Biomarkers of modern plants and soils from Xinglong Mountain in the transitional area between the Tibetan and Loess Plateaus

Organic compounds found in living plants and modern soils in different bioclimatic areas are important in understanding the paleoenvironmental implications of the organic matter signals from geological records. Using GC–MS techniques, a series of biomarkers, mainly including n-alkanes and n-alkan-2-ones, were identified from the typical plants (e.g. broadleaf-deciduous trees and conifers), and the soils collected from Xinglong Mountain, a transitional area between Tibetan and Loess Plateaus. The C15–C33n-alkane homologues were present in all samples. Typically, C27 or C29n-alkanes were most abundant in tree samples and C31 was most abundant in grasses samples. Meanwhile, the soil samples were mainly dominated by C29 and C31 homologues. The n-alkan-2-ones showed a strong odd-over-even predominance of carbon numbers. C23, C25 or C29n-alkan-2-one homologues were most abundant in plant samples, while C27 or C29 was abundant in soils samples. The lipid biomarker distribution patterns of all the plants and soil samples suggest that the vegetation is a primary source of organic matter for the soils, and that reprocessing of microbes and physicochemical reactions in the soil played an important role in the degradation of organic matter. Research has advanced knowledge about transformation of biomarkers in the plants (organic matter)–microbes–forest system. It also can help reconstruct the process of plant successions recorded by the lipids.