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1. Plant phenology of species in dry heath tundra around Toolik Field Station, Alaska, 2011-2023

   https://doi.org/10.18739/A2PC2TB29  

   Kade, Anja; Beaudreault, Seth; Funck, Juliette; Murthy, Adeline; Noguera, Jorge; Nugteren, Aart; Rauch, Robin; Van Dam, Brie; Funck, Juliette; Wesolowski, Dave; et al (January 2023, NSF Arctic Data Center)

   The Toolik Field Station (TFS) plant phenology program monitors the timing of specific phenological developmental stages of plant species commonly found in the dry heath tundra plant community. The TFS phenology program began in response to TFS research community requests to collect baseline environmental data that would be broadly applicable and provide context to research projects conducted near TFS. The TFS plant phenology data collection protocol is based on the International Tundra Experiment (ITEX) (www.geog.ubc.ca/itex) protocol for the Toolik Snowfence Experiment. This dry heath tundra dataset began in 2011 and continues through 2023. 

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2. The tundra phenology database: More than two decades of tundra phenology responses to climate change

   https://doi.org/10.1139/AS-2020-0041  

   Prevéy, Janet; Elmendorf, Sarah; Bjorkman, Anne; Alatalo, Juha; Ashton, Isabel; Assmann, Jakob; Björk, Robert G.; Björkman, Mats P.; Cannone, Nicoletta; Carbognani, Michele; et al (May 2021, Arctic Science)

   null (Ed.)

   Observations of changes in phenology have provided some of the strongest signals of the effects of climate change on terrestrial ecosystems. The International Tundra Experiment (ITEX), initiated in the early 1990s, established a common protocol to measure plant phenology in tundra study areas across the globe. Today, this valuable collection of phenology measurements depicts the responses of plants at the colder extremes of our planet to experimental and ambient changes in temperature over the past decades. The database contains 150,434 phenology observations of 278 plant species taken at 28 study areas for periods of 1 to 26 years. Here we describe the full dataset to increase the visibility and use of these data in global analyses, and to invite phenology data contributions from underrepresented tundra locations. Portions of this tundra phenology database have been used in three recent syntheses, some datasets are expanded, others are from entirely new study areas, and the entirety of these data are now available at the Polar Data Catalogue (https://doi.org/10.21963/13215). 

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3. Tundra Plant Canopies Gradually Close Over Three Decades While Cryptogams Persist

   Betway_May, KR; Gould, WA; Elmendorf, SC; May, JL; Hollister, RD; Oberbauer, SF; Breen, A; Crain, BJ; Cuervo, AMS; Walker, MD; et al (April 2025, Global change biology)

   Global climate change phenomena are amplified in Arctic regions, driving rapid changes in the biota. Here, we examine changes in plant community structure over more than 30 years at two sites in arctic Alaska, USA, Imnavait Creek and Toolik Lake, to understand long-term trends in tundra response to changing climate. Vegetation cover was sampled every 4-7 years on permanent 1 m2 plots spanning a 1 km2 grid using a point-frame. The vascular plant canopies progressively closed at both locations. Canopy cover, defined here as an encounter of a vascular plant above the ground surface, increased from 63% to 91% at Imnavait Creek and from 63% to 89% at Toolik Lake. Both sites showed steady increases in maximum canopy height, increasing by approximately 50% (8 cm). While cover and height increased to some extent for all vascular plant growth forms, deciduous shrubs and graminoids changed the most. For example, at Imnavait Creek the cover of graminoids more than tripled (particularly in wet meadow plots), increasing by 237%. At Toolik Lake the cover of deciduous shrubs more than doubled (particularly in moist acidic plots), increasing by 145%. Despite the steady closing of the plant canopy, cryptogams (lichens and mosses) persisted; in fact, the cover of lichens increased. These results call into question the dominant dogma that cryptogams will decline with increases in vascular plant abundance and demonstrate the resilience of these understory plants. In addition to overall cover, the diversity of vascular plants increased at one site (Imnavait Creek). In contrast to much of the Arctic, summer air temperatures in the Toolik Lake region have not significantly increased over the 30+ year sampling period; however, winter temperatures increased substantially. Changes in vegetation community structure at Imnavait Creek and Toolik Lake are likely the result of winter warming. 

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4. Tundra Plant Canopies Gradually Close Over Three Decades While Cryptogams Persist

   https://doi.org/10.1111/gcb.70155  

   Betway‐May, Katlyn_R; Gould, William_A; Elmendorf, Sarah_C; May, Jeremy_L; Hollister, Robert_D; Oberbauer, Steven_F; Breen, Amy; Crain, Benjamin_J; Cuervo, Ana_Maria_Sanchez; Walker, Marilyn_D; et al (April 2025, Global Change Biology)

   ABSTRACT Global climate change phenomena are amplified in Arctic regions, driving rapid changes in the biota. Here, we examine changes in plant community structure over more than 30 years at two sites in arctic Alaska, USA, Imnavait Creek and Toolik Lake, to understand long‐term trends in tundra response to changing climate. Vegetation cover was sampled every 4–7 years on permanent 1 m²plots spanning a 1 km²grid using a point‐frame. The vascular plant canopies progressively closed at both locations. Canopy cover, defined here as an encounter of a vascular plant above the ground surface, increased from 63% to 91% at Imnavait Creek and from 63% to 89% at Toolik Lake. Both sites showed steady increases in maximum canopy height, increasing by approximately 50% (8 cm). While cover and height increased to some extent for all vascular plant growth forms, deciduous shrubs and graminoids changed the most. For example, at Imnavait Creek the cover of graminoids more than tripled (particularly in wet meadow plots), increasing by 237%. At Toolik Lake the cover of deciduous shrubs more than doubled (particularly in moist acidic plots), increasing by 145%. Despite the steady closing of the plant canopy, cryptogams (lichens and mosses) persisted; in fact, the cover of lichens increased. These results call into question the dominant dogma that cryptogams will decline with increases in vascular plant abundance and demonstrate the resilience of these understory plants. In addition to overall cover, the diversity of vascular plants increased at one site (Imnavait Creek). In contrast to much of the Arctic, summer air temperatures in the Toolik Lake region have not significantly increased over the 30+ year sampling period; however, winter temperatures increased substantially. Changes in vegetation community structure at Imnavait Creek and Toolik Lake are likely the result of winter warming. 

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5. The International Tundra Experiment (ITEX): 30 years of research on tundra ecosystems

   https://doi.org/10.1139/as-2022-0041  

   Henry, Greg H.R.; Hollister, Robert D.; Klanderud, Kari; Björk, Robert G.; Bjorkman, Anne D.; Elphinstone, Cassandra; Jónsdóttir, Ingibjörg Svala; Molau, Ulf; Petraglia, Alessandro; Oberbauer, Steven F.; et al (September 2022, Arctic Science)

   The International Tundra Experiment (ITEX) was founded in 1990 as a network of scientists studying responses of tundra ecosystems to ambient and experimental climate change at Arctic and alpine sites across the globe. Common measurement and experimental design protocols have facilitated synthesis of results across sites to gain biome-wide insights of climate change impacts on tundra. This special issue presents results from more than 30 years of ITEX research. The importance of snow regimes, bryophytes, and herbivory are highlighted, with new protocols and studies proposed. The increasing frequency and magnitude of extreme climate events is shown to have strong effects on plant reproduction. The most consistent plant trait response across sites is an increase in vegetation height, especially for shrubs. This will affect surface energy balance, carbon and nutrient dynamics and trophic level interactions. Common garden studies show adaptation responses in tundra species to climate change but they are species and regionally specific. Recommendations are made including establishing sites near northern communities to increase reciprocal engagement with local knowledge holders and establishing multi-factor experiments. The success of ITEX is based on collegial cooperation among researchers and the network remains focused on documenting and understanding impacts of environmental change on tundra ecosystems. 

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