Plant diversity decreases potential nitrous oxide emissions from restored agricultural soil

Abstract

Plant diversity has been shown to mitigate nitrous oxide (N2O) emissions from soil in some ecosystems. We tested the generality of this diversity effect on ecosystem functioning, as an application of ecological theory by quantifying potential nitrous oxide emissions in grasslands restored from agriculture containing high and low diversity. We performed an initial plant survey to develop the study design from quadrat analyses (used to determine sampling frame size that maximizes variance in plant community structure), semivariogram analyses of plant community PCA scores (used to determine minimum distance between sampling frames), and upper and lower quartiles of plant diversity (Shannon’s diversity). We sampled high (per field n = 6, total n = 60) and low (per field n = 6, total n = 60) diversity (high diversity: mean Shannon diversity index = 1.69; low diversity: mean Shannon diversity index = 0.73) plant communities within 10 to 12 y old restorations co-located at Nachusa Grasslands (Franklin Grove, IL, USA). We found potential N2O emissions were nearly seven times greater in low diversity compared to high diversity communities. Inorganic N availability, relative amounts of nitrification and denitrification, and water extractable C did not explain difference in potential N2O emission from soil with contrasting plant diversity. Although the mechanism for large variation in this ecosystem function corresponding with biodiversity remains undetermined, this work shows that management for plant diversity may reduce N2O emissions from soil.