| Quercus variabilis was an ideal species to study the vegetation response to global environmental change for its widely distribution. The Quercus variabilis seeds derived from south(Anning, Yunnan Province), middle(Hefeng, Hubei Province), and north distribution(Zhuanghe, Liaoning Province) boundary was collected and transported to Wuhan for further study. One-year-old seedlings grew in artifical climate chamber with4treatment:①contrast (ACCK);②nitrogen (120kgN/hm2)(ACN);③CO2enhancement (700μmol/mol)(ECCK);④CO2enhancement (700μmol/mol) and nitrogen (120kgN/hm2)(ECN), then they were transferd to outdoor in the end of growing season and grew in the natural environment in next year for further study. The eco-physiological characteristics was observed to reflect the response of Quercus variabilis seedlings to CO2enhancement, Nitrogen deposition and C-N interaction. The Quercus variabilis s eco-physiological mechanism to environment change was researched, and it could provide a scientific basis for prediction of environment change on plant distribution patterns. The main conclusions are as follows:1. CO2enhancement, Nitrogen fertilization and C-N interaction promoted the seedlings’ growth, resulting in lots of "compound effect", such as the number of branches and biomass increased. The effect continued to accelerate the two-year-old seedlings’ growth. The C-N interaction has the most significant promoting.2. Nitrogen fertilization and C-N interaction increased Liaoning Quercus variabilis leaf length, width and area, but the leaf length/width and special leaf area had not changed. While Hubei and Yunnan Quercus variabilis leaf morphology didn’t change in all treatment.3. The changed environment hadn’t changed the nutrient element allocation in seedlings’ organ. The nitrogen and potassium content showed that leaf>root>stem, whereas phosphorus content showed leaf=stem>root. The nutrient element content (N/P/K) changed with environment. The content of leaf N showed consistent variation, which decreased under CO2enhancement, while increased with additional nitrogen fertilizer, and only Yunnan Quercus variabilis seedlings’decreased C-N interaction. Leaf P and K showed constant or lower. The reason for nutrient elements decreased can be explained by "dilution effection", which was because the biomass increased more than nutrient elements accumulation. The absorption of N element was increased for seedlings under ntrogen fertilizer, which would reduce the absorpion and utilization of P and K. This impact would last long time that two-year-old seedlings also showed P and K content decreased or unchanged.4. The photosynthetic pigments content reduced under CO2enhancement, while increased with nitrogen fertilizer, as well as showed constant under C-N interaction. Leaf N, which was one of the important raw material of photosynthetic pigment synthesis, would affect the content of photosynthetic pigments when it change. Leaf N content and photosynthetic pigment content showed synchronous changes under CO2enhancement and N fertilizer treatments in this article. However, southern Quercus variabilis’leaf N content decreased with no decline of photosynthetic pigment content, which indicated that the N content variation was not the only reason for photosynthetic pigments change.5. The increased photosynthetic parameters showed that the Quercus variabilis seedlings’ photosynthetic ability was increased under enhanced CO2, additional nitrogen and C-N interaction. Their photosynthetic capacity had none significant difference with contrast when two-year-old seedlings grew in natural environment again. Short-term CO2enhancement(30days) would increased Quercus variabilis seedlings’photosynthetic capacity, while the maximum carboxylation rate (VCmax) and the maximum electron transfer efficiency (Jmax) was lower(no significant difference) than contrast with long-term CO2enhancement100days), which meant seedlings appeared slightly "photosynthetic downward adjustment". The downward effect was relieved with additional nitrogen fertilizer, which was verified by C-N interaction. Vcmax and Jmax had no difference between C-N interaction and contrast treatments. The photosynthetic downward adjustment effect continued existence with the Vcmax and Jmax of two-year-old Quercus variabilis seedlings slightly lower(no significant difference) than contrast. 6. The non-structural carbohydrates (NSC) content of three source seedlings showed much differences under different environment, which may be due to the different source Quercus variabilis formed different mechanism of adaptation to the environment for the long-term growth in different environments, in additon, NSC was balanced between assimilation production and alienation consumption in plants, which had a large variability. NSC content affected the growth of plants and plant tolerance, so it may be one of important factors that influenced the distribution of plants. The NSC content of northern boundary Quercus variabilis in "sink"(stems and roots) organs increased in growing season, which enhanced the plant cold resistance.In short, CO2enhancement and nitrogen deposition had a greater impact on Quercus variabilis seedlings, which showed the acceleration of growth and a series of eco-physiological characteristics parameters change. The respose to environment change showed difference for different source Quercus variabilis that meant the mechanism of adaptation to the environment had difference, which due to their grew in different environment for long time. The northern boundary Quercus variabilis was more sensitive to environmental change in contrast. Quercus variabilis distribution boundaries may move in the future global change, and its distribution would expand. |
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