Alaska’s Changing Boreal Forest By Chapin, F.S., III, M.W. Oswood, K. Van Cleve, L.A. Viereck, and D.L. Verbyla (editors). 2006. Oxford University Press, New York.
The boreal forest is the northernmost forested biome, whose organisms and
dynamics have been shaped by cold high-latitude conditions. The Alaskan boreal
forest is now warming as rapidly as any place on earth, providing an unprecedented
opportunity to examine a biome as it adjusts to change. This book, based on
Bonanza Creek LTER research, describes the processes that have shaped the
development and current dynamics of Alaska’s boreal
forest. This forest developed over the last 13,000 years in response to a gradually
cooling, moistening climate, punctuated 6,000 years ago by an increase in wildfires
when flammable black spruce ecosystems became widespread.
Permafrost (permanently
frozen soil) is patchily distributed in the boreal forest. Where present,
it impedes drainage, producing cold wet soils that constrain biogeochemical
cycles and productivity. Landscape patterns of biogeochemistry are therefore
strongly controlled by cycles of disturbance (flooding in lowlands and fire
in uplands), with pulses of nitrogen input and loss in early succession shifting
to tight plant-microbial recycling in later stages. Successional changes in
abundance of a few key functional types (nitrogen-fixing alder, moose, and
snowshoe hares in early succession; mycorrhizal fungi, mosses, spruce, and
beetles in late succession) generate threshold changes in structure and function
through succession.
Recent warming has increased drought stress in trees, frequency of wildfire
and insect outbreaks, sporadic loss of permafrost, loss of nitrogen from nitrogen-limited
watersheds, and changes in feedbacks to regional and global climate. Many of
these changes have substantial societal importance, both regionally and globally,
suggesting that continuing efforts to develop a predictive understanding of
ecological resilience and change are critical. |
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