Plant and shrub aboveground biomass mapped across the North Slope of Alaska using Landsat

Logan T. Berner, Northern Arizona University, logan.berner@nau.edu (Presenter)
Patrick Jantz, Northern Arizona University, patrick.jantz@nau.edu
Kenneth D. Tape, University of Alaska, Fairbanks, kdtape@alaska.edu
Scott J. Goetz, Northern Arizona University, scott.goetz@nau.edu

Rising temperatures are increasing plant biomass and shrub dominance in parts of the Arctic tundra, including northern Alaska. These changes are in turn affecting regional wildlife, climate feedbacks, and northern communities, yet the amount and spatial distribution of plant biomass remains uncertain in tundra ecosystems. In this study, we mapped plant and shrub aboveground biomass (AGB; kg m^-2) across the North Slope of Alaska by combining biomass harvests (n = 24 sites) and a large collection of 30 m resolution Landsat observations (n > 2,000 scenes). We first built non-linear regression models to predict plant and shrub AGB based on Landsat peak summer NDVI (r² ≈ 0.80, P < 0.01). We then predicted regional plant AGB, shrub AGB, and shrub dominance (shrub AGB / plant AGB) by applying these models to a Landsat composite mosaic that covered the North Slope. We quantified pixel-wise uncertainty using a Monte Carlo approach that incorporated sampling and sensor calibration errors. The new maps track landscape variation in AGB visible in high-resolution satellite and aerial imagery, such as the contrast between shrubby water tracks and barren ridgelines. Modeled shrub AGB was closely correlated with a regional map of shrub cover (r_s = 076) and with field measurements of shrub height (r_s = 0.88, n = 25 sites). The spatial distribution of plant and shrub AGB was shaped by local topography, summer temperatures, and prior disturbances, including fires. Future warming will likely increase plant AGB and shrub dominance, yet ecological response to warming will likely be mediated by topography and disturbance. These biomass maps can aid in assessing ecosystem-climate feedbacks associated with ongoing environmental change, and may also inform management of North Slope ecosystems.

Associated Project(s): 

• Goetz-03

Poster Location ID: 61

Session Assigned: Vegetation Dynamics and Distribution