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The creation of chronologies from intra-annual features in tree rings is increasingly utilized in dendrochronology to create season-specific climate histories, among other applications. A conifer latewood-width network has recently been developed for the southwestern United States, but considerable uncertainty remains in understanding site and species differences in signal strength and sample depth requirements. As part of the 22nd annual North American Dendroecological Fieldweek, the first Pinus ponderosa earlywood-width (EW) and latewood-width (LW) chronologies were developed for the Jemez Mountains in northern New Mexico. The aim was to extend an existing total ring-width (TW) chronology and to assess the potential for creating long LW chronologies. Analysis of chronology signal strength suggests that large sample size requirements remain a considerable hurdle for creating P. ponderosa LW chronologies longer than 400 years. At the Cat Mesa site, twenty-three sample trees were required to capture a statistically acceptable common signal in adjusted latewood (LW a), whereas only four samples were required for EW. This is significantly higher than sample depth requirements for LW a from the few other chronologies in the region where this statistic has been reported. A future priority should be to develop a conceptual guide for site and tree selection in order to maximize the potential for enhancing LW signal and for creating a robust network of multi-century LW chronologies.

The recent intensification of floods and droughts in the Fraser River Basin of British Columbia has had profound cultural, ecological, and economic impacts that are expected to be exacerbated further by anthropogenic climate change. In part due to short instrumental runoff records, the long-term stationarity of hydroclimatic extremes in this major North American watershed remains poorly understood, highlighting the need to use high-resolution paleoenvironmental proxies to inform on past streamflow. Here we use a network of tree-ring proxy records to develop 11 subbasin-scale, complementary flood- and drought-season reconstructions, the first of their kind. The reconstructions explicitly target management-relevant flood and drought seasons within each basin, and are examined in tandem to provide an expanded assessment of extreme events across the Fraser River Basin with immediate implications for water management. We find that past high flood-season flows have been of greater magnitude and occurred in more consecutive years than during the observational record alone. Early 20th century low flows in the drought season were especially severe in both duration and magnitude in some subbasins relative to recent dry periods. Our Fraser subbasin-scale reconstructions provide long-term benchmarks for the natural flood and drought variability prior to anthropogenic forcing. These reconstructions demonstrate that the instrumental streamflow records upon which current management is based likely underestimate the full natural magnitude, duration, and frequency of extreme seasonal flows in the Fraser River Basin, as well as the potential severity of future anthropogenically forced events.

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