A comparative study of soil processes in depletion and accumulation zones of permafrost landslides in Siberia
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Oxana V. Masyagina I Svetlana Yu. Evgrafova I Valentina V. Kholodilova I Stanislav G. Prokushkin
A comparative study of soil processes in depletion and accumulation zones of permafrost landslides in Siberia
Abstract Landslides are one of the main reasons for permafrost degradation in high latitudes. Any landslides consist of different top-down slope zones: removal, transit-depletion, and accumulation zones. These slope parts can demonstrate different successional behavior of plant community and carbon (C) cycling during post-sliding seral stages. To address this issue, soil respiration (SR), hydrothermal conditions (mineral soil temperature at a depth of 5 cm (ST5, °C), and gravimetric soil water content at a depth of 0–5 cm in mineral soil horizon (SWC5, %)), total soil C (TC) and nitrogen (TN) contents, and soil microbial activity at the middle (depletion zone) and lower (accumulation zone) slope parts of the landslides with different history have been studied. The most significant differences between the middle and lower slope positions were found at the ground microsites (or G-plots) of the L2001 landslide. Thus, here, a midslope part occurred to be a high source of C compared to the lower part. Midslope of L2001 was characterized by significantly higher SR at G-plots as well because of better hydrothermal conditions and more intensive vegetation regeneration. The accumulation zone of L2001 characterized by the lower SR despite significantly higher microbial activity due to the high nutrient level of the soil moved from the top, likely favored to promotion of the soil C stabilization processes. Despite the registered ST5 differences in the E-plots and the G-plots between middle and lower slope positions of the L1972 landslide, SR, TC, TN, and soil microbial activity did not differ significantly.
type (Hosseini et al. 2019; Masyagina et al. 2019). C cycling and successional processes in high-latitudinal ecosystems affected by landslides and permafrost degradation in relation to climate change were discussed in various studies (Coolen et al. 2011; Abbott and Jones 2015; Loiko et al. 2017). Landslide is a disturbing agent, like wildfires, and it is also influencing ecosystem C stability. In contrast to the wildfires, which consume C and release it directly to the atmosphere, landslides transfer the soil organic C to downslope ecosystems, where it may or may not be released to the atmosphere. Some receiving ecosystems with anoxic conditions can stabilize this C over long periods, like river coastal deposits, but at the same time, these ecosystems might be a serious source of methane (Abbott and Jones 2015). We hypothesize that successional processes in the soil and forest are different in the depletion (middle part of a landslide slope) and accumulation (lower part of a landslide slope) zones, and the recently changing environment might result in the various C fate: source or sink. Thermokarst processes followed landslides are improving environmental conditions (temperature, soil water content, light intensity) a
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