Thomas R. Allen

Influence of snow patterns and snow avalanches on the alpine treeline ecotone

Snow avalanches, snow accumulation, and snow ablation patterns were mapped and analyzed to assess their impact on the three-dimensional position, composition (closed canopy forest, open canopy forest, meadow, krummholz, and non-vegetated surfaces), and spatial structure of the Alpine Treeline Ecotone (ATE) in a portion of Glacier National Park, Montana, USA. Multitemporal Landsat Multispectral Scanner data were processed to derive snow accumulation and ablation patterns throughout a snow season. Landsat Thematic Mapper data were processed and combined with aerial photo interpre- tations for discerning and characterizing snow avalanche paths. Transition matrices were used to assess the change in the state of snow cover conditions, whereas multiple regression analy- ses were used to examine the position and character of snow avalanche paths. The analyses were framed and implemented within a geographic information system (GIS) approach. Re- sults indicate a snowmelt pattern progressing from zonal to azonal; influence of local site and situation factors in snow accumulation and ablation patterns; and the importance of topography, geologic structure, and lithology in defining the starting elevation and source area of snow avalanche paths. Finally, a conceptual process is presented where sites affected by stresses and disturbances are analyzed at a local spatial scale for analysis through a deterministic model, whereas regional stresses and disturbances are assessed through remote sensing and GIS approaches for analysis through empirical models.

Application of spherical statistics to change vector analysis of landsat data: southern appalachian spruce-fir forests.

Abstract This study sought to develop a modified change vector analysis (CVA) using normalized multidate data from Landsat TM to examine spruce–fir ecosystems. The introduction of the balsam woolly adelgid ( Adelges piceae ) to the Great Smoky Mountains in the late 1950s resulted in widespread mortality of Fraser fir ( Abies fraseri ), prompting the need for research on disturbance and regeneration. Drawing from methods in spherical statistics, the extended CVA technique measured absolute angular changes and total magnitude of Tasseled Cap indices (brightness, greenness, and wetness). Polar plots and spherical statistics summarized change vectors to quantify and visualize both magnitude and direction of change. Results separated vectors for forest stands by extent and time interval since infestation, as found along the crest of Smokies Range. Changes in the greenness–wetness plane improved prediction of fir class more than brightness–greenness change. Linear discriminant functions found that magnitude and vector angles combined to predict change class 72% correct with three classes and 57% correct in six spruce-fir classes. The technique demonstrates the ability of change vectors in multiple biophysical dimensions to differentiate forest disturbance and regeneration trends as an alternative to nominal forest or land cover classifications. Introduction High elevation conifer forests in the Southern Appalachians are one of the rarest and most endangered forest types in the eastern United States, encompassing only c. 100 km 2 of which 75% is contained within Great Smoky Mountains National Park (Saunders, 1979; White et al., 1993) . These ecosystems, which are dominated by red spruce ( Picea rubens ) and Fraser fir ( Abies fraseri ), have been impacted by a number of human actions in recent decades, the most serious of which has been the introduction of the balsam woolly adelgid ( Adelges piceae ) in the 1950s. Adelgid-caused mortality of mature Fraser firs has surpassed 90% on some mountains (e.g., Mount Mitchell and Mount Collins; Eagar, 1984; Busing et al., 1988; Smith and Nicholas, 1999 ), and the wave of tree deaths has in turn affected avi-faunal communities (e.g., Alsop and Laughlin, 1991; Rabenold et al., 1998 ).

Creation of environmental health information system for public health service: A pilot study

Despite more than a decade of research on medical information systems, deficiencies exist in our capability of establishing an effective environmental health information infrastructure. In this research, we present a pilot study on creating a feasible environmental health information infrastructure. The newly-developed environmental health information system is a web-based platform that integrates databases, decision-making tools, geographic information systems for supporting public health service and policy making. The study, which is a part of a comprehensive effort known as Environmental Public Health Tracking proposed by the Center for Disease Control and Prevention, opens the door for future research on a large scale nation-wide healthcare information infrastructure.

Topographic context of glaciers and perennial snowfields, Glacier National Park, Montana

Abstract Equilibrium-line altitudes (ELAs) of modem glaciers in the northern Rocky Mountains are known to correspond with regional climate, but strong subregional gradients such as across the Continental Divide in Glacier National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between glacier and snowfield morphology, ELA, and surrounding topography. Glaciers and perennial snowfields were mapped using multitemporal satellite data from the Landsat Thematic Mapper and aerial photography within an integrated Geographic Information System (GIS). Relationships between glacier morphology and ELA were investigated using discriminant analysis. Four morphological categories of perennial snow and ice patches were identified: cirque glacier, niche glacier, ice cap, and snowfield. ELA was derived from overlaid glacier boundaries and Digital Elevation Models (DEMs) within the GIs. DEMs provided topographic variables and models of solar radiation and wind exposure/shelteredness. Regression analysis showed the effects of exposure; on snow accumulation, the strong influence of local topography through upslope zone morphology such as cirque backwalls, and the tendency for glaciers with high ELAs to exhibit compactness in morphology. Results highlight the relatively compact shape and larger area of glaciers adjacent to the Continental Divide. Discriminant analysis correctly predicted the type of glacier morphology in more than half the observations using factored variables of glacier shape, elevation range, and upslope area.

Estuarine shoreline change detection using Japanese ALOS PALSAR HH and JERS-1 L-HH SAR data in the Albemarle-Pamlico Sounds, North Carolina, USA

An edge extraction model has been developed that uses multitemporal satellite synthetic aperture radar data to delineate shorelines in estuaries. Using Japanese ALOS PALSAR HH data acquired in December 2006 and JERS‐1 L‐HH SAR data in December 1994, we mapped shorelines of the outer Pamlico Peninsula, Dare County, North Carolina, USA, spanning 12 years. To assess the validity and accuracy of the delineation, we compared (a) 1994 shorelines versus those derived from the 1993 digital orthophotographs, and (b) 2006 shorelines versus field data collected in February 2007. With promising results, we then analysed and quantified the shoreline changes between 1994 and 2006 on the north, east, and south sides of the Peninsula. Virtually no discernible changes on the north and south sides were found. However, significant landward migration in the middle to southern portion on the east shore was observed. Spatial retreat of shorelines varied greatly, with the maximum rate averaged over a span of 12 years exceeding 11 m year−1. The results support further monitoring of shorelines in estuaries using active remote sensing and the potential for the methodology developed to identify erosional hotspots.

Spectral response and spatial pattern of Fraser fir mortality and regeneration, Great Smoky Mountains, USA

High elevation Fraser fir (Abies fraseri) forests of the Southern Appalachians have undergone widespread mortality since the introduction of the balsam woolly adelgid in the 1950s. Resulting changes in ecosystem pattern and process (e.g., stand dynamic processes) have greatly affected floral and faunal communities. In this project, we integrated field observations, geographic information system topographic models, and 1988–1998 satellite imagery to analyze spatial and temporal conditions of Fraser fir and spruce-fir ecosystems in Great Smoky Mountains National Park. Tasseled cap indices (brightness, greenness, and wetness) and associated spectral changes for Landsat TM digital data were statistically modeled by topographic variables. Spectral changes were recorded using change vector analysis (CVA) and spherical geometry at multiple scales: individual sites, local ridges, and across the east-west gradient of the study area. Significant relationships were found between elevation and observed spectral changes and among mountain sites representing the east-west chronosequence of adelgid infestation. Topographic derivatives were related to tasseled cap and CVA measures in summary statistics, regression, and correlation analysis, revealing significantly different mortality and regeneration pathways that were a function of topographic settings. Geographic variations of these vectors also detail the scope of east-west and localized upslope progression of fir mortality. The application of CVA provided the ability to summarize variation in spectral changes (magnitude and direction) and to ascribe measures to mortality and regeneration processes.

Topographic Normalization of Landsat Thematic Mapper Data in Three Mountain Environments

Abstract A comparative analysis is presented for empirical topographic normalization of Landsat Thematic Mapper (TM) data in varied forest and topographic settings. The paired study included rugged areas of Glacier National Park, Montana, Linville Gorge Wilderness, North Carolina, and Green Mountains, Vermont, U.S.A. Empirical models of topographic bias achieved significant corrections in the Montana and Vermont sites. Relative homogeneity of forest structure offset rugged topography in Montana to yield the highest success of normalization. Significant models could not be derived for Linville Gorge. Topographic normalization is most successful when canopy complexity and altitudinal zonation are low to moderate. Atmospheric pollution and geologic control in ridge‐valley alignment are important considerations when undertaking topographic normalization in mountain environments.

Remote Sensing and Modeling of Mosquito Abundance and Habitats in Coastal Virginia, USA

Abstract: The increase in mosquito populations following extreme weather events poses a major threat to humans because of mosquitoes’ ability to carry disease-causing pathogens, particularly in low-lying, poorly drained coastal plains vulnerable to tropical cyclones. In areas with reservoirs of disease, mosquito abundance information can help to identify the areas at higher risk of disease transmission. Using a Geographic Information System (GIS), mosquito abundance is predicted across the City of Chesapeake, Virginia. The mosquito abundance model uses mosquito light trap counts, a habitat suitability model, and dynamic environmental variables (temperature and precipitation) to predict the abundance of the species Culiseta melanura, as well as the combined abundance of the ephemeral species, Aedes vexans and Psorophora columbiae , for the year 2003. Remote sensing techniques were used to quantify environmental variables for a potential habitat suitability index for the mosquito species. The goal of this study was to produce an abundance model that could guide risk assessment, surveillance, and potential disease transmission. Results highlight the utility of integrating field surveillance, remote sensing for synoptic landscape habitat distributions, and dynamic environmental data for predicting mosquito vector abundance across low-lying coastal plains. Limitations of mosquito trapping and multi-source geospatial environmental data are highlighted for future spatial modeling of disease transmission risk.

Coastal wetland mapping combining multi-date SAR and LiDAR

Inventorying and monitoring are imperative to management of vulnerable coastal wetlands. Multi-date and multi-sensor remote sensing offer new capabilities to wetland programmes such as the US National Wetland Inventory. This pilot study focuses on swamp forests and pocosins, marshes, shrub–scrub and invasive Phragmites australis. Combinations of spaceborne multi-date Synthetic Aperture Radar (SAR) imagery and airborne light detection and ranging (LiDAR) elevation (bare earth elevation and vegetation height) were evaluated. Multi-date SAR data (horizontal-horizontal and horizontal-vertical dual polarizations) highlighted physiognomic dynamics, with LiDAR vegetation canopy discerning selected classes. The highest overall accuracy used SAR, LiDAR canopy and digital elevation model (DEM) data (81% κ = 0.744), but not significantly different from the SAR-only classification (81% κ = 0.742). Both classifications exceeded the data combination using SAR data and DEM (66% κ = 0.521) and SAR data with vegetation canopy (80% κ = 0.725). This approach requires investigation using advanced classification algorithms to prove its potential for monitoring wetland change, sea-level rise, and invasive species.

Spatial characterization of environmental gradients in a coastal lagoon, Chincoteague Bay

Spatial patterns of environmental processes are intrinsic yet complex components of estuaries. Spatial characterization of environmental gradients is a necessary step to better understand and classify estuarine environments. A geographic information system is developed to analyze the major abiotic environmental processes, to evaluate accuracy and spatial uncertainty, and to analyze potential zonation within the choked coastal lagoon of Chincoteague Bay in Maryland and Virginia, USA. Spatially extensive grid-based models of environmental gradients are constructed from existing geospatial and environmental databases, including tidal prism, bathymetry, salinity, wave exposure, and Secchi disk depth. Integration of wetland boundaries and bathymetric data provide for full basin analysis of flushing and tidal prism. Multivariate Principal Components Analysis demonstrates the covariation among gradients and provides an empirical approach to mapping multidimensional zones within the lagoon. The project documents the development of an estuarine geographic information system that can be used to analyze and compare estuarine environments and provide data for environmental decision making.