Change in spatial characteristics of forest openings in the Klamath Mountains of northwestern California,USA

Change in the spatial characteristics of forest openings was investigated in three forested watersheds in north-western Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fire suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based upon fractals. Significant differences were found using the Kolmogorov-Smirnov two-sample test between the perimeters, areas, distance from sample point to nearest opening, and distance between neighboring openings. The perimeters and areas became smaller, and the distances from the sample point to the nearest opening and between neighboring openings became greater over the 41 years between aerial photo sets. The estimated area occupied by openings decreased from 25.8 % to 15.6 % of the study area. No significant difference was found in the shape of the openings except as the shape indices were influenced by changes in size of the openings.This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.     

Mapping and analyzing landscape patterns

Landscapes were mapped as clusters of 2 or 3 land cover^** types, based on their pattern within the clusters and tendency for a single type to dominate. These landscapes, called Landscape Pattern Types (LPTs), were combined with other earth surface feature data in a Geographic Information System (GIS) to test their utility as analysis units. Road segment density increased significantly as residential and urbanized land cover components increased from absent, to present as patch, to present as matrix (i.e., the dominant land cover type). Stream segment density was significantly lower in LPTs with an urbanized or residential matrix than in LPTs with either a forest or agriculture matrix, suggesting an inverse relationship between stream network density and the prevalence of human development other than agriculture in the landscape. The ratio of average forest patch size to total forest in the LPT unit decreased as agriculture replaced forest, then increased as residential and urban components dominated. Wetland fractal dimension increased as agriculture and residential land cover components of LPTs increased. Comparison of LPT and LUDA land cover area statistics in ecoregions suggested that land cover data alone does not provide information as to its spatial arrangement.     

Temporal and spatial changes in an area of the New Jersey Pine Barrens landscape

In order to document the extent of landscape fragmentation for a section of the New Jersey Pine Barrens region, we have used satellite image and spatial analysis to monitor landscape change between 1972 and 1988. Land-cover patterns were quantified by mean, number, and size of patches; and amount of edges between land cover types. During the intervening sixteen year period, fractal dimension, diversity, and contagion generally decreased while dominance, disturbance and edges increased, indicating a trend to a more dissected and disturbed landscape. There was an increase in the number of forest patches and a significant decrease in the average size of forest patches. In contrast, the mean patch size for the non-forest category has increased as a result of a coalescence of patches. The landscape fragmentation is shown by a downward shift in the distribution of forest patches by size class. These changes in landscape pattern have implications for many ecological processes and resources. Management practices need to consider landscape fragmentation in the Pinelands National Reserve in order to preserve the essential character of the Pine Barrens landscape.     

Cumulative effects of roads and logging on landscape structure in the San Juan Mountains,Colorado (USA)

In the southern Rocky Mountains of temperate North America, the effects of Euro-American activities on disturbance regimes and landscape patterns have been less ubiquitous and less straightforward in high-elevation landscapes than in low-elevation landscapes. Despite apparently little change in the natural disturbance regime, there is increasing concern that forest management activities related mainly to timber harvest and to the extensive network of roads constructed to support timber harvest, fire control, and recreation since the late 1800s have altered disturbance regimes and landscape structure. We investigated the magnitude of change in landscape structure resulting from roads and logging since the onset of timber harvest activities in 1950. We found limited evidence for significant impacts in our study area when all lands within the landscape were considered. The relatively minor changes we observed reflected the vast buffering capacity of the large proportion of lands managed for purposes other than timber (e.g., wilderness). Significant changes in landscape structure and fragmentation of mature forest were, however, evident on lands designated as suitable timberlands. Roughly half of the mature coniferous forest was converted to young stands; mean patch size and core area declined by 40% and 25%, respectively, and contrast-weighted edge density increased 2- to 3-fold. Overall, roads had a greater impact on landscape structure than logging in our study area. Indeed, the 3-fold increase in road density between 1950–1993 accounted for most of the changes in landscape configuration associated with mean patch size, edge density, and core area. The extent of area evaluated and the period over which change was evaluated had a large impact on the magnitude of change detected and our conclusions regarding the ecological significance of those changes. Specifically, the cumulative impact on landscape structure was negligible over a 10-year period, but was notable over a 40-year period. In addition, the magnitude of change in landscape structure between 1950–1993 varied as a function of landscape extent. At the scale of the 228000 ha landscape, change in landscape structure was trivial, suggesting that the landscape was capable of fully incorporating the disturbances with minimal impact. However, at intermediate scales of 1000–10000 ha landscapes, change in landscape structure was quite evident, suggesting that there may be an optimal range of scales for detecting changes in landscape structure within the study area.     

Effects of changing spatial scale on the analysis of landscape pattern

The purpose of this study was to observe the effects of changing the grain (the first level of spatial resolution possible with a given data set) and extent (the total area of the study) of landscape data on observed spatial patterns and to identify some general rules for comparing measures obtained at different scales. Simple random maps, maps with contagion (i.e., clusters of the same land cover type), and actual landscape data from USGS land use (LUDA) data maps were used in the analyses. Landscape patterns were compared using indices measuring diversity (H), dominance (D) and contagion (C). Rare land cover types were lost as grain became coarser. This loss could be predicted analytically for random maps with two land cover types, and it was observed in actual landscapes as grain was increased experimentally. However, the rate of loss was influenced by the spatial pattern. Land cover types that were clumped disappeared slowly or were retained with increasing grain, whereas cover types that were dispersed were lost rapidly. The diversity index decreased linearly with increasing grain size, but dominance and contagion did not show a linear relationship. The indices D and C increased with increasing extent, but H exhibited a variable response. The indices were sensitive to the number (m) of cover types observed in the data set and the fraction of the landscape occupied by each cover type (P _k); both m and P _kvaried with grain and extent. Qualitative and quantitative changes in measurements across spatial scales will differ depending on how scale is defined. Characterizing the relationships between ecological measurements and the grain or extent of the data may make it possible to predict or correct for the loss of information with changes in spatial scale.     

Building patterns and landscape fragmentation in northern Wisconsin,USA

Housing growth is prevalent in rural areas in the United States and landscape fragmentation is one of its many effects. Since the 1930s, rural sprawl has been increasing in areas rich in recreational amenities. The question is how housing growth has affected landscape fragmentation. We thus tested three hypotheses relating land cover and land ownership to density and spatial pattern of buildings, and examined whether building density or spatial pattern of buildings was a better predictor for landscape fragmentation. Housing locations were mapped from 117 1:24,000-scale USGS topographic maps across northern Wisconsin. Patch-level landscape metrics were calculated on the terrestrial area remaining after applying 50, 100 and 250 m disturbance zones around each building. Our results showed that building density and the spatial pattern of buildings were affected mostly by lake area, public land ownership, and the abundance of coniferous forest, agricultural land, and grassland. A full 40% of the houses were within 100 m of lakeshores. The clustering of buildings within 100 m of lakeshores limited fragmentation farther away. In contrast, agricultural and grassland areas were correlated with higher building density, higher fragmentation, and more dispersed building pattern possible legacies of agricultural settlement patterns. Understanding which factors influence building density and fragmentation is useful for landscape level planning and ecosystem management in northern Wisconsin and areas that share similar social and environmental constraints.     

Perceived land use patterns and landscape values

Land use patterns and land form are important sources of information that contribute to the formation of landscape perceptions and values. This paper discusses three concepts of human-landscape relationships: the human as an agent of biological and physical impacts on the landscape; the human as a static receiver and processor of information from the landscape; and the human as an active participant in the landscape —thinking, feeling and acting — a transactional concept. A model of the transactional concept and of human perception and response is presented along with a conjectural example of human-landscape transactions. Three empirical research projects are presented to illustrate varying relationships between and among humans and landscapes. Variations in human experiences, needs and desires, personal utility functions for the use of the landscape, and socio-cultural contexts are suggested as mediating variables on perceived values and human responses. The importance of landscape values information to planning and management activities is discussed.     

Changes in landscape patterns in Georgia,USA

The objectives of this study were to determine how landscape patterns in Georgia, USA have changed through time and whether the spatial patterns varied by physiographic region. Historical aerial photography was used to analyze spatial patterns of land use from the 1930's to the 1980's. Land use patterns were quantified by: (1) mean number and size of patches; (2) fractal dimension of patches; (3) amount of edge between land uses; and (4) indices of diversity, dominance, and contagion. Forest cover increased in aerial extent and in mean patch size. The mean size of agricultural patches increased in the coastal plain and decreased in the mountains and piedmont. Edges between land uses decreased through time, indicating less dissection of the landscape. Fractal dimensions also decreased, indicating simpler patch shapes. Indices of diversity and dominance differed through time but not among regions; the contagion index differed among regions but not through time. A geographic trend of decreasing diversity and increasing dominance and contagion was observed from the mountains to the lower coastal plain. Landscape patterns exhibited the greatest changes in the piedmont region. Overall, the Georgia landscape has become less fragmented and more connected during the past 50 years. Changing patterns in the landscape may have implications for many ecological processes and resources.     

Temporal patterns of ecosystem processes on simulated landscapes in Glacier National Park,Montana, USA

The mechanistic, spatially-explicit fire succession model, Fire-BGC (a Fire BioGeoChemical succession model) was used to investigate long-term trends in landscape pattern under historical and future fire regimes and present and future climate regimes for two 46000 ha landscapes in Glacier National Park, Montana, USA. Fire-BGC has two spatial and temporal resolutions in the simulation architecture where ecological processes that act at a landscape level, such as fire, are simulated annually from information contained in spatial data layers, while stand-level processes such as photosynthesis, transpiration, and decomposition are simulated both daily and annually. Fire is spread across the landscape using the FARSITE fire growth model and subsequent fire effects are simulated at the stand-level. Fire-BGC was used to simulate changes in landscape pattern over 250 years under four scenarios: (1) complete fire exclusion under current climate, (2) historical wildfire occurrence and current climate, (3) complete fire exclusion under a possible future climate, (4) future wildfire occurrence and future climate. Simulated maps of dominant tree species, aboveground standing crop, leaf area index, and net primary productivity (NPP) were contrasted across scenarios using the metrics of patch density, edge density, evenness, contagion, and interspersion. Simulation results indicate that fire influences landscape pattern metrics more that climate alone by creating more diverse, fragmented, and disconnected landscapes. Fires were more frequent, larger, and more intense under a future climate regime. Landscape metrics showed different trends for the process-based NPP map when compared to the cover type map. It may be important to augment landscape analyses with process-based layers as well as structural and compositional layers.     

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

Landscape Ecology - Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and human life. Quantifying landscape pattern and its...     

Landscape context of rural residential development in southeastern Wisconsin (USA)

Private on-site sewage systems serve residential development in rural landscapes throughout the United States. In the State of Wisconsin, three major types of private sewage systems facilitate residential development on sites that span gradients in slope, soil permeability, depth to bedrock, and depth to water-table. Conventional soil-absorption sewage treatment systems are constructed on sites with minimal physiographic constraints; more highly engineered alternative sewage treatment systems are installed on sites with moderate to severe constraints; holding tanks provide no on-site sewage treatment and are employed on sites with the most severe physiographic limitations. An environmental impact statement (EIS), prepared in 1979 on the proposed widespread use of alternative private sewage systems, suggested that alternative systems might facilitate in-fill development on poor sites near existing cities and lead to compact, higher density development patterns.The research reported in this paper tested the validity of this EIS scenario by comparing development patterns associated with a sample of conventional systems, alternative systems, and holding tanks installed during the 1980s in Ozaukee County, Wisconsin. Land use data, soils data, and other site attribute data were assembled and analyzed in a vector geographic information system (GIS). Because each type of private sewage system has a unique set of siting criteria, the three sets of sampled systems are located in significantly different physiographic regions within the County. Collectively, installations of all three systems facilitated scattered residential development throughout the rural landscape. This development consists of relatively small residential patches dispersed within an agricultural matrix. Wastewater management technology, if not constrained by public policies or other socioeconomic factors, can be an important anthropogenic factor influencing both the process and pattern of landscape change.     

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。     

Presettlement landscape heterogeneity: Evaluating grain of resolution using General Land Office Survey data

General Land Office Survey (GLOS) records from the A.D. 1840s provide data for quantitative characterization of presettlement vegetation across western Mackinac County, Michigan, located within the mixed conifer-northern hardwoods forest region. We analyzed data from land survey plat maps and 1958 bearing, witness, and line trees from 162 surveyed section and quarter-section corners in order to map vegatation cover types at a level of spatial resolution appropriate for characterizing landscape heterogeneity using standard landscape ecological metrics. As also demonstrated by a number of both classic and contemporary plant-ecological studies, the distribution of landforms, soils properties, hydrology, and location of fire breaks all contribute to the heterogeneity in vegetation observed at a landscape scale in the region. Through a series of spatial landscape analyses with differing grain of resolution, in this study we determine that a grid cell size of 65 ha (0.5 mi×0.5 mi or 0.25 mi²) to 259 ha (1 mi²) gives a conservative characterization of landscape heterogeneity using standard metrics and is therefore appropriate for use of GLOS data to study historical landscape changes.     

Environmental,historical, and contextual determinants of vegetation cover: a landscape perspective

We formulated and tested models of relationships among determinants of vegetation cover in two agroforested landscapes of eastern North America (Haut Saint-Laurent, Quebec, Canada) that differed by the spatial arrangement of their geomorphic features and intensity of agricultural activities. Our landscape model compared the woody plots of each landscape in terms of the relative influence of environmental attributes, land use history (1958 – 1997), and spatial context (i.e., proximity of similar or contrasting land cover). Our vegetation model evaluated the relative contribution of the same sets of variables to the distributions of herbs, trees, and shrubs. Relationships were assessed using partial Mantel tests and path analyses. Significant environmental and contextual differences were found between the vegetation plots of the two landscapes, but disturbance history was similar. Our vegetation model confirms the dominant effect of historical factors on vegetation patterns. Whereas land-use history overrides environmental and contextual control for trees, herbaceous and shrub species are more sensitive to environmental conditions. Context is determinant only for understory species in older, less-disturbed plots. Results are discussed in relevance to vegetation dynamics in a landscape perspective that integrates interactions between environmental and human influences.     

Interdisciplinarity,landscape ecology and the `Transformation of Agricultural Landscapes'

The theme, the `Transformation of Agricultural Landscapes' is used as a context for examining the current status of landscape ecology and its ability to provide a critical set of responses to a defined range of environmental issues. The links between academic structures and the public demand for landscape-based information raises the potential for landscape ecology to provide solutions. Current approaches within landscape ecology are examined and the dominance of the interdisciplinary approach is found to be deficient. A solution is for the land(scape) system itself to become the initial focus of landscape research. A land system has its own systematic properties which extend beyond the biological dominance of ecosystem science which to many is the basis for landscape ecology. For knowledge of the landscape itself to emerge, landscape ecology must develop more as a discipline with its own theoretical bases and foci than as an interdisciplinary area.     

The change of a satoyama landscape and its causality in Kamiseya,Kyoto Prefecture,Japan between 1970 and 1995

We focused on patterns of land use in a particular satoyama landscape (Japanese traditional rural landscape, comprised of an integral social and ecological network of a village and its surroundings, such as agricultural lands, open forestlands and forests), and the effects of human activities upon them during Japan’s economic growth of the last few decades. Changes of landscape patterns and their probable causes were traced since the beginning of the 1900s to the present, and clarified. Societal, economic and technological changes, especially those that occurred after 1970, were considered the focal points from which major landscape changes developed. We compared the spatial features, patterns of land use and landscape diversities of each land unit, defined in terms of both their natural and man-made conditions for the year 1970, to those of 1995. We found land-use diversity to be strongly related to changes in the patterns of land use, with a decrease in diversity for all land units after 1970. Diversity of forest-age distribution on the other hand, increased. These changes, with the complex, changing patterns of each land unit, could be explained by differences in accessibility from the village and variations in the topography, as well as land ownership of the land units. We selected those land units found to have responded to these factors between 1970 and 1995, and classified them into four types of pattern changes, determined mainly by accessibility and topography.This revised version was published online in May 2005 with corrections to the Cover Date.     

Analysis of landscape patterns in coastal wetlands of Galveston Bay,Texas (USA)

High productivity and accessibility have made coastal wetlands attractive sites for human settlements. This study analyzed the patterns of wetland landscapes in Galveston Bay, Texas, USA. The first objective of the study was to describe the relationships between the fractal dimension of wetland boundaries and those factors which affect the wetland landscapes (e.g., land use, type of vegetation, size, location, and level of human disturbance). The second objective was to construct a historical database to contrast wetland areas which had experienced different levels of disturbance between 1956 and 1989. The fractal dimension, a measure of how much of the geographical space is filled by boundaries, was measured by the perimeter-area method. The fractal dimension of wetlands was significantly affected by land use, type of vegetation, size, and level of anthropogenic disturbance. In addition, increasing the size of buffers around roads did not significantly affect the fractal dimension of wetlands. Landscape indices, such as fractal dimension, dominance, and diversity, were used to characterize spatial heterogeneity in the historical database. Lake Stephenson, an area of low anthropogenic disturbance, experienced no changes in wetland composition and abundance over time. Anahuac, an area of medium disturbance, experienced changes in both wetland composition and abundance. Texas City, an area of high disturbance, experienced a change in wetland composition. These differences can be associated with the type and level of disturbance present; however, more evidence is needed to determine whether certain landscape patterns have stable, intrinsic properties which allow persistence in the face of disturbance. These results will be informative to resource managers determining how wetlands can be managed as natural resources and nature reserves.     

Spatial pattern of coniferous and deciduous forest patches in an Eastern North America agricultural landscape: the influence of land use and physical attributes

In agricultural landscapes, most studies have investigated the influence of the spatial pattern of forest patches on other ecological phenomena and processes, such as animal movement and biodiversity. However, few have focused on explaining the spatial pattern of the forest patches themselves. Understanding how these patterns relate to the processes that generate them is fundamental in developing a sound theory of landscape ecology, and in devising rational management strategies. In this paper, the pattern of the overall forest patches, as well as the pattern of deciduous and coniferous patches in an agricultural landscape of Southern Quebec, Canada, were analyzed and related to landscape physical attributes and land use, using remote sensing, geographic information systems and statistical methods. Results show that the role of landscape physical attributes on forest patch pattern has been modified by land use. In the study area, coniferous or deciduous patches are not associated with a specific surface deposit. In addition, physical attributes explain only a small proportion of the abundance of conifers on past abandoned land compared with land-use factors. Physical attributes only indirectly influence the forest pattern because they strongly influence the land-use practices. Our results reveal a conifer recovery process with the abandonment of agricultural land. On past abandoned land, conifers expand with increasing stand age, mostly by invasion from neighboring coniferous patches. Spatially, coniferous patches are usually located on the margins of the overall forest patches, and they are connected to non-forest land-use types such as crop and pasture, the latter being the most important. By showing the importance of some coniferous forest types that did not exist in the precolonial forest, a new perspective emerges when landscape, especially, land-use dynamics are taken into account.     

Effects of site,landscape features,and fire regime on vegetation patterns in presettlement southern Wisconsin

The presettlement tree cover (1831–33) of 3 townships in a southern Wisconsin landscape was analyzed using original survey records. Four forest types were identified: closed forest, open forest, savanna, and prairie. Comparisons of vegetation types and landscape pattern were made between the east and west sides of the Pecatonica River, which bisects the landscape and could have acted as a natural fire barrier. West of the river, presettlement tree species richness and diversity were lower and trees were smaller in diameter and less dense than to the east. The major vegetation types to the west were prairie (42% of landscape) and savanna (40%), both fire-susceptible types. Prairie was more common on gentle slopes than on other landforms. To the east, the landscape was 70% forested (closed plus open forest). Here, prairie was more frequent on steep dry sites. These vegetation differences, including the contrasting landscape placement of prairie, are attributed to distinct site characteristics and to disturbance (fire) regimes, with the west likely having more frequent fires. In terms of the four vegetation types, the east landscape was more homogeneous, being dominated by closed forest (50%). West of the Pecatonica River, the landscape was more heterogeneous because of the high proportion of both prairie and savanna; however, in terms of flammability of vegetation, the west was essentially homogeneous (82% prairie plus savanna).