Studying climate change effects on plant traits: Reflections from an LTER Fellow

Graduate researcher, Kara Dobson, is a Ph.D. student in Dr. Phoebe Zarnetske’s Spatial and Community Ecology (SpaCE) Lab at Michigan State University. Her research focus is on the effects of climate warming and rainfall variability on plant traits.

Kara Dobson thinning plants in a KBS greenhouse experiment. (Photo credit: Phoebe Zarnetske)

Climate change poses a looming threat to the functioning of ecosystems worldwide. Within ecosystems, my interest lies with plants and how they respond to stress caused by climate change. The way plants respond to stress varies widely and is dependent on things such as trait differences between plant species, differences in geographic location (e.g., latitude), or even differences in local climate conditions. Because plant responses to stress vary greatly, there is still a lot that we don’t yet understand in terms of climate change effects on plants.

As a PhD student in Dr. Phoebe Zarnetske’s Spatial and Community Ecology (SpaCE) Lab, my research looks into some of these unknowns. Our lab studies the effects of climate warming on plants using structures known as open-top chambers. We place these chambers directly in the field where they passively increase air temperatures anywhere from 1.5-3.0°C above ambient temperatures, mimicking a warmer climate for the plants within the chambers. Our long-term experiment using these chambers at KBS is coming up on its 8th year of warming, and we investigate changes in plant traits including changes in phenology (i.e., the timing of life cycle events, such as flowering and seed set), plant composition (i.e., diversity and richness), and other traits such as specific leaf area, carbon and nitrogen content, and biomass. 

A set of open-top chambers and rainout shelters in the KBS-LTER REX. (Photo credit: Kara Dobson)

A new experiment in the KBS-LTER, known as the Rain-Exclusion Experiment (REX), introduces a second climate stressor in combination with warming: drought. It is important for scientists to observe the effects of combinations of stressors because future climate projections show that climate stressors will rarely act in isolation and will often co-occur. REX manipulates drought through the use of rainout shelters, which are placed over plants in the field and block rainfall from reaching the plants. These shelters are also tall enough to fit open-top chambers underneath them, allowing for the combination of warming and drought treatments. Within REX, the SpaCE Lab is interested in looking at many of the same plant traits mentioned above, but now investigating how the combination of warming and drought impacts these traits.

Flowering goldenrod in the KBS LTER. (Photo credit: Kara Dobson)

For my PhD research, my main research interest lies with a specific plant trait: plant volatile organic compound (VOC) emissions. VOCs are chemical compounds plants emit from their leaves and flowers, and these compounds can aid plants in defense, pollinator attraction, and communication. They are an important plant trait that help plants in a wide array of stress responses. However, different stressors can alter both the type of VOCs emitted and the amount of VOCs emitted. An interesting example of this is the ability of plants to know when they are being eaten by an insect and emit VOCs that attract parasitoids (insects that lay their eggs in other insects), which then kill the insect eating the plant. Examples such as these have been noted for multiple plant and insect species, demonstrating the effectiveness of plant VOCs functioning as a defense against insect herbivores. However, less is known about how abiotic stressors, such as climate change stressors, affect these VOC emissions. There have been previous studies looking at climate change stress effects on VOC emissions for some plant species, but as stated earlier, much is still unknown for many common species in many regions around the world.

To help fill some of these knowledge gaps, I am interested in looking into the effects of warming and drought stress on VOC emissions from goldenrod (Solidago canadensis/altissima) and possibly red clover (Trifolium pratense). Goldenrod and red clover are common flowering plant species in Michigan that both emit VOCs for defense and communication. Red clover is also occasionally used as a cover crop species, and therefore has an applied agricultural aspect. This past summer, I was able to collect VOCs from goldenrod leaves in the new REX experiment to observe differences in VOC emissions for plants undergoing warming, drought, warming + drought, and ambient climate treatments. I plan to repeat this sampling for 2 more years, giving 3 consecutive years of plant VOC emissions data. This upcoming summer I hope to also begin collections of VOCs from red clover.

These data will demonstrate whether warming and drought stress alter VOC emissions for these species. In turn, this can inform us on how well the plants are able to defend themselves and function within these different climate scenarios. Climate stress experiments such as these are crucial in our efforts to plan for and mitigate the effects of climate change on ecosystems around the globe.