Brugia Malayi - Clark Science Center - Smith College

Comparing Throughfall Chemistry in a Mature Hemlock Forest and
Early Successional Deciduous Forest at the MacLeish Field Station in
Whately, MA
Jenna Zukswert
Removal of foundation species as a result of disturbance events can alter community composition and ecosystem function. 1
The current hemlock woolly adelgid (Adelges tsugae) infestation in eastern North America that threatens the eastern hemlock
(Tsuga canadensis), a foundation species, has motivated salvage logging efforts. 2 Ecological succession following hemlock removal
eventually results in a mature deciduous forest. 1 The chemistry of throughfall, precipitation that passes through the forest canopy
and serves as an important nutrient input to the forest floor, 3 is expected to be more acidic beneath a hemlock forest canopy
than beneath a mature deciduous forest canopy because hemlock foliage releases more organic acids and fewer base cations. The
chemical composition of the throughfall beneath a juvenile deciduous forest canopy, however, is less understood. We hypothesize
that throughfall beneath a juvenile deciduous forest canopy will be more similar to direct precipitation because leaf area index
is smaller. We compared the chemical composition of direct precipitation, hemlock throughfall, and black birch (Betula lenta)
throughfall at the MacLeish Field Station for 26 precipitation events from March through July 2012. The juvenile black birch
forest plot resulted from salvage logging of hemlocks twenty years ago. From the three plots we measured the volume of water
collected and pH, acid neutralizing capacity, dissolved organic carbon (DOC), and concentrations of select cations (Ca 2+ , K + , Na + ,
Mg 2+ , NH 4+
), anions (Cl - , NO 3-
, SO 4
2-
), and dissolved silica.
We found that deposition of base cation and DOC (in kg ha -1 ) were significantly (p