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  • 1
    Electronic Resource
    Electronic Resource
    Distribution of recreational boating across lakes: do landscape variables affect recreational use? (2000)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 43 (2000), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Because people impact lake ecosystems, it is important to consider factors influencing the human use of freshwater resources. We investigated the influence of the landscape position, as well as lake area, recreational facilities, and distance to highways and urban centres, on lake use by boaters in the Northern Highland Lake District of Wisconsin, U.S.A.2. In aerial surveys of ninety-nine randomly selected lakes, we did not see boats on over half of the lakes. Of the lakes with boats, we found a strong correlation between the number of boats and lake area. Recreational boats tended to be found on large, accessible lakes with good boating facilities. Boats were not seen on small, stained lakes with few recreational facilities.3. Regression models showed that lake size and landscape position explained 63% of the variability in the average number of boats per lake and landscape position explained 24% of the variability in boat density on all ninety-nine lakes. Social variables representing the quality of boating facilities and the perception of good fishing explained 70% of the variability in number of boats per lake and 54% of the variation in boat density on all lakes. A combined model using both physical and social variables increased the explanatory power for both number and density. Lake use by boaters was correlated with landscape position, the quality of fishing and the availability of recreational facilities. When the analysis was restricted to the forty-six lakes where boats were found, only the availability of recreational facilities proved a significant predictor of boat density.4. Our results suggest that lake choice by recreational boaters may be best predicted by a combination of the location of a lake in a regional hydrologic landscape, and considerations of available facilities and perceptions regarding fishing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00511.x
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  • 2
    Electronic Resource
    Electronic Resource
    A geomorphic template for the analysis of lake districts applied to the Northern Highland Lake District, Wisconsin, U.S.A. (2000)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 43 (2000), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We tested the degree to which a lake's landscape position constrains the expression of limnological features and imposes a characteristic spatial pattern in a glacial lake district, the Northern Highland Lake District in north-central Wisconsin.2. We defined lake order as a metric to analyze the effect of landscape position on limnological features. Lake order, analogous to stream order, is based solely on geographical information and is simple to measure.3. We examined the strength of the relationship between lake order and a set of 25 variables, which included measures of lake morphometry, water optical properties, major ions, nutrients, biology, and human settlement patterns.4. Lake order explained a significant fraction of the variance of 21 of the 25 variables tested with ANOVA. The fraction of variance explained varied from 12% (maximum depth) to 56% (calcium concentration). The variables most strongly related to lake order were: measures of lake size and shape, concentrations of major ions (except sulfate) and silica, biological variables (chlorophyll concentration, crayfish abundance, and fish species richness), and human-use variables (density of cottages and resorts). Lake depth, water optical properties, and nutrient concentrations (other than silica) were poorly associated with lake order.5. Potential explanations for a relationship with lake order differed among variables. In some cases, we could hypothesize a direct link. For example, major ion concentration is a function of groundwater input, which is directly related to lake order. We see these as a direct influence of the geomorphic template left by the retreat of the glacier that led to the formation of this lake district.6. In other cases, a set of indirect links was hypothesized. For example, the effect of lake order on lake size, water chemistry, and lake connectivity may ultimately explain the relation between lake order and fish species richness. We interpret these relationships as the result of constraints imposed by the geomorphic template on lake development over the last 12 000 years.7. By identifying relationships between lake characteristics and a measure of landscape position, and by identifying geomorphologic constraints on lake features and lake evolution, our analysis explains an important aspect of the spatial organization of a lake district.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00567.x
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  • 3
    Electronic Resource
    Electronic Resource
    Spatial Variation among Lakes within Landscapes: Ecological Organization along Lake Chains (1999)
    Springer
    Ecosystems 2 (1999), S. 395-410 
    Details
    ISSN: 1435-0629
    Keywords: Key words: landscape position; lake variability; lake districts; synchrony; coherence; north temperate lakes; lake chains; lake order; lake number; water residence time.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT Although limnologists have long been interested in regional patterns in lake attributes, only recently have they considered lakes connected and organized across the landscape, rather than as spatially independent entities. Here we explore the spatial organization of lake districts through the concept of landscape position, a concept that considers lakes longitudinally along gradients of geomorphology and hydrology. We analyzed long-term chemical and biological data from nine lake chains (lakes in a series connected through surface or groundwater flow) from seven lake districts of diverse hydrologic and geomorphic settings across North America. Spatial patterns in lake variables driven by landscape position were surprisingly common across lake districts and across a wide range of variables. On the other hand, temporal patterns of lake variables, quantified using synchrony, the degree to which pairs of lakes exhibit similar dynamics through time, related to landscape position only for lake chains with lake water residence times that spanned a wide range and were generally long (close to or greater than 1 year). Highest synchrony of lakes within a lake chain occurred when lakes had short water residence times. Our results from both the spatial and temporal analyses suggest that certain features of the landscape position concept are robust enough to span a wide range of seemingly disparate lake types. The strong spatial patterns observed in this analysis, and some unexplained patterns, suggest the need to further study these scales and to continue to view lake ecosystems spatially, longitudinally, and broadly across the landscape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900089
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of Large-Scale Spatial Heterogeneity in Vegetation Indices among North American Landscapes (1998)
    Springer
    Ecosystems 1 (1998), S. 268-282 
    Details
    ISSN: 1435-0629
    Keywords: Key words: landscapes, spatial heterogeneity, vegetation indices, Landsat TM, AVHRR, scale, topography, land use.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT We analyzed the spatial heterogeneity in vegetation indices among 13 North American landscapes by using full Landsat Thematic Mapper images. Landscapes varied broadly in the statistical distribution of vegetation indices, but were successfully ordinated by using a measure of central tendency (the mean) and a measure of dispersion (the standard deviation or the coefficient of variation). Differences in heterogeneity among landscapes were explained by their topographic relief and their land cover. Landscape heterogeneity (standard deviation of the Normalized Difference Vegetation Index, NDVI) tended to increase linearly with topographic relief (standard deviation of elevation), but landscapes with low relief were much more heterogeneous than expected from this relationship. The latter were characterized by a large proportion of agricultural land. Percent agriculture, in turn, was inversely related to topographic relief. The strength of these relationships was evaluated against changes in image spatial resolution (grain size). Aggregation of NDVI images to coarser grain size resulted in steady decline of their standard deviation. Although the relationship between landscape heterogeneity and explanatory variables was generally preserved, rates of decrease in heterogeneity with grain size differed among landscapes. A spatial autocorrelation analysis showed that rates of decrease were related to the scale at which pattern is manifested. On one end of the spectrum are agricultural, low-relief landscapes with low spatial autocorrelation and small-scale heterogeneity associated with fields; their heterogeneity decreased sharply as grain size increased. At the other end, desert landscapes were characterized by low small-scale heterogeneity, high spatial autocorrelation, and almost no change in heterogeneity as grain sized was increased—their heterogeneity, associated with land forms, was present at a large scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900021
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