More reliable pollen productivity estimates and relative source area of pollen in a forest-steppe ecotone with improved vegetation survey

Pollen productivity estimates (PPEs) and the relevant source area of pollen (RSAP) are critical to the reconstruction of past plant abundances. Extended R-value (ERV) models are commonly used for developing PPEs and estimating the RSAP. In this study, in the forest-steppe ecotone of northern China that is sensitive to climate change and significant in vegetation openness reconstruction, pollen data from surface sediment samples of 24 lakes and highresolution data of vegetation within the lake basins were applied to ERV models to calculate the PPEs of Pinus, Quercus, Betula, Ulmus, Poaceae, Artemisia, Chenopodiaceae, Compositae, and Cyperaceae and the RSAP of different lake sizes. The PPEs of arboreal pollen were higher than herbaceous pollen, and Chenopodiaceae had the highest productivity of herbaceous pollen taxa. The RSAP of lakes with an average lake radius of 400 m was estimated to be 1600 m. Our results suggested that PPEs and RSAP are region specific and that RSAP is also lake size specific even within the same region. Although environmental factors and imperfections in the ERV models may affect the accuracy of results, our study emphasized that a systematic vegetation survey considering zonal and azonal vegetation, the forest and steppe mosaic, and the vertical vegetation belt can help improve the PPEs and RSAP in areas with complicated vegetation distribution, such as the forest-steppe ecotone.