Distributions of soil branched glycerol dialkyl glycerol tetraethers from different climate regions of China

Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from soil bacteria have been recently used for reconstructions of past soil pH and air temperature history. Here, we report the brGDGTs distribution patterns from different climate regions of China, using 42 novel brGDGT data from sub-tropical Chinese soils, compiled alongside previously-published data encompassing different environmental conditions across China. These patterns show high abundance of Ia fraction in soils from humid areas, and high abundance of IIa′ and IIIa′ fractions corresponds to semi-humid or semi-arid conditions, implying a possible relationship with precipitation. The abundance of IIa fraction appears negatively correlated with air temperature. Statistically, the soil pH and temperature factors represent 62% and 30% variations of the total variance respectively. For soils from humid and semi-humid regions, strong correlations between cyclization of branched tetraethers (CBT′) index and soil pH (R(2) = 0.89) and between methylation of branched tetraethers (MBT′(5ME)) index and mean annual temperature (MAT)(R(2) = 0.82) exist. When soils from semi-arid regions are included, the correlations become slightly stronger with pH and significantly weaker with MAT. Our study confirms the usefulness of soil brGDGTs distributions for Quaternary palaeo-climate reconstructions.