Successional Changes in Carbon Stocks After Logging and Deforestation for Agriculture in Interior Alaska: Implications for Boreal Climate Feedbacks
The large boreal carbon (C) stocks in Alaska are vulnerable to losses from disturbance, such as clear-cut logging and deforestation for agricultural devel-opment. Here we investigated impacts of logging in uplands and agricultural deforestation in lowlands on C and nitrogen (N) stocks in Interior Al...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.668.9264 http://www.lter.uaf.edu/pdf/1860_Grunzweig_Valentine_2014.pdf |
| Summary: | The large boreal carbon (C) stocks in Alaska are vulnerable to losses from disturbance, such as clear-cut logging and deforestation for agricultural devel-opment. Here we investigated impacts of logging in uplands and agricultural deforestation in lowlands on C and nitrogen (N) stocks in Interior Alaska, using chronosequences, and synthesized results from other studies in the boreal region. Two years after logging, ecosystem C stocks in upland forests were reduced by 11 kg m-2 (46 % of the original ecosystem C stock), mainly as a consequence of stem removal. Soil C and N stocks increased over the first few years after log-ging, but returned to pre-harvest levels during the following decades to century. Studies across the boreal region showed that mean initial C loss was four times greater, but long-term C cycling was similar in logged as compared to burned forests. Agricultural development in Alaskan lowlands per-manently reduced ecosystem C stocks, reaching losses of 11 kg m-2 (34 % of the ecosystem C stock) on non-permafrost soils after several decades and 31 kg m-2 (69%) on permafrost soils over 6 years. These C losses are much more rapid than the 5– 6 kg m-2 over 500 years that models project to be lost by warming or warming-plus-wildfire in low-land boreal forests. If economic incentives and cli-mate warming augment boreal land-use change in lowlands because of improved agricultural oppor-tunities and performance, this could magnify warming-induced C loss and amplify climate warming. These impacts can be reduced by con-serving permafrost-dominated sites for C storage and focusing agriculture on permafrost-free sites. Key words: agricultural cultivation; Alaska bor-eal forest; clearcut logging; deforestation; land-use change; organic carbon stocks; permafrost; Picea glauca; Picea mariana; soil nitrogen. |
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