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We examined tree diameter, age structure, and successional trends in 100 montane forest plots to identify the effects of variation in the return interval, severity, and extent of fires on forest structure and dynamics in the southern Cascade Range, California. We classified 100 forest plots into 8 groups based on stand structural characteristics. Median point fire return intervals were shortest in lower montane mixed conifer and Jeffrey pine-white fir stands (13-25 y) and upper montane red fir-white fir stands (14.5-19.5 y), intermediate in lodgepole pine stands (50-76.5 y), and longest in high-elevation red fir-mountain hemlock stands (100 y). Fire severity was mainly moderate to high in all forest structural groups except red fir-mountain hemlock. In the late 19 th century, large, mostly high-severity fires burned through all forests. Fire extent varied among structural groups, burning from 13% to 85% of plots in a group on average. Stands differed in composition, but size and age structures were similar across structural groups, with few trees > 100 y old and peaks of establishment between 1895 and 1955 for all groups except red fir-mountain hemlock. Distinct pulses of tree recruitment followed the most recent (1883, 1885, 1889, 1918) large and mainly high-severity fires. Suppression of fire since 1905 has increased understory density of shade-tolerant, fire-intolerant species and caused forest compositional shifts, particularly in lower-elevation Jeffrey pinewhite fir and mixed conifer stands, and lodgepole pine stands on well-drained sites. Structural or compositional change is less pronounced in upper montane red fir-white fir and red fir-mountain hemlock forests. The combination of gently sloping terrain with few fire breaks, extensive, moderate-to high-severity fires in all forest types and gradient positions and fire suppression has promoted homogenization of forest structure that may lead to large and severe fires in the future.

We present a 576-year tree-ring-based reconstruction of streamflow for northern Utah's Weber River that exhibits considerable interannual and decadal-scale variability. While the 20th Century instrumental period includes several extreme individual dry years, it was the century with the fewest such years of the entire reconstruction. Extended droughts were more severe in duration, magnitude, and intensity prior to the instrumental record, including the most protracted drought of the record, which spanned 16 years from 1703 to 1718. Extreme wet years and periods are also a regular feature of the reconstruction. A strong early 17th Century pluvial exceeds the early 20th Century pluvial in magnitude, duration, and intensity, and dwarfs the 1980s wet period that caused significant flooding along the Wasatch Front. The long-term hydroclimatology of northern Utah is marked by considerable uncertainty; hence, our reconstruction provides water managers with a more complete record of water resource variability for assessment of the risk of droughts and floods for one of the largest and most rapidly growing population centers in the Intermountain West.

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