Spatial homogenization of soil-surface pollen assemblages improves the reliability of pollen-climate calibration-set
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atial homogenization of soil-surface pollen assemblages improves the reliability of pollen-climate calibration-set 1*
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Fang TIAN , Xianyong CAO , Ran ZHANG , Qinghai XU , Wei DING , Xingqi LIU , 1 6 Baolin PAN & Jianhui CHEN 1
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College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China; Alpine Paleoecology and Human Adaptation Group (ALPHA), Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; 3 CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China; 4 College of Resources and Environment Sciences, Hebei Normal University, Shijiazhuang 050024, China; 5 Institute of Geological Sciences, Palaeontology, Free University of Berlin, Berlin 12249, Germany; 6 Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China Received May 28, 2019; revised April 16, 2020; accepted June 9, 2020; published online July 29, 2020
Abstract To make a reliable reconstruction of past climate from soil-surface modern pollen, it is necessary to reduce the sources of error. In this paper, pollen percentages of the sub-continental scale modern pollen-climate dataset from China and Mongolia (with 68% soil-surface samples) are homogenized at various spatial scales. A tailored calibration-set is then applied to lake sediment-surface pollen assemblages from north-central China to evaluate their predictive power. Results indicate that spatial homogenization of modern pollen percentages can increase the proportion of inertia explained by climatic variables in CCA and improve the model performance of leave-one-out cross-validation using WA-PLS. Soil-surface pollen assemblages can thus be employed into a calibration-set for reliable climate estimation and they perform better when the calibration-set has been locally homogenized. Small-scale (e.g., radii 2, 5, or 10 km) homogenization reduces the local noise in soil-surface pollen assemblages and improves the cross-validated performance, while broader scale homogenization (more than 20 km radius) blurs the pollen-climate relationship. Lake sediment-surface pollen assemblages from close to the shore could contain pollen grains transported by rivers or from the shore vegetation and thus fail to represent regional climate well like the assemblages from the central part and deep-water area of lake. Keywords Citation:
North-central China, Soil-surface pollen, Climate reconstruction, WA-PLS
Tian F, Cao X, Zhang R, Xu Q, Ding W, Liu X, Pan B, Chen J. 2020. Spatial homogenization of soil-surface pollen assemblages improves the reliability of pollen-climate calibration-set. Science China Earth Sciences, 63, https://doi.org/10.1007/s11430-019-9643-0
1. Introduction One of the ideal options for pollen-based climate reconstruction is that modern pollen data in the calibration-set should be derived from the same type of sedime
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