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. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36790 |
| Date | 23 January 1992 |
| Creators | Korpela, Edwin J. |
| Contributors | Krueger, William C. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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