Close-range remote sensing of aquatic macrophyte vegetation cover

Abstract

Abstract. This study used ground-based hyperspectral radiometry to examine variations in visible and near-infrared spectral re ectance of spatterdock (Nuphar polysepalum Engelm.) as a function of vegetation cover. Sites were sampled in Swan Lake in Grand Teton National Park, Wyoming, using a 512-band spectroradiometer to measure re ectance over the range 326.5-1055.3nm (visible-nearinfrared) and simultaneous estimates of spatterdock cover. Linear correlations between spatterdock cover and spectral re ectance were statistically signi cant at the 0.05 signi cance level in two speci c ranges of the spectrum: 518-607 nm; and 697-900 nm. Predictability of spatterdock cover using spectral variables was best using an NDVI transformationof the data in a non-linear equation (r2 5 0.95). IntroductionSpatterdock (Nuphar polysepalum Engelm.), also known as yellow pond lily or cow lily, is the only species of waterlily native to the western United States. The plant is an emergent aquatic macrophyte, occurring in water depths of up to three meters in ponds, lakes, and oxbows. Spatterdock is characterized by large (10-40 cm) ovate, waxy leaves that oat on the water surface, and large distinctive yellow to red-tinged blossoms. Emergent aquatic macrophytes such as spatterdock are important components of pond ecosystems, providing shade cover and maintaining cooler water temperatures for sh and other aquatic organisms. As spatterdock requires high water quality, poor or declining spatterdock cover may therefore provide an indicator of water quality status and change. In situ sampling of emergent wetland vegetation such as spatterdock presents numerous challenges, including access to and accurate location of sampling plots. While aerial photography and satellite remotely sensed imagery have been used to monitor seasonal and yearly changes in the extent of aquatic macrophytes (Jensen et al. 1993, Jensen 1992, Nohara 1991, Welch et al. 1988, few studies have attempted to address quantitative estimation of cover based on spectral re ectance. Our intent is to quantify relationships between

Remote sensing of aquatic vegetation: theory and applications

“…Values can range between 0.02 and 0.1 in the visible spectrum (with an usual peak in the green region) and 0.06-0.65 in the near infrared (Tilley et al 2003;Jakubauskas et al 2000;Malthus and George 1997;LaCapra et al 1996;Peñuelas et al 1993;Best et al 1981).…”

“…This mixing usually results in a decrease in total reflected radiation, especially in the near to mid infrared regions where water absorption is stronger. The intensity of such effect will be determined by vegetation density and canopy structure (Jakubauskas et al 2000) (Fig. 2), as well as by the nature of the water signal.…”

Retrospective assessment of macrophytic communities in southern Lake Garda (Italy) from in situ and MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) data

“…Developing effective approaches to mapping macrophyte properties would provide baseline data sets for such applications. Many studies have therefore attempted to identify optimal approaches to image processing for a comprehensive analysis of macrophyte ecology (Jakubauskas et al 2000;Buchan, and Padilla 2000;Ozesmi, and Bauer 2002;Heblinski et al 2010). The reliability of an integrated remote sensing data and field survey method for mapping macrophyte properties and for assessing the biodiversity of aquatic plant environments is evaluated in Phinn et al (2008).…”

Use of in situ and airborne reflectance for scaling-up spectral discrimination of coral reef macroalgae from species to communities

“…Algae in temperate environments and seagrass in tropical environments have received some attention (Jakubauskas et al 2000, Wittlinger & Zimmerman 2000, Dekker et al 2001[review], Fyfe 2003, but previous hyperspectral studies in tropical coral reefs have preferentially targeted live, bleached and dead corals (Hedley & Mumby 2002 [review], Minghelli-Roman et al 2002. For coral reefs, several studies have presented spectral signatures of macroalgal species (Maritorena et al 1994, Myers et al 1999, Lubin et al 2001, Kutser et al 2003, Karpouzli et al 2004 or have considered algal morphotypes (fleshy, turf, encrusting) and groups (Phaeophyceae, Chlorophyceae and Rhodophyceae) , but very few studies have addressed the community level (Mumby et al 1997, Hochberg & Atkinson 2000, Purkis & Pasterkamp 2004.…”