Effect of warming temperatures on flowering phenology

Wrobleski, Amy, Phoebe Zarnetske, Kileigh Welshofer, Mark Hammond, Jennifer Lau
Michigan State University

Presented at the All Scientist Meeting and Investigators Field Tour (2017-10-06 to 2017-10-07 )

Warming temperatures have been shown to shift flowering times earlier in the season. However, flowering phenology may vary by species origin, site, and year. To assess these factors, two early successional field study sites were established: one in southern Michigan at the Kellogg Biological Station (KBS) LTER, and the other in northern Michigan at the University of Michigan Biological Station (UMBS). In 2015, we installed a factorial experiment at each site that manipulated warming with large open top chambers (OTCs) to assess effects on flowering (a total of 24 plots per site). Every 3 days beginning in March 2016 and 2017, we recorded flowering onset per species in each plot. We expected that species in warmed plots would flower earlier than those in ambient plots regardless of site or herbivore treatment. However, at KBS, exotic species flowered earlier than native species in both years, but in 2016 warmed and ambient plots flowered at the same time. At UMBS exotics flowered later than natives in 2016, and in 2017 exotics and natives flowered at the same time. In 2016 at UMBS, all warmed plants flowered a few days earlier than ambient plants, however the difference was not significant. This trend did not continue in 2017. Origin is likely too broad a category to explain species responses to climate warming. Instead, factors including life history, physiological traits, and longer-term biotic interactions may provide more insight. Further, the influence of year and site effects in the short term supports the need for longer-term measurements to tease apart the relative influence of these factors on phenological responses to climate change.