Functional Traits And Ecological Strategies Of Common Plants In Muddy Coastal Wetlands Of Shandong Province

Plant functional traits are one of the hot topics in ecological research in recent years.There are complex tradeoffs and synergies among plant functional traits,which reflect the ecological strategies of species and are the basis for plants to cope with changing environment and maintain biodiversity.The study of plant functional traits and their relationship will be helpful to explore ecological phenomena such as niche differentiation,species coexistence mechanism and vegetation dynamic evolution.The differences in functional traits can be used to divide plants into different functional groups.Plants in the same functional group often have the same or similar response mechanism to environmental factors.The division of regional plant functional groups plays an important role in understanding the community building process and ecosystem functions.The functional traits of plants are affected by environmental factors and biological factors.It is of great significance to analyze the key factors affecting the functional traits of plants for understanding the dynamic changes of regional vegetation and precise regulation of vegetation restoration process.Muddy coast is composed of silt and soil particles deposited by rivers.It has the characteristics of flat coast,wide shoal and great influence by tidal action.It plays an important role in maintaining ecosystem function.The widespread distribution of muddy coast is one of the characteristics of coastal in China.In recent years,disturbed by natural and human activities,the landscape spatial pattern shows a trend of fragmentation and serious erosion.Therefore,ecological basic research and conservation and restoration of muddy coastal wetlands have attracted extensive attention.In this study,we divided the plant functional groups of the coastal muddy wetland in Shandong province by field community investigation,specimen and photo collection,functional traits determination,functional group division,environmental factor measurement,biodiversity assessment,model construction and other experimental and analytical methods.Intraspecies variation of functional traits in dominant species Phragmites Australis and Tamarix Chinensis,as well as ecological strategies in different habitats,have been revealed,and synergies and trade-off relationships between functional traits at the species level have been elucidated.The relative contributions of biological and abiotic factors affecting the changes of functional traits were clarified,and the influencing factors of functional traits and ecological strategies of common plants in muddy coastal wetlands in Shandong province were analyzed.The main results of this study are as follows:(1)The species floristic composition of muddy coastal wetlands in Shandong province is typical of temperate zone.C3 plants and herbaceous plants are the main species,and P.australis and Tamarix chinensis are dominant species in herbaceous layer and shrub layer respectively.According to the investigation,specimens and photographic records in recent years,a total of 68 families,236 genera and 470 species of vascular plants(not Including ornamental plants and cash crops)were found in the muddy coastal wetlands of Shandong Province.Gramineae,Compositae,Leguminosae and Cyperaceae are the major families of plant distribution in the region,with the proportion of single species and oligopoly species accounting for 89.4%.Compared with the 1990s,the natural plant species in the region have increased.The results showed that the establishment of nature reserves played a positive role in the increase of species diversity.It was found that the vegetation of muddy coastal wetlands in Shandong province was dominated by C3 plants,accounting for 65.5%of the total plants,including dominant species such as Suaeda salsa and P.australis,and about 33%of C4 plants.These include predominance species such as Miscanthus sacchariflorus and Imperata cylindrica.There are more dicotyledons,accounting for about 60.5%of the total number of plants,and relatively few monocotyledons,but the gramineae plants occupy a dominant position in the herbaceous layer.Herbs dominated,accounting for 69%of the total.P.australis and Tamarix chinensis are dominant species in herb layer and shrub layer respectively.The species composition of muddy coastal wetlands in Shandong province is influenced by adjacent areas and the upper reaches of the Yellow River,and its historical causes and evolutionary trends need to be further studied.(2)The growth of T.chinensis is significantly affected by soil salinity,and there is no significant correlation between nitrogen and phosphorus content in leaves of T.chinensis and soil nitrogen and phosphorus content.Soil phosphorus is the limiting factor for the growth of T.chinensis in typical coastal muddy wetlands of Shandong Province.4 T.chinensis samples in the Yellow River Delta Nature Reserve and Changyi National Marine Special Reserve were selected for experiments.10 T.chinensis samples were randomly selected from each sample to measure functional traits and soil factors.The growth height and canopy area of Tamarix ramosissima were significantly negatively correlated with soil conductivity,while the phosphorus content in leaves was significantly negatively correlated with soil pH value.However,there was no significant correlation between nitrogen and phosphorus content in leaves and soil.The results showed that N:P ratio of T.chinensis leaves varied from 22.75 to 37.07,indicating that soil P was the limiting factor of T.chinensis in typical muddy coastal wetlands in Shandong Province.Therefore,phosphorus improvement may be an important management measure in the practice of vegetation restoration of muddy coastal wetlands in Shandong Province.(3)The individual functional traits and community characteristics of the dominant species(P.australis)in the muddy coastal wetland of Shandong were affected by soil moisture and salinity,and the interannual variation of functional traits and their relationships with precipitation and temperature were not consistent.This section of the research in the core region of shandong muddy coastal wetland chose 4 different water and salt conditions typical of the reed community sample area to carry out the experiment,each kind of random set up 5 1 m*1 m herb samples,on the behavior of plant community characteristics,the function of the reed and soil physical and chemical properties are analyzed in the determination of three consecutive years.The research results show that in the community and the individual level,reed individual properties such as biomass,stem properties such as section base diameter and length,leaf area and leaf thickness,leaf traits were significantly positive correlation with soil water content,soil conductivity and most indicators present negative correlation,but positively related to the blade thickness,show that reed leaves to withstand high salt stress by increasing the thickness.Leaf water content,specific leaf area,individual height and basal diameter increased gradually in three years,but leaf thickness did not change with years in most plots.It should be noted that the inter-annual variation of functional traits and the relationship between traits were not consistent in different habitats,and the effects of rainfall and temperature in different years on different traits were different.Therefore,under the background of future climate change,the evolution trend of P.australis will have habitat heterogeneity.(4)The responses of different functional traits of P.australis to soil water content and salt content were not consistent.Under the condition of high salt content,P.australis improved its osmotic regulation ability by increasing leaf water content and leaf thickness.With the decrease of soil salt content,ecological strategy of P.australis changed from stress tolerance strategy(S)to competition strategy(C).This study further explored the effects of environmental factors on the functional traits of P.australis and the ecological strategies of P.australis in different habitats.In this study,96 1 m×1 m herbaceous plots were selected from the coastal and inland regions of the Yellow River Delta,the core area of muddy coastal wetlands in Shandong Province.Based on the determination of soil physical and chemical properties and plant functional traits,the CSR(competition-tolerance-ruderal)strategy of P.australis was analyzed.The research results show that,within the scope of the study of salt effect on plant functional traits is more important than the soil water content,relative functional properties such as chlorophyll content response is not sensitive to changes of water and salt,under the condition of high salinity,the growth of reed height,leaf area,internode length and internode number have been different degree of inhibition,At the same time,P.australis increased leaf water content and leaf thickness to improve its osmotic adjustment ability.In the wetland ecosystem of the Yellow River Delta,the competitive strategies and stress tolerance strategies of P.australis were dominant.Ruderal strategies were not common.Under high salinity conditions,more resources were used to resist external stress,and ecological strategies tended to be stress tolerance strategy(S),while P.australis increased leaf area and specific leaf area in order to quickly obtain resources and ecological strategy was gradually transformed into a competitive strategy(C)under low salinity conditions.(5)The functional traits and community characteristics of typical herbaceous plant communities in muddy coastal wetlands of Shandong were shaped by environmental factors including soil pH,soil conductivity and the facilitation or competition effect of T.chinensis.The impact of T.chinensis in the Yellow River Delta is more significant,while the influence of soil environmental factors is more important in Changyi.In order to explore the driving factors of the functional traits in herbaceous plant communities,based on the functional traits studies of T.chinensis.The results showed that the soil under the shrub canopy became a salt valley,and the composition of herbaceous community was significantly different inside and outside the shrub canopy.The structural equation model revealed that the presence of T.chinensis had a significant positive effect on species richness and functional traits of herbaceous community in the Yellow River Delta,while the effect of T.chinensis was not significant and the soil environmental factors had a positive effect on community characteristics in Changyi.This chapter provides new evidence for the role of T.chinensis in the succession of wetland communities in muddy coastal of Shandong Province.By combining the temporal and spatial analysis of functional traits and the calculation of the CSR model,the paper revealed P.australis,the dominant species in the muddy coastal wetlands of Shandong,adjusted ecological strategy from competition to tolerance strategy.Based on structural equation models,the relative contributions of biotic factors(e.g.interspecies interactions)and abiotic factors(e.g.salt changes)to the functional traits of individual and community were determined in muddy coastal wetlands.The results also revealed the relationship between shrub(T.chinensis)and neighboring herb species relied on environmental context,and T.chinensis promoted the establishment and reproduction of neighboring herbaceous plants through the salt-valley effect in which soil salinity decreased,instead of the traditional fertile-island effect in which soil nutrients are improved.The findings could strength the understanding of the ecological adaptation mechanism of dominant species and communities in Shandong muddy coastal wetlands,and provide a theoretical basis for the prediction of the vegetation succession under environmental changes.Eventually,the paper offered a scientific reference for the construction,protection and restoration of Shandong muddy coastal wetlands.