Graduate Thesis Or Dissertation
 

Simulated storm runoff characteristics between natural and altered ecosystems in the Oregon Range Validation Area

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/6108vf04g

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  • During the summer of 1980 an infiltration/sedimentation study was conducted on the Oregon Range and Related Resource Validation Project Work Area in the Blue Mountains of east-central Oregon. A modified Rocky Mountain infiltrometer was used to simulate a 28 minute high intensity rainfall event to determine mean infiltration rates and average potential sediment losses on 19 improved resource units consisting of various combinations of productivity and condition classes. Such improvements included seedings, thinnings, herbicide spraying, mechanical brush control and certain combinations of 2 or more practices. Natural or unimproved resource units of similar soil type and ecological expression were sampled and used as controls. On 4 of 9 seeded mountain grassland ecosystems sampled, the control had significantly higher infiltration rates for the entire run. On 2 others, no significant difference in infiltration rates occurred during the 3 -8 time interval. Thereafter, the control had significantly higher infiltration rates. In another instance, the control had significantly higher infiltration rates only for the 3-8 minute time interval after which no significant differences were found. In another case, significantly higher infiltration rates occurred only during the 3-8 and 23-28 minute time intervals for the treated and control areas, respectively. For the remaining site there were no significant differences in infiltration rates between the treated and control areas throughout the storm. The control had a significantly higher average potential sediment loss in all cases except 4. In 3 of these no significant differences in sediment loss was found. On the remaining site the treated area exhibited the significantly higher sediment loss. On the sagebrush ecosystem sampled, where sagebrush was mechanically removed and the area seeded, the treated area had significantly lower infiltration rates than the control and a lower average potential sediment loss. The control for a thinned pine-mixed fir-sedge ecosystem in fair condition not only had a significantly higher average potential sediment loss but also had a significantly higher infiltration rate than the treated area for the 3-8 minute time interval after which no significant differences in infiltration rates occurred. On a thinned and seeded pine mixed fir-sedge ecosystem in good condition, on which seeding establishment appeared unsuccessful, infiltration rates were significantly higher for the treated area for the entire storm. However, no significant differences in average potential sediment loss were found. A thinned larch ecosystem was divided into a pinegrass, a seeded and a bareground area and each area was sampled separately. In all 3 cases, the control had significantly higher infiltration rates throughout the storm as well as a significantly lower average potential sediment loss. On 1 of the 2 pine-sedge ecosystems the treated area had significantly higher infiltration rates for the entire storm as well as a significantly lower average potential sediment loss. On the other pine-sedge ecosystem, divided into non-vegetated and vegetated areas, the control of non-vegetated portion exhibited significantly higher infiltration rates and a lower average potential sediment loss than the treated area, whereas, no significant difference in infiltration rates or sediment loss was found between the control and treated area on the vegetated portion. On a thinned ponderosa pine-bunchgrass ecosystem although infiltration rates were significantly higher for the treated area during the entire run, no significant difference in average potential sediment loss was found.
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