image: Distribution of sampling sites in the global dataset on tree diversity and forest soil N2O flux, constructed via meta-analysis and field observation data (a); Linear relationship between tree diversity and the effect size of tree diversity on N2O flux (b).
Credit: ©Science China Press
Driven by human activities and land-use transformations, forest biodiversity is declining rapidly, thereby altering carbon and nitrogen cycles as well as greenhouse gas emissions in forest ecosystems. As the third most significant global greenhouse gas, N₂O is predominantly emitted by forests—the largest natural source of N₂O in terrestrial ecosystems—making fluctuations in forest N₂O emissions a key driver of climate warming. However, the relationship between changes in forest biodiversity and soil N₂O emissions has remained poorly understood.
To address this knowledge gap, Prof. Xiaoqi Zhou from East China Normal University and his ecological research team compiled global datasets on tree diversity and forest N₂O flux. Based on the large-scale Biodiversity-Ecosystem Functioning Experiment China Platform (BEF-China), they conducted long-term in-situ observations of N₂O fluxes and integrated these with a global dataset on tree diversity and forest soil N₂O emissions. The study revealed a significant negative correlation between increased tree diversity and global forest soil N₂O emissions (R² = 0.64, P < 0.05), offering novel insights for climate mitigation strategies.
To unravel the mechanisms behind this N₂O reduction, Prof. Zhou’s team collaborated with Prof. Lijun Hou’s group, using natural abundance isotope techniques to differentiate microbial processes of in-situ soil N₂O production across varying tree diversity levels. Results showed that higher tree diversity concurrently suppressed N₂O production from both nitrification and denitrification. Notably, the proportion of N₂O derived from denitrification dropped from approximately 70% to 40%, identifying denitrification as the primary process driving N₂O flux changes. "Increased tree diversity enhances plant uptake and utilization of soil inorganic nitrogen, thereby reducing substrates available for denitrifying microbes," explained Prof. Zhou.
Finally, the researchers developed a plant diversity-soil-N₂O flux model to simulate global forest soil N₂O emissions under different tree diversity scenarios. Predictive modeling showed that compared to monocultures, two-species forests could reduce global N₂O emissions by 10.39%, while forests with 24 tree species achieved the maximum mitigation effect, cutting emissions by 56.30%.
"Our findings demonstrate the potential of tree diversity to mitigate soil N₂O emissions in forests," concluded Prof. Zhou. "We hope this research provides a scientific foundation and data-driven support for forest management, reforestation initiatives, and climate change mitigation strategies."
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See the article:
Enhanced plant diversity reduces nitrous oxide emissions in forest soils worldwide https://doi.org/10.1093/nsr/nwaf186
Journal
National Science Review