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I
have used desert plant communities as a model system to address questions
of how the individualistic responses of plants average out in population
dynamics. Measuring the distinct responses of individual plants to availability
of ecosystem-level variables such as light, water or soil nutrients allows
for scaling up to community or landscape level dynamics where we can measure
or predict the distribution of such variables. Deserts present a model system
for two reasons: 1) all members share a common limiting resource, water,
and 2) the clear spatial pattern of desert plants both influences and is
influenced by soil resources. This research has highlighted the importance
of spatial structure by showing that although competitive effects do not
appear to have an overriding effect on the spatial structure of plants within
the study site (Miriti et. al 1998), plants that remain at least one canopy
distance from conspecific neighbors have a disproportionate contribution
to population dynamics (Miriti et. al 2001). Predominant clumped spatial
patterns albeit with little demographic contribution suggest a trade-off
in the roles of competition and facilitation in plant demography. <top> |
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| Study
site at Joshua Tree National Park. Photo by M. Miriti. |
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| Participants
of the most recent census of Joshua Tree study site in spring 2004. Pictured
from left to right are (back row) Hillary Sweigard, Christina Barba, Pia
Sethi, M. Miriti; (front row) Maria Angela Rodriguez, Elaine Hooper, Susana
Rodriguez. |
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PRAIRIE
RESTORATION |
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restoration of human altered, biologically depauperate landscapes to more
diverse, functionally intact ecosystems provides an ideal arena in which
to test ecological theory while providing practical guidance of direct benefit
to public and private sectors. We are conducting series of greenhouse and
field experiments to quantify competitive and demographic responses of North
American tallgrass prairie species (prairie-natives) as compared to species
associated with old-field succession (prairie-invasives) in response to
varying levels of available soil nutrients. Our core objective is to test
the hypothesis that population-level measures of plant competitive ability
are driven by the integrated response of all life-history stages. A key
element of our work is to parameterize demographic models of long-term population
dynamics for a suite of prairie-native and prairie-invasive species under
reduced or elevated soil nitrogen and calcium availability. Comparison of
model predictions with results from an experimental prairie restoration
will be an important and novel test of current ecological theories of differential
resource use among species and the effect these differences have on community
composition. <top> |
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