Spatio-temporal differences in leaf physiology are associated with fire, not drought, in a clonally integrated shrub

Authors: WEDEL, EMILY - Kansas State University; O'KEEFE, KIMBERLY - University Of Wisconsin; NIPPERT, JESSE - Kansas State University; HOCH, BRADEN - Kansas Department Of Agriculture; O'Connor, Rory

Submitted to: AoB Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2021
Publication Date: 6/9/2021
Citation: Wedel, E.R., O'Keefe, K., Nippert, J.B., Hoch, B., O'Connor, R.C. 2021. Spatio-temporal differences in leaf physiology are associated with fire, not drought, in a clonally integrated shrub. AoB Plants. 13(4). Article plab037. https://doi.org/10.1093/aobpla/plab037.
DOI: https://doi.org/10.1093/aobpla/plab037

Interpretive Summary: Many woody plants that are expanding their range in grasslands resprout after a disturbance such as herbivory or fire, and some of these woody plants are also clonal. Clonal woody plants spread laterally through horizontal connections and belowground buds in the soil. Clonal woody plants are unique in that they can potentially distribute resources like water and nutrients to other parts of the clone to mitigate stress caused from disturbances. However, we do not know how variable the plant’s physiology is from the oldest to the youngest part of the clone, and how that changes after a disturbance like fire. In our study we found that Cornus drummondii’s leaf physiological traits do not vary depending on if they are in the center, middle, or edge of the clone. However, differences were found between the center and edge of clones that had resprouted with new growth following a disturbance like fire. These findings will help better inform ecosystem and climate change models when determining carbon or water dynamics of woody encroached mesic grasslands like the Tallgrass Prairie of North America.

Technical Abstract: In highly disturbed environments, clonality facilitates plant survival via resprouting after disturbance, resource sharing among interconnected stems and vegetative reproduction. These traits likely contribute to the encroachment of deep-rooted clonal shrubs in tallgrass prairie. Clonal shrubs have access to deep soil water and are typically thought of as relatively insensitive to environmental variability. However, how leaf physiological traits differ among stems within individual clonal shrubs (hereafter ‘intra-clonal’) in response to extreme environmental variation (i.e. drought or fire) is unclear. Accounting for intra-clonal differences among stems in response to disturbance is needed to more accurately parameterize models that predict the effects of shrub encroachment on ecosystem processes. We assessed intra-clonal leaf-level physiology of the most dominant encroaching shrub in Kansas tallgrass prairie, Cornus drummondii, in response to precipitation and fire. We compared leaf gas exchange rates from the periphery to centre within shrub clones during a wet (2015) and extremely dry (2018) year. We also compared leaf physiology between recently burned shrubs (resprouts) with unburned shrubs in 2018. Resprouts had higher gas exchange rates and leaf nitrogen content than unburned shrubs, suggesting increased rates of carbon gain can contribute to recovery after fire. In areas recently burned, resprouts had higher gas exchange rates in the centre of the shrub than the periphery. In unburned areas, leaf physiology remained constant across the growing season within clonal shrubs (2015 and 2018). Results suggest single measurements within a shrub are likely sufficient to parameterize models to understand the effects of shrub encroachment on ecosystem carbon and water cycles, but model parameterization may require additional complexity in the context of fire.