Landscape ecologists often deal with aggregated data and multiscaled spatial phenomena. Recognizing the sensitivity of the results of spatial analyses to the definition of units for which data are collected is critical to characterizing landscapes with minimal bias and avoidance of spurious relationships. We introduce and examine the effect of data aggregation on analysis of landscape structure as exemplified through what has become known, in the statistical and geographical literature, as the Modifiable Areal Unit Problem (MAUP). The MAUP applies to two separate, but interrelated, problems with spatial data analysis. The first is the "scale problem", where the same set of areal data is aggregated into several sets of larger areal units, with each combination leading to different data values and inferences. The second aspect of the MAUP is the "zoning problem", where a given set of areal units is recombined into zones that are of the same size but located differently, again resulting in variation in data values and, consequently, different conclusions. We conduct a series of spatial autocorrelation analyses based on NDVI (Normalized Difference Vegetation Index) to demonstrate how the MAUP may affect the results of landscape analysis. We conclude with a discussion of the broaderscale implications for the MAUP in landscape ecology and suggest approaches for dealing with this issue.

Habitat fragmentation has been implicated as a major cause of population decline in grassland birds. We tested the hypothesis that a combination of area and shape determines the use of grassland patches by breeding birds. We compared both species richness and individual species presence in 45 wet meadow grasslands in the floodplain of the central Platte River, Nebraska. Bird data were collected through the use of belt transects and supplemented by walking and listening outside transects. Our data supported our primary hypothesis that perimeter-area ratio, which reflects both the area and shape of a patch, is the strongest predictor of both individual species presence and overall species richness. The probability of occurrence for all six common species (Grasshopper Sparrows, Bobolinks, Upland Sandpipers, Western Meadowlarks, Dickcissels, and Red-winged Blackbirds) was significantly inversely correlated with perimeter-area ratio. The probability of occurrence of Grasshopper Sparrows, Bobolinks, Upland Sandpipers, and Western Meadowlarks was also correlated with area. We conclude that species richness is maximized when patches are large (Ͼ50 ha) and shaped so that they provide abundant interior areas, free from the impacts of edges.

The onshore deposition of macroalgal and macrophyte wrack provides a potentially significant marine subsidy to intertidal and supratidal herbivore and decomposer communities. Based on the study of daily input loads to beaches, we estimated summer wrack deposition of up to 140 Mg (dry mass)/km shoreline in Barkley Sound, British Columbia. However, input rates were highly variable depending on beach type, nearshore hydrodynamics, and buoyancy characteristics of the wrack. Cobble beaches retained ∼10 times and 30 times more wrack than did gravel and sand beaches, respectively. Cobble and gravel beaches also differed in species composition of new (fresh) wrack input, with Macrocystis integrifolia being characteristic for the former and Nereocystis luetkeana for the latter, which we attribute to buoyancy characteristics of the floating debris. On sand beaches, Phyllospadix spp. and Enteromorpha spp. were the dominant wrack species. Species composition of freshly deposited wrack also depended on wave exposure, but predictability based on the species pool within a beach's catchment was restricted. Drift lines of aging wrack differed from freshly deposited wrack in species composition, probably due to wrack decomposition that results in fluxes of nutrients and energy between the adjacent marine and terrestrial habitats. We hold that the characteristics of a given beach, e.g., substratum and wave exposure, and their effects on wrack input, will have important ecological and biogeochemical implications for the marine–terrestrial ecotone.

A major goal of landscape ecology is to understand the formation, dynamics, and maintenance of spatial heterogeneity. Spatial heterogeneity is the most fundamental characteristic of all landscapes, and scale multiplicity is inherent in spatial heterogeneity. Thus, multiscale analysis is imperative for understanding the structure, function and dynamics of landscapes. Although a number of methods have been used for multiscale analysis in landscape ecology since the 1980s, the effectiveness of many of them, including some commonly used ones, is not clear or questionable. In this paper, we discuss two approaches to multiscale analysis of landscape heterogeneity: the direct and indirect approaches. We will focus on scale variance and semivariance methods in the first approach and 17 landscape metrics in the second. The results show that scale variance is potentially a powerful method to detect and describe multiple-scale structures of landscapes, while semivariance analysis may often fail to do so especially if landscape variability is dominant at broad scales over fine scales. Landscape metrics respond to changing grain size rather differently, and these changes are reflective of the modifiable areal unit problem as well as multiple-scale structures in landscape pattern. Interestingly, some metrics (e.g., the number of patches, patch density, total edge, edge density, mean patch size, patch size coefficient of variation) exhibit consistent, predictable patterns over a wide range of grain sizes, whereas others (e.g., patch diversity, contagion, landscape fractal dimension) have nonlinear response curves. The two approaches to multiple-scale analysis are complementary, and their pros and cons still need to be further investigated systematically.

No abstract

Trembling aspen (Populus tremuloides Michx.), a clonal angiosperm, is the most geographically widespread tree in North America. It is generally thought that most extant populations in the western interior of Canada and the United States became established shortly after glacial retreat, but sexual recruitment then effictively ceased owing to inimical climatic conditions. Six populations of trembling aspen were studied in the prairie and montane environments of Waterton Lakes National Park, Alberta. Vegetative tissues were analyzed for electrophoretically detectable variation in 13 enzymes encoded by 14 polymorphic loci and three monomorphic loci. All populations maintained high levels of inter‐ and intrapopulation diversity (P = 0.891; H = 0.319; A = 2.4). The mean fixation index, F, was ‐0.102, indicating some deviation from Hardy‐Weinberg expectations. Genetic differentiation (FST = 3.0) was apparent in this ecologically diverse, but geographically small‐scale, spatial setting. It is suggested that the maintenance of diversity in the absence of frequent modern‐day recruitment, and resistance to further geographic differentiation in this spatially heterogeneous environment reflect occasional seedling establishment through “windows of opportunity” and more importantly, the species' clonal morphology. The phalanx growth form and concomitant physiological integration between ramets combine to spread the risk of death and buffer the effects of selection over time and space.

Aim The spatial extent of western Canada's current epidemic of mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae), is increasing. The roles of the various dispersal processes acting as drivers of range expansion are poorly understood for most species. The aim of this paper is to characterize the movement patterns of the mountain pine beetle in areas where range expansion is occurring, in order to describe the fine-scale spatial dynamics of processes associated with mountain pine beetle range expansion.Location Three regions of Canada's Rocky Mountains: Kicking Horse Pass, Yellowhead Pass and Pine Pass.Methods Data on locations of mountain pine beetle-attacked trees of predominantly lodgepole pine (Pinus contorta var. latifolia) were obtained from annual fixed-wing aircraft surveys of forest health and helicopter-based GPS surveys of mountain pine beetle-damaged areas in British Columbia and Alberta. The annual (1999)(2000)(2001)(2002)(2003)(2004)(2005) spatial extents of outbreak ranges were delineated from these data. Spatial analysis was conducted using the spatial-temporal analysis of moving polygons (STAMP), a recently developed pattern-based approach. ResultsWe found that distant dispersal patterns (spot infestations) were most often associated with marginal increases in the areal size of mountain pine beetle range polygons. When the mountain pine beetle range size increased rapidly relative to the years examined, local dispersal patterns (adjacent infestation) were more common. In Pine Pass, long-range dispersal (> 2 km) markedly extended the north-east border of the mountain pine beetle range. In Yellowhead Pass and Kicking Horse Pass, the extension of the range occurred incrementally via ground-based spread.Main conclusions Dispersal of mountain pine beetle varies with geography as well as with host and beetle population dynamics. Although colonization is mediated by habitat connectivity, during periods of low overall habitat expansion, dispersal to new distant locations is common, whereas during periods of rapid invasion, locally connected spread is the dominant mode of dispersal. The propensity for long-range transport to establish new beetle populations, and thus to be considered a driver of range expansion, is likely to be determined by regional weather patterns, and influenced by local topography. We conclude that STAMP appears to be a useful approach for examining changes in biogeograpical ranges, with the potential to reveal both fine-and large-scale patterns.

No abstract