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Carbon Cycle & Ecosystems

The goal of this research is to develop methods based on exploiting the structural rather than the spectral signals in NASA Earth Observing System data from the Multiangle Imaging SpectroRadiometer (MISR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) in order to map changes in northern high latitude vegetation. The focus is on estimating shrub abundance and structure in arctic tundra to decouple the contributions of different terrestrial factors (vegetation, soils, surface water) to terrestrial albedo. A strong structural signal is available in multiangle MISR and MODIS data because of the high solar zenith angles at high latitudes that enhance shadowing from woody plants. This structural approach builds on recent advances in using multiangle EOS data for mapping woody canopies and has several advantages: explicitly acknowledging and exploiting structural effects provides alternative, potentially less ambiguous measures than spectral indices; MISR and MODIS cover large areas efficiently, allowing evaluation of trajectories through time from 2000; and MISR views closer to the solar principal plane where the structural signal is strongest. Other remote sensing methods (commercial high resolution imaging, hyperspectral imaging, active instruments) do not have records that extend back to the start of the EOS era, sample too infrequently, and/or are too costly for annual mapping over large areas. Current maps of pan-arctic vegetation are based on spectral vegetation indices that are compound metrics that reflect vegetation cover, photosynthetic activity, foliage depth, canopy architecture, and soil color and brightness; no temporally dynamic maps of woody plant abundance, canopy height, or aboveground woody biomass exist that allow the assessment of trends in structural parameters. Reference data will be obtained from a number of well-characterized field sites in Alaska, Russia, and N. Europe, through an important collaboration with the International Polar Year PPS Arctic Program, field survey, and the construction of high resolution maps. This research is important because changes in tundra - and increasing shrub abundance in particular - are occurring as a result of global warming. Woody plant abundance is important in terms of ecosystem structure and function, land albedo, and feedbacks to climate. Changes in temperature, hydrologic cycling, and matter and energy exchanges with the atmosphere are happening more rapidly in northern high latitudes than anywhere else because arctic ecosystems exist near the freezing point of water and are especially sensitive to climate change. On land, these changes have already been manifested as shifts in seasonality with an earlier spring snowmelt and permafrost melting, earlier green-up, generally higher photosynthetic activity, conversion to wetland, and increases in shrub abundance. However because these trends are not uniformly distributed across the arctic, many important science questions can only be answered by dynamic large-scale mapping and through evaluating trajectories in terrestrial albedo and canopy structure parameters, for example, the height of woody plants is directly related to vegetation community type and also has important interactions with the snow pack, including biogeochemical feedbacks. Furthermore, shrubs are capable of much more rapid expansion than trees: there is thus a pressing need to assess trends in shrub abundance and canopy structural parameters over the entire arctic.

Project PI: Mark Chopping/Montclair State University

Department of Earth and Environmental Studies Montclair State University, Montclair, NJ 07043, USA.

Phone: (973) 655-7384

Fax: (973) 655-4072

Email: chopping@pegasus.montclair.edu

http://www.montclair.edu/profilepages/view_profile.php?username=choppingm

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Started: Aug 10, 2010

Last Activity: Mar 14, 2011

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