Study Overview
This study included a total of 28 streams surveyed in summer or early
fall across northern New York and New Hampshire. Riparian forests for
all streams were classified as mixed northern hardwood forests, a
forest community that includes both hardwoods and conifers. The
dominant riparian trees included: white pine (Pinus strobus), red
spruce (Picea rubra), eastern hemlock (Tsuga canadensis), red maple
(Acer rubrum), sugar maple (Acer saccharum), yellow birch (Betula
alleghaniensis), ash (Fraxinus spp.), and American beech (Fagus
grandifolia). No large-scale forest disturbances were documented at
any study sites during the study. Stream gradient ranged from 1% to
24% and mean bankfull widths ranged from 1.4 to 15.1 m. The age of the
dominant canopy trees in the riparian forest ranged from approximately
20 to 370 years. The mean age of the dominant canopy trees was highly
variable, especially in older uneven-aged stands.
Sampling Methods
Riparian Forest Characteristics. New riparian forest surveys were
conducted at eighteen of the 28 sites. Riparian forests in the
remaining ten streams were surveyed in association with Keeton et al.
(2007) or in later comparable surveys by Keeton et al. (unpublished
data) and included all relevant metrics for the current study. All
sample plots were taken within the broader riparian forest area and
characterize the general forest condition in areas adjacent to the
stream. Basal area and the relative abundance of species in the
‘‘dominant’’ canopy were estimated from these plots. At sites where
forest age was unknown, and in which we could obtain permission to
core trees, one core was taken from a dominant canopy tree at each
plot to determine the mean age of the dominant canopy of the riparian
forest following methods used in Keeton et al. (2007). All cores were
mounted, sanded, and analyzed under a dissecting microscope. For sites
where we could not core trees, the age of the dominant canopy trees
was determined using existing data from recent surveys, historical
data on forest management, and/or historical data from earlier studies
where trees were cored and aged (Warren, 2008).
Stream Characteristics. Mean stream bankfull width was measured with
five to fifteen evenly spaced bankfull width measurements along each
reach. Surveyed stream reaches ranged from 120 to 1200 m in length and
from 23 to >150 times the stream bankfull width, depending on the
size of the stream.
Large Wood Surveys. All large wood (LW) within the bankfull channel of
each study reach was counted, and the approximate wood volume was
estimated for each piece. Large wood was defined as dead wood greater
than 10- cm diameter and 1-m length occurring within the bankfull
stream channel. For each piece of large wood, we recorded: (1) the
total estimated length of the piece >10-cm diameter, and (2) a
single diameter measurement taken from a central point. Large wood
length was estimated to the nearest 0.5 m using a 0.01 m delineated
wading staff, and length estimates were verified using a field tape
for the first 5 pieces in each stream. Similarly, wood diameter was
estimated to the nearest 0.01 m and estimates were verified for the
first 10 pieces in each stream. In this survey, wood volume for each
individual piece was calculated using the formula of a cylinder, and
total wood volume for each study reach was estimated by summing the
total volume of wood within the bankfull channel. To allow comparison
with other studies in both terrestrial and stream environments, we
report both the volume of wood per linear 100 m of stream and the
volume per hectare of streambed.
Wood Jams. Wood jams – also commonly referred to as organic debris
dams – were defined as accumulations of multiple pieces of coarse wood
(dead wood between 0.5- and 1-cm diameter) against or around at least
one key piece of large wood (Keeton et al., 2007). Wood jams were
counted and measured during the large wood surveys. Size of the wood
accumulation was approximated by estimating the length, width, and
height of the structure (excluding impounded sediment) to the nearest
0.1 m. Wood accumulations without a key piece of LW that served a
geomorphic function were not recorded. However, based on field
observations, potentially functional wood accumulations lacking a key
piece were rare or absent in these streams.
Citations
Keeton, W. S., C. E. Kraft and D. R. Warren. 2007. Mature and
old-growth riparian forests: Structure, dynamics, and effects on
Adirondack stream habitats. Ecological Applications, 17:852-868
Warren, D. R. 2008. Large Wood in Northeastern US Streams: Spatial and
Temporal Dynamics and the Influence of Wood on Stream Nutrient
Cycling. Cornell University, Ithaca, NY.
Warren, D. R., C. E. Kraft, W. S. Keeton, J. S. Nunery and G. E.
Likens. 2009. Dynamics of wood recruitment in streams of the
northeastern US. Forest Ecology and Management 258(5):804-81
https://doi.org/10.1016/j.foreco.2009.05.020
