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Human impact is a well-known confounder in pollen-based quantitative climate\udreconstructions as most terrestrial ecosystems have been artificially\udaffected to varying degrees. In this paper, we use a <q>human-induced</q> pollen\uddataset (H-set) and a corresponding <q>natural</q> pollen dataset (N-set) to\udestablish pollen–climate calibration sets for temperate eastern China (TEC).\udThe two calibration sets, taking a weighted averaging partial least squares\ud(WA-PLS) approach, are used to reconstruct past climate variables from a\udfossil record, which is located at the margin of the East Asian summer\udmonsoon in north-central China and covers the late glacial Holocene from\ud14.7 ka BP (thousands of years before AD 1950). Ordination results suggest\udthat mean annual precipitation (Pann) is the main explanatory\udvariable of both pollen composition and percentage distributions in both\uddatasets. The Pann reconstructions, based on the two calibration\udsets, demonstrate consistently similar patterns and general trends,\udsuggesting a relatively strong climate impact on the regional vegetation and\udpollen spectra. However, our results also indicate that the human impact may\udobscure climate signals derived from fossil pollen assemblages. In a test\udwith modern climate and pollen data, the Pann influence on pollen\uddistribution decreases in the H-set, while the human influence index (HII)\udrises. Moreover, the relatively strong human impact reduces woody pollen taxa\udabundances, particularly in the subhumid forested areas. Consequently, this\udshifts their model-inferred Pann optima to the arid end of the\udgradient compared to Pann tolerances in the natural dataset and\udfurther produces distinct deviations when the total tree pollen percentages\udare high (i.e. about 40 % for the Gonghai area) in the fossil sequence.\udIn summary, the calibration set with human impact used in our experiment can\udproduce a reliable general pattern of past climate, but the human impact on\udvegetation affects the pollen–climate relationship and biases the\udpollen-based climate reconstruction. The extent of human-induced bias may be\udrather small for the entire late glacial and early Holocene interval when we\uduse a reference set called natural. Nevertheless, this potential bias\udshould be kept in mind when conducting quantitative reconstructions,\udespecially for the recent 2 or 3 millennia

Examining bias in pollen-based quantitative climate reconstructions induced by human impact on vegetation in China