Leaf Functional Traits Of Main Plants And Their Relationships With Environmental Factors On The Western Slope Of Wuyi Mountains

Plant functional traits are the measurable functional properties of plants which is the result of a long-term adaption and evolution of plants in the environment.In the context of global environmental change,it’s essential for understanding the responses and adaptations of plants,the functions and processes of cosystem,and biodiversity maintenance mechanisms.Leaf is the largest organs of the plant with the largest contact area with the environment,hence the leaf usually has highly phenotypes plasticity variability and is very sensitive to environmental changes.Therefore,leaf traits and their variation based on the theoretical framework of leaf economics spectrum have been widely used as a key index to evaluate resource tradeoff strategies of plant functional attributes on the organ scale and their responses to environmental factors.Subtropical forests are the most widely distributed,largest and most complex and diverse forest ecosystems in the southern part of China,and play a vital role in maintaining the regional ecological environment and global carbon balance.The most obvious characteristic of subtropical forest ecosystems is high species diversity,‘nitrogen-rich and phosphorus-poor’.In this case,the resolution to the problems of collaborative trade-off relationships between leaf functional traits,correlation between leaf traits and environmental factors and the influences on species coexistence and ecosystem function still needs to be explored based on a large amount of actual measurement data.For this reason,this study selected subtropical forest vegetation including three typical vegetation types:deciduous broad-leaved forest,coniferous and broad-leaved mixed forest and evergreen broad-leaved forest in Jiangxi Matou mountians national nature reserve located on the western slope of Wuyi Mountain.We set up four 40 m×40 m fixed plots,and measured six leaf morphological traits（leaf thickness,leaf area,leaf water content,specific leaf area,specific leaf weight and leaf dry-matter content）,eight leaf ecological stoichiometric traits（leaf carbon content,leaf nitrogen content,leaf phosphorus content,leaf C:N ratio,leaf C:P ratio,leaf N:P ratio,leaf nitrogen content per unit area and leaf phosphorus content per unit area）and four leaf hydraulic traits（leaf stable carbon isotope,carbon isotope discrimination,the ratio of intercellular CO₂ to atmospheric CO₂ concentration and water use efficiency）of 78 dominant and common plants.In addition,we also measured the corresponding environmental factors indicators,topographic factors（elevation,slope aspect and slope gradient）and soil factors（soil p H,soil organic carbon,soil total nitrogen content,soil total phosphorus content,soil water content）.And based on the above measured datas,we systematically analyzed the variation characteristics of leaf functional traits of main dominant plants in subtropical forests on the western slope of Wuyi Mountains at interspecific and functional levels,the synergistic relationship between leaf traits,and the effects of environmental factors on leaf traits.The main results are as follow:1)The plants in the western slope of Wuyi Mountain are mainly C3 plants.The variation degree of 18 leaf traits in this region was small,and the variation degree of each trait was different,which ranging from 0.23%to 5.65%.Among them,the variation of leaf area was the largest,and the variation of leaf carbon content（LCC）and leafδ¹³C was the smallest.Due to the high precipitation of nearly 2000 mm,the forest plants on the western slope of Wuyi Mountain have higher specific leaf area（SLA）and leaf area（LA）,but lower leaf thickness（LT）and water use efficiency（WUE）compared with the same latitude area.At the same time,the plants in this area showed the characteristics of‘nitrogen-rich and phosphorus-poor’,and the average leaf N:P ratio was 12.2,which is close to the threshold of 14,indicating that the plants in this area may be limited by both N and P.In addition,the leaf functional traits are different in species,dominant families,life forms（trees,shrubs,vines,herbs）,leaf types（single leaf and compound leaf,evergreen and deciduous）and vegetation types（deciduous broad-leaved forest,coniferous and broad-leaved mixed forest and evergreen broad-leaved forest）,which essentially reflects the adaptive strategies of different functional plants to the environment.2)There are not only general correlations among leaf morphological traits,leaf ecological stoichiometric traits and leaf hydraulic traits of forest plants on the western slope of Wuyi Mountain.Futhermore,leaf ecological stoichiometric traits have also highly significant correlation with leaf morphological traits and leaf hydraulic traits,respectively.It is suggesting that forest plants in this area are not work through only a single leaf functional trait,they mainly act on plants through the combination of leaf functional traits,and continuously regulate themselves through the collaboration and tradeoff mechanisms between different leaf traits to adapt to changes in the external environment.3)Regression analysis showed that the influence of soil factors on the variation of leaf functional traits was more direct than that of topographic factors.Among them,leaf morphological traits are only closely related to soil water content（SWC）and elevation.Soil total nitrogen（TN）and total phosphorus（TP）are the dominant environmental factors for the variation of leaf nutrients and their ecological stoichiometric traits.The leaf hydraulic traits such as WUE are mainly regulated by soil moisture and soil P element.Moreover,elevation and slope aspect indirectly impact on leaf functional traits mainly by affecting soil moisture and soil P content,and thus put into the environmental filtering effect on leaf functional traits.