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Download Temperate Grasslands Konza Prairie and Shortgrass Steppe
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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
