AUTHOR=Harrington Constance A. , Gould Peter J. , Cronn Richard 

TITLE=Site and provenance interact to influence seasonal diameter growth of Pseudotsuga menziesii

JOURNAL=Frontiers in Forests and Global Change

VOLUME=Volume 6 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/forests-and-global-change/articles/10.3389/ffgc.2023.1173707

DOI=10.3389/ffgc.2023.1173707

ISSN=2624-893X

ABSTRACT=Provenances of Douglas-fir (Pseudotsuga menziesii var. menziesii) planted across a wide range of environments were used to evaluate diameter growth and phenology to an extreme heat event and to seasonal conditions. Sampling was done in nine common gardens in western Oregon and Washington, USA that included a coastal site, a low elevation interior site, and high elevation interior site on three latitude bands. In 2021, three provenances at four sites were monitored for late-season diameter growth following an extreme heat event in June. In 2022, five provenances were evaluated for full-seasonal diameter growth at four growth intervals across all nine sites. Growth after the 2021 extreme heat event varied by planting site, with the greatest growth observed at mild (cooler/wetter) sites and the least growth observed at arid (hotter/drier) sites. Comparisons of diameter growth over the late season period (i.e., July – October) showed that 2022 growth was 1.25-fold to 3.70-fold higher, presumably due to premature growth cessation in 2021. In 2022, diameter growth rates showed significant variation by site and provenance; the interaction between site and provenance was significant in all but the first growth interval. Intra-seasonal growth rates were not consistent across sites; there was substantial diameter growth early in the season on sites with continental climates, little diameter growth by any provenance after early August at three high elevation sites, and most sources continued growth later in the season at coastal sites.  Some sources had consistent patterns of growth across sites, but other sources were more variable in their growth patterns; a key factor in this variability was susceptibility of some provenances to foliar diseases. Cambial phenology varied with genetic and site factors that control the timing of growth and intrinsic growth rates. In addition, the interaction between genotype and site resulted in some provenances performing better than others on some sites as a function of disease susceptibility or response to environmental factors. Understanding phenology of seed sources under a range of site conditions should help predict diameter growth under different climate conditions in the future.