| Abstract |
- This project was a part of larger work that compared major factors controlling patterns
of carbon dynamics in two regions of the globe, the Pacific Northwest, USA and
northwestern Russia. It was funded through the NASA foundation (grant # NAG5-
6242).
Human economic activity is causing the release of pollutants such as carbon dioxide.
The increased concentration of pollutants in the atmosphere is thought to cause
greenhouse effect, in other words - the warming of the earth and lower atmosphere.
Different methods are proposed to reduce concentration of greenhouse gases (GHG) in
the atmosphere. Some involve development of more clean technologies. Some involve
reductions in the use of fossil fuels. Another possibility is to store carbon (C) as live
biomass. Plants use C for growth and development. Using forests to sequester C is one
strategy for mitigating effects of GHG emissions. There are many methods in forestry
to grow trees and produce wood products. Some of them include clearcutting,
thinning, fertilizing, burning, and partial cutting.
This project had three purposes. First, was to investigate the effect of a wide variety of
silvicultural treatments on C storage and the economic value of harvested forest
products. We measured economic value as soil expectation value. Second, was to use
Data Envelopment Analysis to determine the efficient set of treatments, which make
up the Production Possibility Frontier (PPF) in terms of C and economic value. Third,
was to use the PPF to measure the marginal cost of carbon storage in moving from
high SEV and relatively low C storage to lower SEV and relatively high C storage.
C storage and timber harvest were simulated using the STANDCARB model for forest
types common in north-western Oregon with two tree species, Douglas fir
(Pseudotsuga menziesii) and Western hemlock (Tsuga heterophylla). Fifty
silvicultural regimes were investigated. They included clearcutting with rotations of
50, 70, 90, 110, 130, and 150. Each of the six rotation ages had eight combinations of
silvicultural treatments consisting of artificial and natural regeneration, growth
enhancement (GE) and thinning. Two partial cutting regimes: group selection and
single-tree selection were also used in the analysis.
C storage was calculated for every output year of each model run as a sum of live,
dead, and stable C. C storage for each silvicultural regime was measured as the
average over five full rotations from the steady state portion of the run.
The analysis showed that average C increases with rotation age from 335.99 MgC/ha
with 50-year rotation with natural regeneration and thinning to 826.36 MgCIha with
150-year rotation with artificial regeneration and GE. The use of artificial regeneration
compared to natural regeneration gave a 20-30 MgC/ha improvement for all regimes.
The total harvest from thinning and clearcutting over the rotation period averaged for
several runs varied from 505.34 m3/ha (with 50-year rotation no treatment) to 1782.24
m3/ha (with 150-year rotation with GE and thinning) The use of artificial compared
to natural regeneration gave a 20-50 m3/ha increase in harvest for all regimes.
SEV is the present value of net revenues from perpetually growing tree crops
following the specified regime. It measures the economic value of each regime.
Generally, SEV has a negative correlation with rotation length. Using a 3.5 percent real discount rate, the maximum SEV ($7904.3/hectare) was obtained from 50-year
rotation with artificial regeneration, GE and thinning In contrast, SEV for 130-year
rotation with artificial regeneration was only $446.68/hectare.
Using Data Envelopment Analysis (OnFront software) we found that 8 of the 50
regimes investigated were efficient in their ability to store C and produce economic
value. The efficient regimes included 50, 110, 130 and 150-year rotations with
artificial regeneration, GE and thinning; 110, 130 and 150-year rotations with natural
regeneration, GE and thinning, and the 150-year rotation with natural regeneration and
GE.
When regimes with GE were excluded, we found 7 efficient regimes: 50 and 150-year
rotations with artificial regeneration and thinning, 50, 110, 130 and 150-year rotations
with natural regeneration and thinning, and the 150-year rotation with natural
regeneration.
The marginal cost of C storage is the SEV lost per unit of C due to change in
silvicultural regimes that results in increase of average C stored. Marginal cost
analysis indicated that marginal cost values were similar for regimes with GE and
without. As C storage increased, the marginal cost generally increased. The increase in
C storage from 428 MgC/ha to 589 MgC/ha implied a marginal cost of $13.28IMgC.
In case of increasing C storage from 683 MgC/ha to 802.7 MgC/ha, the marginal cost
would increase to $32.79JMgC.
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