Graduation date: 2007Stream temperature, as an important component of stream ecosystems, can be affected by forest harvesting through removal of riparian shade and changes in hydrology. Riparian Management Areas (RMAs), as implemented through the current Oregon Forest Practice Rules, are designed, in part, to maintain stream temperature following forest harvesting. However, effectiveness of RMAs in achieving this outcome is uncertain. The objective of this research was to examine effectiveness of RMAs, as outlined by the current Oregon Forest Practices Act and the Northwest State Forests Management Plan, in maintaining warm-season temperature patterns of streamwater. Twenty-two headwater streams, on either private- or state-owned forestlands in the Oregon Coast Range that encompassed a range of RMA widths and harvest prescriptions, were evaluated for effectiveness of RMAs on stream temperature. A Before-After-Control-Impact/Intervention design was used, and each stream had an upstream control and a downstream treatment reach. Temperature probes were placed 1) at the top of the control reach, 2) at the boundary between the control and treatment reaches, and 3) at the bottom of the treatment reach from June to September for four years starting in 2002. All but one stream have at least two years of pre2 harvest temperature data, and one year of post-harvest temperature data. Selected stream and riparian characteristics were collected every 60 m within the control and treatment reaches once prior to and once following harvest. I hypothesized that RMAs would be effective if pre-harvest warmseason maximum temperature patterns were maintained following harvest treatments. Comparisons of temperature patterns between control and treatment reaches both pre- and post-harvest indicate that my hypothesis should be rejected because warm-season maximum temperature patterns were not maintained when mean values in treatment reaches across all study streams were considered. Difference in temperature gradients between control and treatment reaches averaged 0.6°C, based on two years of pre-harvest and one year of post-harvest data. This indicates that more warming or less cooling occurred in treatment reaches than occurred in control reaches when pre-harvest and post-harvest periods were compared, suggesting that current RMAs for small- and medium fishbearing streams of the Oregon Coast Range are not effective for maintenance of warm-season maximum temperature patterns.