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

Abstract

The 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 13 C 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 13 C in trees, shrubs, herb vegetation, and mosses were investigated using isotope tracing techniques, redundancy analysis, and structural equation modeling.Mohe had the largest 13 C excess and more transfer of shrubs and herbs to the underground carbon pool. The recoveries of photosynthate-13 C 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-13 C transfer was larger in Mohe than in Heihe and Yichun. The allocation of photosynthetic 13 C 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-13 C. The allocation and transfer of photosynthetic 13 C 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 13 C in the vegetation-soil system were affected by the soils' physicochemical properties and the environmental changes after permafrost degradation. K E Y W O R D S 13 C isotope tracer, permafrost degradation, photosynthetic 13 C allocation and transfer, soil physical and chemical properties, Xing'an Mountains

The choice of rice rotation system affects the composition of the soil fungal community and functional traits

“…In agreement, the results showed that soil bacteria-to-fungi ratio was significantly and negatively correlated with SOC (R = −0.680; P < 0.05). Previous studies have found that plants channel up to 60 % of photosynthetically-derived C to the root system, including tissues, mucilage, or the exudation of organic compounds [ 35 , 36 ]. It can be mainly metabolized by soil fungi rather than bacteria, as fungi have a high ability in assimilating plant derived C, which results in the formation of more complex C compounds with lower degradability [ 37 , 38 ].…”