Leaf And Stem Economics Spectrum And Of Broadleaved Seedlings And Their Relationship With Defense Traits In A Temperate Forest

Understanding the relationship with plant traits has long been a hot topic in ecological research.While there have been many studies on leaf economics spectrum-related traits of adult trees,relatively fewer studies on other key traits(such as defense traits)during the seedling stage.Because the biotic and abiotic understory environments are able to influence seedling growth and survival,it is particularly important to assess key traits in response to these environmental factors.This study focused on the leaves and stems of seedlings from eight broad-leaved tree species and eleven broad-leaved shrub species that exist In a broadleaved Korean pine(Pinus koraiensis)forest and a spruce-fir valley forest in the Liangshui National Nature Reserve,Heilongjiang Province.By measuring a total of 16 economic traits and defense traits of seedlings’ leaves and stems,the study analyzed the differences in seedling functional traits among different life forms,forest types and orangs,as well as the relationship between traits.The study found that there was no significant difference in leaf traits between the seedlings of trees and shrubs.The total phenolic content and tannin content of plants in the spruce-fir valley forest were significantly higher than those in broadleaved Korean pine forest.Compared with broadleaved Korean pine forest,the spruce-fir valley forest has lower undercanopy light intensity but higher air and soil moisture.There were no significant differences in stem traits between tree and shrub seedlings or among different forest types.Leaf chlorophyll content was positively correlated with specific leaf area,leaf nitrogen and phosphorus content.Leaf nitrogen content was positively correlated with leaf phosphorus content.Moreover,there was a significant and positive correlation between leaf defense traits.Leaf chlorophyll and nitrogen content were negatively correlated with total phenolic content,tannin content and content of flavonoids.This suggests the existence of a trade-off between leaf carbon economics and defense.The seedlings of trees and shrubs had similar carbon economics strategies.The results of this study have implications for predicting forest dynamics and community composition based on leaf functional traits.The stem nitrogen content was significantly positively correlated with the stem phosphorus content.The stem total phenol content was extremely significantly positively correlated with the stem tannin content,and significantly positively correlated with the stem flavonoid content.The stem flavonoid content was significantly positively correlated with the stem tannin content and the stem condensed tannin content.The economic spectrum traits of the stem and the defense traits of the stem existed in two independent dimensions,possibly due to the fact that the stem mainly plays a role in support and transport during plant growth and development,while the leaves mainly play a role in resource acquisition,they play a more active role in the seedling stage.The tradeoffs relationship suitable for leaves does not apply to the stem.There was a collaborative relationship between leaf traits and stem traits in seedlings.For seedling economic spectrum traits,plants gradually changed from "resource-acquiring" species with high photosynthetic rate,high stem phosphorus content,low woody density and low leaf dry matter content to "resource-conserving" species with low photosynthetic rate,low stem phosphorus content,high woody density and high leaf dry matter content;for seedling defense traits,stem condensed tannin content was positively correlated with total leaf phenol content,leaf tannin content,leaf flavonoid content and leaf condensed tannin content,and stem tannin content and total stem phenol content were positively correlated with leaf tannin content and total leaf phenol content.