Hot spots, hot moments, and spatiotemporal drivers of soil CO₂ flux in temperate peatlands using UAV remote sensing

Abstract. CO₂ emissions from peatlands exhibit substantial spatial and temporal variability due to their heterogeneous nature, presenting challenges to identify their underlying drivers and to accurately quantify and model CO₂ fluxes. Here, we integrated field measurements with Unmanned Aerial Vehicle (UAV)-based multi-sensor remote sensing to investigate soil respiration across a temperate peatland landscape. Our research addressed two key questions: (1) How do environmental factors control the spatial-temporal distribution of soil respiration across complex landscapes? (2) How do hot spots and hot moments of biogeochemical processes influence landscape-level CO₂ fluxes? We find that dynamic variables (i.e., soil temperature and moisture) play significant roles in shaping CO₂ flux variations, contributing 43 % to seasonal variability and 29 % to spatial variance, followed by semi-dynamic variables (i.e., NDVI and root biomass) (19 % and 24 %). Relatively static variables (i.e., soil organic carbon (SOC) stock and C/N ratio) have a minimal influence on seasonal variation (2 %) but contribute more to spatial variance (10 %). Additionally, predicting time series of CO₂ fluxes is feasible by using key environmental variables (test set: R² = 0.74, RMSE = 0.57 μmol m^-2 s^-1), while UAV remote sensing is an effective tool for mapping daily soil respiration (test set: R² = 0.75, RMSE = 0.54 μmol m^-2 s^-1). By the integration of in-situ high-resolution time-lapse monitoring and spatial mapping, we find that despite occurring in 10 % of the year, hot moments contribute 28 %–31 % of the annual CO₂ fluxes. Meanwhile, hot spots – representing 10 % of the area – account for 20 % of CO₂ fluxes across the landscape. Our study demonstrates that integrating UAV-based remote sensing with field surveys improves the understanding of soil respiration mechanisms across timescales in complex landscapes, providing insights into carbon dynamics and supporting peatland conservation and climate change mitigation efforts.