Dataset consists of the annual aboveground net primary production (ANPP) across 3
habitats grouped by plant form and total ANPP. The habitats are grassland, mesquite
shrubland, and the ecotone between the 2. The plant forms are winter annual forb,
annual forb, bi-annual forb, perennial forb, annual grass, perennial grass, shrub, and
sub-shrub.
OBJECTIVE: The purpose of the study is to investigate how pulses of precipitation
translate into pulses of plant aboveground net primary productivity (NPP) and how the
small mammal community responds to such changes also in relation to shrub gradient
across the landscape. Particularly we are interested in how the energy flows through
the ecosystem in response to pulses of rain, how the small mammal community partition
resources (in terms of C3 (forbs and shrubs) and C4 (grasses) plants) and how the
genetic structure of some species (e.g., Dipodomys spp.) is affected by their
population dynamics.
HYPOTHESES:
1) Small mammal abundance should respond positively to precipitation and NPP.
2) On a temporal scale, the small mammal energy use should show parallel fluxes along
the shrub gradient.
3) The small mammal community should consume C3 and C4 plants according to their
availability (or NPP).
4) At low population density, dispersal should be limited and the genetic variance will
be distributed among populations rather than within (i.e., Fst will trend towards
higher values). After pulses of rain and NPP, population densities will be greater,
dispersal prevalent, and the genetic variance of populations will be distributed within
populations (i.e., Fst will approach zero) as dispersal homogenizes populations.
Total aboveground annual net primary productivty is calculated for winter annual forb,
annual forb, bi-annual forb, perennial forb, annual grass, perennial grass, shrub,
sub-shrub, and the total of these.
