Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 13, 3847-3861, 2016
https://doi.org/10.5194/bg-13-3847-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Jul 2016
Spaceborne potential for examining taiga–tundra ecotone form and vulnerability
Paul M. Montesano1,2, Guoqing Sun2,3, Ralph O. Dubayah3, and K. Jon Ranson2 1Science Systems and Applications, Inc., Lanham, MD 20706, USA
2Biospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
3University of Maryland, Department of Geographical Sciences, College Park, MD 20742, USA
Abstract. In the taiga–tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density, and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, variable, and widespread vegetation change warrants the application of spaceborne data including high-resolution (< 5 m) spaceborne imagery (HRSI) across broad scales for examining TTE form and predicting dynamics. This study analyzes forest structure at the patch scale in the TTE to provide a means to examine both vertical and horizontal components of ecotone form. We demonstrate the potential of spaceborne data for integrating forest height and density to assess TTE form at the scale of forest patches across the circumpolar biome by (1) mapping forest patches in study sites along the TTE in northern Siberia with a multi-resolution suite of spaceborne data and (2) examining the uncertainty of forest patch height from this suite of data across sites of primarily diffuse TTE forms. Results demonstrate the opportunities for improving patch-scale spaceborne estimates of forest height, the vertical component of TTE form, with HRSI. The distribution of relative maximum height uncertainty based on prediction intervals is centered at  ∼  40 %, constraining the use of height for discerning differences in forest patches. We discuss this uncertainty in light of a conceptual model of general ecotone forms and highlight how the uncertainty of spaceborne estimates of height can contribute to the uncertainty in identifying TTE forms. A focus on reducing the uncertainty of height estimates in forest patches may improve depiction of TTE form, which may help explain variable forest responses in the TTE to climate change and the vulnerability of portions of the TTE to forest structure change.

Citation: Montesano, P. M., Sun, G., Dubayah, R. O., and Ranson, K. J.: Spaceborne potential for examining taiga–tundra ecotone form and vulnerability, Biogeosciences, 13, 3847-3861, https://doi.org/10.5194/bg-13-3847-2016, 2016.
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We demonstrate the potential of spaceborne data for integrating forest height and density to assess forest structure for patches in the taiga–tundra ecotone. We map forest patches at sites in northern Siberia with spaceborne data and examine the uncertainty of forest patch height estimates across these ecotone sites. Results demonstrate the opportunities for improving patch-based spaceborne estimates of forest height and forest structure patterns in the circumpolar domain.
We demonstrate the potential of spaceborne data for integrating forest height and density to...
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