Distribution of lipids in modern soils from various regions with continuous climate (moisture-heat) change in China and their climate significance

摘要

Total 26 modern soil samples were collected from various regions under different climate conditions from tropical to arid temperate in China and systematically analyzed for their organic matters by GC/MS in order to evaluate climatic impacts on soil organic components. Abundant lipids molecules were recognized, including n-alkanes, n-alkenones, and long-chain branched alkanes. We find the predominance of main peaks of long-chain n-alkanes (nC_(29), nC_(31), nC_(33)) and short-chain ones (nC_(16), nC_(17), nC_(18)) records information of soil generation in warm-humid and cold-dry regions. The proportion of n-alkanes (nC_(16)+nC_(17)+nC_(18)) to (nC_(29)+nC_(31)+nC_(33)) varies in good agreement with moisture-heat conditions and thus probably can serve as a new index for climate change. The ratios of C_(21)~-C_(22)~+, nC_(17)C_(31) and (nC_(15)+nC_(17)+nC_(19)) / ( nC_(27)+nC_(29)+nC_(31)) of n-alkanes, indicating respectively input ratios of lower bacterial alga, aquatic organisms, and higher plants and terraneous organisms, co-vary well in different climate regions from forest to grassland and desert, suggesting that they have also reflected the difference of climates between monsoon region and inland one. The C_(21)~-/C_(22)~+ ratio of n-alkan-2-one records largely the discrepancy of temperature from north to south of China bordered by the Qinling Mountains, but less humidity. The C_(21)~-/C_(22)~+ ratio of n-alkan-3-ones changes well with climatic factors, such as temperature and humidity. The biogenic source of series A-D long-chain branched alkanes may be derived from some kinds of special epiphyte that most likely live in weak oxic-anoxic and moisture-heat environments, suggesting their distribution record as well some information on climatic change. All these researches demonstrate that the distributions of lipids molecules in modern soils in China record well signals of climates from quite different climatic regions, and can serve as important climatic proxies to reveal climatic change over China.