Biotic And Abiotic Driving Mechanisms Of Ecosystem Multifunctionality In Coastal Wetland Of The Yellow River Delta

Ecosystem multifunctionality is used to characterise the ability of an ecosystem to provide multiple ecosystem functions,which is influenced by biodiversity and environmental change.The coastal wetland of Yellow River Delta is one of the most representative wetlands in China.The coastal wetland of Yellow River Delta is the youngest,most extensive and most complete wetland ecosystem in the country,with unique value in biodiversity conservation,making it a hotspot for biodiversity and ecosystem conservation in China.Under the joint influence of the Yellow River and the Bohai Sea,the soil environmental factors and vegetation in the coastal wetlands of the Yellow River Delta show obvious strip-like distribution characteristics and heterogeneous habitat characteristics.However,the multifunctional distribution pattern in the heterogeneous habitats of the Yellow River Delta coastal wetlands is still unclear.Plant diversity is considered to be an important driver of ecosystem multifunctionality,and plant diversity is closely related to fungal diversity,but the mechanisms by which fungal diversity and plant diversity contribute to ecosystem multifunctionality are still not sufficiently studied.The Yellow River Delta faces the threat of global change,and there is still a lack of systematic research on how wetland ecosystem multifunctionality changes with multiple global change factors.Based on long-term field survey data,this study selected areas with high heterogeneity and significant plant community changes in the coastal wetlands of the Yellow River Delta.This study used a combination of sample lines and methods to investigate the changes in soil physical and chemical properties,biodiversity and ecosystem multifunctionality in the heterogeneous habitats of the coastal wetlands of the Yellow River Delta.A mesocosm system was constructed by selecting common plants in the Yellow River Delta and combining the field survey data to elucidate the mechanisms of plant diversity and fungal diversity on ecosystem multifunctionality.By constructing a mesocosm system simulating various global change factors,such as nitrogen deposition,soil salinization,drought,plant invasion,over grazing,oil pollution,microplastic pollution,antibiotic pollution,heavy metal pollution and pesticide pollution,and plant diversity on ecosystem multifunctionality were explored.The following conclusions were obtained:(1)Ecosystem multifunctionality in the coastal wetlands of the Yellow River Delta showed a clear trend of reduction along the sample line perpendicular to the coast and river banks.The relationships between plant richness,plant diversity and fungal diversity and ecosystem multifunctionality showed a clear threshold effect.There were maximum ecosystem multifunctionality at neutral soil pH and low soil conductivity and soil water content.Plant richness can contribute directly to ecosystem multifunctionality and can also regulate it indirectly by promoting soil fungal richness.(2)In the mesocosms to explore the effects of plant diversity and fungal diversity on ecosystem functions,plant diversity clearly promoted the ecosystem multifunctionality and the reduction in soil fungal diversity clearly decreased the ecosystem multifunctionality.Reducing fungal diversity decreased the ecosystem multifunctionality by 10%and 11%at plant richness levels of 1 and 2,respectively.However,the reduction in fungal diversity promoted the positive effect of plant diversity on the ecosystem multifunctionality,which may be caused by that the reduction in fungal diversity promoted the selection effects of plant diversity.(4)In the mesocosms to simulate multiple global change factors,global change factors inhibited the multifunctionality in both high and low plant diversity mesocosms.In the absence of the global change factors,the ecosystem multifunctionality in the high plant diversity mesocosms was significantly higher than that in the low plant diversity mesocosms.The ecosystem multifunctionality in the high plant diversity mesocosms was more sensitive to the global change factors compared to the multifunctionality of the low plant diversity mesocosms.In summary,this study elucidates the synergistic mechanisms by which soil environmental factors and biodiversity drive ecosystem multifunctionality in the heterogeneous habitats of the coastal wetlands of the Yellow River Delta,demonstrating that soil environmental factors regulate ecosystem multifunctionality through direct and indirect effects on plant richness and soil fungal richness;revealing that the mediating effect of fungal diversity on plant diversity on ecosystem multifunctionality is achieved by It is clear that global change factors can reduce the contribution of plant diversity to ecosystem multifunctionality by reducing the selective effects of biodiversity.This study finds that the multifunctionality of the high biodiversity Yellow River Delta wetland ecosystem may be vulnerable to future complex global changes,and further research and targeted and precise conservation measures are needed.This study provides research ideas to further investigate the geographical patterns and driving mechanisms of ecosystem multifunctionality in the Yellow River Delta,and also provides a theoretical reference for biodiversity and ecosystem conservation in the Yellow River Delta under global change.