Fine root and leaf functional traits of coastal herbs and their relationship with soil factors

Abstract

Leaf and root are the most sensitive organs to environment, exploring the relationship between root and leaf functional traits and their responses to environmental factors is helpful to reveal the utilization of resources by plants and their adaption trategies to environment. In order to explore the adaptive strategies of coastal plants, the sandy coastal herbaceous plants in Pingtan Island were taken as the research objects. Three distance gradients were set up from sea and land. Six leaf function traits, leaf thickness, individual leaf area, leaf dry matter content, specific leaf area, leaf tissue density, leaf phosphorus content, and five fine root function traits, root average diameter, root tissue density, specific root length, specific root area, root phosphorus content, were measured to analyze the function traits of leaf and root of coastal plants and their responses to soil factors. The results were as follows: (1) The variation coefficient amplitude of root and leaf function traits in intertidal zone was the smallest, and it was the largest on the gradient 30-60 m away from the high tide line. The individual leaf area, leaf phosphorus content, root average diameter, root tissue density, and root phosphorus content increased with the distance from sea to land; the leaf dry matter content, leaf tissue density, specific root length and specific root area decreased. (2) Plants balanced resource allocation between growth and defense through trait combinations, which showed that there were different degrees of correlation among leaf traits, root traits and root-leaf traits. Among the aboveground and underground corresponding traits, leaf thickness-root average diameter, leaf-root phosphorus content were significantly positively correlated. Specific leaf area with specific root length, specific root area, leaf tissue density-root tissue density had no significant correlation. (3) The interpretation degree of soil factors to the changes of coastal plant functional properties was 52.05%, of which the soil salt content had the greatest impact, followed by soil water content, soil electrical conductivity and soil pH value. In conclusion, in the harsh coastal environment, the soil salt content, soil electrical conductivity, soil water content and soil pH value decrease gradually from sea to land, and the overall environment is low in phosphorus and high in salinity. The plants have shown different survival strategies: the plants closer to the sea adopted the strategy of leaf resource conservation type and root resource acquisition type; the plants farther away from the sea, the strategy of leaf resource acquisition type and root resource conservation type is adopted. The results of this study provide a certain reference value for understanding the response mechanism and adaptability of coastal herbs to environmental gradient changes, which is conducive to the analysis of soil and other environmental characteristics to screen and plant suitable species according to gradient, and promote the restoration and protection of coastal plants.

Keywords

• coastal plants
• leaf
• fine root
• functional traits
• soil factors
• ecological strategy