Changes in albedo and surface energy budgets associated with high-latitude vegetation dynamics

Michael Loranty, WHRC, mloranty@whrc.org (Presenter)
Pieter Beck, Woods Hole Research Center, pbeck@whrc.org
Scott J. Goetz, Woods Hole Research Center, sgoetz@whrc.org
Yufang Jin, University of California, yufang@uci.edu
James T. Randerson, UC Irvine, Dept. of Earth System Science, jranders@uci.edu
Michelle Cailin Mack, University of Florida, mcmack@ufl.edu
Heather Dawn Alexander, Univ. of Florida, hdalexander@ufl.edu

High latitude ecosystems are undergoing changes to ecosystem structure directly as a consequence of shifts in vegetation communities, and indirectly as a result of intensifying fire disturbance regimes. The resulting changes in albedo dynamics have the potential to alter a number of biogeophysical processes in high latitude ecosystems. Specifically, shrub expansion in tundra ecosystems reduces winter albedo as vegetation protrudes above snowpack, which impacts shortwave radiation fluxes with effects on snowmelt, soil thermal regimes, and, ultimately, ecosystem carbon fluxes. In boreal ecosystems fire-mediated successional changes are leading to shifts from coniferous to deciduous dominated stands. This shift toward forests dominated by deciduous species leads to increases in both summer and winter albedo.

Evidence exists at local scales to support some of these hypotheses, however there is a paucity of information regarding the interaction between vegetation stature and albedo within high-latitude ecosystems at regional and pan-Arctic scales. Here we present analyses of albedo across a series of vegetation gradients. In tundra we use the Circumpolar Arctic Vegetation Map (CAVM) in conjunction with MODIS albedo data to quantify differences in albedo between tundra vegetation communities with different dominant vegetation types, with particular focus on the dynamic spring snowmelt period. Additionally, vegetation indices and climate data are used to examine other physical differences between vegetation types that may lead to variation in albedo dynamics. In boreal forests we use information on fire disturbance history and stand composition to examine differences in albedo between successional chronosequences dominated by deciduous and coniferous species. Our analyses reveal differences in albedo across vegetation gradients within boreal forest and tundra ecosystems, at regional scales, that support current hypotheses. Relative differences in surface radiation budgets are used to quantify the results in the context of feedbacks to climate.

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

Associated Project(s): 

• Goetz, Scott: Quantifying Changes in Northern High Latitude Ecosystems and Associated Feedbacks to the Climate System ...details

Poster Location ID: 225