Annual and seasonal CO₂ flux in a temperate north-Patagonian peatland exposed to varying intensities of commercial Sphagnum moss harvesting

Abstract. Peatlands hold the largest carbon (C) reserves worldwide and therefore play a fundamental role in climate change mitigation. In the Southern Hemisphere, peatlands distributed in the Patagonia represent the principal extratropical C sink. Nevertheless, increasing anthropogenic pressures, such as the commercial harvesting of Sphagnum moss, threaten their capacity to regulate CO₂ fluxes, a situation that has been scarcely studied.

We conducted a field study that quantified and analyzed the annual and seasonal CO₂ fluxes in a North Patagonian peatland subjected to varying intensities of commercial Sphagnum harvesting: high, moderate, and undisturbed. Using closed chamber techniques, we measured the components of the CO₂ flux over the course of one year, while also identifying the predominant environmental drivers influencing these fluxes.

The results showed that moss harvesting intensity was directly correlated with net ecosystem exchange (NEE) fluxes. The high-intensity extraction site acted as a net CO₂ source (375.7 g CO₂-C m⁻² yr⁻¹), the moderately harvested site was approximately carbon neutral (10.2 g CO₂-C m⁻² yr⁻¹), and the undisturbed site functioned as an annual CO₂ sink (−167.1 g CO₂-C m⁻² yr⁻¹). Seasonal fluxes revealed that disturbed sites emitted more CO₂ in summer and acted as sinks in spring, while the undisturbed site sequestered CO₂ year-round. In winter, all three sites functioned as CO₂ sinks due to environmental conditions that favored productivity and minimized respiration.

Photosynthetically active radiation was the key bioclimatic driver regulating gross primary production and NEE, while air and soil temperature primarily influenced ecosystem respiration. These findings provide relevant evidence for understanding carbon dynamics in peatlands affected by commercial Sphagnum harvesting and underscore the need for sustainable management regulations to preserve their role as carbon sinks in Chilean Patagonia.