Continuous acceleration of soil heterotrophic respiration over 16 years of soil warming in a sub-boreal forested peatland

Ma, R.*; Takagi, Kentaro*; Kondo, Toshiaki*; Koarashi, Jun   ; Atarashi-Andoh, Mariko  ; Kobayashi, Makoto*; Aguilos, M.*; Ryhti-Laine, K.*; Sun, L.*; Takahashi, Yoshiyuki*; Hirano, Takashi*; Liang, N.*

To quantify the effect of long-term warming on soil heterotrophic respiration (R) in a forested peatland in northern Hokkaido, Japan, we measured the hourly soil CO efflux from 2007 to 2022 in three treatments: (1) unwarmed, root invasion prevented; (2) soil warmed by 3C during snow-free period, root invasion prevented; and (3) control, unwarmed, root invasion allowed. We evaluated the interannual variations in soil CO efflux, temperature sensitivity of respiration (Q), and basal respiration rate at 10C at 5 cm deep (R). Over the 16 years, the effect of warming on R (an average increase of 111%, or 35%/C) was much higher than in most previous studies, attributable to the high soil organic carbon stocks at our site. An average 15% decrease in Q and a doubling of R after 3 years suggest a sustained enhancement of microbial basal metabolism. Synergistic effects of functional redundancy of the microbial community, new carbon inputs from litter, and slow release of refractory carbon maintained the enhancement of R by warming over the long term.