13 Increasing Vulnerability of Alaska’s Boreal Forest as a Result of Climate Warming and the Changing Fire Regime

• Main Author: Eric S. Kasischke
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; permafrost; Tundra; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.420.425; http://www.lter.uaf.edu/pdf/1255_Kasischke_Chapin_2008.pdf

The boreal region extends across the Earth’s land surface between around 50ºN and 67ºN and covers some 15 million square kilometers. The biomes found in this region include forests, wetlands, peatlands and sub-alpine/alpine tundra. Most of this region has an average annual surface temperature around 0ºC, with long, cold winters (average January low temperatures <-30°C) and short, warm summers (average July high temperatures>20°C). This temperature regime has resulted in the formation of permafrost (defined as any soil that has remained below 0ºC for more than two years) throughout a significant portion of the boreal region. In turn, the presence of permafrost results in poor site drainage, low tree growth rates, and decreased rates of soil decomposition, leading to the development of deep organic layers lying on top of the ground surface. A pronounced increase in the rate of summer-time warming (between 0.3 and 0.4ºC per decade) began in the early 1960s throughout the western Arctic and Alaska (Chapin et al, 2005). While rates of precipitation have also increased, the rise in available soil water has not been sufficient to offset requirements for