Michelle Trogdon

GEOG 4401/5401 Soils GeographyFall 2007 – Univ of Colorado, Boulder

3,487 ha of native tallgrass prairie in Flint Hills, KA

6,280+ ha of shortgrass rangeland in the piedmont of eastern CO

• Flint Hills- steep sloped and overlain with shallow limestone soils• unplowed tallgrasses• soil depth varies with topo• silty clay loams • multi level ecological studies of abiotic/biotic factors influencing ecosystemDominant Hypothesis: Fire, grazing, and climate variability are essential and interactive factors responsible for the structure and function of tallgrass prairie.

• seed predation of vertebrates and invertebrates• fire frequency and topographic variation• vertebrates consumed more seeds• fire decreases dead plant matter (litter) which increases potential for rodent seed predation• seed preference, large seeds all yr, millet, C4 population?

• essential to mesic grasslands• managed to limit tree growth and promote C4 grasses• changes light and soil environment of plants• changes reduce biodiversity• changes soil temperature, increases hydrocarbons, water infiltration• difficult conditions for plant succession, rapid regrowth

• two forbs (flowering plant) and one C4• grazing tolerance• bison graze perennials increasing species diversity• grazing (bison) negative affects on biomass and reproduction• highest grazing tolerance, smaller reductions in biomass, growth rates, and reproductive effort

• human controlled cattle grazing• reintroduction of bison• bison vs. cattle• grazing (bison) negative affects on biomass and reproduction• responses indicate population differentiation and genetic adaptation to grazing pressures

Dominant Research themes…

• factors regulate ecological structure and function over space and time• how do these factors with abiotic/biotic vary spatially and temporally?• what are the abiotic/biotic factors that determine vulnerability of the ecosystem to change?

• historical cattle grazing• B. gracilis C4 70-80% community• newly grazed responds rapidly• dominates long-term grazed• root biomass greater at grazed sites• root organic matter inputs influence soil organic carbon• grazing decreases biodiversity of grazed plants

Temperate Grassland

• soil development is inhibited by fire, climate, and topo depleting organic matter, nutrients• fire alters soil conditions, difficult for plant succession reduces plant diversity, optimal foraging• grazing induces genetic adaptation, rapid regrowth is favored• C4 grasses fair better under these conditions