When I started my field season in mid-February this year, I thought about a recent snow storm that we had just experienced a few weeks back (Jonas). In January, I remember watching the snow and ice lay gently outside of my window. I immediately thought about how hard life must be for the understory spring plants. You and I can quickly put on our winter jacket when it begins to snow and easily shed layers on days that reach 60 °F, but plants don’t have this luxury. In addition to chilly temperatures, the native plants residing in the bottomlands where I work experienced heavy rains in December. The thick, insulating layer of leaf litter was washed away, leaving many plants in the spring ephemeral community exposed to the recent frost. Dealing with irregular weather conditions is not a new challenge to the early bloomers, but with increasing variability in weather patterns due to climate change, should we be worried?
If you live in North Carolina, you might remember those unusually warm December temperatures. Scientists know that warming temperatures cause some plants to begin making flowers earlier in the season than in the past, while some species are unaffected. If all of the species in the community respond differently to the same environmental cues, species’ flowering periods might begin to overlap, even if they have not in the past. If these plant species share common resources (e.g. nutrients, water, pollinators), they might now have to compete with one another for access to these resources.
How species sharing a limited number of resources are able to live in the same place at the same time is a fundamental question in ecology. If two species share common resources, their ability to coexist is sensitive to environmental conditions, and any change in their interactions with the environment and each other could result in extinction of one of the species. My research examines the relationship between timing of life cycle events and the ability of two plant species, Claytonia virginica and Erythronium umbilicatum, to coexist. From 1978-1982 in Durham, NC, two researchers, Alexander Motten and Diane Campbell, both former graduate students at Duke University, studied the timing of flowering and competition for pollinators between native, understory flowering plants. I can now use their data from 35 years ago to understand if changes in phenology, or timing of life cycle events, influence competitive interactions between two forest herbs.
In February 2015, I set out to work in the Duke Forest in Durham, NC to begin answering these questions. What I wanted to know first was, has flowering time shifted significantly in these native flowering communities since 1980? Second, does flowering time affect how reproductively successful a plant is? I spent the first few weeks setting up 50 meter transects, where I would return every few days to observe flowering in Claytonia virginica. I recorded first day of flowering, last day of flowering, plant size, and number of fruits and flowers for over 400 plants. Even controlling for the unusually cool weather last spring in my analysis, I found that the length of the bloom period in 2015 was very similar to the 1980s. In addition, I found that C. virginica plants with longer bloom periods produce more fruits and flowers, but fruit set (fraction of flowers producing fruits) was unaffected by length of flowering period. These data suggest that flowering phenology does influence how reproductively successful a plant is, and phenology hasn’t significantly shifted in one of my species of interest. These spring plants are perennials, which means they can live and reproduce multiple years. Because of this life schedule, one year doesn’t give me enough information to draw conclusions, so I am returning to these communities this year to dig deeper into my questions.
This spring, I set up a few field experiments and identified pollinators of Claytonia virginica and Erythronium umbilicatum in order to elucidate the mechanisms enabling coexistence between these two species. Over the next few years, I will collect data that will help me understand how competition for shared resources is altered in response to climate change. While we can easily adjust our routines in response to atypical weather events, plants have fewer ways to cope. Next time you are enjoying the warm, spring weather or experiencing a freezing cold walk with the dog, think about the forest understory plant community and how they must feel!
About this blog:
I created this blog as part of the Phipps Botany in Action Program, 2015 - 2017