Quantifying ecosystem respiration and nitrous oxide emissions from greenhouse cultivation systems via a novel...

Greenhouse cultivation has expanded rapidly over the past three decades, significantly contributing to global food security and diversity. However, greenhouse gas (GHG) emissions from these systems remain poorly quantified due to methodological limitations. Here, we introduce a novel framework treating the greenhouse as a large static chamber to infer GHG emissions via nighttime gas accumulation. This approach was validated using two monitoring systems: automated 16-chambers soil flux measurements and whole-greenhouse concentration monitoring over 70 days. Mean soil carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) fluxes were 29.2 ± 12.9 kg C ha^-1 day^-1, -1.08 ± 2.31 g C ha^-1 day^-1, and 105.3 ± 65.6 g N ha^-1 day^-1 (mean ± SD), respectively. Although CH₄ flux was negligible, CO₂ and N₂O fluxes were significant with high spatiotemporal variability, driven primarily by chamber location and soil temperature. Whole-greenhouse CO₂ concentrations accumulated steadily at night and declined rapidly under daylight, whereas N₂O concentrations rose continuously, with ventilation events driving release. Nighttime accumulation between 18:00-24:00 provided robust estimates of ecosystem respiration (Re) and N₂O emissions, minimizing biases from temperature fluctuations. Validated across 15 greenhouses, this method yielded annualized emissions of 17.8 ± 8.0 Mg C ha^-1 yr^-1 (Re) and 21.3 ± 19.7 kg N ha^-1 yr^-1 (N₂O). This highlighted N₂O as the dominant direct GHG after accounting for photosynthetic recapture of Re. By bridging spatial heterogeneity and diurnal variability, the whole-greenhouse static-chamber approach advanced GHG quantification in controlled agricultural systems and offered a scalable framework for optimizing management practices and mitigating climate impacts.