title: Arctic plant responses to changing abiotic factors in northern Alaska.
abstract: OBJECTIVE
  Understanding the relationship between plants and changing abiotic factors is necessary to document and anticipate the impacts of climate change.
  
  
  METHODS
  We used data from long-term research sites at Barrow and Atqasuk, Alaska, to investigate trends in abiotic factors (snow melt and freeze-up dates, air and soil temperature, thaw depth, and soil moisture) and their relationships with plant traits (inflorescence height, leaf length, reproductive effort, and reproductive phenology) over time.
  
  
  RESULTS
  Several abiotic factors, including increasing air and soil temperatures, earlier snowmelt, delayed freeze-up, drier soils, and increasing thaw depths, showed nonsignificant tendencies over time that were consistent with the regional warming pattern observed in the Barrow area. Over the same period, plants showed consistent, although typically nonsignificant tendencies toward increasing inflorescence heights and reproductive efforts. Air and soil temperatures, measured as degree days, were consistently correlated with plant growth and reproductive effort. Reproductive effort was best predicted using abiotic conditions from the previous year. We also found that varying the base temperature used to calculate degree days changed the number of significant relationships between temperature and the trait: in general, reproductive phenologies in colder sites were better predicted using lower base temperatures, but the opposite held for those in warmer sites.
  
  
  CONCLUSIONS
  Plant response to changing abiotic factors is complex and varies by species, site, and trait; however, for six plant species, we have strong evidence that climate change will cause significant shifts in their growth and reproductive effort as the region continues to warm.
authors.affiliation: Biology Department, Grand Valley State University, 1 Campus Drive, Allendale, Michigan 49401 USA West Michigan Academy of Environmental Science, 4463 Leonard Street, Walker, Michigan 49534 USA robertbarrett@choiceschools.com.
authors.forename: Robert T S
authors.initials: RT
authors.lastname: Barrett
authors.affiliation: Biology Department, Grand Valley State University, 1 Campus Drive, Allendale, Michigan 49401 USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Hollister
authors.affiliation: Department of Biological Sciences, Florida International University 11200 SW 8th Street, Miami, Florida 33199 USA.
authors.forename: Steven F
authors.initials: SF
authors.lastname: Oberbauer
authors.affiliation: Department of Biology, University of Texas at El Paso, El Paso, Texas 79968 USA.
authors.forename: Craig E
authors.initials: CE
authors.lastname: Tweedie
mesh_terms: D000413:Alaska; D001110:Arctic Regions; D057231:Climate Change; D019684:Magnoliopsida / Q000254:growth & development / Q000502:physiology*; D012098:Reproduction; D013696:Temperature; D065929:Tundra
keywords: ITEX; LMM; abiotic factors; climate change; northern Alaska; phenology; tundra plants