Responses of soil background N₂O emissions to land use, soil properties, and climate parameters based on a global Meta analysis

Soil background N₂O emission is the N₂O released from soil without nitrogen fertilizer application or soil management during the planting cycle. With the increase of human activities, the amount of background N₂O emission from soil gradually increases, and its impact on environment and climate is increasingly significant. However, the key controlling factors and underlying mechanisms related to background N₂O emission from soil are remain unclear. To address this knowledge gap, the distribution of the 282 studes included in this research was mapped based on field observations data of soil background N₂O emissions, as well as climate and soil factor data, from around the world The study sites are globally distributed across six continents and cover three predominant land-use types: cropland, forestland, and grassland. The results showed that the global background N₂O emission ranged from 0.01 kg to 56.40 kg(N)∙hm⁻²∙a⁻¹, with an average of 1.68 kg(N)∙hm⁻²∙a⁻¹. Among them, the range of soil background N₂O emission in grassland ecosystem was the widest, from 0.03−56.40 kg(N)∙hm⁻²∙a⁻¹. The soil background N₂O emissions in cropland and forestland ecosystems ecosystems were in the range of 0.01 to 7.10 and 0.12 to 4.70 kg(N)∙hm⁻²∙a⁻¹, respectively. Further, a systematic evaluation and in-depth investigation of the various factors affecting soil background N₂O emissions including soil pH, soil bulk density, soil total nitrogen, annual mean temperature, annual mean precipitation.Additionally, we explored the relationships between soil properties and meteorological parameters and soil background N₂O emissions across different land use types. The main results were as follows: 1) compared with climate factors, soil properties had a greater impact on soil background N₂O emissions; 2) soil background N₂O emissions under different land use patterns were different on a global scale; 3) soil pH had significant effects on soil background N₂O emissions in cropland, forestland and grassland ecosystems. This study provides valuable insights into the development and management strategy of sustainable agriculture and offers a scientific basis for mitigating N₂O emissions from soil. It also provides critical support for reducing greenhouse gas emissions, protecting the ozone layer, and mitigating the impacts of climate change on ecosystems.