Drainage increases CO₂ and N₂ O emissions from tropical peat soils

Area of Science:

• Environmental Science
• Ecology
• Climate Science

Background:

• Tropical peatlands are crucial for global carbon storage.
• Estimates of greenhouse gas (GHG) emissions from these ecosystems are uncertain due to environmental variability.
• Understanding GHG fluxes is vital for climate change mitigation and peatland management.

Purpose of the Study:

• To provide the first comprehensive analysis of GHG fluxes (CO2, CH4, N2O) in managed and natural tropical peatlands.
• To investigate the influence of land use and groundwater levels on soil respiration and GHG emissions.
• To compare tropical peatland emissions with other peatland types and mineral soils.

Main Methods:

• Compilation and analysis of 372 soil GHG flux measurements from diverse tropical peatland studies.
• Statistical analysis of data considering land use, groundwater depth, and environmental conditions.
• Quantification of heterotrophic respiration, total CO2 respiration, CH4, and N2O fluxes.

Main Results:

• Managed peatlands exhibited higher total soil respiration (median 52.3 Mg CO2 ha-1 year-1) than natural forests (median 35.9 Mg CO2 ha-1 year-1).
• Groundwater level significantly impacted CO2 emissions; a 100 mm drop increased emissions by 5.1 and 3.7 Mg CO2 ha-1 year-1 for plantations and cropping, respectively.
• Deeper groundwater levels (≥0.5 m) led to higher N2O emissions (15% of total GHG), while shallow levels increased CH4 emissions.
• Tropical peatlands showed approximately double the CO2 emissions compared to temperate and boreal peatlands and were comparable to tropical mineral soils.

Conclusions:

• Groundwater level is a more critical factor than land use in controlling tropical peatland CO2 emissions.
• High N2O emissions at deeper groundwater levels contribute significantly to overall GHG burden.
• Tropical peatlands are significant sources of CO2, comparable to mineral soils, necessitating effective management strategies for sustainability.