Complexity revealed in the greening of the Arctic

Myers‐Smith, Isla H.; Kerby, Jeffrey T.; Phoenix, Gareth K.; Bjerke, Jarle W.; Epstein, Howard E.; Assmann, Jakob J.; John, Christian; Andreu-Hayles, L.; Angers-Blodin, Sandra; Beck, Pieter S. A.; Berner, L. T.; Bhatt, Uma S.; Bjorkman, Anne D.; Blok, Daan; Bryn, Anders; Christiansen, Casper T.; Cornelissen, Johannes H. C.; Cunliffe, Andrew M.; Elmendorf, Sarah C.; Forbes, Bruce C.; Goetz, Scott J.; Hollister, Robert D.; Jong, Rogier de; Loranty, M. M.; Macias‐Fauria, Marc; Maseyk, Kadmiel; Normand, Signe; Olofsson, Johan; Parker, Thomas C.; Parmentier, Frans-Jan W.; Post, Eric; Schaepman‐Strub, Gabriela; Stordal, Frøde; Sullivan, Patrick F.; Thomas, Haydn J. D.; Tømmervik, Hans; Treharne, Rachael; Tweedie, C. E.; Walker, Donald A.; Wilmking, Martin; Wipf, Sonja

doi:10.32942/osf.io/mzyjk

Cited by 55 publications

(75 citation statements)

References 112 publications

(225 reference statements)

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“…In contrast, estimates for Australia are much lower at around 1% per decade, while those for South America are much higher (7.4% per decade; Stevens et al, ). This cross‐biome quantification of woody encroachment agrees with previous studies of global (Eldridge et al, ; Naito & Cairns, ) and regional scope from the tundra (Myers‐Smith et al, ; Tape et al, ) and the savanna (Mitchard et al, ; O’Connor & Page, ; Stevens et al ), and is consistent with the observed heterogeneous vegetation responses within and between biomes (Bjorkman et al, ; Myers‐Smith et al, ; Stevens et al ; Venter et al, ).…”

Section: Discussionsupporting

confidence: 89%

Woody plant encroachment intensifies under climate change across tundra and savanna biomes

Criado

Myers‐Smith

Bjorkman

et al. 2020

Global Ecol Biogeogr

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155

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Aim Biomes worldwide are shifting with global change. Biomes whose extents are limited by temperature or precipitation, such as the tundra and savanna, may be particularly strongly affected by climate change. While woody plant encroachment is prevalent across both biomes, its relationship to temperature and precipitation change remains unknown. Here, we quantify the degree to which woody encroachment is related to climate change and identify its main associated drivers. Location Tundra and savanna biomes. Time period 1992 ± 20.27–2010 ± 5.62 (mean ± SD). 1876–2016 (range). Major taxa studied Woody plants (shrubs and trees). Methods We compiled a dataset comprising 1,089 records from 899 sites of woody plant cover over time and attributed drivers of woody cover change across these two biomes. We calculated cover change in each biome and assessed the degree to which cover change corresponds to concurrent temperature and precipitation changes using multiple climate metrics. Finally, we conducted a quantitative literature review of the relative importance of attributed drivers of woody cover change. Results Woody encroachment was widespread geographically and across climate gradients. Rates of woody cover change (positive or negative) were 1.8 times lower in the tundra than in the savanna (1.8 vs. 3.2%), while rates of woody cover increase (i.e., encroachment) were c. 1.7 times lower in the tundra compared with the savanna (3.7 vs. 6.3% per decade). In the tundra, magnitudes of woody cover change did not correspond to climate, while in the savanna, greater cover change corresponded with increases in precipitation. We found higher rates of woody cover change in wetter versus drier sites with warming in the tundra biome, and higher rates of woody cover change in drier versus wetter sites with increasing precipitation in the savanna. However, faster rates of woody cover change were not associated with more rapid rates of climate change across sites, except for maximum precipitation in the savanna. Main conclusions Woody encroachment was positively related to warming in the tundra and increased rainfall in the savanna. However, cover change rates were not predicted by rates of climate change, which can be partially explained by climate interactions in both biomes. Additional likely influences include site‐level factors, time‐lags, plant‐specific responses, and land use and other non‐climate drivers. Our findings highlight the complex nature of climate change impacts in biomes limited by seasonality, which should be accounted for to realistically estimate future responses across open biomes under global change scenarios.

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Section: Discussionsupporting

confidence: 89%

Woody plant encroachment intensifies under climate change across tundra and savanna biomes

Criado

Myers‐Smith

Bjorkman

et al. 2020

Global Ecol Biogeogr

Self Cite

155

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“…Moisture gradients, vegetation cover, and climate have an important impact on the net CH 4 exchange between high latitude ecosystems and the atmosphere. The ongoing and anticipated increases in temperature (AMAP 2017) and precipitation (Bintanja 2018) are expected to have impacts on land cover (e.g., physical disturbance and thermal perturbation) and vegetation distribution (Myers-Smith et al 2019) in this region. These climatological and biophysical changes will affect the future trajectory of net GHG emissions in the High Arctic.…”

Section: Discussionmentioning

confidence: 99%

Net greenhouse gas fluxes from three High Arctic plant communities along a moisture gradient

et al. 2019

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Climate in high latitude environments is predicted to undergo a pronounced warming and increase in precipitation, which may influence the terrestrial moisture gradients that affect vegetation distribution. Vegetation cover can influence rates of greenhouse gas production through differences in microbial communities, plant carbon uptake potential, and root transport of gases out of the soil into the atmosphere. To predict future changes in greenhouse gas production from High Arctic ecosystems in response to climate change, it is important to understand the interaction between trace gas fluxes and vegetation cover. During the growing seasons of 2008 and 2009, we used dark static chambers to measure CH4 and N2O fluxes and CO2 emissions at Cape Bounty, Melville Island, NU, across a soil moisture gradient, as reflected by their vegetation cover. In both years, wet sedge had the highest rates of emission for all trace gases, followed by the mesic tundra ecosystem. CH4 consumption was highest in the polar semi-desert, correlating positively with temperature and negatively with moisture. Our findings demonstrate that net CH4 uptake may be largely underestimated across the Arctic due to sampling bias towards wetlands. Overall, greenhouse gas flux responses vary depending on different environmental drivers, and the role of vegetation cover needs to be considered in predicting the trajectory of greenhouse gas uptake and release in response to a changing climate.

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“…These images provide broad coverage of the pan-Arctic, are relatively continuous temporally, and are useful for determining global trends. However, due to the coarse spatial resolution, fine details of patterns and processes are indiscernible and has limited our understanding of greening and browning (Bartsch et al 2016, Myers-Smith et al 2019, particularly in ecosystems characterized by fine spatial heterogeneity such as Arctic tundra (Webber 1978, Billings andPeterson 1980).…”

Section: Introductionmentioning

confidence: 99%

Arctic greening associated with lengthening growing seasons in Northern Alaska

Arndt

Santos

Ustin

et al. 2019

Environ. Res. Lett.

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Many studies have reported that the Arctic is greening; however, we lack an understanding of the detailed patterns and processes that are leading to this observed greening. The normalized difference vegetation index (NDVI) is used to quantify greening, which has had largely positive trends over the last few decades using low spatial resolution satellite imagery such as AVHRR or MODIS over the pan-Arctic region. However, substantial fine scale spatial heterogeneity in the Arctic makes this large-scale investigation hard to interpret in terms of vegetation and other environmental changes. Here we focus on one area of the northern Alaskan Arctic using high spatial resolution (4 m) multispectral satellite imagery from DigitalGlobe ™ to analyze the greening trend near Utqiaġvik (formerly known as Barrow) over 14 years from 2002 to 2016. We found that tundra vegetation has been greening (τ=0.65, p=0.01, NDVI increase of 0.01 yr −1 ) despite no overall change in vegetation community composition. The greening is most closely correlated to the number of thawing degree days (R 2 =0.77, F=21.5, p<0.001) which increased in a similar linear trend over the 14 year study period (1.79±0.50 days per year, p<0.01, τ=−0.56). This suggests that in this Arctic ecosystem, greening is occurring due to a lengthening growing season that appears to stimulate plant productivity without any significant change in vegetation communities. We found that vegetation communities in wetter locations greened about twice as fast as those found in drier conditions supporting the hypothesis that these communities respond more strongly to warming. We suggest that in Arctic environments, vegetation productivity may continue to rise, particularly in wet areas.

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Complexity revealed in the greening of the Arctic

Cited by 55 publications

References 112 publications

Woody plant encroachment intensifies under climate change across tundra and savanna biomes

Woody plant encroachment intensifies under climate change across tundra and savanna biomes

Net greenhouse gas fluxes from three High Arctic plant communities along a moisture gradient

Arctic greening associated with lengthening growing seasons in Northern Alaska

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