Allocation and transfer of photosynthetic 13C in the vegetation‐soil system and its response to permafrost degradation

Abstract

AbstractThe Xing'an Mountains, located on the southern edge of the Eurasian permafrost zone, are sensitive to permafrost degradation. In particular, the impact of wetland degradation in permafrost regions on carbon sequestration capacity cannot be ignored. Therefore, there is an urgent need to understand the allocation and transfer of photosynthetic 13C in the wetland vegetation‐soil system and its response to permafrost degradation. Three regions with different types of permafrost were selected predominantly continuous and island permafrost (located in Mohe); sparse island permafrost (located in Heihe); and isolated patches of permafrost (located in Yichun). The effects of permafrost degradation on the allocation and transfer of photosynthetic 13C in trees, shrubs, herb vegetation, and mosses were investigated using isotope tracing techniques, redundancy analysis, and structural equation modeling. Mohe had the largest 13C excess and more transfer of shrubs and herbs to the underground carbon pool. The recoveries of photosynthate‐13C for Larix gemlini, Vaccinium uliginosum, and Sphagnum sp. were significantly different in different permafrost regions using Tukey's honestly significant difference (HSD) post hoc comparisons of means tests. The amount of Δphotosynthate‐13C transfer was larger in Mohe than in Heihe and Yichun. The allocation of photosynthetic 13C in the plant roots in the three permafrost regions was positively correlated with the total soil phosphorus content. The active layer thickness was an important factor affecting the transfer of Δphotosynthate‐13C. The allocation and transfer of photosynthetic 13C to the subsurface were larger in the predominantly continuous and island permafrost areas than in the sparse island and isolated patch permafrost regions. The allocation and transfer of photosynthetic 13C in the vegetation‐soil system were affected by the soils' physicochemical properties and the environmental changes after permafrost degradation.