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

Climate change, disturbance, and plant invasion threaten grassland ecosystems, but their combined and interactive effects are poorly understood. Here, we examine how the combination of disturbance and plant invasion influences 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 (-17% vs. +10%). At the same time, warming interacted with disturbance/invasion and year, reducing the rate of topsoil carbon recovery following disturbance. The strength of these interactions demonstrates the need to incorporate disturbance 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.USAGE NOTES: Climate treatments included: (1) ct: ambient CO2 and temperature, (2) cT: infrared warming to increase canopy temperature 1.5 ˚C during the day and 3 ˚C at night, (3) Ct: free-air CO2 enrichment to 600 ppmv, and (4) CT: CO2 enrichment plus warming. Climate treatments were applied to "rings" (i.e. whole plots). Within rings, vegetation treatments (i.e. subplots) included (1) intact prairie, and (2) disturbed/invaded prairie. Within disturbed/invaded prairie subplots, we tilled two 20-cm × 100-cm strips, separated by a 15-cm x 100-cm strip of existing prairie vegetation in the center, and bordered by two 7.5-cm x 100-cm strips of prairie vegetation on the sides. For Centaurea diffusa biomass data in Table 2, strip types are coded as (1) tilled, and (2) vegetated. For both tables, the harvested area is indicated in the "area of harvested subplot" column. For more details, please refer to Figures 1 and S1 in the associated manuscript. DATA DESCRIPTION: This dataset includes two data tables and a readme file.Funding provided by: USDA-ARS Pasture, Forage and Rangeland Systems Program*Crossref Funder Registry ID: Award Number: Funding provided by: USDA-CSREES Soil Processes Program*Crossref Funder Registry ID: Award Number: Grant No. 2008-35107-18655Funding provided by: US DOE Office of Science (Biological and Environmental Research) through the Western Regional Center of the National Institute for Climatic Change Research at Northern Arizona University*Crossref Funder Registry ID: Award Number: Funding provided by: US NSFCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: DEB no. 102155