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Determining past leaf‐out times of New England's deciduous forests from herbarium specimens
Author(s) -
Everill Peter H.,
Primack Richard B.,
Ellwood Elizabeth R.,
Melaas Eli K.
Publication year - 2014
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.1400045
Subject(s) - herbarium , deciduous , temperate deciduous forest , temperate climate , biology , phenology , temperate rainforest , ecology , botany , geography , ecosystem
• Premise of the study: There is great interest in studying leaf‐out times of temperate forests because of the importance of leaf‐out in controlling ecosystem processes, especially in the face of a changing climate. Remote sensing and modeling, combined with weather records and field observations, are increasing our knowledge of factors affecting variation in leaf‐out times. Herbarium specimens represent a potential new source of information to determine whether the variation in leaf‐out times observed in recent decades is comparable to longer time frames over past centuries. • Methods: Here we introduce the use of herbarium specimens as a method for studying long‐term changes in leaf‐out times of deciduous trees. We collected historical leaf‐out data for the years 1834–2008 from common deciduous trees in New England using 1599 dated herbarium specimens with young leaves. • Key results: We found that leaf‐out dates are strongly affected by spring temperature, with trees leafing out 2.70 d earlier for each degree C increase in mean April temperature. For each degree C increase in local temperature, trees leafed out 2.06 d earlier. Additionally, the mean response of leaf‐out dates across all species and sites over time was 0.4 d earlier per decade. Our results are of comparable magnitude to results from studies using remote sensing and direct field observations. • Conclusions: Across New England, mean leaf‐out dates varied geographically in close correspondence with those observed in studies using satellite data. This study demonstrates that herbarium specimens can be a valuable source of data on past leaf‐out times of deciduous trees.