Drought and warming interact to stimulate N2O emissions in pasture crops
Abstract
Climate change is leading to increases in the frequency and severity of drought and warming for many agricultural regions of the world. Soil temperature and moisture are important factors regulating nitrogen (N) mineralization and nitrous oxide (N2O) emissions, both directly and indirectly via plant mediated processes. We measured effects of future climate changes on N2O emissions in well-drained pasture soil exposed to drought (60% precipitation reduction in cool season), warming (+3°C year-round), and their combination, on crops of alfalfa and tall fescue in temperate southeastern Australia. N2O emission rates were determined using the closed chamber method throughout the cool drought season and warm recovery seasons. Soil nutrient availability was monitored with ion exchange resins, and aboveground biomass production was measured by clipping. The N2O emission rates significantly differed by season, species, climate change treatments, and their interactions. In general, alfalfa (N-fixing legume) had higher N2O emissions than tall fescue (a common pasture grass), especially during winter. Negative fluxes were observed in non-droughted tall fescue plots, whereas droughted plots had net positive fluxes. Warming amplified the effect of drought on increasing emissions compared to ambient temperature plots. In contrast, in alfalfa, both climate treatments produced net positive N2O fluxes, while warming reduced the magnitude of drought-associated increase in N2O emissions, relative to ambient control plots. Drought decreased aboveground biomass in both crops to a larger degree than warming, and N2O fluxes tended to be negatively correlated with aboveground biomass. Nitrate and ammonium availabilities were affected by climate treatments, season, and species, but were not significantly correlated with N2O fluxes. Our research suggests that productive pasture crops diminish N2O emissions, while drought and warming decrease pasture yields and increase N2O emissions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB002.0022P
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0495 Water/energy interactions;
- BIOGEOSCIENCES;
- 1843 Land/atmosphere interactions;
- HYDROLOGY