ESTIMATING PLANT SPECIES MIGRATION RATES IN THE PAST AND FUTURE
Amended Abstract
Models of future vegetation resulting from climate change
scenarios often assume that tree species will either geographically
respond instantaneously to new climates, or that species could
not expand outside of their current ranges – Both unlikely
outcomes.
Estimates of the amount of likely population expansion within the
next century can be obtained from reviewing species movements
over the last century. Data are available recording movements of
major tree species following logging, fire, and other disturbances.
Permanent plot networks and historical photographs document
the rate of movements across landscapes. Autecological data on
major tree species record their capacity for establishing in
disturbed areas, their maturation time, and their capabilities for
seed dispersal. Quaternary fossil records can reveal their
capacity for long-term, large-scale movements. When these types
are records are compiled, they allow a comprehensive overview of
a species potential migration rate and classification into a
generalized rate class. Rate classes are an appropriate level of
quantification considering the generalized models that they will be
applied to, and the fact that a precise number cannot be
calculated.
Subsequent population modeling using such generalized
migration rate classes (such as: 50, 100, or 250 meters/year),
demonstrate that the specific rate class chosen is of minor
importance to the final outcome. Other factors, such as the GCM
scenario chosen, have a far greater influence on the results (as in:
Pinus ponderosa). If the species, like many, is likely to be
contracting in range rather than expanding, then the migration rate
class chosen is largely irrelevant (as in: Picea engelmannii).
The HADGEM1 model depicts a greatly enhanced
southwestern monsoon in the near future. This GCM
scenario would seem to be a questionable anomaly if
it were not for the fact that this scenario performed
the best in hindcasting the Twentieth Century
monsoon extent. This enhanced monsoon results in
substantial migrational expansion of Pinus ponderosa
(light green) shown here at the rapid pace of 500
meters/year (50 km over the entire period), and
substantial potential areas of suitable climate for
assisted migration (turquoise).
Kenneth L. Cole1,2,3, Charles M. Truettner 1, Neil S. Cobb1, and Kirsten Ironside2
1Northern
Arizona University Merriam-Powell Center (Ken.Cole@nau.edu); 2USGS Colorado Plateau Research
Station
These and other many other modeled projections are available
at: http://www4.nau.edu/swplantatlas/endemic.html
Picea engelmannii
Wind Dispersal - Slow Growing – Long Lived Seral
Engelmann Spruce model
Engelmann spruce populations are predicted to contract by the 2070 to
2099 period using the most likely predictions from a suite of GCMs.
Application of a migration estimate of 100 m/year (8 km for the entire
period), produces minimal differences in the future range because of its
severe contraction in most areas.
Pinus ponderosa
Avian & Wind Dispersal – Disturbance
Adapted – Fast Growing
Comparison of three GCM scenarios
Biometric models of Pinus ponderosa var. scopulorum suggest that its distribution is highly
dependent upon the summer moisture brought to the Colorado Plateau region during the
southwestern monsoon season. Thus, it should be most reliably modeled using GCM
scenarios that demonstrate the capability of depicting this summer climatic reversal. An
analysis (Garfin et al., 2010) of the Twentieth Century climates depicted by the 22 GCM
scenarios used for the AR4 dataset (ICCP, 2007) suggested that this climatic feature did not
occur in as many as half of these GCM scenarios. Two scenarios, the HADGEM1 and MPIECHAM5, did a superior job of hindcasting the history of this seasonal precipitation change.
In the future, these two scenarios project opposite changes in the strength of this feature.
The HADGEM1 GCM projects a strengthening of the summer monsoon to the north and
west, while the MPI-ECHAM5 projects a weakening of the monsoon and a shift eastward
toward New Mexico.
retreat
expansion
Southwestern Colorado
Plateau
The Englemann Spruce
Biometric model (see poster
by Truettner et al.) and GCM
model suite correctly predicted
the recent massive spruce
mortality at Cedar Breaks
National Monument (above),
and the thinning of spruce in
permanent plots on the north
rim of the Grand Canyon
National Park (below). Future
climates portrayed by the
GCMs suggest the elimination
of spruce in these areas as
soon as mid-century.
Southwestern Colorado
Plateau
The Englemann Spruce
Biometric model (see poster
by Truettner et al.) and GCM
model suite correctly predicted
the recent massive spruce
mortality at Cedar Breaks
National Monument (above),
and the thinning of spruce in
permanent plots on the north
rim of the Grand Canyon
National Park (below). Future
climates portrayed by the
GCMs suggest the elimination
of spruce in these areas as
soon as mid-century.
This ensemble of 48 runs of the 22 AR4 GCMs
projects a future drought-stressed southwestern
United States producing extreme contraction of
populations of Pinus ponderosa (red). While this
ensemble results from a more robust GCM dataset
than any individual GCM scenario, at least half of
these GCMs did not indicate any significant airflow
or precipitation reversal during the summer in this
region over the Twentieth Century. This suggests
that the scale of this climatic feature is too small for
most of these GCMs to model.
mortality has already
occurred on the west side
of Rocky Mountain
National Park (arrow).
Table of paleoecological and autecological data contrasting both species.
Paleoecological record
The MPI-ECHAM5 model depicts a decreased
southwestern monsoon. This GCM scenario
performed second-best (of 22 GCMs) in hindcasting
the Twentieth Century monsoon extent. This
decreased monsoon results in significant reduction
in population (red) for this southern interior race of
Pinus ponderosa, especially by the end of this
Century.
Colorado Front Range
The models predict upslope
retreat of spruce from its
lower elevations and a lesser
expansion into higherelevation habitats (green)
applying a migration rate of
100 m/year. Extreme
Pinus
ponderosa
Picea
engelmanii
Successional Status and Maturation Seed dispersal
Time (from USDA Forest Service FEIS web site: http://www.fs.fed.us/database/feis/)
Earliest, highly adapted to disturbance First Movement within SW of about 500 meters per year, from arrival seeds at 7, maximum production 60 years, mast years every 3 to 8 years. 10 year maturation at Mogollon Rim during Allerod
Interval (Anderson, 1993), at estimate to decent seed productivity produces 7 Grand Canyon by 11.2 ka (Cole, steps until 2070‐2099 time period.
1990), and North Rim of Grand Canyon by 11.0 ka (Weng and Jackson, 1999).
Clark’s nutcracker caches. Reliable dispersal must be 7 km to produce this class rate.
Migration Class
500 meters/year
Wind dispersal, generally 50 Climax species, but establishes in mineral soil. Seedlings establish near mature trees within 5‐10 within 100 m, large crops meters/year
(Modeled at years. Seedlings grow slowly after establishment. may travel 200 m. 100 m/yr
Near treeline, perhaps > 100 years until re‐
above for establishment. First seeds produced between 15 illustrative to 40 years of age. Mast years every 2‐5 years.
purposes)
References
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Martin, P.S. (Eds.), Packrat Middens: the Last 40,000 Years of Biotic Change. University of Arizona Press, Tucson, pp. 240–258.
Garfin, G., J. K. Eischeid, M. Lenart, K. Cole, K. Ironside, & N. Cobb. 2010. Downscaling climate projections to model ecological change on topographically diverse landscapes of the arid southwestern U.S. Pages
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