Organic carbon and total nitrogen stocks in soils of the Lena River Delta

[摘要] The Lena River Delta, which is the largest delta in the Arctic, extends over an area of 32 000 km² and likely holdsmore than half of the entire soil organic carbon (SOC) mass stored in the seven major deltas in the northern permafrost regions. Thegeomorphic units of the Lena River Delta which were formed by true deltaic sedimentation processes are a Holocene river terraceand the active floodplains. Their mean SOC stocks for the upper 1 m of soils were estimated at29 kg m⁻² ± 10 kg m⁻² and at 14 kg m⁻² ± 7 kg m⁻²,respectively. For the depth of 1 m, the total SOC pool of the Holocene river terrace was estimated at121 Tg ± 43 Tg, and the SOC pool of the active floodplains was estimated at120 Tg ± 66 Tg. The mass of SOC stored within the observed seasonally thawed active layerwas estimated at about 127 Tg assuming an average maximum active layer depth of 50 cm. The SOCmass which is stored in the perennially frozen ground at the increment 50–100 cm soil depth, which is currently excluded from intensebiogeochemical exchange with the atmosphere, was estimated at 113 Tg. The mean nitrogen (N) stocks for the upper1 m of soils were estimated at 1.2 kg m⁻² ± 0.4 kg m⁻² for the Holocene river terraceand at 0.9 kg m⁻² ± 0.4 kg m⁻² for the active floodplain levels, respectively. For the depth of1 m, the total N pool of the river terrace was estimated at 4.8 Tg ± 1.5 Tg, and the total N poolof the floodplains was estimated at 7.7 Tg ± 3.6 Tg. Considering the projections for deepening of theseasonally thawed active layer up to 120 cm in the Lena River Delta region within the 21st century, these largecarbon and nitrogen stocks could become increasingly available for decomposition and mineralization processes.

[学科分类] 地球化学与岩石