; University of Idaho (Principal Investigator)
Start Year: 2012
Duration: 3.00 year(s)
Evidence accumulating from many disciplines shows that the Arctic is undergoing significant climatic warming, and that North American Arctic tundra is already responding to warming with increased vegetation greenness in both spatial and temporal domains. In northern Alaska, this greening has at least in part resulted from recent increases in the size, abundance, and range of deciduous shrubs, mainly in valley bottoms and hillslopes, and there is mounting evidence that upland tundra will also respond strongly to warming via increased shrub dominance. Changes in canopy height and other ecosystem properties in response to greater shrub dominance can cause shifts in carbon pools and fluxes that may have far-reaching consequences. In addition, habitat quality and availability for local fauna are likely to be affected in ways yet to be determined.
Quantifying fine-scale variation and change in shrub structure across the full continuum of shrub heights is therefore likely to reveal several important biophysical and ecological shifts occurring in Arctic tundra communities. Until now, mapping variation in shrub density and height across the full range of Arctic shrub types using passive remote sensing approaches has been challenging. While light detection and ranging (LiDAR) is an excellent remote technique for quantifying variation in three-dimensional canopy structure across a wide range of ecosystems, we are aware of no studies that have used LiDAR to quantify the canopy structure of tundra vegetation communities.
Given the sensitive links between shrub dominance and tundra ecological function, detecting subtle changes in canopy stature and density could serve as an early warning sign or indicator that a cascade of ecological changes is unfolding. Further, these transformations of the tundra ecosystem may act as harbingers of new feedbacks that may occur as warming continues at high latitudes. Our overarching goal is therefore to develop novel remote sensing-based methods for identifying, scaling, and understanding the onset of a cascade of immediate/near-term ecological shifts - related to both canopy carbon pools and exchange and trophic dynamics at the base of the terrestrial Arctic food chain - that are associated with increases in shrub height, shrub density, and canopy leaf area in the tundra ecosystem. We will use terrestrial laser scanning (TLS), airborne laser scanning (ALS), and ground-based spectral data in combination with field-collected physiological, entomological, and micrometeorological data collected on the North Slope of Alaska to build and test relationships among ecological variables and remote sensing metrics across the full ranges of shrub height, leaf area, and species composition. We will then use these statistical relationships to scale across the broader Arctic landscape using fine spatial resolution WorldView-2 satellite imagery.
This work will directly address two of the main priorities of the NASA Terrestrial Ecology program 2011 NRA. By characterizing subtle changes in the sensitive Arctic
ecosystem using combined TLS, ALS, and spectral remote sensing methods, we will address (a) the impacts of warming on a cascade of ecosystem vulnerabilities in the Arctic (TE RFP priority 2.1) using (b) powerful combinations of remote sensing datasets that have never before been employed to study Arctic ecosystem change (TE RFP priority 2.2). This work also addresses key issues important for the development and evaluation of the NASA ICESat-2 laser altimetry mission.