route under forest cover (detour). We performed the experiment in winter and late summer near Quebec City, Quebec, Canada. We recorded 1078 travel paths from 6 resident and 12 migratory species in 249 experimental sites. In both seasons, birds preferred to travel under forest cover rather than cross open areas, even when the forested detour conveyed a substantially longer route than the short cut in the open. Only when the detour under forest cover. This was considerably longer than the short-cut in the open, in both relative and absolute terms, were birds more likely to take short cuts, indicating that gap-crossing decisions are scale dependent. However, birds rarely ventured >25 m from forest edges despite having the opportunity to do so. Except for Hairy Woodpeckers (Picoides villosus) which ventured further into the open, all species showed similar gap-crossing decisions. Residents remained marginally closer to forest edges in late summer as compared to in winter. Conspecific group size had no influence on gap-crossing decisions. This experiment supports the hypothesis that forest bird movements are constrained in fragmented landscapes, and provides opportunities to calibrate spatially-explicit, individual-based models addressing the influence of landscape composition and configuration on dispersal.

The influence of research scale on bald eagle habitat selection along the lower Hudson River, New York (USA)

Abstract: As the concepts of landscape ecology have been incorporated into otherdisciplines, the influence of spatial patterns on animal abundance anddistribution has attracted considerable attention. However, there remains asignificant gap in the application of landscape ecology theories and techniquesto wildlife research. By combining landscape ecology techniques withtraditionalwildlife habitat analysis methods, we defined an ‘organism-centeredperspective’for breeding bald eagles (Haliaeetus leucocephalus) alongthe Hudson River, New York, USA. We intensively monitored four pairs ofbreedingeagles during the 1999 and 2000 breeding seasons, and collected detailedinformation on perch and forage locations. Our analysis focused on threecritical habitat elements: available perch trees, access to foraging areas, andfreedom from human disturbance. We hypothesized that eagle habitat selectionrelative to each of these elementswould vary with the spatial scale of analysis, and that these scalingrelationships would vary among habitat elements. We investigated two elementsofspatial scale: grain and local extent. Grain was defined as the minimum mappingunit; local extent was defined by the size of an analysis window placed aroundeach focal point. For each habitat element, we quantified habitat use over arange of spatial scales. Eagles displayed scale-dependent patterns of habitatuse in relation to all habitat features, including multi-scale andthreshold-like patterns. This information supports the existence ofscale-dependant relationships in wildlife habitat use and allowed for a moreaccurate and biologically relevant evaluation of Hudson River breeding eagle habitat.

Impact of data integration technique on historical land-use/land-cover change: Comparing historical maps with remote sensing data in the Belgian Ardennes

Abstract: Historical reconstructions of land-use/cover change often require comparing maps derived from different sources. The objective of this study was to measure land-use/cover changes over the last 225 years at the scale of a Belgian landscape, Lierneux in Ardennes, on the basis of a heterogeneous time series of land cover data. The comparability between the land-cover maps was increased following a method of data integration by map generalisation. Two types of time series were built by integrating the maps either by reference to the initial map of the time series or by pair of successive maps. Land-cover change detection was performed on the initial time series without data integration and on the two types of integrated time series. Results reveal that land cover and landscape structure have been subject to profound changes in Lierneux since 1775, with an annual rate of change at the landscape level of up to 1.40%. The major land-cover change processes observed are expansion of grasslands-croplands and reforestation with coniferous species, leading to amore fragmented landscape structure. The annual rates of land-cover change estimated from integrated data are significantly different from the annual rates of change estimated without a prior integration of the data. There is a trade-off between going as far back in time as possibleversus performing change detection as accurately as possible.

Landscape ecology: a framework for integrating pattern and process in river corridors

Abstract: Investigations of European floodplain rivers demonstrate how landscape ecology can provide an effective framework to integrate pattern and process in river corridors, to examine environmental dynamics and interactive pathways between landscape elements, and to develop viable strategies for river conservation. The highly complex and dynamic nature of intact river corridors is particularly amenable to a landscape ecology perspective. Analysis of spatial patterns has provided considerable insight into environmental heterogeneity across river corridors and is an essential prelude to examining dynamic interactions. For example, data from aerial photographs, digitized maps and year-round field measurements in a glacial flood plain, enabled us to distinguish six channel types, based on the correspondence between connectivity and physicochemical attributes. Spatial data were also used to analyze longitudinal changes in landscape elements along the course of a morphologically-intact riverine corridor, providing insight into the structural complexity that must have characterized many Alpine rivers in the pristine state. Landscape indices were employed to investigate seasonal dynamics in a glacial flood plain of the Swiss Alps which exhibits a predictable expansion/contraction cycle, with corresponding shifts in flow paths (surface and subsurface) and water sources (snowmelt, englacial, subglacial, alluvial aquifer, hillslope aquifer). Surface connectivity exhibited an unexpected biphasic relationship with total channel length, whereas riverscape diversity progressively increased along the entire range of channel length. Reconstituting the functional integrity that characterizes intact river corridors should perhaps be the major goal of river conservation initiatives. Although understanding functional processes at the landscape scale is essential in this regard, few data are available. In the Alluvial Zone National Park on the Austrian Danube, three phases of hydrological connectivity were identified (disconnection, seepage connection and surface connection) that corresponded to the predominance of three functional processes (biotic interactions, primary production and particulate transport) within the river corridor.

Multi-scale effects of habitat loss and fragmentation on lesser prairie-chicken populations of the US Southern Great Plains

Abstract: Large-scale patterns of land use and fragmentation have been associatedwith the decline of many imperiled wildlife populations. Lesserprairie-chickens(Tympanuchus pallidicinctus) are restricted to thesouthernGreat Plains of North America, and their population and range have declined by> 90% over the past 100 years. Our objective was to examine scale-dependentrelationships between landscape structure and change and long-term populationtrends for lesser prairie-chicken populations in the southern Great Plains. Weused a geographic information system (GIS) to quantify landscape composition,pattern and change at multiple scales (extents) for fragmented agriculturallandscapes surrounding 10 lesser prairie-chicken leks. Trend analysis oflong-term population data was used to classify each population and landscape(declined, sustained). We analyzed metrics of landscape structure and changeusing a repeated measures analysis of variance to determine significant effects(α = 0.10) between declining and sustained landscapes across multiplescales. Four metrics of landscape structure and change (landscape change index,percent cropland, increases in tree-dominated cover types, and changes in edgedensity) contained significant interactions between population status andscale,indicating different scaling effects on landscapes with declining and stablepopulations. Any single spatial scale that was evaluated would not have givencomplete results of the influences of landscape structure and change on lesserprairie-chicken populations. The smallest spatial scales (452, 905, and 1,810ha) predicted that changes in edge density and largest patch sizewere the only important variables, while large-scale analysis (7,238ha) suggested that the amount of cropland, increase in trees(mostly Juniperus virginiana), and general landscapechanges were most important. Changes in landscape structure over the pastseveral decades had stronger relationships with dynamics of lesserprairie-chicken populations than current landscape structure. Observed changessuggest that these local populations may be appropriately viewed from ametapopulation perspective and future conservation efforts should evaluateeffects of fragmentation on dispersal, colonization, and extinction patterns.

Landscape-scale controls over 20th century fire occurrence in two large Rocky Mountain (USA) wilderness areas

Abstract: Topography, vegetation, and climate act together to determine thespatial patterns of fires at landscape scales. Knowledge oflandscape-fire-climate relations at these broad scales (1,000s hato 100,000s ha) is limited and is largely based on inferences andextrapolations from fire histories reconstructed from finer scales. In thisstudy, we used long time series of fire perimeter data (fire atlases) and datafor topography, vegetation, and climate to evaluate relationships between large20thcentury fires and landscape characteristics in two contrastingareas: the 486,673-ha Gila/Aldo Leopold Wilderness Complex (GALWC)in New Mexico, USA, and the 785,090-ha Selway-BitterrootWilderness Complex (SBWC) in Idaho and Montana, USA. There were importantsimilarities and differences in gradients of topography, vegetation, andclimatefor areas with different fire frequencies, both within and between study areas.These unique and general relationships, when compared between study areas,highlight important characteristics of fire regimes in the Northern andSouthernRocky Mountains of the Western United States.Results suggest that amount and horizontal continuity of herbaceous fuels limitthe frequency and spread of surface fires in the GALWC, while the moisturestatus of large fuels and crown fuels limits the frequency of moderate-to-highseverity fires in the SBWC. These empirically described spatial and temporalrelationships between fire, landscape attributes, and climate increaseunderstanding of interactions among broad-scale ecosystem processes. Resultsalso provide a historical baseline for fire management planning over broadspatial and temporal scales in each wilderness complex.

The influences of patch shape and boundary contrast on insect response to fragmentation in California grasslands

Abstract: Landscape ecologists typically identify boundaries to demarcate habitatpatches. The boundary between two habitat types may be abrupt, such as thetransition between a grassland and a parking lot, or more gradual, such as theshift between successional forest stages. Two key aspects of landscapeboundaries, their shape and contrast, are predicted to influence movement ofmaterials, plants, and animals. Ecological theory suggests that a patch’sperimeter-to-area ratio should strongly influence animal emigration when patchboundaries are relatively permeable, but not when boundaries are more severe.Weinvestigated the interactive effects of patch shape and boundary contrast onmovement of ground-dwelling beetles (Carabidae and Tenebrionidae) in nativegrassland habitat at Jepson Prairie, Solano County, California, USA. Weconducted a field experiment with two patch shape treatments, square andrectangle, that held patch area constant, and two boundary contrast treatmentscreated by mowing grass surrounding each plot at two different heights. Wemonitored the number of beetles leaving each patch over a three-week periodfollowing treatment establishment. We observed a significant effect of boundarycontrast on net movement of beetles, with low contrast boundaries exhibitingnetimmigration and high contrast boundaries experiencing net emigration. Moreover,the importance of patch shape appeared to be greater for low contrast versushigh contrast boundaries, consistent with theoretical expectations. Ourcombinedobservations indicate that these ground-dwelling beetles were more likely tomove into patches that were rectangular and surrounded by a low contrast matrixthan patches that were square or surrounded by a high contrast matrix. Weconclude that net movement of beetles across patch boundaries is stronglyinfluenced by boundary contrast and may be affected by patch shape whenboundarycontrast is low.

A leakiness index for assessing landscape function using remote sensing

Abstract: The cover, number, size, shape, spatial arrangement and orientation of vegetation patches are attributes that have been used to indicate how well landscapes function to retain, not ‘leak’, vital system resources such as rainwater and soil. We derived and tested a directional leakiness index (DLI) for this resource retention function. We used simulated landscape maps where resource flows over map surfaces were directional and where landscape patch attributes were known. Although DLI was most strongly related to patch cover, it also logically related to patch number, size, shape, arrangement and orientation. If the direction of resource flow is multi-directional, a variant of DLI, the multi-directional leakiness index (MDLI) can be used. The utility of DLI and MDLI was demonstrated by applying these indices to three Australian savanna landscapes differing in their remotely sensed vegetation patch attributes. These leakiness indices clearly positioned these three landscapes along a function-dysfunction continuum, where dysfunctional landscapes are leaky (poorly retain resources).

Estimating the consequences of habitat fragmentation on extinction risk in dynamic landscapes

Abstract: Analyzing the population dynamic consequences of spatio-temporal changes in landscape structure is a formidable challenge for spatial ecology. One key population dynamic process in fragmented landscapes is the influence of isolation on colonization rate and thereby on the occurrence of species in habitat fragments, but it is not obvious how isolation should be measured in landscapes that are affected by on-going habitat loss and fragmentation. We suggest the following procedure for the measurement of spatio-temporal isolation. First, a historical record of habitat loss and fragmentation in the landscape is prepared based on snapshots of the extent of the suitable habitat for the focal species. Second, a metapopulation model is used to simulate the occurrence of the species in this landscape, assuming the empirically observed landscape change. The model-predicted pattern of habitat occupancy at a particular point in time (usually the present time) is then compared with empirical observations on the occurrence of the species. We describe a metapopulation model that has been constructed for this purpose, and we apply it to a changing landscape of boreal forests in eastern Finland. We give an example on the occurrence of four threatened polyporous fungi in 18 small fragments of old-growth forest. In none of the species does the current isolation of the fragments nor the time since their isolation explain the occurrence of the species in the study fragments, but in three species the model-predicted occupancy probability had a significant effect on the observed abundance of the species. The model-predicted occupancy probabilities were also calculated by ignoring past landscape changes, that is, by assuming that the landscape had remained in the present configuration for a long time. These probabilities had a significant effect on the abundance of only one of the four species, suggesting that the occurrence of the species tracks landscapes changes with a noticable time lag.

Setting targets in strategies for river restoration

Abstract: Since about 90% of the natural floodplain area of rivers in Europe has been reclaimed and now lacks river dynamics, nature rehabilitation along rivers is of crucial importance for the restoration of their natural function. Flood protection, self-purification of surface water, groundwater recharge, species protection and migration are all involved in this process. It is now generally recognised that rivers form natural arteries in Europe but are also of economic importance and are recognisable cultural landscape. Many examples are already available of successful small river restoration projects. Several species thought to be extinct have now reappeared and characteristic species have also expanded in recent years. This paper concentrates on the concept of setting targets for river restoration as exemplified by the Meuse River. A modelling exercise shows the restraints of current habitat configuration and the potential for habitat restoration along the river. A policy analysis, using a strategic approach, illustrates the influence of the decision making process on the targets for natural river development. River dynamics play a key factor in determining the potential for persistent populations of target animal species along the river, with the help of an expert system (LARCH, Landscape ecological Analysis and Rules for the Configuration of Habitat). The potentials for the increase of dispersion and biodiversity and the maximisation of ecological benefits at different scales, are also considered.

Landscape pattern in topographically complex landscapes: issues and techniques for analysis

Abstract: Ecological research provides ample evidence that topography can exert a significant influence on the processes shaping broad-scale landscape vegetation patterns. Studies that ignore this influence run the risk of misinterpreting observations and making inappropriate recommendations to the management community. Unfortunately, the standard methods for landscape pattern analysis are not designed to include topography as a pattern-shaping factor. In this paper, we present a set of techniques designed to incorporate the topographic mosaic into analyses of landscape pattern and dynamics. This toolbox includes adjustments to ‘classic’ landscape indices that account for non-uniform landscape topography, indices that capture associations and directionality in vegetation pattern due to topographic structure, and the application of statistical models to describe relationships between topographic characteristics and vegetation pattern. To illustrate these methods, we draw on examples from our own analysis of landscape pattern dynamics in logged and unlogged forest landscapes in southwestern British Columbia. These examples also serve to illustrate the importance of considering topography in both research and management applications.

Microphytic crusts, shrub patches and water harvesting in the Negev Desert: the Shikim system

Abstract: Human-made contour banks are a central component of theShikim water harvesting system in Israel’s Negev Desert.Efficient water capture depends on the presence of a stable microphytic crustwhich directs surplus surface runoff into the banks where it is stored. We usedsimulated rainfall to examine the impact of soil surface disturbance on runoffand sediment transport, and the effect of this on the efficiency of resourcecapture within the Shikim system. Two disturbance regimes:1) removal of the microphytic crust only, and 2) removal of the crust and shrubpatches by cultivation, were compared with an undisturbed control. In theundisturbed state, 32% of rainfall was redistributed as runoff. This runoffpenetrated approximately 27% deeper under the shrub patches compared with themicrophytic crust. When the microphytic crust was destroyed by simulatedtrampling, the runoff coefficient declined to 13%, and there was no significantdifference in water penetration between shrub and crust patches. Completedestruction of the shrub hummocks and crust by cultivation resulted in adeclinein the runoff coefficient to 6%. The result of sustained disturbance in thesepatchy Negev shrublands is a breakdown in spatial heterogeneity, a loss ofecosystem function, a reduction in ecosystem goods and services such as plantdiversity and production, and ultimately a reduction in pastoral productivity.These results reinforce the view that microphytic crusts are critical for theefficient operation of the Shikim water harvesting system.Given that practices such as cultivation and trampling which disturbmicrophyticcrusts result in enhanced infiltration, crusts should be left intact tomaximisethe water harvesting efficiency in these desert landscapes.

Spatial structuring and floral avoidance behavior prevent ant-pollinator conflict in a Mexican ant-acacia

Abstract: Ant-acacias represent a classic insect–plant mutualism: the ants defend the plant from attack by herbivores, and in return are provided with trophic rewards and living space within swollen thorns. A potential drawback of this and other ant–plant mutualisms is that ant-guards may drive away useful insects, particularly pollinators. We assess the potential for ant–pollinator conflict in a Mexican ant-acacia, Acacia hindsii. This Acacia is guarded by a highly aggressive ant (Pseudomyrmex veneficus), which resides entirely within the host plant canopy and is provided with extrafloral nectar and protein-rich Beltian bodies. Acacia hindsii flowers released their pollen from 0700 to 0830 hours, and were visited by pollinators from 0730 to 1300 hours. Over the same time period ants maintained high activity levels at extrafloral nectaries on young leaves. Although daily activity of ants and pollinators overlapped substantially in time, it was largely separated in space: resources exploited by the ants are predomin...

The use of herders' accounts to map livestock activities across agropastoral landscapes in Semi-Arid Africa

Abstract: Improved understandings of the agricultural and range ecologies ofsemi-arid Africa require better information on the spatiotemporal distributionof domestic livestock across agropastoral landscapes An empirical GIS-basedapproach was developed for estimating distributions of herded livestock acrossthree agropastoral territories (around 100 km2 each)over a two-year period Algorithms developed from regression analyses of herdtracking data (with R2s ≥ 067) are used to transform a morecomprehensive but incomplete set of data generated from herders’ accounts oftheir herds’ grazing itineraries (400 herds following 6500 itineraries) Theresulting characterization registers 40 000 days of livestock activitiesacross694 land units (averaging 70 ha) over the study period This studydemonstrates that rural producers’ knowledge of their daily extractionpracticescan be translated to fine-grained characterizations of extraction densitiesacross mixed landscapes The spatiotemporal distribution of livestock that isrevealed by this approach diverges strongly from that predicted bycommonly-usedpoint-diffusion estimation procedures Instead, the distribution reflects localpatterns of land use, topography, vegetation, settlements, and water pointsGrazing and nongrazing times spent in land units are not spatially correlatedand the seasonality of grazing pressure is spatially variable Therefore, theecological impacts of livestock grazing are spatially variable at fine scalesand there is a significant potential for livestock-mediated nutrient transfersacross agropastoral landscapes The georeferenced data produced by thisapproachnot only will help evaluate the impact and sustainability of differentmanagement practices but also provides a strong empirical base for improvedspatial modeling of herded livestock

Testing landscape metrics as indicators of habitat loss and fragmentation in continuous eucalypt forests (Queensland, Australia)

Abstract: Landscape metrics are widely applied in landscape ecology to quantify landscape structure However, many are poorly tested and require rigorous validation if they are to serve as reliable indicators of habitat loss and frag-mentation, such as Montreal Process Indicator 11e We apply a landscape ecology theory, supported by explor-atory and confirmatory statistical techniques, to empirically test landscape metrics for reporting Montreal Process Indicator 11e in continuous dry eucalypt forests of sub-tropical Queensland, Australia Target biota examined included: the Yellow-bellied Glider (Petaurus australis); the diversity of nectar and sap feeding glider species including P australis, the Sugar Glider P breviceps, the Squirrel Glider P norfolcensis, and the Feathertail GliderAcrobates pygmaeus; six diurnal forest birds species; total diurnal bird species diversity; and the density of nec-tar-feeding diurnal bird species Two scales of influence were considered: the stand-scale (2 ha), and a series of radial landscape extents (500 m –2 km;78–1250 ha) surrounding each fauna transect For all biota, stand-scale structural and compositional attributes were found to be more influential than landscape metrics For the Yellow-belliedGlider, the proportion of trace habitats with a residual element of old spotted-gum/ironbark eucalypt trees was a significant landscape metric at the 2 km landscape extent This is a measure of habitat loss rather than habitat fragmentation For the diversity of nectar and sap feeding glider species, the proportion of trace habitats with a high coefficient of variation in patch size at the 750 m extent was a significant landscape metric None of the landscape metrics tested was important for diurnal forest birds We conclude that no single landscape metricadequately captures the response of the region’s forest biota per se This poses a major challenge to regional reporting of Montreal Process Indicator 11e, fragmentation of forest types

Agriculture intensification and forest fragmentation in the St. Lawrence valley, Québec, Canada

Abstract: Quantifying remaining forest cover and understanding how thefragmentation process operates with respect to the various land-use practicesare important steps when working to preserve the biodiversity associated withwoodlots in agricultural landscapes. We used LANDSAT satellite imagery, soiltypes, and boundaries of regional county municipalities (RCM) as the samplingunit of a 6 million-ha territory located in southern Quebec (Canada), to provide a picture of the forest situation in the St. Lawrence Valley.We assessed the effect of human population densities and various types ofagricultural production on the fragmentation process. On average, 45% of thetotal land area of RCMs is forested. However, in 8 of the 59 RCMs studied 20%orless of the total area is still forest habitat. As agricultural use of landincreased, the density of woodlots also increased but their average sizedecreased. An overall fragmentation effect seems to occur where less than 50%ofthe territory is forested, as it is the case for 31 of the 59 studied RCMs.Fragmentation increased along a gradient from traditional dairyagriculture to more intensive cash crop agriculture. Finally, we foundthat the forest discontinuity index, mean woodlot area, and woodlot densitywerethe best indicators of the ongoing forest fragmentation process, but overallhuman population density is the most useful predictive variable.

Spatial dependence and the relationship of soil organic carbon and soil moisture in the Luquillo Experimental Forest, Puerto Rico

Abstract: We used geo-spatial statistical techniques to examine the spatial variation and relationship of soil organic carbon (SOC) and soil moisture (SM) in the Luquillo Experimental Forest (LEF), Puerto Rico, in order to test the hypothesis that mountainous terrain introduces spatial autocorrelation and crosscorrelation in ecosystem and soil properties. Soil samples (n = 100) were collected from the LEF in the summer of 1998 and analyzed for SOC, SM, and bulk density (BD). A global positioning system was used to georeference the location of each sampling site. At each site, elevation, slope and aspect were recorded. We calculated the isotropic and anisotropic semivariograms of soil and topographic properties, as well as the cross-variograms between SOC and SM, and between SOC and elevation. Then we used four models (random, linear, spherical and wave/hole) to test the semi-variances of SOC, SM, BD, elevation, slope and aspect for spatial dependence. Our results indicate that all the studied properties except slope angle exhibit spatial dependence within the scale of sampling (200 – 1000 m sampling interval). The spatially structured variance (the variance due to the location of sampling sites) accounted for a large proportion of the sample variance for elevation (99%), BD (90%), SOC (68%), aspect (56%) and SM (44%). The ranges of spatial dependence (the distances within which parameters are spatially dependent) for aspect, SOC, elevation, SM, and BD were 9810 m, 3070 m, 1120 m, 930 m and 430 m, respectively. Cross correlograms indicate that SOC varies closely with elevation and SM depending on the distances between samples. The correlation can shift from positive to negative as the separation distance increases. Larger ranges of spatial dependence of SOC, aspect and elevation indicate that the distribution of SOC in the LEF is determined by a combination of biotic (e.g., litterfall) and abiotic factors (e.g., microclimate and topographic features) related to elevation and aspect. This demonstrates the importance of both elevation and topographic gradients in controlling climate, vegetation distribution and soil properties as well as the associated biogeochemical processes in the LEF.

Prediction of total and rare plant species richness in agricultural landscapes from satellite images and topographic data

Abstract: The diversity of future landscapes might depend on our ability to predict their potential species richness. The predictability of patterns of vascular plant species richness in a Finnish agricultural river landscape was studied using generalized linear modeling, floristic records from fifty-three0.25-km grid squares in the “core” study area, and environmental variables derived from Landsat TM images and a digital elevation model. We built multiple regression models for the total number of plant species and the number of rarities, and validated the accuracy of the derived models with a test set of 52 grid squares. We tentatively extrapolated the models from the core study area to the whole study area of 601 km2 and produced species richness probability maps using GIS techniques. The results suggest that the local ‘hotspots’ of total flora (grid squares with > 200species) are mainly found in river valleys, where habitat diversity is high and a semi-open agricultural-forest mosaic occurs. The ‘hotspots’ of rare species (grid squares with > 4 rare species) are also found in river valleys, in sites where extensive semi-natural grasslands and herb-rich deciduous forests occur on steep slopes. We conclude that environmental variables derived from satellite images and topographic data can be used as approximate surrogates of plant species diversity in agricultural landscapes. Modeling of biological diversity based on satellite images and GIS can provide useful information needed in land use planning. However, due to the potential pitfalls in processing satellite imagery and model-building procedures, the results of predictive models should be carefully interpreted.

Population dynamics and habitat connectivity affecting the spatial spread of populations – a simulation study

Abstract: In this paper we show how the spatialconfiguration of habitat quality affects the spatial spread of apopulation in a heterogeneous environment. Our main result is thatfor species with limited dispersal ability and a landscape withisolated habitats, stepping stone patches of habitat greatlyincrease the ability of species to disperse. Our results showthat increasing reproductive rate first enables and thenaccelerates spatial spread, whereas increasing the connectivity has aremarkable effect only in case of low reproductive rates. Theimportance of landscape structure varied according to thedemographic characteristics of the population. To show this wepresent a spatially explicit habitat model taking into accountpopulation dynamics and habitat connectivity. The population dynamicsare based on a matrix projection model and are calculated on eachcell of a regular lattice. The parameters of the Leslie matrix dependon habitat suitability as well as density. Dispersal between adjacentcells takes place either unrestricted or with higher probability inthe direction of a higher habitat quality (restricted dispersal).Connectivity is maintained by corridors and stepping stones ofoptimal habitat quality in our fragmented model landscape containinga mosaic of different habitat suitabilities. The cellular automatonmodel serves as a basis for investigating different combinations ofparameter values and spatial arrangements of cells with high and lowquality.

Changes in mixed deciduous forests of boreal sweden 1866-1999 based on interpretation of historical records

Abstract: Current knowledge of patterns and abundance of deciduous trees in thepre-industrial landscape of boreal Sweden is limited This is due to a dramatictransformation of the forest landscape during the last 100 years and the lackofrepresentative forest reserves We used historical records to study change infive mixed deciduous forests between 1866 and 1999 The results show that largechanges occurred due to complex interactions between fire disturbance, firesuppression, logging and silviculture Before fire suppression, the presence ofdeciduous trees was mainly determined by earlier fire influence Laterselectivelogging disturbed natural succession and favoured regeneration of deciduoustrees During the 20th century deciduous trees were removed bygirdling, thinning and herbicide spraying Much of the mixed deciduous standschanged to coniferous stands between 1906–15 and 1969–70, and thendeciduous trees were totally removed from these stands between late 1960s and1999 Today mixed deciduous forest occurs mainly in young stands and on othersites than previously Our results also show that large coniferous trees andmulti-aged forest occurred in all sites in the early 1900s Most sites weredominated by coniferous species and forest dominated by deciduous treesoccurredonly in smaller areas These results are not consistent with the current viewthat deciduous-dominated forest occupied substantial areas in boreal Swedenbefore fire suppression Appropriate changes in forest management arediscussed,as is the value of historical data in interpreting changes in forestlandscapes