Science
A mystery in the fingerprint of global warming
For plants, the timing of flowering is a critical part of their life cycle. If plants flower too early or too late, they could miss the timing of their important pollinators or the timing of when animals like migrating birds come through and disperse their fruit.
Many flowering plants bloom earlier in response to warmer temperatures, and earlier flowering times of plants is often considered a fingerprint of global warming. Some species, however, either do not respond to warm temperatures, and others flower LATER when it was warm the PREVIOUS summer! Here's our earlier work finding this strange pattern.
What explains these exceptions? It could be due to several things: 1) plants could be responding to other cues like day length or soil moisture that may oppose the effects of warming, 2) increased snow fall that may result in delayed snow melt, or 3) warmer winter temperatures could result in unmet chilling requirements that delay when a plant emerges from dormancy.
We think that another reason may help explain why some species seem to break the rule: the timing of bud formation and its interaction with warmer temperatures and longer growing seasons. Shrubs, trees and berry plants in the northern latitudes start to develop their flower buds one or two years before they are needed. Our hypothesis is that in a year with a longer than usual growing season, a first set of buds may open in spring (as usual) and then some of the some of the buds intended for the next spring develop so far that they open in late summer or fall (a “late bloomer,” as we are calling it). The following spring, even if the timing of spring is early, these plants could take longer to flower as the remaining buds are less developed than the ones that already burst in the previous fall. Our research, funded by the National Science Foundation, is testing this idea.
Research Goal
We seek to evaluate whether unusual timing of flowering in response to warming temperatures (delayed or no apparent change in date of flowering) is explained, in part, by disruptions of flower development.
University of Connecticut scientist Dr. Pam Diggle sets up an open top chamber for the warming experiment in the boreal forest at Bonanza Creek LTER. Photo by C. Mulder.
Our approach
1. Open Top Chamber Experiment
We are using open top chambers (pictured above) in the Bonanza Creek Long Term Ecological Research Program sites near the University of Alaska Fairbanks to experimentally warm woody boreal forest species for one or two years, and leaving some plots as controls. These species include Arctostaphylos rubra (bearberry), Rhododendron groenlandicum (Labrador tea), Rosa acicularis (prickly rose), Rubus chamaemorus (cloudberry), Shepherdia canadensis (buffaloberry), Vaccinium vitis-idaea (lowbush cranberry, Vaccinium uliginosum (blueberry), and Viburnum edule (highbush cranberry). Using Scanning Electron Microscopy at the University of Connecticut, we are looking at the development of leaf and flower primordia (the leaves or flowers forming in the buds) in the year following warming and two years after warming.
2. Citizen Science
Join scientists from University of Alaska Fairbanks and University of Connecticut in this research by collecting winter buds or making observations of late bloomers.
Using overwintering Vaccinium vitis-idaea buds collected by volunteers from a wide range of locations across Alaska will allow us to determine whether our results for the impact of environmental conditions on the flower bud development near Fairbanks are representative of those from a much larger area.
Observations of late-flowering plants of any of our focal species, recorded through our project on the Local Environmental Observers (LEO) Network, a program of the Alaska Native Tribal Health Consortium, will also allow us to determine if there are any geographic or climatic patterns in late blooming plant observations.
A late blooming prickly rose (Rosa acicularis) observed by Arctic Light Elementary STEM Afterschool Club citizen scientists, October 16, 2017. Photo by G. Nelson.
Why is this research important?
The timing of flowering of the species we are studying, many of which are berry species, is important for wildlife and people. If insects come out early in a warm, early spring, but the flowers are delayed, there could be a mismatch in timing, decreasing pollination and berry abundances. This could have rippling effects for animals and people who depend on berries. In the far North, timing is EVERYTHING, and we are helping better understand how this timing works in a more variable, warmer climate.
Models used to study climate change include predictions of how warming will effect plant phenology (the timing of leaf-out, flowering, etc.). Existing phenological models cannot explain exceptions to the common association of advancing phenologies with warming temperatures. Through this research, we can help make these models better, and hopefully provide better predictions for climate change research, planning, and decision making.