『Abstract
Global environmental changes are expected to alter ecosystem
carbon and nitrogen cycling, but the interactive effects of multiple
simultaneous environmental changes are poorly understood. Effects
of these changes on the production of nitrous oxide (N2O),
an important greenhouse gas, could accelerate climate change.
We assessed the responses of soil N2O fluxes
to elevated CO2, heat, altered precipitation,
and enhanced nitrogen deposition, as well as their interactions,
in an annual grassland at the Jasper Ridge Global Change Experiment
(CA, USA). Measurements were conducted after 6, 7 and 8 years
of treatments. Elevated precipitation increased N2O
efflux, especially in combination with added nitrogen and heat.
Path analysis supported the idea that increased denitrification
due to increased soil water content and higher labile carbon availability
best explained increased N2O efflux, with
a smaller, indirect contribution from nitrification. In our data
and across the literature, single-factor responses tended to overestimate
interactive responses, except when global change was combined
with disturbance by fire, in which case interactive effects were
large. Thus, for chronic global environmental changes, higher
order interactions dampened responses of N2O
efflux to multiple global environmental changes, but interactions
were strongly positive when global change was combined with disturbance.
Testing whether these responses are general should be a high priority
for future research.
Keywords: Interactions; Global environmental change; Elevated
CO2; Warming; Precipitation; Nitrogen deposition;
Soil; Grassland; FACE; Nitrification; Denitrification; Meta-analysis』
Introduction
Materials and methods
Study site and experimental design
Field N2O fluxes
Drivers of N2O efflux
Statistical analyses
Analysis of variance
Correlations and path analysis
Observed versus expected interactive effects: Jasper Ridge Global
Change Experiment
Observed versus expected interactive effects: meta-analysis
Results
Field N2O efflux
Drivers of N2O efflux
Combined effects and interactions - Jasper Ridge Global Change
Experiment
Combined effects and interactions - meta-analysis
Discussion
Soil N2O emissions and microbial drivers
Responses to precipitation and interactions with heat and nitrogen
Responses to N, heat, and CO2
Interactive responses of soil N2O emissions
to global environmental change
Conclusions
Acknowledgments
References