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

Abstract

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.

Agricultural Research Service Weed Science Research: Past, Present, and Future

“…The RRSRU scientists found that elevated CO 2 greatly increased diffuse knapweed ( Centaurea diffusa Lam.) biomass in disturbed mixed-grass prairie, leading to corresponding decreases in plant diversity (Blumenthal et al 2022). In western rangeland, B. tectorum can reduce fire return times from decades to less than 5 yr, with concomitant decreases in ecosystem diversity and the establishment of B. tectorum monocultures (Fusco et al 2019).…”

Intraspecific Variation in Functional Traits of Medicago sativa Determine the Effect of Plant Diversity and Nitrogen Addition on Flowering Phenology in a One-Year Common Garden Experiment

“…Human activities such as agricultural production and fossil fuel combustion add ~200 Tg/year of nitrogen (N) to global ecosystems, approximately equal to that provided by natural N fixation [ 1 ]. Land use changes, climate changes, and N deposition increase are the major causes of biodiversity loss [ 2 , 3 ]. Numerous studies showed that plant functional traits and ecosystem functions changed significantly under N deposition increase and biodiversity loss [ 4 , 5 , 6 ].…”