PS 15-216 - The state of knowledge on western larch (Larix occidentalis), a deciduous conifer, through systematic literature review

Abstract: Western larch (Larix occidentalis) is a long-lived deciduous conifer species native to interior northwest of North America. It is an early-successional species known its high fire tolerance due to thick bark, and high drought tolerance relative to other co-occurring trees. Western larch is a commercially important timber species, used in the production of laminated beams, trusses, and joists. Its dense wood also makes it a popular for use as firewood. Western larch is also known for its appealing golden-yellow foliage during the fall. However, much is still unknown about this species, particularly regarding its foliar senescence, relative to other larch species.

We conducted a systematic literature review to determine the current state of knowledge on western larch senescence, the chemistry of senescence, the impacts of senescence on other species, and how its foliar characteristics compare to sympatric evergreen conifers. Literature was retrieved through Google Scholar, Web of Science, and Wiley Online Library databases using the search terms “western larch” or “larix occidentalis” in combination with either “senescence”, “phenology”, “chemistry”, “ecology”, or “evergreen foliar relationship”. Additionally, we quantified the amount of literature that pertained to western larch and compared it to the amount of literature available for other species of larch, including alpine larch (Larix lyallii), tamarack (Larix laricina) and European larch (Larix decidua), using the same search terms mentioned previously, changing only the taxonomic descriptor.

Preliminary results showed that there is a lack of literature concerning how western larch senescence impacts other species. Additionally, it revealed that there was also a lack of literature comparing the foliar characteristics of western larch and co-occurring evergreen conifers. Furthermore, we also discovered there is a significant lack of literature for western larch in general as compared to other species of larch, with a majority of the literature pertaining to either European larch or tamarack, or other species of larch not included in this review. When considered relative to the extent of species ranges, western larch is particularly underrepresented, and European larch overrepresented in the literature. Our assessment of these literature gaps constitutes a potential research agenda for improving our knowledge of western larch ecology, as this species faces unprecedented changes in climate across its range in the future.