<p>Northeast China&#8212;located near the northern limit of the influence by the East Asian summer monsoon&#8212;receives most moisture through the westerly airflow, but variations in moisture contributions from the Yellow Sea in the western Pacific Ocean determine its hydroclimate during summer monsoon season. The proportion of moisture from the Yellow Sea is strongly modulated by the location and intensity of the Western Pacific Subtropical High (WPSH). However, it is still unclear how sensitive regional hydroclimate to WPSH-modulated change in moisture sources and its impact on peatland carbon accumulation. Here, we used macrofossil data and paired &#948;<sup>13</sup>C and &#948;<sup>18</sup>O isotope analysis of Sphagnum moss cellulose from a well-dated bog from a steep mountain slope in the Greater&#160;Khingan Mountains (~47&#730;N) to reconstruct peatland moisture changes and elucidate past shifts in moisture sources. &#948;<sup>13</sup>C values reflect peatland surface moisture, as dry conditions with less water film effects would increase isotopic discrimination against <sup>13</sup>C and result in lower &#948;<sup>13</sup>C values. Our results from a 250-year peat record show a decrease of ~3&#8240; in &#948;<sup>13</sup>C from -25 to -28&#8240;&#8212;with corresponding increase in dry-adapted moss Polytrichum&#8212;suggesting a drying trend since about 1980 AD. Also, the down-core &#948;<sup>18</sup>O and &#948;<sup>13</sup>C&#160;data show a&#160;positive correlation (r = 0.65, p < 0.001), in contrast with evaporative enrichment of &#948;<sup>18</sup>O being the dominant effect. We argue that &#948;<sup>18</sup>O values reflect the input of moisture derived from the Yellow Sea&#8212;that has higher &#948;<sup>18</sup>O values than that from the westerlies&#8212;as modulated by the WPSH. When the WPSH extends westward, it blocks moisture transport from the Yellow Sea to North China, causing low &#948;<sup>18</sup>O values in summer precipitation, dry conditions, and negative shifts in &#948;<sup>13</sup>C, and vice versa. Furthermore, carbon accumulation rates show a major decrease after the 1980s&#8212;despite that more recent peat tends to have higher apparent accumulation rates&#8212;suggesting a sensitive response of this steep-slope mountain peatland to shift in regional hydroclimate in monsoon-margin region of Northeast China.</p>
Recent Carbon Accumulation in Changbai Mountain Peatlands, Northeast China
