Assessing invasive plant infestation and disturbance gradients in a freshwater wetland using a GIScience approach

Abstract

The assessment of aquatic ecosystems requires information on biological and disturbance gradients in order to evaluate quality. As a result decision makers need improved monitoring tools for characterizing relationships between invasive species infestation and disturbance to make informed choices regarding wetland condition and management plans. The overarching goal of this research was to assess invasive plant infestation and disturbance gradients using a GIScience approach. The study was conducted in a fresh-water, coastal wetland in the Muskegon River watershed, Michigan, USA. Airborne hyperspectral imagery (20 bands, 440-880 nm) was classified for Phragmites australis distribution using the Spectral Angle Mapper algorithm. Indicator semivariograms were utilized to define landscape structure and associated spatial scales, and assist in creating a transect scheme to generate landscape pattern metrics quantifying valued ecosystem attributes. Hydrological modifications, as measured by an area-weighted fractal dimension index, served as a proxy for human disturbance and was found to moderately influence Phragmites percent cover (R 2 = 0.4, n = 40), mean patch size (R 2 = 0.5), and patch shape (R 2 = 0.5). A general conclusion was that increased hydrological disturbances were correlated with increased infestation magnitude. The systematic approach executed in this study outlined how geospatial monitoring tools can be used as an assessment framework to provide more meaningful information that lends itself to comprehensive wetlands assessment.

Mapping inland lake water quality across the Lower Peninsula of Michigan using Landsat TM imagery

“…In the study region, similar to many coastal watersheds, land-use practices can result in stress on water quality (Lougheed, Parker, and Stevenson 2006;Torbick et al 2006Torbick et al , 2010. Agricultural runoff, erosion, urban development, and loss of wetland are the processes that have been shown to adversely impact aquatic integrity and promote eutrophication and algal blooms.…”

“…The metrics chosen for this investigation have been found to be useful in related applications investigating the influences of land patterns on aquatic integrity (Liu and Cameron 2001;Kearns et al 2005;Torbick et al 2006Torbick et al , 2010. We generated number of patches (NP), interspersion and juxtaposition (IJI), percentage of landscape (PLAND), and fractal dimension index (FDI) at the class level following methods outlined by Torbick et al (2006).…”

High Resolution Mapping of Peatland Hydroperiod at a High-Latitude Swedish Mire

“…The initial step in the first analysis stage applied variogram methods to the fully preprocessed PALSAR and LiDAR products to understand spatial structure of the data and mire. The use of variograms to help guide image processing and landscape analysis has been shown to be useful in other high resolution wetland assessments [33]. Variogram models were used to to identify spatial dependency and landscape structure of the mire as measured by the remote sensing platforms (i.e., PALSAR and LiDAR).…”