title: Temperature-induced responses of xylem structure of Larix sibirica (Pinaceae) from the Russian Altay.
abstract: OBJECTIVE
  Xylem structure determines the hydraulic and mechanical properties of a stem, and its plasticity is fundamental for maintaining tree performance under changing conditions. Unveiling the mechanism and the range of xylem adjustment is thus necessary to anticipate climate change impacts on vegetation.
  
  
  METHODS
  To understand the mechanistic process and the functional impact of xylem responses to warming in a cold-limited environment, we investigated the relationship between temperature and tracheid anatomy along a 312-yr tree-ring chronology of Larix sibirica trees from the Altay Mountains in Russia.
  
  
  RESULTS
  Climate-growth analyses indicated that warming favors wider earlywood cell lumen, thicker latewood walls, denser maximum latewood, and wider rings. The temperature signal of the latewood was stronger (r > 0.7) and covered a longer and more stable period (from June to August) than that of earlywood and tree-ring width. Long-term analyses indicated a diverging trend between lumen and cell wall of early- and latewood.
  
  
  CONCLUSIONS
  Xylem anatomy appears to respond to warming temperatures. A warmer early-growing season raises water conduction capacity by increasing the number and size of earlywood tracheids. The higher-performing earlywood tracheids promote more carbon fixation of the latewood cells by incrementing the rate of assimilation when summer conditions are favorable for growth. The diverging long-term variation of lumen and cell wall in earlywood vs. latewood suggests that xylem adjustments in latewood increase mechanical integrity and support increasing tree size under the ameliorated growing conditions.
authors: WSL Swiss Federal Research Institute, Landscape Dynamics, Zürcherstr 111, CH-8903 Birmensdorf, Switzerland. patrick.fonti@wsl.ch
authors: Patrick
authors: P
authors: Fonti
authors: Marina V
authors: MV
authors: Bryukhanova
authors: Vladimir S
authors: VS
authors: Myglan
authors: Alexander V
authors: AV
authors: Kirdyanov
authors: Oksana V
authors: OV
authors: Naumova
authors: Eugene A
authors: EA
authors: Vaganov
mesh_terms: D057231:Climate Change; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D028221:Larix / Q000033:anatomy & histology* / Q000502:physiology*; D012426:Russia; D013696:Temperature; D013997:Time Factors; D052584:Xylem
keywords: Larix sibirica; Pinaceae; climatic conditions; tracheid lumen; tracheid wall; tree-ring anatomy; wood density; xylem anatomical traits