Evidence and implications of recent and projected climate change in Alaska's forest ecosystems

Wolken, Jane M.; Hollingsworth, Teresa N.; Rupp, T. Scott; Chapin, Stuart F.; Trainor, Sarah F.; Barrett, Tara M.; Sullivan, Patrick F.; McGuire, A. David; Euskirchen, Eugénie; Hennon, Paul E.; Beever, Erik A.; Conn, Jeff S.; Crone, Lisa K.; D’Amore, D. V.; Fresco, Nancy; Hanley, Thomas A.; Kielland, Knut; Kruse, James J.; Patterson, Trista; Schuur, Edward A. G.; Verbyla, David L.; Yarie, John

doi:10.1890/es11-00288.1

Cited by 96 publications

(72 citation statements)

References 175 publications

(151 reference statements)

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“…These changing hydrologic regimes will alter the seasonality and biogeochemistry of Alaskan river discharge by increasing the winter portion and, in some locations, may increase total discharge (Peterson et al, 2002). Second, a longer growing season (Høye et al, 2007) will favor some species over others and this will alter vegetation composition, abundance, and productivity (Wolken et al, 2011), soils (Grosse et al, 2011) and their associated controls on the boreal carbon cycle. Due to the heterogeneous nature of soils, vegetation, and permafrost extent in interior Alaska and the potential feedbacks between a longer growing season and ecosystem respiration it is difficult to determine at a regional scale whether the longer growing season will result in a greater CO 2 or CH 4 sink (Euskirchen et al, 2006;Parmentier et al, 2011).…”

Section: Anticipated Impacts Of a Warming Climate On Interior Alaska mentioning

confidence: 99%

“…Climate warming is expected to have pronounced effects on high latitude ecosystems, especially in locations underlain by relatively warm, discontinuous permafrost such as interior Alaska ( excellent synthesis of the impacts of climate change on Alaskan forests was provided by Wolken et al (2011) and terrestrial ecosystem feedbacks to the climate system are presented in Field et al (2007). However, the aforementioned studies and review papers were not focused on supporting land management activities with respect to assessing and managing carbon sources and sinks.…”

Section: Introductionmentioning

confidence: 99%

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Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Douglas

Jones

Hiemstra

et al. 2014

Elementa: Science of the Anthropocene

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Boreal ecosystems store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region in Alaska and Canada, largely underlain by discontinuous permafrost, presents a challenging landscape for itemizing carbon sources and sinks in soil and vegetation. The roles of fire, forest succession, and the presence (or absence) of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in boreal ecosystems for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape and carbon cycle changes over the next 20 to 50 years. To assist land managers in interior Alaska in adapting and managing for potential changes in the carbon cycle we developed this review paper by incorporating an overview of the climate, ecosystem processes, vegetation, and soil regimes. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to guide policy and land management decisions on how to best manage carbon sources and sinks. We surveyed estimates of aboveground and belowground carbon stocks for interior Alaska boreal ecosystems and summarized methane and carbon dioxide f luxes. These data have been converted into similar units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance. A novel research question is how compounding disturbances affect carbon sources and sinks associated with boreal ecosystem processes. Finally, we provide recommendations to address the challenges facing land managers in efforts to manage carbon cycle processes. The results of this study can be used for carbon cycle management in other locations within the boreal biome which encompasses a broad distribution from 45° to 83° north.

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Section: Anticipated Impacts Of a Warming Climate On Interior Alaska mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Douglas

Jones

Hiemstra

et al. 2014

Elementa: Science of the Anthropocene

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“…Warming has already caused extensive thawing of permafrost, accompanied with changes in hydrology, which are likely driving changes in vegetation, wildfires, and insect outbreaks (2,3). Despite these major changes, the potential response of boreal systems to further climate change is poorly understood.…”

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confidence: 99%

Thresholds for boreal biome transitions

Scheffer¹,

Hirota

Holmgren

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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310

295

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Although the boreal region is warming twice as fast as the global average, the way in which the vast boreal forests and tundras may respond is poorly understood. Using satellite data, we reveal marked alternative modes in the frequency distributions of boreal tree cover. At the northern end and at the dry continental southern extremes, treeless tundra and steppe, respectively, are the only possible states. However, over a broad intermediate temperature range, these treeless states coexist with boreal forest (∼75% tree cover) and with two more open woodland states (∼20% and ∼45% tree cover). Intermediate tree covers (e.g., ∼10%, ∼30%, and ∼60% tree cover) between these distinct states are relatively rare, suggesting that they may represent unstable states where the system dwells only transiently. Mechanisms for such instabilities remain to be unraveled, but our results have important implications for the anticipated response of these ecosystems to climatic change. The data reveal that boreal forest shows no gradual decline in tree cover toward its limits. Instead, our analysis suggests that it becomes less resilient in the sense that it may more easily shift into a sparse woodland or treeless state. Similarly, the relative scarcity of the intermediate ∼10% tree cover suggests that tundra may shift relatively abruptly to a more abundant tree cover. If our inferences are correct, climate change may invoke massive nonlinear shifts in boreal biomes.remote sensing | tipping point | resilience | permafrost | wildfire T he boreal forest is one of the most extensive biomes on Earth.Together with tundra, it is warming more rapidly than other biomes-approximately twice as fast as the global average (1). Warming has already caused extensive thawing of permafrost, accompanied with changes in hydrology, which are likely driving changes in vegetation, wildfires, and insect outbreaks (2, 3). Despite these major changes, the potential response of boreal systems to further climate change is poorly understood. One of the big questions is whether boreal biomes will change gradually, as assumed by most dynamic vegetation models (4, 5), or might have tipping points where changing conditions can invoke critical transitions.Many factors, including fire, insects, climate, permafrost, and human land use, play a role in vegetation dynamics in the boreal region (2, 3, 6, 7). However, although detailed studies have revealed separate mechanisms, an understanding of large-scale stability properties and dynamics cannot easily be constructed from these separate elements. To address the question of potential critical transitions, we therefore complement the existing studies by analyzing the distribution of tree cover densities on continental scales. Tree cover is admittedly a rather crude descriptor of the vegetation state. However, it is one of the most defining characteristics not only for the structure of the landscape, but also for functional characteristics such as carbon storage and albedo.Our central goal is to determine whether the frequ...

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“…Models predict continued increases in area burned and carbon emissions in boreal North America in the future [11][12][13][14] in response to a strengthening of arctic amplification of global climate change [15]. However, there are indications of an ecosystem shift from highly flammable mature spruce to less flammable early successional deciduous vegetation [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Differences in Human versus Lightning Fires between Urban and Rural Areas of the Boreal Forest in Interior Alaska

Calef

Varvak

McGuire

2017

Forests

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Abstract:In western North America, the carbon-rich boreal forest is experiencing warmer temperatures, drier conditions and larger and more frequent wildfires. However, the fire regime is also affected by direct human activities through suppression, ignition, and land use changes. Models are important predictive tools for understanding future conditions but they are based on regional generalizations of wildfire behavior and weather that do not adequately account for the complexity of human-fire interactions. To achieve a better understanding of the intensity of human influence on fires in this sparsely populated area and to quantify differences between human and lightning fires, we analyzed fires by both ignition types in regard to human proximity in urban (the Fairbanks subregion) and rural areas of interior Alaska using spatial (Geographic Information Systems) and quantitative analysis methods. We found substantial differences in drivers of wildfire: while increases in fire ignitions and area burned were caused by lightning in rural interior Alaska, in the Fairbanks subregion these increases were due to human fires, especially in the wildland urban interface. Lightning fires are starting earlier and fires are burning longer, which is much more pronounced in the Fairbanks subregion than in rural areas. Human fires differed from lightning fires in several ways: they started closer to settlements and highways, burned for a shorter duration, were concentrated in the Fairbanks subregion, and often occurred outside the brief seasonal window for lightning fires. This study provides important insights that improve our understanding of the direct human influence on recently observed changes in wildfire regime with implications for both fire modeling and fire management.

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Evidence and implications of recent and projected climate change in Alaska's forest ecosystems

Cited by 96 publications

References 175 publications

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Thresholds for boreal biome transitions

Differences in Human versus Lightning Fires between Urban and Rural Areas of the Boreal Forest in Interior Alaska

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