Geoscience Reference
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about the same, drought stress is likely to be more fre-
quent—a trend that is apparent for the western states
as a whole (see fig. 2.11).
overall, the data suggest a slight decline in annual
precipitation in the Laramie Basin during the past
10 years, a trend further substantiated by declining
streamflow in some rivers, as is illustrated for the Green
However, no similar decline occurred for the Laramie
River. there is the potential that summer precipitation
might be more closely associated with plant growth in
grasslands than is annual precipitation, but such analy-
ses have not yet been done for the Laramie Basin. Also,
winter precipitation can be a significant factor for grass-
lands if it results in considerable water in the soil at the
end of winter.
two scenarios for climate change have been proposed
for the east-central Rocky Mountain region that are per-
increase in mean annual temperature of 2°-5°F, which
would likely increase potential evapotranspiration by
0.01-0.04 inch/day. For this exercise, the first scenario
proposes increased winter precipitation and decreased
growing season precipitation. the net effect would
cause a shift from grassland to mixed desert shrubland.
the second scenario projects the same increase in tem-
perature, but with increased summer precipitation
rather than winter precipitation. this scenario would
favor continuing dominance of grassland, but with an
increase in cheatgrass. Ponderosa pine may also become
more widespread than it is today, because of its apparent
reliance on warmer, wetter summers.
35
in general, much remains to be learned about the impli-
cations of climate change combined with habitat frag-
mentation, invasive plants, and the long-term effects
of living on the land—a topic discussed further in the
next chapter.
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