Relationship of Soil Nitrogen Availability to Riparian Tree Growth on the Queets River
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Trees in riparian forests of the Pacific Northwest attain very large diameters |
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Project Summary
Large wood creates channel diversity and important habitat for salmonids
(Oncorhynchus spp.). Generally, trees must be greater than 1 m in length and 0.1 m in
diameter before they can play an effective geomorphic role. However,
attaining a large diameter in a riparian zone altered by frequent
channel movement requires rapid growth rates. The purpose of this study
is to better understand the relationship between nitrogen availability
(influenced by soil texture and depth, and rates of mineralization) and
tree growth.
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Bank undercutting recruits large wood to rivers |
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Objectives and Methods
This study will compare the growth rates of trees in permanent plots
characterized by fine-textured soils and those characterized by
coarse-textured soils. A second objective is to compare species
composition of similar aged plots with fine- or coarse-textured soils.
One of the subsidiary goals of this study is to determine if certain
tree species are associated with soils with higher or lower levels of N
mineralization. Plots of differing ages (20-400 yr) will be used, as
soil depth and particle size, and N mineralization rates vary with
stand age.
The work will take place on the Queets River, Olympic National Park,
Washington, USA. Tree growth rates will be estimated by taking cores
from the dominant trees in each plot, and analyzing the width of annual
rings. Growth rates will be correlated with soil particle size and
depth, and N mineralization.
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Root wads add stability to log jams |
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Intellectual Merit
This study will contribute to the synthesis of biological and
geomorphic knowledge of the Queets River assembled by Dr. Robert
Naiman's lab group over the last 17 years. Although there were a few
settlements in the Queets from 1890 to the 1950s, the Queets is still a
very natural system. Protection of the Queets River has increased since
the formation of Olympic National Park in 1938. Currently,
approximately 98% of all rivers in the United States have had their
flow modified in some way. The Queets is unique for a river its size in
that it has never had its flow altered. As such, the Queets presents an
often sought but rarely found entity in that it provides restoration
teams and river managers with baseline data with which other, disturbed
systems may be compared. A thorough understanding of a mostly
undisturbed system will contribute greatly to the body of riparian
knowledge. As one of the more natural rivers in the region, increased
knowledge about soils and tree production in the Queets can inform
management and restoration practices in coastal watersheds throughout
the Pacific Northwest.
Broader Impact
This research will add critical information to a long-term ecological
study of a relatively pristine area. The information gathered from this
study will be combined with data collected over the past 17 yr on the
Queets River to produce a broad document assessing the relationship
linking riparian soils and vegetation, river processes, and fish
habitat. The resultant document will not only aid in general scientific
knowledge, but will be actively used by managers of undeveloped areas
to determine proper riparian buffers and by city planners to improve
degraded riparian areas for improved water quality and fish and
wildlife habitat. This research will aid the expansion and improvement
of the health of people in the Pacific Northwest, as well as improve
their opportunties for recreation.
Photo credit: All photos by J.J. Latterell 2005
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