Results and Accomplishments
We used a spatial modelling technique to assess
the influence of climatic variability on the annual productivity
of P. ponderosa in the Pacific Northwest (PNW) of North America,
over the past 100 years and infer how a sustained change in
climate might alter the geographic distribution of this species
across defined ecotones. Field observations were used to establish
three criteria to define where P. ponderosa should maintain
(1) maximum summer leaf area index, (LAI), should fall between
1.5 and 2.5
(2) up to 80% of available soil water will be depleted during
(3) soil water storage will reach capacity sometime during
Where these three criteria were not met,
we predicted that P. ponderosa would be eventually replaced.
We used a simple physiological model, 3-PG. to predict annual
variation in LAI from climatic data provided by the Oregon
Climate Service over the period from 1900 -2000 and from broad
scale 0.5° spatial resolution future climate projections
produced by the Hadley Climate Center, UK. From these simulations
we produced a series of maps that display predicted shifts
of zones where ponderosa pine might be expected to contract
or expand its range if modeled climatic conditions at annual
and decadal intervals were sustained.
- Historical simulations indicated that the most favorable
decade was in the 1900ís and the least favorable in the
- Future predictions suggested a reduction in the current
range of ponderosa pine along the western Cascade Mountains,
but an increase along the east side of the Cascades and
inland towards the eastern Oregon/Washington border (Figure 1).
- Model predictions are that pine dominance should increase
between 5 and 10% over the next century, mainly in inland
Oregon, Idaho and Washington.