The effect of climate manipulation on CO2 fluxes in a temperate peatland: higher fluxes, more frequent irregularities, and seasonality displacements

Peatlands play a vital role in the global carbon cycle, serving as carbon sinks in their natural state, and are key ecosystems for climate change mitigation. European future climatic scenarios predict warmer and drier conditions, and both CO₂ uptake and emission are driven by temperature and water availability. Therefore, to address this, a study was conducted to investigate how these environmental changes impact peatland carbon dynamics. In a temperate peatland under warming and reduced precipitation treatments, CO₂ fluxes were analysed using a combination of continuous Morlet wavelet transform, decomposition trend analysis, and partial least squares regression to study their changing trends and relationships with hydroclimatology. The results highlight the differences between non-floating and floating-mat peatland areas (CL and CR, respectively). In CL, warming intensified the switch to a CO₂ source, while its combination with reduced precipitation triggered a faster vegetation change, and the increment in source potential was lower. In CR, the higher wetness of the area enabled warming to have a positive effect, increasing the CO₂ sink potential, extending the growing season, increasing vascular plant coverage and a lower drop in Sphagnum spp. abundance. Water table depth was the main driver of CL's fluxes, producing shared trends of controls and treatments, while in CR, air temperature, water balance and vapour pressure deficit were equally important for fluxes. Peatlands with sufficient water availability could increase their sink potential under warmer conditions, while under drier conditions, the temperature will trigger further CO₂ emissions and peatlands' source potential.