Legacies of precipitation influence primary production in Panicum virgatum

Authors: HECKMAN, ROBERT - University Of Texas; RUEDA, AUSTIN - University Of Arizona; BONNETTE, JASON - University Of Texas; ASPINWALL, MICHAEL - Auburn University; KHASANOVA, ALBINA - Lawrence Berkeley National Laboratory; HAWKES, CHRISTINE - North Carolina State University; JUENGER, THOMAS - University Of Texas; Fay, Philip

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2022
Publication Date: 11/14/2022
Citation: Heckman, R.W., Rueda, A., Bonnette, J.E., Aspinwall, M.J., Khasanova, A., Hawkes, C.V., Juenger, T.E., Fay, P.A. 2022. Legacies of precipitation influence primary production in Panicum virgatum. Oecologia. 201(1):269-278. https://doi.org/10.1007/s00442-022-05281-x.
DOI: https://doi.org/10.1007/s00442-022-05281-x

Interpretive Summary: Plant productivity tends to increase with precipitation. However, this relationship is not always straight-forward. Frequently, the water availability that plants have previously experienced will impact their responses to current water availability. To better understand how plants will respond to precipitation, which is becoming increasingly variable from year to year, we need to quantify the impact of past water availability on current responses and what drives that effect. In this study, we examined how the candidate biofuel species, switchgrass, responds to changes in precipitation. We found that plants subjected to drought, which had previously grown under wet conditions were frequently larger than plants that had grown under consistent, longer-term drought. Additionally, the number of tillers that a plant had in the previous year was a strong predictor of plant responses to precipitation in the current year. Together, this work improves our understanding of switchgrass responses to precipitation and may improve our ability to predict switchgrass yields under a changing climate.

Technical Abstract: Precipitation is a key driver of primary production worldwide, but primary production does not always track year-to-year variation in precipitation linearly. These time lags, or legacies, in plant responses to changes in precipitation are important for understanding how communities and ecosystems will respond to increasingly variable precipitation. Legacies can be driven by multiple mechanisms, including persistent changes in plant physiological and morphological traits, as well as changes to the physical environment, such as water table depth. Because multiple mechanisms can promote legacies, the magnitude of legacies can also differ when the system shifts from wet-to-dry versus dry-to-wet conditions. We used multiple precipitation manipulation experiments in central Texas, USA to evaluate the magnitude, duration, and potential mechanisms driving precipitation legacies on aboveground primary production of the perennial C4 grass, Panicum virgatum. Across these experiments, P. virgatum exhibited stronger legacies of past wet years? on current-year productivity responses to drought than of past dry years?. Plants that had previously grown under wet conditions generally performed better than expected when exposed to drought. Additionally, previous year tiller counts, a proxy for meristem availability, was an important mechanism of legacy effects on aboveground production. As climate changes and precipitation extremes—both dry and wet—become more common, better understanding legacies of precipitation will improve our ability to predict community and ecosystem dynamics.