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Aerial Photo taken
June 2015 near Jefferson, NH by R. Hanavan
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A late spring frost in the White Mountains,
NH resulted in swaths of autumn-like color in trees at around 2500 feet in
elevation this summer. The AMC Research team monitoring tree canopy development
as part of an Appalachian Trail wide ecological monitoring program (AT Seasons)
also
observed this unusual coloration in individual trees. Starting in late May and early June we
noticed that some of the leaves looked reddish brown.
The culprit was frost
damage that stopped leaf development at the tops of the trees before they had
grown to full size. We recorded below freezing temperatures at the AMC Pinkham
Notch Visitor Center’s NOAA climate station during May 23rd to May
25th. According to the NH Division of Forests and Lands the frost
damage was widespread throughout the White and Green Mountains. A similar event happened in 2010 when record
warm spring temperatures were followed by a late frost event May 9th-11th. Researchers examined that earlier event in
the context of leaf development and overall damage (Hufkens et al., 2012) in
trees up to 2,700 elevation. They concluded
that sugar maple leaf out responds relatively stronger to warming spring
temperatures, therefore they may be more at risk from spring frosts than beech
and yellow birch, putting them at a competitive disadvantage.
Fall
foliage bust?
How
this year’s late frost will impact the higher elevation fall foliage colors is
still to be determined. Other variables from the amount of spring and summer
rainfall to the number of cool September and October nights also play a role in
the final fall landscape color palette. Just
look at the fall of 2010 (http://naturenotes.outdoors.org/2010/10/peak-foliage-is-here.html), even with the
documented spring frost event it was not a bust for autumn colors. So there is
still hope for our fall fix of yellow, orange, and reds. The damage appears
isolated to the upper canopy of the trees, which can be explained by the upper
canopy acting as a heat retention blanket that prevented damaging below freezing
temperatures in the trees’ lower canopy.
G. Murray, AMC Staff Scientist