Internal Carbon Transport
A CO2 sensor positioned inside of a sweetgum tree to measure internal [CO2].
Our current research on the internal transport of root-derived CO2 represents a transformative contribution to the fields of tree ecophysiology and forest biogeochemistry and has potential to add significantly to our mechanistic understanding of carbon cycle functioning in forest ecosystems. Specifically, we have provided empirical evidence that the internal flux of CO2 from root systems into tree stems can be as large as the total CO2 efflux from the soil surface. This observation directly challenges a long-standing paradigm in plant physiological ecology that suggests root-respired CO2 has a single fate—diffusion to the soil atmosphere. A corollary to this paradigm is that all CO2 derived from root respiration can be measured as part of soil CO2 efflux to the atmosphere. Thus, measures of soil CO2 efflux may substantially underestimate belowground respiration. Additionally, the conventional approach to estimating belowground carbon allocation hinges on the paradigm that root-respired CO2 has only a single pathway to enter the atmosphere suggesting that this approach may also substantially underestimate belowground carbon allocation. We have a number of on-going and collaborative projects related to the internal transport of CO2 in tree stems and plan to continue exploring this promising field of inquiry into the future.
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