Trends in circumpolar photosynthetic activity from 1982-2003
Scott
Goetz, Woods Hole Research Center, sgoetz@whrc.org
(Presenting)
Andy
Bunn, Woods Hole Research Center, abunn@whrc.org
Greg
Fiske, Woods Hole Research Center, gfiske@whrc.org
Temperature increases in the northern high latitudes over the past few decades have led to a wide variety of ecosystem changes, including modification of the productivity of plants as measured by ground cover (growth) and associated changes in global CO2 exchange. Well-known studies of “greening” trends between 1982 and 1991 in high latitude vegetation indicate an earlier onset of growing season and more active photosynthesis in the mid-summer months. Our recent work indicates that these trends do not continue uniformly in time or space but instead vary between vegetation types and different periods of the growing season. These results provide some of the first evidence that high latitude forests may be in decline following an initial growth spurt associated with CO2 and warming. Although the observational time scales of not as long as hoped, there is evidence that ecosystem response has been rapid, even accounted for lags in tree growth to recent past climate trends. The satellite observations are supported by a range of field observations, and indicate that natural ecosystems may be responding to climate change in unexpected ways that could have significant further effects on the biosphere.