Acknowledgements
The study was supported by the National Natural Science Foundation of
China (41730854, 41877157, 41530854); the Project supported by State Key
Laboratory of Loess and Quaternary Geology (SKLLQG1904); the Science and
technology support plan for Youth Innovation of colleges and
universities of Shandong (2019KJH009); the Natural Science Foundation of
Shandong Province (ZR2019BD005; ZR2019MD040); the Key Research and
Development Plan of Shandong Province (2018GSF117021); the Science and
technology program of colleges and universities of Shandong (J17KA192);
and the Project supported by State Key Laboratory of Earth Surface
Processes and Resource Ecology (2017-KF-15).