Comparison of carbon and nitrogen accumulation rate between bog and fen phases in a pristine peatland with the fen-bog transition

Long-term carbon and nitrogen dynamics in boreal peatlands are affected by both vegetation production and decomposition processes. Here, we examined the carbon accumulation rate (CAR), nitrogen accumulation rate (NAR) and δ13C, δ15N of plant residuals in a peat core dated back to ~8500 cal yr BP in a temperate peatland in Northeast China. Impacted by the tephra during 1160 and 789 cal yr BP and climate change, the peatland changed from a fen dominated by vascular plants to a bog dominated by Sphagnum mosses. We used the Clymo model to quantify peat addition rate and decay constant for acrotelm and catotelm layers during both bog and fen phases. Our studied peatland was dominated by Sphagnum fuscum during the bog phase (789 ~ -59 cal yr BP) and lower accumulation rates for the upper sections in the acrotelm layer during this phase, suggesting the dominant role of volcanic eruption in the CAR of the peat core. Both mean CAR and NAR were higher during the bog phase than during the fen phas..., Study site description and sampling
The peat core (42.185° N, 128.312° E) was collected in Dongfanghong peatland in the basalt plateau platform of Changbai Mountains region, with a present mean elevation of 1730 m, a total area of 16 km2, MAP of 780 mm, and MAT of 2.2 ℃. The present dominant plants include Vaccinium uliginosum, Cyperaceae (Carex and Eriophorum angustifolium), S. fallax, S. magellanicum and S. fuscum. The length of the peat core was 2 m. The core was divided into 1 cm slices for plant macrofossil and elemental analysis. The average DWT near the studied peat core was ~18 cm based on the monitor for three years (Yang et al., 2022).
AMS 14C dating of the peat core
The chronology of the peat core was based on the 14C accelerator mass spectrometer (AMS) analyses of plant residual stems and leaves subjecting to an acid–alkali–acid treatment (Table 1). The graphite samples were finished in the AMS14C dating preparation lab in Northeast Normal University and then were sent to th...,

北方泥炭地长期碳氮动态受植被生产与分解过程共同调控。本研究针对中国东北温带泥炭地一根可追溯至约8500校准年前（cal yr BP）的泥炭柱，分析了其碳积累速率（carbon accumulation rate, CAR）、氮积累速率（nitrogen accumulation rate, NAR）以及植物残体的δ¹³C、δ¹⁵N值。
受1160 cal yr BP与789 cal yr BP时期火山碎屑（tephra）以及气候变化的影响，该泥炭地从以维管植物占优的低位沼泽（fen）演变为以泥炭藓（Sphagnum）为主的高位沼泽（bog）。
本研究采用Clymo模型量化了低位沼泽与高位沼泽两个阶段的表层泥炭层（acrotelm）和深层泥炭层（catotelm）的泥炭添加速率与分解常数。本研究的泥炭地在高位沼泽阶段（789~-59 cal yr BP）以棕泥炭藓（Sphagnum fuscum）为优势种，该阶段表层泥炭层上部的积累速率较低，表明火山喷发对该泥炭柱的碳积累速率起到主导作用。高位沼泽阶段的平均碳积累速率与氮积累速率均高于低位沼泽阶段。

研究地点描述与采样
该泥炭柱（坐标42.185°N，128.312°E）采自长白山玄武岩台地的东方红泥炭地，现今平均海拔1730米，总面积16 km²，年均降水量（mean annual precipitation, MAP）780 mm，年均气温（mean annual temperature, MAT）2.2 ℃。当前优势植物包括越橘（Vaccinium uliginosum）、莎草科（薹草属Carex和白毛羊胡子草Eriophorum angustifolium）、S. fallax、S. magellanicum及S. fuscum。泥炭柱总长2 m，被切割为1 cm厚的切片以用于植物大化石分析与元素分析。基于三年监测数据，研究区泥炭柱附近的平均地下水位深度（depth to water table, DWT）约18 cm（Yang et al., 2022）。

泥炭柱的AMS ¹⁴C定年
该泥炭柱的年代框架基于植物残体茎、叶的加速器质谱（accelerator mass spectrometer, AMS）¹⁴C分析，样品经酸-碱-酸前处理（表1）。石墨样品在东北师范大学AMS¹⁴C定年制备实验室完成制备，随后送往……