PROCEEDINGS: Index of Abstracts
CALCIUM STATUS OF THE FOREST FLOOR IN RED SPRUCE
FORESTS OF THE NORTHEASTERN U.S. - PAST, PRESENT AND FUTURE
1-Department of Forestry, University of Illinois,
1102 S. Goodwin, Urbana, IL 61801. 2-Research Hydrologist, U.S.
Geological Survey, 425 Jordan Rd., Troy, NY 12180. 3-USDA Forest
Service, Northeastern Forest Experiment Station, Durham, NH 03824.
4-USDA Forest Service, Northeastern Forest Experiment Station, Hubbard
Brook Experimental Forest, Campton, NH.
Dieback and growth decline of red spruce (Picea rubens) in the
eastern U.S. coincides with the period of acidic deposition, and
has led to much speculation as to whether this decline is caused
by decreased root-available Ca in the soil. Results of intensive
research at several sites have led to conflicting conclusions as
to whether acidic deposition has depleted Ca concentrations in the
rooting zone to the degree that would cause growth decline in red
spruce. Regional evaluations of the current status of soil Ca in
red spruce forests have been limited by the small number of sites
at which soil and soil solution Ca concentrations have been measured
with comparable methods. Comparisons with historical data have also
been limited by a lack of current data that is directly relatable.
To obtain the additional data necessary for a regional analysis
of soil Ca in red spruce forests, either 18 or 36 soil and soil
solution samples were collected in 1992-93 from 12 sites in New
York, Vermont, New Hampshire and Maine in a study supported by the
USDA Forest Service Global Change Research Program. These sites
represent the range of environmental conditions and stand health
for red spruce in the northeastern U.S. Comparison with results
from separate studies by Heimburger and Lunt in the 1930s indicate
that current acid-extractable Ca concentrations in the Oa horizon
are less than one-half the average measured in the 1930's. A statistically
significant decrease of similar magnitude was also observed for
both exchangeable and acid-extractable Ca, over the past two decades,
in archived samples collected in red spruce stands at the Hubbard
Brook Experimental Forest, N.H. The average ratio of inorganic Al
to Ca in mineral-soil solution for the 12 sites was 5.0, indicating
that inhibition of Ca uptake by Al in the mineral soil may have
contributed to the decline of Ca concentrations in the forest floor.
A Ca budget, developed through the use of Sr isotope ratios to estimate
weathering rates, suggests that root-available Ca in the northeastern
U.S. will likely continue to decline.