Establishing biomass-spectra relationships at Ivotuk, Alaska using LASSO regression

Sara Bratsch, University of Virginia, sb9ef@virginia.edu (Presenter)
Howard Epstein, University of Virginia, hee2b@virginia.edu
Heather Landes, University of Virginia, hal4ca@virginia.edu

Warming in the Arctic has resulted in changes in the distribution and composition of tundra vegetation and a lengthening of the growing season. Past studies have mapped tundra vegetation at relatively coarse spatial scales; however, vegetation changes in the Arctic are occurring at spatial scales within a few meters. This research relates plant functional types (PFTs) to hyperspectral remote sensing data from Ivotuk, Alaska (68.49°N, 155.74°W). Ivotuk is located on the North Slope of the Brooks Mountain range, and consists of the four vegetation communities of moist acidic tundra (MAT), moist nonacidic tundra (MNT), mossy tussock tundra (MT), and shrub tundra (ST). Hand-held hyperspectral data were collected during the 1999 growing season (5 June-27 August) at biweekly intervals using narrow, ~1.42 nm wavebands ranging from 400-1062 nm. Biomass data were collected from areas adjacent to these measurements, and sorted into PFTs including graminoids, forbs, mosses, horsetails, lichens, and deciduous and evergreen shrubs. Spectral bands were grouped into nine sections: Blue (400-450 nm), Green 1 (450-500 nm), Green 2 (500-550 nm), Yellow (550-580 nm), Orange (580-600 nm), Red (600-680 nm), Red Edge (680-725 nm), NIR (725-900 nm), and NIR plateau (900-1062 nm). Each section was averaged for a total of nine spectral variables, and PFTs were regressed against regular and continuum-removed (CR) spectral variables using LASSO regression. Preliminary results for peak growing season indicate no significant relationships for MAT. Strong relationships (adjusted r² .42-.53) were found between MNT and four PFTs for spectra and two PFTs for CR spectra. In MT, strong relationships (adjusted r² .42-77) were found for eight PFTs in both regular and CR spectra. In ST, strong relationships (adjusted r² .47-79) were found for eight PFTs in regular and seven PFTs in CR spectra. Additional analysis will be performed using early growing season data.

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Walker, Skip: Recovery and Archiving of Key Arctic Alaska Vegetation Map and Plot Data for Long-Term Vegetation Analyses ...details
• Related Activity: Related Activity or Previously Funded CC&E Activity not listed ...details

Poster Location ID: 240