全球变化知识资源中心

The high concentrations of lipid biomarkers in peat and the close relation between peatland development and hydrological conditions merit further assessment of the paleohydrological proxy potential of the H-2/H-1 ratio of leaf wax n-alkanes (delta H-2(alk)) in peat deposits. In the context of the dynamics of the East Asian summer monsoon, detailed investigation of modern processes is an important way to improve our understanding of the controls on delta H-2(alk), records from Chinese peat deposits. This review first synthesizes the results of investigations of modern processes in the Dajiuhu peatland of central China, complemented by results from other peatlands and nearby non-peatland sites, to evaluate how the H-2/H-1 ratio changes from source water to leaf water and then to lipids in leaf waxes and ultimately to peat deposits. The results reveal that the precipitation delta H-2 values and the peatland plant types are the two major factors that control the delta H-2(alk) signals preserved in peat at Dajiuhu. Comparison of results from Holocene delta H-2(alk) sequences from other Chinese peat deposits illustrates how peat delta H-2(alk) values respond to paleoclimate changes on centennial to millennial timescales throughout the East Asian summer monsoon region. Finally, proposed incubations of peat-forming plants in controlled chambers that could assess the response of plant delta H-2(alk) values to environmental stresses are described. As an example, responses of the compound-specific biomarker delta H-2 and delta C-13 values of Sphagnum, the dominant plant in the Dajiuhu peatland, could provide important information on the symbiotic relation between Sphagnum and microbes. It is expected that experiments such as these that combine the carbon and hydrogen isotope compositions of multiple lipids will yield important new insights into the responses of peatland ecosystems to climate changes.