Wallin,
D.O, M. Harmon, W. Cohen (in press) Modeling
regional-scale carbon dynamics in Pacific Northwest forests: 1972-95. Pages xx-xx In: O. Krankina and M.E. Harmon (eds.)
Carbon Dynamics of Two Forest Regions: Northwestern Russian and the Pacific
Northwest. Springer-Verlag, New York
Most
analyses suggest that balancing the global carbon budget requires a significant
sink on land in the temperate zone of the northern hemisphere. Clarifying this issue will require better information
on regional carbon budgets. We discuss
the use of a simple carbon model, in conjunction with satellite data, to
quantify carbon flux from 49,000 km2 of forested lands in western
Oregon. The model quantifies carbon
storage in living, detrital and forest products pools. Between 1972 and 1995, total carbon flux
from this study area to the atmosphere averaged 0.67 Mg C/ha/yr with
considerable spatial and temporal variation.
Values ranged from -4.7 to +13.2 Mg C/ha/yr for different portions of
the study area. This spatial
variability in C flux was related to site quality and land use. Temporal variability in C flux was primarily
related to changes in timber harvest rates.
The largest net release of C to the atmosphere
(1.2 Mg C/ha/yr) occurred during 1972-77 and the study area continued to be a
net source of C to the atmosphere through the 1988-91 time period. Large reductions in timber harvest rates on federally
managed lands during the 1990s resulted in a net accumulation of 0.1 Mg
C/ha/yr in our
study area during 1991-95. These
results are used to illustrate the natural and anthropogenic sources of
heterogeneity that can influence carbon budgets at the regional scale and how
remotely sensed data can be used to help quantify this heterogeneity.
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