Hydroclimate controls of the distribution and abundance of mosses in Hani mire, Northeast China: modern vegetation survey and peat-core analysis

Abstract Located on the western flank of the Changbai Mountains in Northeast China, Hani (HN) peatland has been studied intensively for Holocene paleoclimate reconstruction on decadal to centennial scales. This study presented new datasets of hydroclimatic controls on the distribution and abundance of mosses through modern vegetation survey and plant macrofossil analysis of a historical peat profile. Survey on the abundance of ten different moss species in 40 vegetation quadrats and their depths to water table (DWT) in the HN mire have been conducted during the growing season (June to October) in 2015 and 2016. Our results indicated that (1) the abundances of these mosses showed close relationship with DWTs; and (2) DWT was a function of local precipitation with lower DWT corresponding to higher precipitation. Sphagnum fallax, S. cuspidatum and S. subsecundum preferred wet microhabitats under higher precipitation (i.e., lower DWT), and vice versa. Hence, the variation in the abundance of these sphagna was considered to be an indicator of changes in precipitation. An equation for quantitative estimation of DWT based on the abundances of the moss species along different moisture habitats has been established based on the modern survey, which was able to reconstruct the variation of DWT in the past from plant macrofossil analysis. A 50 cm core from HN mire was dated by AMS 14C, 210Pb, and 137Cs methods, providing a 50-year record of hydroclimate. Plant macrofossils were identified at 1 cm intervals of the peat core, which exhibited detailed variations of the moss assemblages. The variation of DWT reconstructed from the coverage of S. fallax and the total coverage of S. fallax, S. cuspidatum and S. subsecundum in the core matched well in peak-to-peak and trough-to-trough with local growing season precipitation on annual scale during the past 50 years. Our study suggests that selecting well-responsive Sphagnum species is a key factor to reconstruct hydroclimate by using plant macrofossils.