中国干旱-半干旱区表土bGDGTs与气候环境因子数据再分析

文章通过收集中国北方干旱-半干旱区域已发表的bGDGTs数据，重新计算了不同地区表土bGDGTs各组分与温度及pH等环境因子之间的相关关系。主要获得以下认识：1）不同于干旱区，半干旱区bGDGTs的异构体指标与土壤pH表现为强相关，在4个异构体指标（IBT、CBT'、IR'_IIa、IR'_IIIa）中CBT'、IR'_IIIa计算的pH结果精度较高；2）半干旱区f（5 me）与pH表现为强相关（-0.847），指示了基于5-甲基bGDGTs的指标同样具有重建半干旱区pH的潜力。但是目前缺乏CBT'_5ME-pH之间的转换函数；3）全球温度校正方程计算得出的温度误差普遍大于中国区域校正方程（中国北方、青藏高原等区域）获取的温度误差。通过整合数据重新计算发现4个区域温度校正方程（MBT'_5ME、Tmr、MAATsr、Index 1）计算的温度结果具有较小的误差，且在半干旱区重建的温度结果更为精确；另外MAATsr、Index 1的区域温度校正方程也适用于干旱区的温度重建，但是由于本文集成数据中包含的干旱区样本较少，因此在实际应用中需要谨慎。在未来的研究中需要加强干旱-半干旱区尤其是干旱区的地表过程研究，为建立该地区的温度校正方程提供更多有用的信息。

REANALYSIS OF SURFACE SOILS AND CLIMATIC AND ENVIRONMENTAL FACTORS IN ARID AND SEMI-ARID REGIONS OF CHINA

This study reanalysis the correlation of the bGDGTs from the surface soils with the environmental factors(pH, MAP and MAT etc.) based on the published data in arid and semi-arid regions of China. The results show that (1) There is a strong relationship between index based on 6-methyl bGDGTs and pH in semi-arid regions(e.g. with MAP ranging from 200 mm to 500 mm), with no correlation in arid regions(e.g. with MAP less than 200 mm). Among the isomerization index of bGDGTs(IBT, CBT', IR' Ⅱa and IR' Ⅲa), the CBT' and IR' Ⅲa are more applicable for soil pH reconstructions in semi-arid regions. (2) The f(5-me) is negatively correlated with pH(-0.847) in semi-arid regions shows that index based on 5-methyl bGDGTs can provide potential for pH reconstructions in semi-arid regions, but it needs to be verified in the further studies. (3) The regional equations(such as for the Northern China and the Tibetan Plateau) show more accurate MAT and soil pH estimation than global equations. After reconstructing the temperature using the selected equations to the published bGDGTs data from surface soils, the estimated temperature by the four regional equations(MBT' 5ME, Tmr, MAATsr and Index 1) have the highest correlation and smallest errors(RMSE) with the measured data. These four equations are more suitable for the paleo-temperature reconstructions in semi-arid regions than the others. Furthermore, the local temperature equations(MAATsr and Index 1) may potentially provide more reliable temperature estimation in arid regions. However, there are still many uncertainties for the paleo-temperature reconstructions in arid regions because the study of the surface soil in the area is still limited. More investigation should be applied to the surface modern process, especially in arid regions, which could provide more useful information for establishing the objective temperature equations in the region.