Browsing by Author "White, Mark A"

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    Great Lakes Assessment: Assessing Landscape Pattern and Structure in Great Lakes Forests
    (University of Minnesota Duluth, 1997) Host, George E; White, Mark A; Polzer, Philip L.; Wolter, Peter T.
    A fundamental component of assessing ecological integrity across regional landscapes is an understanding of basic landscape pattern in terms of the types, structure, and spatial relationships of forest patches. Landscape patterns affect animal migration (Weines and Milne 1989), dispersal (Geritz et al. 1987) and species coexistence (Pacala 1987). Spatial analyses in the past, however, have been confounded by a lack of high resolution data, lack of analytical tools, and hardware limitations. Equally important, spatial analyses are extremely scale-dependent, and yet the appropriate spatial scales for answering ecological relevant questions are uncertain. For example, forest birds (Hanowski et al. in press)., stream macroinvertebrates (Richards et al 1996), and large mammals (Johnson et al. 1991) are all affected by factors operating at multiple spatial scales, but the relative importance of local vs regional scale factors is largely unknown. There is therefore a need to improve our ability to analyze and interpret the spatial structures of landscapes, both in terms of analytical techniques well as underlying ecological theory. We have recently been able to improve the classification resolution of interpreted LANDSAT imagery. By using LANDSAT scenes from different seasons, we have used differences in plant phenology (e.g. timing of leaf development and senescence) to discriminate among spectrally- similar forest types, such as red and pin oak, or black ash and other hardwoods (Wolter et al. 1996). The resulting classification consists of 22 cover classes, with many classes at the species level. This technique has since been applied across much of northern Minnesota and northwestern Wisconsin. In addition to a high classification resolution, the spatial resolution of LANDSAT imagery is 28.5 m, resulting in a relatively fine-scale classification with respect to spatial pattern. Concurrently, a number of workstation-based analytical tools to conduct sophisticated analysis of landscape spatial structure have been developed (Boeder et al. 1995; McGarigal and Marks 1993, Turner and Gardner 1991). These techniques generally use raster data files (e.g. ERDAS GIS files) to calculate numerous landscape statistics, such as fractal dimension, Shannon-Weiner diversity, dominance and contagion, and lacunarity indices. This suite of statistics provides the ability to quantify numerous aspects of landscape pattern, and potentially relate these indices to measures of integrity of forest and aquatic ecosystems. While we now have well-developed ecological databases and analytical tools at our disposal, we lack fundamental information on some of the most basic questions on regional-scale landscape structure in the Lake States. Where are the largest contiguous patches of our dominant forest types? How are these distributed within the regional hierarchy? Where are the most highly fragmented and most intact landscapes? The objective of this study was therefore to use the databases and techniques described above to quantify landscape structure in the context of higher- level ecological classification units for the Lake States. Specifically, we will use the recently- developed subsection-level ecological classification of the eastern United States (Keys and Carpenter 1995) as a framework for summarizing and interpreting spatial statistics derived from a multitemporal LANDSAT classification of northern Minnesota and Wisconsin.
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    Identification of Risk Factors for Blister Rust ( Cronartium ribicola) on Eastern White Pine (Pinus strobus L.).
    (University of Minnesota Duluth, 1999) Brown, Terry; White, Mark A; Host, George E
    Mature white pine forest has been significantly reduced in Northeastern Minnesota over the past 120 years. Blister rust, a usually lethal fungal disease of white pine, was also introduced about 120 years ago, and now poses a major challenge to attempts to reestablish white pines in the region. A map delineating hazard zones for blister rust was prepared in 1961 - this report details the procedure used to update that map using modem GIS techniques. The new map (above, and page 26) is more detailed than the old, and recognizes that even within areas previously classified as "high hazard'', there are places where white pine regeneration may be possible and desirable.
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    Mapping Range of Natural Variation Ecosystem Classes for the Northern Superior Uplands: Draft Map and Analytical Methods
    (University of Minnesota Duluth, 2000-08-09) White, Mark A; Host, George E
    Our primary goal was to create a map of generalized ecological potential for the 8 range of natural variation (RNV) ecosystem classes for the Northern Superior Uplands ecological section (Frelich 1999). The natural range of variability has been shown to be a useful concept for both evaluating the extent of change from historical conditions and for creating tangible models of sustainable ecosystems (Morgan et al. 1994). At present, the finest level of ecological classification that exists for the Northern Superior Uplands is the Land Type Association (LTA). Our objective was to create a map that nests within the current ecological classification system and shows some of the potential variability of upland and lowland habitats within LTAs. We mapped the 8 ecosystem classes based on the relationship between sample vegetation data representing these broad habitat classes and a suite of environmental variables representing soil, landform and climate patterns in the Northern Superior Uplands. In this report we document our methods, data sources and initial results including an accuracy assessment.