-- A new model simulates how climate impacts vegetation patterns
in Yosemite National Park's Tuolumne Meadows.
-- As climate change threatens to reduce snowpack in the Sierra
Nevada mountains, the next step is to use the model to predict how
changes, such as falling groundwater levels, might impact the kind
of plants growing in mountain meadows.
BUFFALO, N.Y. -- Researchers from three universities have
partnered to create a new, high-tech tool for mapping changing
plant patterns at Tuolumne Meadows, a mountain meadow in Yosemite
The tool is a model that stitches together years of data from
the study area, including meteorological observations, stream gage
measurements, water levels at 55 wells, and vegetation surveys that
the National Park Service conducted at 222 locations.
By combining these and other factors, the model successfully
simulated how past groundwater levels influenced the type of plants
growing in the meadow.
A paper describing the new model, which generates "probabilistic
vegetation maps," was published online in the journal Water
Resources Research on Sept. 24.
The next step is to use the model to predict how future climate
change could affect vegetation patterns, and to test the
effectiveness of potential, future restoration strategies.
"Our work confirms what John Muir wrote back in 1911 about his
journey through Yosemite, which is, 'When we try to pick out
anything by itself, we find it hitched to everything else in the
universe,'" said Chris Lowry, the University at Buffalo geologist
who led the study.
"Our results showed that the distribution of vegetation in
Tuolumne Meadows is controlled by cascading hydrologic flows,
starting with rain and snow and moving through the watershed to the
meadow and finally discharging to the stream," Lowry said. "Each of
these elements -- climate , hillslope, riparian zone and stream --
contributes to the distribution of water within Tuolumne Meadows
and as a result controls the type of vegetation within the
Lowry's partners on the project included Steven Loheide II of
the University of Wisconsin-Madison, and Courtney Moore and Jessica
Lundquist of the University of Washington at Seattle. The research
is part of a larger study on mountain meadow restoration in a
changing climate that the University of Wisconsin and University of
Washington are heading. A National Science Foundation grant
supports that work.
The reason groundwater levels are so important in determining
meadow vegetation patterns is because different plants have evolved
to flourish in different environments.
Where the water table is low, drought-tolerant species dominate
because of their superior skills in acquiring and conserving
Where the water table is high, in contrast, plants that flourish
are those whose internal machinery enables them to survive under
wet conditions. These include species that have developed something
called an "aerenchyma" -- a spongy tissue that allows for exchange
of gases between root and shoot, enabling a plant's roots to
"breathe" even when limited air is directly available.
With climate change threatening to reduce snowpack and encourage
earlier melting in the Sierra Nevada, groundwater levels at
Tuolumne Meadows and other parts of Yosemite could rise or fall
enough to influence vegetation patterns.
In the face of such changes, predictive modeling could "save
time and financial resources by identifying both meadows that will
be most affected by climate change, as well as restoration
techniques most suitable to maintain or enhance ecological
function," Lowry and his colleagues wrote in their paper.
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