Grasslands were perceived to have several multiple equal uses as watershed, wildlife habitat, recreation, and livestock grazing. This concept assumed that if one of the uses were reduced another use could be increased. A standard undisturbed treatment developed that removed the livestock grazing use with the intent to increase wildlife, rare plants, and special interest insects.
Removal of livestock grazing in order to protect a grassland ecosystem is based on presumptions that livestock grazing causes damage to a grassland ecosystem and interfere with the life cycles of wildlife, scarce plants, and precarious insects. Livestock grazing is not what causes damage to grasslands; poor management of grazing livestock can cause serious damage to grasslands, however, maybe the greatest antagonistic effects to grassland ecosystems occur from no livestock-idle land management concepts that rest grasslands from grazing defoliation.
The term “rest” is a misnomer; resting a grassland does not cause revitalizations of crucial biological and ecological processes. Resting a grassland by withholding partial defoliation by grazing results in regression of ecosystem processes and biological growth mechanisms.
Several negative changes occur relatively soon after grazing graminivores are removed from grasslands; the live root biomass of grasses decrease, standing dead leaves and litter accumulate, and ecosystem biogeochemical processes diminish.
The reduction of live root surface area causes a decrease in active root biomass and diminishment of grass plant health vigor result in a loss of resource uptake efficiency and a suppression of competitiveness of grass plants to take up mineral nitrogen, essential elements, and soil water.
Grass plants produce double the quantity of leaf biomass than needed for normal plant growth and maintenance. Without grazing animals to remove the surplus herbage production, the standing leaf material accumulates rapidly and changes from an asset to a detriment.
The accumulation of nondefoliated live and standing dead leaves of grasses reduce light penetration below native grass light saturation points and shade the lower leaves, increasing the rate of leaf senescence and reducing the rate of photosynthesis, causing a decrease in the supply of carbohydrates that results in a reduction in growth of leaves and roots. Lack of grazing reduces grass tiller densities by decreasing tiller development and increasing native grass tiller mortality through shading.
Introduced cool season domesticated grasses have lower light saturation points than native grasses, permitting domesticated grass to live in low light conditions resulting in increases of the composition of shade-tolerant or shade-adapted replacement species, like smooth bromegrass and Kentucky bluegrass.
Standing dead material not in contact with soil does not decompose through microbial activity. Dead plant material on non-grazed treatments breaks down slowly over several years by leaching and weathering and builds up into a thick mulch layer.
Thick mulch blocks sunlight from reaching understory young grass leaves and modifies soil temperatures. Thick mulch ties up organic nutrients above the soil surface preventing accession to the soil organic matter. This limits nutrient cycling through biogeochemical processes increasing the deficiencies of essential elements and decreases grass growth of leaves and roots.
Without partial defoliation by grazing, there are great reductions in the quantity of carbohydrate energy exudated from the grass roots into the rhizosphere (root zone). This reduces rhizosphere biomass and decreases the ecosystem biogeochemical processes with greatly reduced rates of organic material decomposition. Thus, mineralization of nitrogen and other essential elements is greatly reduced.
The successful sustainability of grassland ecosystems depends upon the implementation of biologically effective grazing management strategies that provide the biological and physiological requirements of the forage grass plants, soil microorganisms, and large grazing graminivores. Those factors activate and maintain the grass plant growth mechanisms and the ecosystem biogeochemical processes. Those processes can revitalize soil structure and functionality, that increases forage growth and nutritional quality, and can improve livestock growth and weight performance along with the capture of greater wealth per acre.
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