Project Funding: 2016 - 2019

NRA: 2016 NASA: Terrestrial Ecology   

Funded by NASA

Abstract:
The Arctic Boreal Zone (ABZ) is one of the most important and sensitive regions on Earth in the context of climate change. Recent evidence points to ongoing changes to ecosystem structure and function that have the potential to significantly feed back to global climate processes. A key to understanding the resilience and vulnerability of the ABZ to environmental change is the collection and analysis of observations spanning functional and structural aspects of these systems, across geographical regions sufficient to resolve the key ecophysiological and phenological processes guiding the future trajectories of these ecosystems. The primary motivation for this proposal is to augment the core ABoVE datasets with acquisitions from the Chlorophyll Fluorescence Imaging Spectrometer (CFIS), a new NASA airborne sensor that has been demonstrated to produce high spatial resolution estimates of solar-induced chlorophyll fluorescence (SIF), a variable tightly linked to terrestrial vegetation photosynthesis. SIF measures a direct outcome of foliar light absorption by chlorophyll, modified by biochemical feedbacks, and has been shown to provide a direct proxy for photosynthesis. Satellite-based estimates of SIF have been used to explore global-scale spatial and temporal patterns of carbon flux associated with photosynthesis, and at regional scales within the ABoVE domain have been used to represent the timing of spring photosynthetic onset and the duration of growing season carbon uptake in tundra and boreal forest ecosystems. These results have shed light on the structural and functional controls of seasonal carbon fluxes across key Arctic biomes, and helped quantify the overall carbon balance of the Arctic Boreal Zone. Moving forward, high-resolution airborne studies are needed to resolve functional relationships between SIF and carbon flux controls across heterogeneous Arctic landscapes. Airborne observations provide an intermediate scale from which to extend findings from detailed site-level observations, and abasis to scale-up to satellite footprints for improved interpretation of global datasets. Careful coordination with planned measurements of land surface (vegetation structure and traits) and subsurface (soil moisture, active layer thickness, and freeze-thaw cycles) properties from VSWIR reflectance (AVIRIS-NG), LiDAR (LVIS), and radar (UAVSAR, AirMOSS) instruments will help elucidate phenological and environmental drivers of seasonal carbon exchange across the ABZ. Here we propose to augment the ABoVE Foundational Airborne Measurements (FAM) planned for 2017 and 2019. We will collect, analyze and interpret SIF observations collected by CFIS in coordination with the planned acquisitions of the FAM, to optimize the value of SIF observations for integrated analyses. These CFIS campaigns will focus on ABoVE Core Study Area regions and will be designed to provide concurrent acquisitions with both (a) AVIRIS / MASTER acquisitions planned for mid-growing season, to examine the relationships between SIF and reflectance indices and thermal status of the land surface; and (b) UAVSAR / AIRMOSS acquisitions at the beginning of the thaw period for an understanding of the role SIF observations can play in quantifying the emergence and increase in photosynthetic activity across the rapid transition between northern latitude winter and summer seasons. These CFIS airborne observations are highly complementary to the planned FAM measurements, by providing proxy information on photosynthetic function that can provide a link between the structural and functional variables and the hydrological measurements collected by FAM platforms. These CFIS acquisitions are highly pertinent to the ongoing OCO-2 mission by increasing understanding of SIF and its relationship to GPP, and to OCO-3 as well, recognizing that OCO-3 will not observe the domain directly.

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile
• NASA Arctic-Boreal Vulnerability Experiment (ABoVE) Project Profile