Greenhouse gas emissions in natural and managed peatlands of America: Case studies along a latitudinal gradient

Abstract

Processes affecting CO2 and CH4 emissions and their budgets have been relatively well studied in northern temperate peatlands, whereas similar studies are almost absent in southern Patagonia and the high-altitude Andean peatlands, both of which are currently under heavy anthropogenic pressure. The objectives of this study were to compare greenhouse gas (GHG) emissions in natural and managed peatlands to examine the effect of management on GHG emissions and identify the environmental parameters affecting them. We analysed CO2, CH4 and N2O emissions related to the physical and chemical conditions of the peat: in a natural and managed transitional bog in Quebec, Canada, a natural páramo and grazed peatland in the Colombian Andes, and a bog and a fen in Tierra del Fuego, Argentina. GHG fluxes were measured using the dark static chamber method. Groundwater table, temperature, O2 content, pH and redox potential were measured from observation wells, soil temperature was measured at four depths, peat samples were analysed for pH, soil organic matter and dry matter content, P, K, Ca, Mg, NH4-N, NO3-N, total N and C. In all regions, human-impacted peatlands showed significantly higher CO2-C, N2O-N and CH4-C emissions than their natural counterparts. The Canadian managed transitional bog showed the highest average CO2-C (575mgCm−2h−1) and N2O-N (0.08mgNm−2h−1) emissions, whereas the Colombian pasture was the largest emitter of CH4-C (2.35mgCm−2h−1). CO2-C emissions were controlled by soil temperature and C content, whereas CH4-C flux was negatively correlated to dissolved oxygen content in peat water, and positively to water table level and soil log (C/NO3-N) ratio. Total Inorganic Nitrogen (TIN), C/N ratio, and soil temperature were the main factors controlling N2O emissions. Intensive peatland management alters the soil C/N balance, and increases and leads to higher variability of GHG emissions. Agricultural activities, especially crop production in peatlands, as well as intensive grazing in mountain peatland pastures, are the main factors increasing GHG emissions in the peatlands studied. Mitigation is possible via regulation of grazing intensity and replacing arable fields with grasslands.