Year: 2026
Type: article
Abstract: . Greenhouse gas release due to microbial decomposition of thawing permafrost organic matter receives ample attention but the other side of the permafrost soil carbon budget, the stabilization of organic matter due to rising plant litter input in a greening Arctic has hardly been addressed. Here we explore whether thawing permafrost may act as a long-term sink of fresh plant litter carbon. To identify the magnitude and drivers of litter carbon stabilization in thawing permafrost, we incubated permafrost samples under oxic and anoxic conditions with 13C-labelled plant litter for nine years, used the microbial CO2 and CH4 production to calibrate a carbon decomposition model, and finally fractionated the remaining organic matter into a dissolved, a mineral-associated and a particulate fraction. At the end of the experiment, on average 38.9 ± 21.1 (mean ± SD, oxic) and 59.1 ± 12.2 % (anoxic) of the added litter-C was still present in the thawed permafrost. The mean residence times of the stable litter carbon pool of 17.6 (22.3) yr (median (IQR), oxic) and 52.4 (54.2) yr (anoxic) indicate a substantial stabilization of fresh litter carbon in thawing permafrost. Most of the remaining litter carbon (82.5 (35.3) % oxic and 83.8 (21.4) % anoxic) was part of the mineral-associated fraction, but in contrast to current understanding, litter decomposability is positively correlated with the size of the mineral bound litter pool. Although the fraction of mineral-bound permafrost carbon (64.4 (20.0) % oxic and 68.0 (17.0) % anoxic) was significantly smaller than of litter carbon, the mean residence times of the stable permafrost carbon pools were more than 10-fold higher. We identified interactions between new litter carbon and pre-existing mineral-bound permafrost carbon as an important driver of litter carbon stabilization. Such interactions may reduce net carbon emissions from thawing permafrost and add complexity to the permafrost carbon climate feedback.
Source: Biogeosciences
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDGs: Climate action, Life on land
Open Access status: gold
Estimated APC paid: $1,628
OpenAlex ID: W7162486807