| Coastal shelter forests play an important role in ecological,social and economic benefits.At present,researches on the adaptability of coastal gradient trees mostly focus on leaf physiological and morphological traits,and the adaptive changes and synergistic relationship between leaf traits and stoichiometry are still unclear.Therefore,this study takes Metasequoia glyptostroboides plantation in Dongtai forest farm as the research object,and sets up 3 vertical coastal sample lines near and far from the coast.The spacing between the sample lines is 100 m.each sample line is divided into four gradients.The distance between the gradients is 1000 m,and each gradient is set at 20 m×20 m fixed quadrat,3 lines,12 quadrats in total.In each sample plot,3 average trees with good growth were selected,and the morphological,physiological,nutrient and other character indexes of leaves were measured by standard branch method to explore the adaptive changes of leaf characters of Metasequoia glyptostroboides under different coastal gradients.The results are as follows;（1）The changes of leaf characteristics of Metasequoia glyptostroboides on the coastal gradient are as follows:the specific leaf area decreased significantly with the decrease of coastal distance（P<0.05）.The dry weight increased gradually with the decrease of coastal distance,but there was no significant difference.The length,width and perimeter of leaves decreased significantly at the third gradient（2000 m）from the coastline,and the length width ratio decreased significantly at the fourth gradient（3000 m）.Leaf nitrogen and phosphorus decreased significantly with the decrease of coastal distance（P<0.05）.The first and fourth gradients of soil total nitrogen（0 m,3000 m）decreased significantly.There was no significant difference in soil total phosphorus on the coastal gradient.The minimum initial fluorescence Fo and the maximum initial fluorescence Fm of leaves increased significantly at the fourth gradient（3000 m）,the electron transfer share q P（P<0.05）,the electron transfer rate ETR（P<0.05）,and the actual photochemical efficiencyΦPSⅡ（P<0.05）was significantly higher than other gradients in the third gradient（2000 m）.（2）Synergetic relationship between leaf traits of Metasequoia glyptostroboides on the coastal gradient:there was a significant positive correlation between leaf nitrogen and leaf phosphorus（P<0.01）.Leaf nitrogen was positively correlated with specific leaf area（P<0.05）,and negatively correlated with leaf length and perimeter（P<0.01）.There was a significant positive correlation between leaf phosphorus and specific leaf area（P<0.05）,a significant negative correlation with leaf length width ratio（P<0.05）,and a curve relationship with leaf length and perimeter（P<0.05）.Leaf nitrogen was significantly negatively correlated with non photochemical quenching NPQ（P<0.05）,positively correlated with electron transfer share q P（P<0.01）,and correlated with electron transfer rate ETR（P<0.05）,actual photochemical efficiencyΦPSⅡ（P<0.05）was significantly positively correlated.Leaf phosphorus was significantly positively correlated with initial fluorescence Fo（P<0.01）and maximum fluorescence Fm（P<0.001）,and with electron transfer share q P（P<0.05）,electron transfer rate ETR（P<0.05）and actual photochemical efficiencyΦPSⅡ（P<0.05）was significantly correlated with the curve,but not with non photochemical quenching NPQ.（3）Hierarchical partitioning method was used to analyze the explanatory degree of various influencing factors on coastal gradient on leaf stoichiometry,leaf morphology and chlorophyll fluorescence parameters of Metasequoia glyptostroboides.Among them,canopy wind speed has the greatest impact on leaf stoichiometry.Leaf nitrogen,phosphorus and nitrogen phosphorus ratio had the highest explanation for the changes of leaf morphology and chlorophyll fluorescence.At the same time,the structural equation was used to verify the synergy between them.The leaf stoichiometry on the coastal gradient drives the changes of leaf morphology and leaf photochemical efficiency,showing a synergistic relationship. |
