Study On The Environmental Response To Ecophysiological Features Of Quercus Variabilis Seedlings

Under the background of global climate change, vegetation dynamics were getting more and more attention, climate factors such as Temperature, precipitation and so on had been regarded that plant distribution pattern. At present, ecophysiological mechanism of plant distribution pattern had become the hot spot, however, most of the research were focused on vertical distribution pattern (altitudinal gradient).Environmental factors often showing a gradual change tendency with latitudinal gradient, so in this paper, according to the natural distribution of Quercus variabilis, seedlings of Q. variabilis derived from its south, middle, and north distribution area had been replanted in the same site.In vigorous growth period,sampling and photosynthetic assessment work were conducted in provenance site and replanting site at the same time. In order to explore the ecophysiological mechanism and deriving factors in its south and north distribution, research were foucused on the environmental response to ecophysiological features of Q.varisbilis seedlings. Conclusions are as follows:1. The Q.variabilis population at different latitudes had become different ecotype in evolution because of the enormous environment gradient variations in its distribution area, its ecophysiological features were influenced more by its hereditary character. Except leaf traits and biomass allocation, other ecophysiological features had been influenced by environment change at different level.2. In provenance site, leaf length and leaf area were positively correlated with latitude, leaf width and leaf length to width ratio of north limit population also performanced higher, hence, leaves of Q. variabilis population in its north border were larger than lower latitudinal distribution area, however, specific leaf area did not show a significant difference at different latitudes. In biomass allocation, mid and south population invested more in the under-ground part, while north population assigned more dry matters to the above-ground part.3. Nitrogen contents in each organ of Q. variabilis was positively correlated with latitude, while phosphorus contents in stem and root decreased with increasing latitude, and stem's phosphorus contents was negatively correlated with latitude, potassium contents did not differ from each latitude. Source-sink ratio of seedlings of Q. variabilis decreased with increased latitude, and source (leaf) had the higher proportion of each nutrient element contents.4. In provenance site, overall NSC contens of the Q. variabilis population in north border was higher than in south and mid, and the source-sink ratio was comparatively stable; north border also had higher starch contents, and the soluble sugar contents did not change with the latitude. Soluble sugar and NSC contents in stem as well as starch contents in root were positively correlated with latitude. In non-structural carbohydrate allocation, the proportion of NSC and its components in root is the biggest among different organs. C-N ratio in source and sink of the Q. variabilis population in north border was lower than in its south border and middle distribution area, and sink tissues had a higher C-N ratio among different latitudes.5. Comprehensive comparison in photosynthetic parameters of Q. variabilis at different latitudes indicated that, south border Q.variabilis population's photosynthetic ability was higher than middle and north border, while north border population had advantages in using weak light.6. Nitrogen and phosphorus contents in different organs of Q. variabilis population north border decreased with environmental change, but mid population and south border population did not show significant changes, potassium contents of Q. variabilis at different latitudes did not change obviously. Concerning non-structural carbohydrate, contents of NSC and soluble sugar did not show significant variation, however, starch contents changes obviously. The appropriate light and temperature conditions in replanting site lead to an increase of maximum net photosynthesis rates at each latitude, especially in north border; and after environmental change, north border Q. variabilis population's light adapting and using capacity went up.7. Nitrogen contens played an important role in the formation of plant's distribution patterns, while nitrogen, phosphorus and potassium were unlikely to be the major factors which would restricted the formation of Q. variabilis's north border; there were no "carbon limitation" in north border of Q.variabilis.8. Ecophysiological features of north border Q.variabilis population were significantly different compared with mid and south border population and more sensitive toward environment change, it proned to enhance the use efficiency of weak light and the adaptbility of low temperature.