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Abstract Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra 1 , thereby reducing albedo 2–4 , altering carbon cycling 4 and further changing climate 1–4 , yet the patterns and processes of this biome shift remain unclear 5 . Climate warming, required for previous boreal advances 6–17 , is not sufficient by itself for modern range expansion of conifers forming forest–tundra ecotones 5,12–15,17–20 . No high-latitude population of conifers, the dominant North American Arctic treeline taxon, has previously been documented 5 advancing at rates following the last glacial maximum (LGM) 6–8 . Here we describe a population of white spruce ( Picea glauca ) advancing at post-LGM rates 7 across an Arctic basin distant from established treelines and provide evidence of mechanisms sustaining the advance. The population doubles each decade, with exponential radial growth in the main stems of individual trees correlating positively with July air temperature. Lateral branches in adults and terminal leaders in large juveniles grow almost twice as fast as those at established treelines. We conclude that surpassing temperature thresholds 1,6–17 , together with winter winds facilitating long-distance dispersal, deeper snowpack and increased soil nutrient availability promoting recruitment and growth, provides sufficient conditions for boreal forest advance. These observations enable forecast modelling with important insights into the environmental conditions converting tundra into forest.
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Sufficient conditions for climate-driven range expansion of a boreal conifer, Alaska, 2019-2021
Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra, thereby reducing albedo, altering C-cycling (carbon-cycling), and changing global climate, yet the patterns and processes of this biome shift remain unclear. We describe the 20th century colonization of an Arctic basin by a widespread boreal conifer, Picea glauca, 40 km (kilometer) north of the nearest established treelines. The population approximately doubled each decade, with radial growth in main stems increasing exponentially and correlating positively to July air temperature. Juvenile height and adult lateral growth were 90% faster than at established treelines. This climate-forced range expansion, cast in the context of invasion theory, informs forecast models of vegetation change with the ecological conditions driving this biome shift. While surpassing temperature thresholds is a necessary condition for boreal forest advance, our empirical results indicate high soil nutrient availability, deep snow, and winter winds facilitate long-distance dispersal and promote recruitment.
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- PAR ID:
- 10468979
- Publisher / Repository:
- NSF Arctic Data Center
- Date Published:
- Subject(s) / Keyword(s):
- boreal forest advance treeline white spruce foliar nutrients snow invasion forest tundra ecotone Arctic Alaska
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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