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• Surface pollen spectra from different coastal wetlands in northwest Bohai Bay are compared. • Chenopodiaceae pollen can indicate variations in halophytes, salinity, and pH. • Pollen concentrations are related to vegetation coverage and sediment grain size. • Back-trajectory modelling can help estimate the potential source of arboreal pollen. • Remote sensing LUCC data are used to understand pollen-vegetation relationships. Understanding the relationship between modern pollen and vegetation in coastal wetlands is essential for reconstructing long-term land cover changes, and for determining the response of coastal wetland ecosystems to global changes. We selected 68 sampling sites in different types of coastal wetland in northwest Bohai Bay, North China, for palynological analysis, and hence to determine the relationships between pollen and environmental factors, such as soil grain size, salinity, and pH. A back-trajectory model and remote sensing LUCC data were used to reveal the pollen source area and the pollen representation for different land cover types. The results show that the pollen assemblages of these coastal wetlands are dominated by Chenopodiaceae and Poaceae. The pollen assemblages are significantly different between silty and sandy coastal wetlands, and they also reflect different vegetation landscapes. Chenopodiaceae pollen is a potential indicator of saline-alkali soil environments in coastal areas. In addition to the vegetation coverage and sedimentary environment, pollen concentrations are negatively correlated with the grain size of the surface soil. The pollen diversity is higher in areas with strong human influences (e.g., cultivated land, villages, roads), but lower in natural wetlands with a high vegetation coverage. The arboreal pollen is generally sourced from the northern and northwestern mountains, while the major dispersal area of halophyte and hygrophyte pollen is on a local scale, constrained by the local vegetation canopy and its settlement characteristics. Fern spores are mainly waterborne, carried by rivers and surface runoff from mountain areas. The arboreal and upland herbaceous pollen is over-represented for forest and grassland landscapes. Halophyte and hygrophyte pollen show a good correlation with the area of coastal wetland, and they can be used as an indicator of the extent of coastal wetland influenced by climate change and human activities. [ABSTRACT FROM AUTHOR]

• Pollen assemblages reflect well the vegetation types at different altitudes. • The RSAP in the mountain area in the Taihang Mountains is about 600 m. • The RPPs can be well estimated in the human influenced Taihang Mountains. • Implications for land cover reconstruction in the North China Plain are discussed. Pollen-based land cover reconstructions are important for understanding the history of regional environmental responses to natural and anthropogenic factors, and for managing the ecological environment. The vegetation in the mountain landscape of North China has been significantly influenced by human activities, and evaluating the pollen-vegetation relationship for the region is important for reconstructing anthropogenic land-cover changes in the North China Plain. In this study, 35 sampling sites were randomly selected in representative vegetation zones of the Taihang Mountains in North China. Based on a detailed vegetation survey (field work combined with the analysis of remote sensing images), we evaluated the pollen-vegetation relationships in the area. In addition, the relevant pollen source area (RSAP) of the sampling sites and the relative pollen productivity (RPP) of the major plant taxa were estimated using ERV (Extended R-Value) models. The results show that the pollen spectra in the Taihang Mountains reliably reflect the vegetation landscape of different altitudinal zones. The estimated RSAP in the Taihang Mountains is ~ 600 m. Using Poaceae as a reference taxon (RPP = 1), the RPPs of the dominant plant taxa in the Taihang Mountains can be ordered as follows: Pinus > Hippophae > Caryophyllaceae > Betula > Quercus > Rhododendron > Artemisia > Asteraceae > Cyperaceae. Our results suggest the importance and complexity of RPP estimates in the Taihang Mountains, and provide valuable implications for improving the accuracy of reconstructions of land-cover changes in the North China Plain. [ABSTRACT FROM AUTHOR]

• A new study on the modern pollen-vegetation relationships in southeastern China. • Pollen signals are compared with LUCC data in different categories and distances. • Hydrologic process plays a key role in pollen dispersal and deposition. • Human activities deeply impact the pollen-vegetation relationships in the YHRB. • The p/v ratios have potential value for the reconstruction study in the YHRB. Fossil pollen, as a key indicator of vegetation landscapes, can provide abundant information of long-term land use dynamics. However, pollen-vegetation relationships are complex, and the relevant studies are rare in the large sedimentary basins associated with strong human disturbances. This study aims to investigate the pollen-vegetation/land use relationships at a large regional scale, and to supplement reference for more accurate paleoenvironmental reconstruction in the future. A total of 124 modern pollen samples were collected from 66 lakes in the Yangtze-Huaihe River Basin (YHRB), southeastern China. We conducted a contrastive analysis of both pollen and land use data in different spatial extents and categories. Our results reveal that the pollen assemblages of the YHRB are dominated by both arboreal and herbaceous taxa, such as Pinus , Quercus , Pterocarya , Juglans , Poaceae, Artemisia , Cruciferae, Chenopodiaceae, Compositae, and Humulus. The spatial differences of pollen assemblages in the YHRB are obvious, resulted from the confounded effects of natural environment and human disturbance. Hydrologic process plays a key role in pollen dispersal and deposition in the YHRB. Waterborne pollen is an important component of the lacustrine pollen assemblages, and fern spores and total pollen concentration can be used to indicate the degree of hydrologic process. The main source of lacustrine pollen here generally derives from sub-basins, and the source area is about 80 km. Anthropogenic impact is another significant factor determining the pollen-vegetation relationships in the YHRB. Cereal and anthropochore pollen as well as pollen diversity indexes are ideal indicators of agricultural activities. We suggest that the 4 types of estimated pollen/land-use ratios in this study, covering forest, farmland, rural land, and wetland could be used as a reference for reconstructing past land cover. Our study also demonstrates the existing problems and the potential improvements for the further studies on pollen-based paleoenvironmental reconstruction. [ABSTRACT FROM AUTHOR]