Posted by Amanda Gallinat
Woody plants in Thoreau’s Concord are leafing out earlier
with warmer temperatures. All of the species Thoreau observed have advanced
their leaf-out dates, and the order of leaf out has not changed since the
1850’s, with plants that leaf out earliest responding the most strongly to
temperature changes.
This led the Primack lab to question whether- after leafing
out early- the trees, shrubs, and vines of Concord will respond differently to
an unexpected frost.
This spring, we conducted experiments to determine the
relative frost tolerance of the young leaves of woody plants in Concord. We
collected dormant twigs in the field and brought them into the lab to leaf out,
then subjected young leaves of each species to multiple levels of freezing
temperatures. We focused our study on 1) the species Thoreau monitored in the
1850’s, 2) selected species at the Arnold Arboretum that leaf out very early
and very late, and 3) fifteen birch species at the Arboretum.
We hypothesized:
-Early leafing out species are more frost tolerant than late
species
-Species with high leaf water content are less frost tolerant
than those with low water content
-Invasive species are more frost tolerant than native
species
Stay tuned for the results from these experiments!
We clipped and labeled each new twig—this took the combined
effort of many helpers, including (from left to right) Luca Russo, Meg Boeni,
Jasper Primack, and Sam Roberts.
Species from Thoreau’s Concord, like multiflora rose,
experienced different amounts of frost damage from different strengths of frost
treatment. There were also differences between species within treatments. As
shown in this photograph, frost damage can be very apparent during a visual
assessment.
