No abstract

To test whether and how morphological traits are linked with growth responses of plants to temperature and CO 2 is important for understanding the mechanism underlying how plant growth will respond to global warming. In this study, using closed-top chambers to mimic future elevated CO 2 and temperature, the growth response, morphological traits of Minjiang fir (Abies faxoniana Rehd.et Wils.) and the relationship of the two were investigated after two years of exposure to the single and combined elevation of CO 2 and temperature. The results showed that biomass of Minjiang fir was 21%, 31%, and 35% greater than the control in elevated CO 2 , elevated temperature and the combination of elevated CO 2 and temperature treatments, respectively. Elevated CO 2 and temperature significantly affected the morphology of Minjiang fir, and a few morphological traits were highly correlated with growth responses. Larger branch angles at the upper layer, crown volume, and relative crown length contributed to positive growth responses to elevated CO 2 , while decreased specific leaf area (SLA) constricted any further growth response. Leaf morphological traits were more closely correlated with the response ratio than crown did in the elevated temperature, while in the combination of elevated CO 2 and temperature, crown was more correlated with the response ratio than the leaf morphological traits. Thus, our results indicate that morphological traits may contribute differently to growth responses under different experimental conditions.

Little is known about the reasons for the high dropout rate of students from poor Southwest China families under various policies support. The dropout rate of 27312 junior high school students was 6.90%, and the dropout rate of grade 7-9 increased with the grade. Principal Component Analysis was conducted on 21 attributes of 299 dropout students. We found that parents with higher educated degree and late marriage, parents working close to home, large family size, family with sick or disabled members, higher grade and non-boarding and unhealthy students increased the dropout rate. The dropout prevention requires reducing the inducers from family, school management and students themselves.