International Journal of Biometeorology

, Volume 61, Issue 12, pp 2213–2216 | Cite as

Humidity does not appear to trigger leaf out in woody plants

  • Lucy ZipfEmail author
  • Richard B. Primack
Original Paper


In order to anticipate the ecological impacts of climate change and model changes to forests, it is important to understand the factors controlling spring leaf out. Leaf out phenology in woody trees and shrubs is generally considered to be strongly controlled by a combination of spring warming, winter chilling requirement, and photoperiod. However, researchers have recently suggested that temperature-related air humidity, rather than temperature itself, might be the main trigger of the spring leaf-out of woody plants. Here, we sought to examine the relationship between air humidity and leaf-out across a range of humidities and plant functional groups. We did not find any consistent, measurable effect of high humidity advancing leaf-out in the 15 woody shrubs and trees examined in this study, and we did not see progressive patterns of earlier leaf-out in successively higher humidities. Our results indicate that more work must be done on this topic before researchers can properly determine the effect of humidity on the leafing out process for woody species.


Humidity Leaf-out Phenology Spring Dormant twigs 



We thank Amanda Gallinat, Luca Russo, Dillon Travis, Melissa Ruano, and Eddie Donovan for field and lab assistance, and Abraham J. Miller-Rushing, Nick Ray, Pam Templer, and Caitlin McDonough MacKenzie for providing comments on the paper.


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Copyright information

© ISB 2017

Authors and Affiliations

  1. 1.Biology DepartmentBoston UniversityBostonUSA

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