Above-ground plant properties are not leading indicators of grazing-induced soil carbon accrual in the Northern Great Plains

Authors: Reinhart, Kurt; Rinella, Matthew - Matt; Waterman, Richard; SANNI WOROGO, HILAIRE - University Of Parakou; Vermeire, Lance

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2023
Publication Date: 12/30/2023
Citation: Reinhart, K.O., Rinella, M.J., Waterman, R.C., Sanni Worogo, H., Vermeire, L.T. 2023. Above-ground plant properties are not leading indicators of grazing-induced soil carbon accrual in the Northern Great Plains. Global Change Biology. 158. Article 111509. https://doi.org/10.1016/j.ecolind.2023.111509.
DOI: https://doi.org/10.1016/j.ecolind.2023.111509

Interpretive Summary: Problem- Managing grasslands to sequester carbon is of global importance, but effects of grazing on soil organic carbon (SOC) stocks remain uncertain. Grazing induced changes to vegetation may foretell change in SOC of rangelands. Accomplishment- We determined that several metrics of plant biomass and composition were useful predictors of SOC accrual in the short-term (~5 years) and may inform the practice of carbon ranching.

Technical Abstract: A new aim for grassland management is to increase soil carbon stocks and to offset CO2 emissions by companies. Shifts in plant biomass and composition likely foretell a change in SOC stocks and may inform the practice of carbon ranching. Unfortunately, little is known about how grazing-induced shifts in vegetation correspond with changes in SOC stocks. Here, we tested for relationships between changes in (and average) plant properties on changes in SOC stocks. We used data from a (5-yr) bovine grazing experiment with four grazing treatments in a semi-arid grassland dominated by C3 perennial graminoids. We analyzed how plant biomass, diversity, and species composition relate to grazing-induced changes in SOC stocks for three stock metrics. In grazed paddocks, SOC stocks tended to decrease with increases in plant diversity and root biomass. In surface soils, SOC accrued with increases in plant above-ground biomass. A large fraction of the variation in changes in SOC stocks was explained by shifts in plant composition, especially shifts in biomass of key graminoid species. Specifically, SOC stocks increased with increasing biomass of some C3 perennial grasses and decreased with increasing biomass of other C3 perennial grasses. An increase in the biomass of a C4 perennial grass was associated with reductions in SOC stocks while an increase in the biomass of a C3 invasive annual grass was associated with SOC accrual. Several plant properties exhibited inverse relationships with SOC accrual depending on whether the plant data were estimates of changes in versus averages over the experiment. Our findings support that grazing affected changes in SOC by affecting plant composition, diversity, above-ground biomass, and root biomass.