Gram-negative bacterial 3-hydroxy fatty acids (3-OH-FAs) 20 biomarkers are widespread in a variety of environments including both marine 21 and terrestrial sediments (including speleothems). In this study we analysed 22 the hydroxylated membrane lipids of 26 soil samples from an altitudinal 23 transect of Shennongjia Mountain (Mt.) in central China to study the 24 environmental factors controlling the relative distribution of 3-OH-FAs. Our 25 results show that both the ratio of the summed iso and anteiso to the total 26 amount of normal 3-OH-FAs (RIAN), and the ratio of summed iso and anteiso 27 to the total amount of all 3-OH-FAs (Branched Index) were primarily related to 28 the pH of soil (R 2 = 0.70 and 0.70, respectively). Additionally, the anteiso to 29 normal 3-hydroxy fatty acids ratio of the C15 and C17 homologues (RAN15 and 30 RAN17) shows a significant negative correlation with mean annual air 31 temperature (MAAT) (R 2 =0.51 and 0.48, respectively). When comparing the 3-32 OH-FA based indices with established glycerol dialkyl glycerol tetraether 33 (GDGT) based indices from the same soil samples, the RIAN and Branched 34 Index show strong linear correlations with the cyclisation ratio of branched 35 tetraethers (CBT) (R 2 = 0.77 and 0.74, respectively), and the RAN15 and RAN17 36 show negative correlations with the MBT/CBT-MAAT (MBT, methylation index 37 of branched tetraethers) (R 2 = 0.61 and 0.36, respectively). Our new field-based 38 correlations demonstrate the physiological response of Gram-negative bacterial 39 cell membranes to the external environment and suggest that 3-hydroxy fatty 40 3 acids can be applied in palaeoenvironmental studies to estimate past MAAT 41 and soil pH.

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According to a core from Tianchi Lake, Liupan Mountain in Loess Plateau sediment, fossil pollen assemblages, magnetic susceptibility (MS) and color scale were measured based on reliable Abies leaf macrofossils radiocarbon chronology. We recovered a very good high-resolution mid-late Holocene climate change achieve for the transition area of the East Asia monsoon region and northwest arid region. The results show that the basic climate background was in agreement with the records from cave records in monsoon regions in eastern China. Besides, it shows more detailed records in abrupt climate change.high resolution, mid-late Holocene, Tianchi Lake