Graduate researcher, Moriah Young, is a Ph.D. student in Dr. Phoebe Zarnetske’s lab at Michigan State University. The lab uses open top chambers (OTCs) to study how biotic interactions and climate change directly and indirectly affect community structure and function at the KBS LTER.
Climate change is a pressing threat to ecosystems around the world. From warmer temperatures to more unpredictable rainfall, climate change has shown to have a myriad of effects on ecosystems. Most research has focused on direct effects of climate change on species. For example, how does warming affect plants? How does it affect the insects that eat plants? How does drought affect plants? And so forth. But in reality, ecosystems are complex webs of interactions between species and their surrounding environments. This means that to determine the effects of climate change on ecosystems, we need to not only study things in isolation, but also climate change’s impact on their complex interactions.
The response of soil communities to climate change is particularly complex and difficult to untangle. Interactions between plants and the soil community take place through plant-soil feedbacks (PSF), which describe a process where plants alter the abiotic and biotic properties of the soil where they live. These changes in turn feed back on the plant and change their performance and physiology.
Soil biota can have both beneficial or harmful effects on plants. To add even more complexity, plant-soil feedbacks can in turn affect the insects that feed on plants aboveground! For example, soil organisms, such as plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi, have been shown to increase plant growth by improving nitrogen fixation, making plants more palatable to herbivores. Thus, this feedback between plants and the soil biota has multi-trophic effects and therefore plays an important role in community structure, function, and response to environmental change. Despite this knowledge, however, we still lack a mechanistic understanding of how climate change will alter multi-trophic interactions among soil microbial communities, plants, and insect herbivores.
Given these knowledge gaps, my PhD research focuses on understanding the effects of climate change on soil biota, plant, and insect herbivore interactions and more specifically, how soil microbes mediate those above ground responses to climate stressors.
The Rain Exclusion eXperiment (REX) is a large-scale rainfall manipulation experiment that began this past spring 2021 at the KBS LTER Main Cropping System Experiment (MCSE). It also happens to be a perfect field experiment for me to address my research questions. This experiment uses rainout shelters to create droughts throughout the growing season. Additionally, in the early successional treatments (T7s) of the MCSE, there are also Open Top Chambers (OTCs) that simulate climate warming by passively increasing air temperature. At the same time, these structures allow natural levels of precipitation, light, and gas exchange to occur. The OTCs warm the inside on average about +1.8°C above ambient temperatures and they stay up all year round through the winter. An insecticide is also applied to manipulate insect herbivory. This all means that I am using three different manipulations in my research – drought, warming, and the presence of herbivores.
My PhD research works to leverage the REX project by collecting samples and using additional experiments to quantify the direct and indirect effects of climate warming, insect herbivory, and drought on soil biota, plant, and herbivore interactions. I seek to answer the following broad questions: (1) How does the composition and structure of a soil microbial community differ in the presence and absence of warming temperatures, insect herbivores, and drought? And (2) What is the soil community’s influence on plant traits, stress responses and insect preferences in the presence or absence of warming, insect herbivory, and drought?
One of my favorite moments in the field this past summer was collecting soil cores with a large group of researchers. We collected soil cores from every plot within the REX project, which was a huge group effort! Despite the extreme heat and large task at hand, we marched across the LTER into marked REX plots with smiles across our sweat glistened faces. Working with this large group reminded me of why I love fieldwork so much – it’s the people and the comradery that comes out when you’re working in the field together. It can be sweaty, dirty, straining work, but with a good group of people, the work is rewarding, and dare I say fun. With the samples that I collected, I am specifically interested in uncovering the short and long-term temporal changes of the bacterial and fungal communities within these plots. To do this I will extract DNA from these samples, which I’m excited to do this spring 2022, so that I can analyze the microbial communities within each sample and compare them across treatments and time.
Another exciting experiment I conducted this past summer was an insect preference trial. I studied two species that are very common in the LTER – Canada goldenrod (Solidago canadensis) and red-legged grasshoppers (Melanoplus femurrubrum). I wanted to answer the question: do climate stressors affect the relationship between these two species? I collected grasshoppers from the early successional fields in the LTER and then didn’t feed them for 24 hours so they would be hungry. I then gathered goldenrod leaves from ambient, warmed, drought, and warmed + drought treatments in REX. Once I had the grasshoppers and goldenrod, I began the preference trials where grasshoppers fed on leaves of goldenrod of each treatment for 20 hours inside insect cages. After the 20 hours, I measured the amount of leaves eaten before and after the trials. In the end I found no differences among treatments for how much each grasshopper ate. However, I did find that warming appeared to have a stronger effect on preference compared to drought. This could be due to the fact that the grasshoppers are too generalist of an insect herbivore to see differences among treatments. Our warming treatment also started before and therefore is longer than the drought treatment which could explain warming’s stronger effect on insect preferences. Trait variation in goldenrod and subsequently plant palatability might also change overtime with persistent long-term drought and warming. Finally, I could be overestimating herbivory due to the shrinking effect of leaves after harvesting. I plan to conduct this experiment again in summer 2022 which will help me address these factors.
My research at the KBS LTER is only beginning and I’m looking forward to continuing to look at the data in hand from the experiments carried out from the 2021 field season and future summers. Ultimately my research will help us better understand how climate change will affect plant communities so we can improve our ability to predict future changes in community structure and function in a changing world.