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Trees have evolved to time flowering to maximize outcrossing, minimize exposure to damaging frosts, and synchronize development with soil moisture and nutrient availability. Understanding the environmental cues that influence the timing of reproductive budburst will be important for predicting how flowering phenology of trees will change with a changing climate, and aid in the time-sensitive management of seed orchards. We examined how temperature influenced the timing of female flowering of coastal Douglas-fir with over 4500 flowering observations of trees from 12 sites across western Oregon and Washington. We predicted flowering dates by modifying chilling and forcing effectiveness functions from a model of vegetative budburst of Douglas-fir. We also examined whether genetic variation in Douglas-fir influenced the relationships between chilling and forcing accumulations using flowering observations from two common-garden experiments with trees from 60 populations from a diverse range of climates. Our reproductive budburst model predicted the day of flowering within an average of five days of the observed flowering dates across all sites and years. Fewer hours of forcing temperatures were required for flowering on sites that had experienced high chilling. Warmer temperatures in the future will likely result in earlier flowering on sites which currently have high chilling; however, sites which currently experience low chilling may display no change or possibly even a delay in flowering. Douglas-fir genotypes from different geographic regions flowered in the same order from year to year in common gardens, indicating that both temperature and genetic variation influence flowering. Genetic variation in flowering dates was more strongly related to summer drought of seed source locations than to cold winters. Knowledge of the environmental cues and genetic variation in timing of flowering can help predict how future changes in temperature under various climate models could change flowering time across the range of coastal Douglas-fir. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model the climate niche of Pinus ponderosa and Pseudotsuga menziesii varieties. [•] Classification errors were less than 5% and were mostly false positives. [•] Niche space was mapped for the decade surrounding 2060 using GCM ensemble output. [•] Projected impacts were more severe for P. ponderosa than for P. menziesii. [•] Projections were dire for the varieties occurring in Mexico. [Copyright &y& Elsevier]

• Stem volume yields at rotation age can be predicted by growth model simulation. • Relative genetic gain decreased, but absolute genetic gain increased over time. • Simulated gain at rotation age 50 was about 30% of the realized gain at age 10/12. Application of progeny test breeding values to forecast yield gains at rotation-age in genetically improved stands remains a very challenging yet crucial task for breeders of Douglas-fir and other long-rotation timber species such as western hemlock, white spruce, Norway spruce, and Scots pine. Evaluation of the economic returns on genetic improvement requires reliable estimates of yield gains at rotation age. Large-plot realized gain trials should provide more accurate estimates of yield gain than inferences from progeny tests, but are most dependable when they reach rotation age or at least approach rotation age. A set of coastal Douglas-fir realized genetic gain trials in western Oregon, based on a first-generation breeding program, was measured most recently at plantation ages ranging between 17 and 21 years. The trial was established on five sites at a spacing wide enough (3.6 × 3.6 m) to assume that the trees could be grown to rotation age with no further silvicultural intervention. A growth model, CIPSANON v. 4.0, projected the current tree lists from these trials to plantation age 60 years to facilitate estimation of yield gains at various rotation ages up to 60 years. The following two simulation approaches were explored: (1) apply genetic-gain multipliers developed from a previous study for diameter and height growth, and (2) assume that genetic gain differences were fully represented by plot-level site index expressed at the most recent measurement. The two approaches resulted in similar estimates of realized yield gain at plantation ages up to 60 years. Relative gain decreased over time, but absolute gain (in cubic meters or board feet) increased over time. Relative stand volume gain simulated to the average current rotation age of 50 years was about 30% of the relative realized gain measured at plantation age 10/12 years (birth age 13/15 years) and about 38% of the relative realized gain measured at plantation age 17–21 years (birth age 20–24 years). Several validation needs were identified including magnitude of genetic-gain multipliers, duration of annual multiplier application over the duration of a simulation, adjustment of multipliers as the stand ages, and most appropriate multiplier resolution (tree versus stand). A potentially critical knowledge gap remains about any genetic improvement effects on yield gains associated specifically with increased carrying capacity that would be consistent with the crop ideotype concept. [ABSTRACT FROM AUTHOR]