Soil disturbance and invasion magnify CO2 effects on grassland productivity, reducing diversity

Authors: Blumenthal, Dana; CARILLO, YOLIMA - Western Sydney University; Kray, Julie; PARSONS, MATTHEW - Resource Environmental Solutions, Llc; MORGAN, JACK - Retired ARS Employee; PENDALL, E - Western Sydney University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Grasslands are threatened by climate change, disturbance, and plant invasion, but the combined effects of these changes are poorly understood. We tested effects of elevated carbon dioxide (CO2) and warming on plant and soil responses in both intact mixedgrass prairie and disturbed prairie seeded with native and invasive forbs. Over five years, the combination of disturbance and invasion dramatically increased the sensitivity of prairie to elevated CO2 and warming, increasing aboveground plant biomass ten-fold, reducing diversity, and slowing soil carbon accumulation. These results demonstrate the need to incorporate land use into predictions of climate change effects. For rangeland managers, limiting anthropogenic soil disturbance will be critical for maintaining ecosystem services as CO2 and temperatures continue to increase.

Technical Abstract: Climate change, disturbance, and plant invasion threaten grassland ecosystems, but their combined and interactive effects are poorly understood. Here, we demonstrate that the combination of disturbance and plant invasion greatly increases the sensitivity of mixedgrass prairie to elevated carbon dioxide (eCO2) and warming. We established subplots of intact prairie and disturbed/invaded prairie within a Free Air CO2 enrichment (to 600 ppmv) by infrared warming (+1.5° C day, 3° C night) experiment and followed plant and soil responses for five years. Elevated CO2 initially led to moderate increases in biomass and plant diversity in both intact and disturbed/invaded prairie, but these effects shifted due to strong eCO2 responses of the invasive forb Centaurea diffusa. In the final three years, biomass responses to eCO2 in disturbed/invaded prairie were 10 times as large as those in intact prairie (+186% vs. +18%), resulting in reduced rather than increased plant diversity (+10% vs. -17%). At the same time, warming interacted with disturbance/invasion to reduce the rate of topsoil carbon accumulation. The strength of these interactions demonstrates the need to incorporate land use into predictions of climate change effects. In contrast to expectations from studies in intact ecosystems, eCO2 may threaten plant diversity in ecosystems subject to soil disturbance and invasion. In semiarid grassland, limiting anthropogenic soil disturbance will be critical for maintaining ecosystem services as CO2 and temperatures continue to increase.