Geographic Differentiation Of Functional Traits Of Main Tree Species In Temperate Zone Of NSTEC

The study of geographical distribution pattern has long been important in ecology. Plantfunctional traits not only reflect the response and adopt of plants to habitat conditions, but alsoconnect the environment to plants and the structure, process and function of ecological system.Under the background of global climate change, studies on the relationships between plantfunctional traits and environment can better understand the driving mechanism of theenvironment to the changes of plant distribution pattern, and provide the theoretical basis topredict the future trend of vegetation development. The North-South Transect of Eastern China(NSTEC) is one of15land belts in the world, with the unique vegetation distribution patternhere created by the environmental change. In temperate zone of NSTEC, the distribution ofQuercus trees presents a geographical vicarism pattern.Hence, the purpose of this study was to analyze the pattern of functional traits change ofmain tree species along the environmental gradient, discuss the adaptive strategy of main treespecies, and then reveal the mechanism of the Quercus trees geographical vicarism at differentlife-history stages. This study included four aspects:(1) the relationships between theenvironmental conditions and functional traits of main tree species;(2) the change pattern offunctional traits of Quercus trees along the environmental gradient;(3) the response andadaptation of seeds traits of Quercus trees to the environmental conditions;(4) thedifferentiation of functional traits of Quercus trees seedling. The study was conducted intemperate zone of NSTEC, which includes two climatic zones, so the change of climate isdramatic.The main research methods and results were as follows:(1) To study the geographic differentiation of functional traits of main tree species intemperate zone of NSTEC,55kinds of main tree species at11sites were sampled. SimpleLinear Regression and Multiple Linear Stepwise Regression were used to analysis relationships between the functional traits and environmental factors, and Standardised Major Axis was usedto analysis relationships among the functional traits. The results showed that compared to thesoil factor, the climate factors play a greater role in driving the change of traits. With thedecrease of precipitation and the increase of soil phosphorus content, leaf mass per area (LMA)and leaf dry matter content (LDMC) tended to increase; leaf nitrogen content (Nmass) increasedwith the increase of sunlight time and the decrease of soil nitrogen content; leaf phosphoruscontent (Pmass) increased with the increase of soil organic matter content and sunlight time;temperature was the only factor to drive the change of ratio of bark to diameter at breast height,the thickness of bark increased with the decrease of temperature; leaf potassium content (Kmass)didn’t change significantly in the study area. In addition, the relationships among functionaltraits reflected the adaptative strategies of main tree species, such as the tree species of highLMA and LDMC could live better in the habitat of lack of water, as their ability to useenvironmental resources are stronger; tree species which are higher Nmassand Pmass, adapte tothe environment with slower speed of nutrient circulation; and Kmass was also the key factorwhich affect the growth of main tree species.(2) Through refering to plant specimens, the leaf morphological information of12kindsof Quercus species at23sites was got. Pearson Correlation analysis was used to analysis thechange of leaf morphological traits of Quercus trees along the gradient of climate, andStandardised Major Axis method was used to discuss the relationships among leafmorphological traits. In addition, the other studies of functional traits of Quercus trees wereused to discuss the environment driving mechanism of Quercus trees geographic differentiation.On the whole, leaf morphological traits of Quercus trees changed significantly along thegradient of climate. Leaf areas and dissection of leaf margin increased with temperaturedropping and sunlight time increasing; leaf vein density increased with the increases oftemperature and precipitation，while decreased with the increase of sunlight time. Moreover,leaf morphological traits were relative to each other, and Quercus trees develop the optimalleaf morphology to grow maximumly with limited resources. The leaf size was the most important morphological traits: it correlated positively with petiole length and dissection ofleaf margin, but negatively with leaf vein density; when leaf tend to become the elongatedshape, the petiole length and leaf vein density also increased. The integration of several studiesindicated that the distribution pattern of Quercus trees is restricted primarily by climate,Quercus trees are adapted to the environment by adjusting the change of traits of morphology,structure and physiology.(3) In order to reveal the change pattern of seed traits of Quercus trees along environmentgradient and the relationship among seed chemical compositions, Quercus species from9coredistribution areas were selected in temperate zone of NSTEC. Seeds were collected in the field,and then seed mass and chemical compositions were measured. The results showed that climatewas the main affective condition on the change of seed traits, while temperature was the mostimportant climate factor, and the sunlight time took second place. The kind of Quercus treeswhich seed mass is heavier tended to distribute in northern area of temperate zone of NSTECof low temperature and long sunlight time. With decreasing of temperature, the accumulationof starch content decreased, but some cold-tolerant substances such as protein, soluble sugarand proline increased gradually. Furthermore, the adaptive strategy of Quercus trees byadjusting changes of seed chemical compositions was also synchronized, as there were positiverelationships among the content of soluble sugar, protein and praline, and all of them werenegative relations with starch.(4) The seeds which collected from different core distribution areas of Quercus trees werepretreated and sown in the same environment. In order to minimize effect of environmentalstress on the study, the central site in temperate zone of NSTEC was choose as the site ofcommon garden experiments.1year seedlings of Quercus trees are acted as research objects tocompare the difference and variation of different functional traits in intra-species andinter-species, and the relationships between functional traits of seedlings and mature trees areanalyzed, and the relationships between seed mass and seedlings traits are discussed. Theintraspecies differences of all functional traits were smaller than the interspecies difference, and so were the variation coefficients, and all functional traits of seedling were weaklycorrelation with mature trees. Seed mass was little effect on leaf functional traits of seedling,but important influence on the biomass and its allocation (RSR).As all the results proved, the formation and change of plant species distribution pattern arenot random and accident, the environment can influence plants functional traits. Meanwhile,plants respond and adapt to environment through a series of modulation of morphology,structure and physiological function, and develop different adaptation strategies in differentgrowth phases, so plants are able to establish, grow and reproduce in the appropriate location.