title: Environmental drivers of cambial phenology in Great Basin bristlecone pine.
abstract: The timing of wood formation is crucial to determine how environmental factors affect tree growth. The long-lived bristlecone pine (Pinus longaeva D. K. Bailey) is a foundation treeline species in the Great Basin of North America reaching stem ages of about 5000 years. We investigated stem cambial phenology and radial size variability to quantify the relative influence of environmental variables on bristlecone pine growth. Repeated cellular measurements and half-hourly dendrometer records were obtained during 2013 and 2014 for two high-elevation stands included in the Nevada Climate-ecohydrological Assessment Network. Daily time series of stem radial variations showed rehydration and expansion starting in late April-early May, prior to the onset of wood formation at breast height. Formation of new xylem started in June and lasted until mid-September. There were no differences in phenological timing between the two stands, or in the air and soil temperature thresholds for the onset of xylogenesis. A multiple logistic regression model highlighted a separate effect of air and soil temperature on xylogenesis, the relevance of which was modulated by the interaction with vapor pressure and soil water content. While air temperature plays a key role in cambial resumption after winter dormancy, soil thermal conditions coupled with snowpack dynamics also influence the onset of wood formation by regulating plant-soil water exchanges. Our results help build a physiological understanding of climate-growth relationships in P. longaeva, the importance of which for dendroclimatic reconstructions can hardly be overstated. In addition, environmental drivers of xylogenesis at the treeline ecotone, by controlling the growth of dominant species, ultimately determine ecosystem responses to climatic change.
authors.affiliation: DendroLab, University of Nevada, Reno, NV 89557, USA eziaco@unr.edu.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Ziaco
authors.affiliation: DendroLab, University of Nevada, Reno, NV 89557, USA.
authors.forename: Franco
authors.initials: F
authors.lastname: Biondi
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Chicoutimi, QC G7H2B1, Canada Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Provincial Key Laboratories of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Chicoutimi, QC G7H2B1, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Deslauriers
mesh_terms: D000222:Adaptation, Physiological; D000388:Air; D058506:Cambium / Q000254:growth & development*; D057231:Climate Change; D055864:Droughts; D017753:Ecosystem; D004777:Environment; D009505:Nevada; D009656:North America; D028223:Pinus / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development*; D012621:Seasons; D012987:Soil; D013696:Temperature; D014197:Trees / Q000254:growth & development; D014867:Water / Q000502:physiology; D014934:Wood / Q000254:growth & development; D052584:Xylem / Q000254:growth & development
chemical_list: D012987:Soil; D014867:Water
keywords: Gompertz function; NevCAN; Pinus longaeva; conifers; logistic regression; soil temperature; tree rings; wood formation; xylogenesis