13CO2 pulse labeling campaign of young oak trees (Quercus rubra) in Innsbruck University Botanical Garden
Meet an Ecology-PhD student: Akira Yoshikawa
Impact of drought on carbon allocation in tree species with contrasting hydraulic architecture
It was only after living abroad for years that I realized how strongly my childhood memories were connected to the forest I grew up in. While there wasn’t anything extraordinary about the planted forest of cedar and cypress of my youth, we knew as kids where we could catch rhinoceros beetles, dig up bamboo shoots, or find persimmons and plums. Today when I find myself in similar forrests, it feels like home. I believe such a sense of belonging to an ecosystem, as opposed to a sociopolitical system, is common for many people, regardless of their native landscape.
I became interested in trees as a subject of study when I started my master’s degree in Kyoto. I was surprised how little I understood about the inner workings of a subject that is so ubiquitous in my daily life. How do trees maintain water and nutrient transport in a dynamic environment? How do sessile trees live for so many years while exposed to a variety of stressors and “bad years”? These questions eventually led me to become specifically interested in the fate of carbon in trees and as well as carbon’s role in survival of trees during stress.
Plants assimilate CO2 to synthesize carbohydrates, converting light energy into the chemical energy that most terrestrial life rely on. This carbon is then transported through phloem and allocated for various life processes, including growth and respiration. The allocation of carbon in trees has been a focus of extensive research because of its implications for the well-being of trees, as well as its effects on the global terrestrial carbon cycle. My PhD research focuses on the role of hydraulic architecture in carbon allocation of trees under varying intensities of drought. Responses of tree species to drought stress differ greatly based on the architecture of their vascular system. Recent studies have highlighted coordination between hydraulic traits in roots, stem, and leaves, but little is known about how the coordinated hydraulic function affects phloem transport and subsequent carbon allocation during and after drought. Using a stable carbon isotope (13C), we aim to trace how recently assimilated carbon is allocated under different intensities of drought and subsequent recovery in species that possess contrasting hydraulic architecture. By monitoring the coupling of hydraulic architecture and carbon-cycle during drought, as well as evaluating the vulnerability of phloem transport to drought, we aim to contextualize the observed carbon allocation responses in the broader framework of drought resilience.
Our research group, Plant, Soil and Ecosystem Processes at University of Innsbruck, studies biogeochemical processes, particularly those related to carbon, water, and nitrogen in forest and grassland ecosystems. We are a part of broader global efforts to predict future ecological responses to climate change. Many of the ecological studies of this sort feel particularly urgent in the face of climate crisis. While this is certainly our primary concern, fundamental curiosity - which will always have its place in science - often stems from a simple connection to our land.
