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Alaska's Changing Boreal Forest$
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F. Stuart Chapin, Mark W. Oswood, Keith Van Cleve, Leslie A. Viereck, and David L. Verbyla

Print publication date: 2006

Print ISBN-13: 9780195154313

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195154313.001.0001

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Patterns of Biogeochemistry in Alaskan Boreal Forests

Patterns of Biogeochemistry in Alaskan Boreal Forests

(p.241) 15 Patterns of Biogeochemistry in Alaskan Boreal Forests
Alaska's Changing Boreal Forest

David W. Valentine

Knut Kielland

Oxford University Press

As the northernmost forest on Earth, boreal forests endure a combination of environmental challenges common only in subalpine forests elsewhere: extremely cold winters, short growing seasons, cold soils, and limited nutrient availability. Consequently, decomposition has lagged plant production, making circumpolar boreal forest soils one of the largest terrestrial reservoirs of carbon (C). Soil organic matter also constitutes a major source of nutrients, particularly nitrogen (N), that promote plant productivity when released during decomposition. If current trends in high-latitude warming continue (Chapter 4), how will accelerated soil C losses from decomposition compare to the C gains from enhanced plant productivity? This remains an open question of great interest to climate modelers seeking to incorporate biological feedbacks into future generations of general circulation models. This chapter builds on earlier chapters on plants (Chapters 11 and 12), herbivores (Chapter 13), and soil microbes (Chapter 14) to describe the patterns and processes of C and N dynamics in Alaska’s boreal forest, paying particular attention to responses of these processes to the interacting influences of disturbance and climatic variations that occur across the landscape and through time. Other nutrients have received less attention in Alaskan research, and that data gap is reflected in this chapter. Interior Alaska’s boreal forest is a patchwork of successional forest types. The major physiographic zones into which we categorize them reflect the contrasting influences of two major disturbance types: fire in upland and lowland areas results in multiple secondary successional pathways, while a more ordered array of forest types results from a combination of primary succession and variation in flooding frequency during succession on active floodplains (Chapter 7). Within each general physiographic zone (uplands and lowlands, floodplains), differences in the postdisturbance environment further influence vegetation establishment, plant species composition, and, ultimately, element cycling. The state factor approach has proven useful in understanding landscape variation in biogeochemistry (Chapter 1; Van Cleve et al. 1991). As with other aspects of ecosystem function, element cycling reflects control exerted by major state factors: climate, parent material, potential vegetation, topography, and time since the most recent disturbance event.

Keywords:   active layer, biogeochemistry, crowberry, immobilization, lignin, methane, nitrification, paludification, tannins

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