Graduate Thesis Or Dissertation
 

Modeling riparian zone processes : biomass production and grazing

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/w0892g42q

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  • Seasonal trends in forage production and environmental parameters for five plant community types within a northeastern Oregon riparian zone were described and modeled using correlation and path analysis. Wet meadows produced the greatest amount of herbage biomass, followed by moist bluegrass meadows, gravel bars, forests and dry bluegrass meadows. Trends in soil moisture generally increased and then declined from spring to fall. Depth to the water table declined and then increased. Soil temperatures steadily increased. Variables driving seasonal forage production varied by community type. Soil moisture was most important in dry bluegrass meadows and least important in wet meadows. Depth to the water table was most important in wet meadows and least important in dry bluegrass meadows. The amount of herbage production which had already occurred was also an important variable in describing biomass production. Streamflow levels and the amount of production having occurred were driving variables in the gravel bar communities. Preference for grazing different riparian vegetation community types and forage intake by cattle was monitored over a three-week grazing period occuring at the end of summer. Concurrent to preference and intake, vegetative and nutritional characteristics of the forage available for grazing were monitored and relationships between these variables and both community preference and intake described through correlation and path analyses. Grazing cattle initially favored communities with highly digestibile forage, hence communities dominated by Kentucky bluegrass were most preferred. Late in the grazing period community preference was best associated with community abundance, indicating that cattle were grazing communities in proportion to their abundance in the pasture. Intake levels were greater during the first year of the study than the second (2.15 versus 1.81 percent of body weight). Daily grazing time declined as livestock neared the end of the grazing period. Intake was correlated with in vitro dry matter digestibility and the amount of time spent grazing, but poorly related to the amount of forage available. The indirect effect of the amount of forage available on intake was greater than the direct effect and functioned through increases in grazing time as a result of increased availability of highly digestible forage.
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file details KorpelaEdwinJ1992.pdf 2017-11-01 Öffentlich Herunterladen