Transcript Temperate Grasslands Konza Prairie and Shortgrass Steppe

Michelle Trogdon
GEOG 4401/5401 Soils Geography
Fall 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 ecosystem
Dominant 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