Arctic Mineral Soils Lose SOC More Easily than Peat Soils Following Thaw
Abstract
It is estimated that the Arctic contains half of the global soil carbon pool, and climate warming will lead to considerable degradation of permafrost. This degradation may lead to the expansion or drainage of Arctic peatlands, which would alter the global carbon budget. Despite numerous Arctic soil incubation experiments and modeling efforts to predict future changes to the global carbon budget, there is still no consensus regarding the responses of Arctic soil carbon to climate warming. To address this uncertainty, we measured carbon dioxide (CO2) emissions from two soil types (lowland peatland and upland, mineral tundra) using 16 intact, replicate soil cores (8 of each type) that were incubated aerobically at 1 °C and 6.5 °C for 136 days. Soils were sampled from the active layer near Toolik Lake, Alaska, and soil moisture content was maintained near field conditions throughout the incubation process. An additional component of the study measured CO2 emissions from individual, partitioned soil layers (live biomass vs. organic litter vs. mineral layer) from the same sites as the whole cores. These individual layers were incubated under the same conditions as the whole cores to better understand the sensitivities of different soil types to permafrost thaw and climate warming.
We found that carbon in active layer soils from upland (mineral) sites was more sensitive to decomposition than lowland (peat) soils. Our findings suggest that oxygen availability, soil type, and carbon quality may be more important in controlling soil CO2 respiration than temperature, as temperature effects were not statistically significant in the intact incubation experiment or in the partitioned layer experiment. Our findings also highlight potential issues in utilizing homogenized, partitioned soil for incubation studies; in the partitioned layer incubation, average layer C-CO2 production was 6.1 times greater than intact, whole core C production from the same source material. This finding indicates that Arctic incubation studies utilizing homogenized, partitioned soil may overestimate CO2 emissions, and that the usage of carbon production values from homogenized soils in earth systems models should be carefully considered or minimized.
Citation
Sanders, Jillian (2022). Arctic Mineral Soils Lose SOC More Easily than Peat Soils Following Thaw. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197296.