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The following report documents the findings of a client-focused group Master’s Project
completed at the
Nicholas School of the Environment at Duke University. The project’s purpose is to
support the client’s
goal to optimize nutrient and timber management in a 750-acre forested tract owned
by the Town of
Butner in Granville County, North Carolina. Excess nitrogen and phosphorus delivery
to drinking water
reservoirs has become a concern in the North Carolina piedmont as development pressure
increases in
surrounding watersheds. The Falls Lake Nutrient Strategy is among several new regulations
aimed at
reducing nitrogen and phosphorus delivery to an increasingly eutrophic public water
supply. While the
regulation pressures upstream communities to reduce their impact, mitigation strategies
are diverse and
can be costly to local governments. Even though a market-driven nutrient trading credit
system is
included in the Falls Lake Nutrient Strategy, there is currently no opportunity to
earn credits through
avoided deforestation or land conservation, commonly called “conservation credits”.
The Town of
Butner is interested in novel approaches to managing its nutrient loading and the
possibility of earning
conservation credits while managing its forestland for timber. There were four objectives
to this project,
1) to estimate the value of timber on the property, 2) to determine the range of impacts
that different
timber management scenarios will have on nitrogen and phosphorus loading from the
property, 3) to
develop a simple tool that land managers can use to predict optimal outcomes for different
timber and
nutrient management scenarios, and 4) to inform state policy on the value of conservation
credits and the
effects of forest management on nutrient loading. A range of forest management scenarios
with different
harvest practices and maintaining 50-ft to 200-ft streamside management zones were
modeled over a 30-
year timeline. The USDA Forest Service’s Forest Vegetation Simulator (FVS) and Timber-Mart
South
were used to project harvested and standing timber values under each scenario. GIS-based
models were
employed to predict nitrogen and phosphorus delivery to perennial and intermittent
streams under each
scenario. The future value of conservation credits was assumed to be the sum of the
value of nitrogen and
phosphorus credits in the existing NC Department of Environment and Natural Resources,
Nutrient Offset
Program. The findings of this project suggest that the monetary value of timber within
the 50-ft to 200-ft
buffer zone far exceeds any reasonable economic value of conservation credits earned
by not harvesting
within the buffer zone during a 30-year time horizon. Timber harvesting, and in particular
changing the
buffer zone width from 50-ft to 200-ft, had a relatively small impact on nitrogen
and phosphorus loading
when compared to other land uses. The implication is that nutrient management and
productive forest
management are not mutually exclusive. The minimum buffering requirement of 50-ft
was effective at
removing nutrients, while still permitting the maximization of timber revenue.
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