title: Changes in autumn senescence in northern hemisphere deciduous trees: a meta-analysis of autumn phenology studies.
abstract: OBJECTIVE
  Many individual studies have shown that the timing of leaf senescence in boreal and temperate deciduous forests in the northern hemisphere is influenced by rising temperatures, but there is limited consensus on the magnitude, direction and spatial extent of this relationship.
  
  
  METHODS
  A meta-analysis was conducted of published studies from the peer-reviewed literature that reported autumn senescence dates for deciduous trees in the northern hemisphere, encompassing 64 publications with observations ranging from 1931 to 2010.
  
  
  RESULTS
  Among the meteorological measurements examined, October temperatures were the strongest predictors of date of senescence, followed by cooling degree-days, latitude, photoperiod and, lastly, total monthly precipitation, although the strength of the relationships differed between high- and low-latitude sites. Autumn leaf senescence has been significantly more delayed at low (25° to 49°N) than high (50° to 70°N) latitudes across the northern hemisphere, with senescence across high-latitude sites more sensitive to the effects of photoperiod and low-latitude sites more sensitive to the effects of temperature. Delays in leaf senescence over time were stronger in North America compared with Europe and Asia.
  
  
  CONCLUSIONS
  The results indicate that leaf senescence has been delayed over time and in response to temperature, although low-latitude sites show significantly stronger delays in senescence over time than high-latitude sites. While temperature alone may be a reasonable predictor of the date of leaf senescence when examining a broad suite of sites, it is important to consider that temperature-induced changes in senescence at high-latitude sites are likely to be constrained by the influence of photoperiod. Ecosystem-level differences in the mechanisms that control the timing of leaf senescence may affect both plant community interactions and ecosystem carbon storage as global temperatures increase over the next century.
authors.affiliation: Department of Biology and.
authors.forename: Allison L
authors.initials: AL
authors.lastname: Gill
authors.affiliation: Department of Biology and.
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Gallinat
authors.affiliation: Department of Biology and.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Sanders-DeMott
authors.affiliation: Department of Earth and Environment, Boston University, Boston, MA 02215, USA.
authors.forename: Angela J
authors.initials: AJ
authors.lastname: Rigden
authors.affiliation: Department of Earth and Environment, Boston University, Boston, MA 02215, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Short Gianotti
authors.affiliation: Department of Earth and Environment, Boston University, Boston, MA 02215, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Mantooth
authors.affiliation: Department of Biology and ptempler@bu.edu.
authors.forename: Pamela H
authors.initials: PH
authors.lastname: Templer
mesh_terms: D016922:Cellular Senescence; D057231:Climate Change; D017753:Ecosystem; D065928:Forests; D005843:Geography; D016014:Linear Models; D010641:Phenotype; D017440:Photoperiod; D018515:Plant Leaves / Q000502:physiology* / Q000528:radiation effects; D011891:Rain; D012621:Seasons; D013696:Temperature; D013997:Time Factors; D014197:Trees / Q000502:physiology* / Q000528:radiation effects
keywords: Autumn phenology; climate change; deciduous tree; growing season; leaf senescence; temperature; woody plants