Meteorological observations, and 210Pb and 14C ages of peat profiles from subarctic Canada

Stable carbon and oxygen isotope ratios in single plant components in Sphagnum peat have a good potential to reveal environmental changes in peat archives. Two peat profiles, covering the past ~6000 years, and a Sphagnum hummock from a discontinuous permafrost area in west central Canada were studied in order to evaluate the effect of decomposition rate on isotope records and to assess which plant components are most suitable for climate reconstructions. The stable isotope values from the most recently forming Sphagnum tissues were compared with observational climate data to study the impact of variations in temperature and precipitation on the peat isotopes. Our results show that there is high correlation between d13C values in alpha-cellulose isolated from Sphagnum fuscum stems and summer temperatures, whereas d18O in the plant tissues is controlled by several factors, such as summer precipitation, summer temperature and evaporation. According to our results, decomposition as derived from C/N values and colorimetry does not seem to affect the oxygen and carbon isotope values of alpha-cellulose from Sphagnum fuscum peat significantly. There is, however, a (quasi-) constant offset between the isotope values of branches and stems and between whole plant material and alpha-cellulose, which makes it crucial to select single moss-fractions when past climate and environmental changes are to be derived from the isotope record.泥炭藓（Sphagnum）泥炭单株植物组分中的稳定碳、氧同位素比值，在揭示泥炭档案的环境变化方面具有极佳应用潜力。本研究针对加拿大中西部不连续多年冻土区的两处覆盖过去约6000年的泥炭剖面，以及一处泥炭藓丘开展分析，旨在评估分解速率对同位素记录的影响，并筛选出最适用于气候重建的植物组分。我们将泥炭藓最新形成组织的稳定同位素值与实测气候数据进行对比，以探究温度与降水变化对泥炭同位素的调控机制。研究结果显示，从褐泥炭藓（Sphagnum fuscum）茎部提取的α-纤维素（alpha-cellulose）中δ¹³C值与夏季气温呈显著相关；而植物组织中的δ¹⁸O则受夏季降水、夏季气温及蒸发作用等多重因素共同调控。此外，基于碳氮比（C/N）与比色法得到的分解程度，并未对褐泥炭藓泥炭α-纤维素的碳、氧同位素值产生显著影响。但枝条与茎部的同位素值之间，以及全株植物材料与α-纤维素之间存在（准）恒定偏移，因此若要通过同位素记录反演过去的气候与环境变化，选取单一苔藓组分至关重要。