The ability of 23 year old volcanic soils from Mount St. Helens, USA, to nodulate actinorhizal Sitka alder (Alnus viridis ssp. sinuata) was studied by estimating Frankia Inoculation Unit density (FIU) in four types of primary successional communities using a host-plant bioassay. Rhizospheric Mycelial Inoculation Unit (MIU) density and the effects of inoculation with alder soil and phosphorus (P) on seedling growth were also examined. FIU and MIU were highest in alder thickets, lower in lupin patch and riparian zone sites, and lowest, with no FIUs, in bare areas. Seedling dry mass was higher in treatments inoculated with alder soil but not with P addition, while root: shoot mass ratios decreased with both inoculation and P. The extremely low densities of suitable symbionts in sparsely vegetated primary successional areas at Mount St. Helens may explain the surprisingly slow rate of spread of alder from nearby seed sources.

We present the results of a replicated before‐after‐control‐impact study on 33 streams to test the effectiveness of riparian rules for private and State forests at meeting temperature criteria in streams in western Oregon. Many states have established regulatory temperature thresholds, referred to as numeric criteria, to protect cold‐water fishes such as salmon and trout. We examined across‐year and within‐year patterns of exceedance at control and treatment stream temperature probes. Determining whether an exceedance at the downstream end of a harvest was unambiguously related to harvest proved surprisingly difficult. The likelihood of a site exceeding its numeric criterion appeared related, in part, to the site's preharvest temperature range. Four control reaches as well as three preharvest treatment reaches exceeded their numeric criteria, necessitating additional analysis to evaluate timber harvest impacts. Nine percent of sites (3 of 33) both exceeded their numeric criteria and exhibited a potential harvest effect (16.7% of private sites [3 of 18], 0% of State sites [0 of 15]). After harvest, exceedances were typically observed in only the first of the two post‐harvest years. These findings highlight the importance of including temporal and spatial controls in temperature assessments of numeric criteria when the assessment's purpose is to determine whether exceedances are related to human activities.