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1. Leaf and root phenology and biomass of Eriophorum vaginatum in response to warming in the Arctic

   https://doi.org/10.1093/jpe/rtac010  

   Ma, Ting ; Parker, Thomas ; Fetcher, Ned ; Unger, Steven L. ; Gewirtzman, Jon ; Moody, Michael L. ; Tang, Jianwu ; Hui, ed., Dafeng ( March 2022 , Journal of Plant Ecology)

   The response of plant leaf and root phenology and biomass in the Arctic to global change remains unclear due to the lack of synchronous measurements of above- and belowground parts. Our objective was to determine the phenological dynamics of the above- and belowground parts of Eriophorum vaginatum in the Arctic and its response to warming. We established a common garden located at Toolik Lake Field Station; tussocks of E. vaginatum from three locations, Coldfoot, Toolik Lake and Sagwon, were transplanted into the common garden. Control and warming treatments for E. vaginatum were set up at the Toolik Lake during the growing seasons of 2016 and 2017. Digital cameras, a handheld sensor and minirhizotrons were used to simultaneously observe leaf greenness, normalized difference vegetation index and root length dynamics, respectively. Leaf and root growth rates of E. vaginatum were asynchronous such that the timing of maximal leaf growth (mid-July) was about 28 days earlier than that of root growth. Warming of air temperature by 1 °C delayed the timing of leaf senescence and thus prolonged the growing season, but the temperature increase had no significant effect on root phenology. The seasonal dynamics of leaf biomass were affected by air temperature, whereas root biomass was correlated with soil thaw depth. Therefore, we suggest that leaf and root components should be considered comprehensively when using carbon and nutrient cycle models, as above- and belowground productivity and functional traits may have a different response to climate warming.

    

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2. Landscape Genomics Provides Evidence of Ecotypic Adaptation and a Barrier to Gene Flow at Treeline for the Arctic Foundation Species Eriophorum vaginatum

   https://doi.org/10.3389/fpls.2022.860439  

   Stunz, Elizabeth ; Fetcher, Ned ; Lavretsky, Philip ; Mohl, Jonathon E. ; Tang, Jianwu ; Moody, Michael L. ( March 2022 , Frontiers in Plant Science)

   Global climate change has resulted in geographic range shifts of flora and fauna at a global scale. Extreme environments, like the Arctic, are seeing some of the most pronounced changes. This region covers 14% of the Earth’s land area, and while many arctic species are widespread, understanding ecotypic variation at the genomic level will be important for elucidating how range shifts will affect ecological processes. Tussock cottongrass ( Eriophorum vaginatum L.) is a foundation species of the moist acidic tundra, whose potential decline due to competition from shrubs may affect ecosystem stability in the Arctic. We used double-digest Restriction Site-Associated DNA sequencing to identify genomic variation in 273 individuals of E. vaginatum from 17 sites along a latitudinal gradient in north central Alaska. These sites have been part of 30 + years of ecological research and are inclusive of a region that was part of the Beringian refugium. The data analyses included genomic population structure, demographic models, and genotype by environment association. Genome-wide SNP investigation revealed environmentally associated variation and population structure across the sampled range of E. vaginatum , including a genetic break between populations north and south of treeline. This structure is likely the result of subrefugial isolation, contemporary isolation by resistance, and adaptation. Forty-five candidate loci were identified with genotype-environment association (GEA) analyses, with most identified genes related to abiotic stress. Our results support a hypothesis of limited gene flow based on spatial and environmental factors for E. vaginatum , which in combination with life history traits could limit range expansion of southern ecotypes northward as the tundra warms. This has implications for lower competitive attributes of northern plants of this foundation species likely resulting in changes in ecosystem productivity. 

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3. Differential responses of ecotypes to climate in a ubiquitous Arctic sedge: implications for future ecosystem C cycling

   https://doi.org/10.1111/nph.15790  

   Curasi, Salvatore R. ; Parker, Thomas C. ; Rocha, Adrian V. ; Moody, Michael L. ; Tang, Jianwu ; Fetcher, Ned ( April 2019 , New Phytologist)

   The response of vegetation to climate change has implications for the carbon cycle and global climate. It is frequently assumed that a species responds uniformly across its range to climate change. However, ecotypes − locally adapted populations within a species − display differences in traits that may affect their gross primary productivity (GPP) and response to climate change.

   To determine if ecotypes are important for understanding the response of ecosystem productivity to climate we measured and modeled growing seasonGPPin reciprocally transplanted and experimentally warmed ecotypes of the abundant Arctic sedgeEriophorum vaginatum.

   Transplanted northern ecotypes displayed home‐site advantage inGPPthat was associated with differences in leaf area index. Southern ecotypes exhibited a greater response inGPPwhen transplanted.

   The results demonstrate that ecotypic differentiation can impact the morphology and function of vegetation with implications for carbon cycling. Moreover they suggest that ecotypic control ofGPPmay limit the response of ecosystem productivity to climate change. This investigation shows that ecotypes play a substantial role in determiningGPPand its response to climate. These results have implications for understanding annual to decadal carbon cycling where ecotypes could influence ecosystem function and vegetation feedbacks to climate change.

    

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4. Prairie plant phenology driven more by temperature than moisture in climate manipulations across a latitudinal gradient in the Pacific Northwest, USA

   https://doi.org/10.1002/ece3.4995  

   Reed, Paul B. ; Pfeifer‐Meister, Laurel E. ; Roy, Bitty A. ; Johnson, Bart R. ; Bailes, Graham T. ; Nelson, Aaron A. ; Boulay, Margaret C. ; Hamman, Sarah T. ; Bridgham, Scott D. ( February 2019 , Ecology and Evolution)

   Plant phenology will likely shift with climate change, but how temperature and/or moisture regimes will control phenological responses is not well understood. This is particularly true in Mediterranean climate ecosystems where the warmest temperatures and greatest moisture availability are seasonally asynchronous. We examined plant phenological responses at both the population and community levels to four climate treatments (control, warming, drought, and warming plus additional precipitation) embedded within three prairies across a 520 km latitudinal Mediterranean climate gradient within the Pacific Northwest, USA. At the population level, we monitored flowering and abundances in spring 2017 of eight range‐restricted focal species planted both within and north of their current ranges. At the community level, we used normalized difference vegetation index (NDVI) measured from fall 2016 to summer 2018 to estimate peak live biomass, senescence, seasonal patterns, and growing season length. We found that warming exerted a stronger control than our moisture manipulations on phenology at both the population and community levels. Warming advanced flowering regardless of whether a species was within or beyond its current range. Importantly, many of our focal species had low abundances, particularly in the south, suggesting that establishment, in addition to phenological shifts, may be a strong constraint on their future viability. At the community level, warming advanced the date of peak biomass regardless of site or year. The date of senescence advanced regardless of year for the southern and central sites but only in 2018 for the northern site. Growing season length contracted due to warming at the southern and central sites (~3 weeks) but was unaffected at the northern site. Our results emphasize that future temperature changes may exert strong influence on the timing of a variety of plant phenological events, especially those events that occur when temperature is most limiting, even in seasonally water‐limited Mediterranean ecosystems.

    

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5. Interspecific and intraspecific variation in leaf toughness of Arctic plants in relation to habitat and nutrient supply

   https://doi.org/10.1139/as-2020-0016  

   Fetcher, Ned ; Iglesia, Sofia ; Turner, Stephen J. ; Parker, Thomas C. ( January 2021 , Arctic Science)

   Leaf toughness is an important functional trait that confers resistance to herbivory and mechanical damage. We sought to determine how species composition, climate, seasonality, and nutrient availability influence leaf toughness in two types of tundra in northern Alaska. We measured leaf toughness as force to punch for 11 species of Arctic plants in tussock tundra and dry heath tundra at 17 sites distributed along a latitudinal gradient. Rubus chamaemorus L. and the graminoids occupied opposite ends of the leaf toughness spectrum, with Rubus chamaemorus requiring the least force to punch, whereas one of the graminoids, Eriophorum vaginatum L., required the most. Leaf toughness increased with mean summer temperature for Eriophorum vaginatum and Betula nana L., whereas it declined with warmer temperatures for the other species. Toughness of mature leaves of Eriophorum vaginatum did not vary through the growing season but declined significantly after senescence. Application of N and P fertilizer in an experimental site decreased leaf toughness in three species but had no effect on four others. Leaf toughness of four out of five species in dry heath was greater than for the same species in tussock tundra, but there was no difference in community-weighted mean toughness between tussock tundra and dry heath. 

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