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As a key component of the ecosystem, soil seed banks (SSBs) play a vital role in the evolution and renewal of plant communities. Although the pattern and mechanisms of influence of SSBs along the altitudinal gradient have been reported, most studies have focused on forest, grassland and alpine meadow ecosystems. The pattern and factors of SSBs across the altitudinal gradient in sedge peatlands remain largely unknown. Through vegetation surveys and seed germination experiments, we studied the changes in aboveground vegetation and SSBs in sedge peatlands at altitudes ranging from 300 m to 1300 m in the Changbai Mountains, China, and discussed the direct and indirect effects of climatic factors, soil properties and aboveground vegetation on SSBs. The results showed that the richness and density of the SSBs of sedge peatlands decreased with the altitude. Similarly, aboveground vegetation richness and density declined with altitude. A Spearman correlation analysis showed that SSB richness and density were mainly correlated with mean annual temperature, soil total phosphorus and ammonia nitrogen and the plant composition and richness of aboveground vegetation. A structural equation model analysis showed that climatic factors and aboveground vegetation directly affected seed bank richness, while soil properties indirectly affected it by directly affecting aboveground vegetation. Climatic factors, soil properties and aboveground vegetation directly affected SSB density, and soil properties indirectly affected it by directly affecting aboveground vegetation. This finding enhances our understanding of the altitude patterns of the SSBs in sedge peatlands and the response to future climate and environmental changes. [ABSTRACT FROM AUTHOR]

Purpose: Soil degradation through salinization and alkalinization is one of the most widespread abiotic stresses threatening the health and functions of wetlands in the world. However, the relationship of this degradation to vegetation change in salt-affected inland wetlands is not well understood. Methods: We studied the structure, density, and richness of aboveground vegetation, and soil physicochemical properties in Carex and Phragmites-dominated wetlands along a soil saline-alkalinization gradient in the Songnen Plain, China. We also compared the seed bank responses of Carex- and Phragmites-dominated communities to saline-alkaline stress in a greenhouse study. Results: Following a structural equation model (SEM), the soil salinity and alkalinity were related to a decrease in the density and richness of aboveground vegetation. These environments indirectly affected the aboveground vegetation by reducing soil nutrients as well as the species richness and seed density of soil seed banks. Greenhouse experiments found that soil seed banks of Carex communities were more sensitive to saline-alkaline stress than Phragmites communities, especially the sedge species. SEM linked pathways of soil degradation, seed bank change, and plant diversity decline. Conclusions: Our study indicates that soil salinity and alkalinity, as a critical environmental filter, could drive the decline of native freshwater species, especially for certain keystone sedge species, in salt-affected wetlands. Limiting agricultural development and restoring flood pulses across landscapes is necessary to alleviate soil salinization, deliver seeds and maintain the region's freshwater vegetation in salt-affected inland wetlands. [ABSTRACT FROM AUTHOR]

• The dominant species were almost missing in soil seed banks of farmed fields. • The structure and composition of soil seed banks changed after farming. • Restoration potential of plant communities differed due to salt tolerance. Wetlands have degraded dramatically in recent decades due to wetland drainage, agricultural reclamation, and soil salinization in China. Soil seed banks, as a way of natural regeneration, can efficiently restore the aboveground vegetation if seeds can survive after farming. To explore the response of soil seed bank to farming and consequent environmental changes, we compared the structure and composition of soil seed banks between Carex -dominated and Phragmites -dominated natural wetlands and their adjacent farmed fields in the Songnen Plain, China. We found that the responses of soil seed banks to farming and saline-alkaline stress were different between the two community types. The seed density and species richness in Carex -dominated natural wetlands were significantly higher than nearby farmed fields, however, there was no significant difference between Phragmites -dominated natural wetlands and nearby farmed fields. Carex schmidtii and Phragmites australis , dominated in natural wetlands, were both missing after farming. At the same time, the invasive species Typha angustifolia dominated in the farmed fields. Redundancy analysis identified that soil salt content was one of the major factors which significantly affected seed bank composition. Saline-alkaline stress significantly restricted the seed germination in farmed Carex fields, however, it had no significant effect in farmed Phragmites fields. Our study indicated that the potential of vegetation restoration was restricted by seed limit and soil salinization, and it differed significantly between the original community types in the Songnen Plain. In addition to hydrological connection, special technologies (such as planting and seeding) and the improvement of soil conditions are also necessary for successful restoration in salt-affected wetlands. [ABSTRACT FROM AUTHOR]

• The dominant sedge species were almost absent in soil seed banks of farmed fields. • Slight saline-alkaline stress strongly restricted seed germination. • Active revegetation and soil improvement are necessary to restore sedge meadows. Inland wetlands have declined dramatically in the past century due to land drainage, agricultural intensification and soil saline-alkalization in China. Soil seed banks can be an important component of ecological restoration of farmed wetlands if seeds of aquatic species can survive cultivation. To explore the response of soil seed bank to farming and accompanied environmental stress, we compared the structure and composition of seed banks between natural sedge meadows and adjacent soybean and paddy fields under two water levels (moist and flooded) and two salinity treatments (non-saline-alkaline and saline-alkaline stress) in the Songnen Plain, China. We found that the species richness and seed density in the natural wetland were significantly higher than the two farmed fields. Carex species that are dominant species in the natural sedge meadows were seldom present in the soil seed banks. Instead, other high productive species (e. g. Echinochloa crusgalli and Typha angustifolia) survived cultivation as seeds in the farmed fields. Redundancy analysis identified that soil pH, soil salt content and soil water content explained most variance in seed bank composition. Saline-alkaline stress restricted the seed germination and establishment of wetland species even if hydrology was restored. This study indicates that seed limitation and saline-alkaline stress of soil together restricted seed germination and natural restoration potential in the Songnen Plain. In addition to hydrological regulation, the active revegetation of tussock sedges, and improvement of soil saltine-alkaline condition are necessary to support regional biodiversity in the inland wetlands. [ABSTRACT FROM AUTHOR]