Effects of stand ages on soil enzyme activities in Chinese fir plantations and natural secondary forests.

Forest type and stand age are important biological factors affecting soil enzyme activities. However, the changes in soil enzyme activities across stand ages and underlying mechanisms under the two forest restoration strate-gies of plantations and natural secondary forests remain elusive. In this study, we investigated the variations of four soil enzyme activities including cello-biohydrolase (CBH), ß-1,4-glucosidase (ßG), acid phosphatase (AP) and ß-1,4-N-acetylglucosaminidase (NAG), which were closely associated with soil carbon, nitrogen, and phosphorus cycling, across Cunninghamia lanceolata plantations and natural secondary forests (5, 8, 21, 27 and 40 years old). The results showed that soil enzyme activities showed different patterns across different forest types. The acti-vities of AP, ßG and CBH in the C. lanceolata plantations were significantly higher than those in the natural secon-dary forests, and there was no significant difference in the NAG activity. In the plantations, AP activity showed a decreasing tendency with the increasing stand ages, with the AP activity in the 5-year-old plantations significantly higher than other stand ages by more than 62.3%. The activities of NAG and CBH decreased first and then increased, and ßG enzyme activity fluctuated with the increasing stand age. In the natural secondary forests, NAG enzyme activity fluctuated with the increasing stand age, with that in the 8-year-old and 27-year-old stand ages being significantly higher than the other stand ages by more than 14.9%. ßG and CBH enzyme activities increased first and then decreased, and no significant difference was observed in the AP activity. Results of the stepwise regression analyses showed that soil predictors explained more than 34% of the variation in the best-fitting models predicting soil enzyme activities in the C. lanceolata plantations and natural secondary forests. In conclusion, there would be a risk of soil fertility degradation C. lanceolata plantations with the increasing stand age, while natural secondary forests were more conducive to maintaining soil fertility.

Health literacy of junior high school students in Jiaxing and its influencing factors / 预防医学

Objective@#To learn the health literacy level and its influencing factors among junior high school students in Jiaxing, so as to provide basis for health promotion of adolescents. @*Methods@#The junior high school students who had been studying and living in Jiaxing for more than six months were selected by multistage cluster random sampling method. A questionnaire survey was conducted to collect general information and health literacy level (including basic knowledge and concept, healthy lifestyle and behaviors, and basic skills) of these selected students. The multivariate logistic regression model was used to analyze the influencing factors for health literacy.@*Results @#Of 1 773 questionnaires collected, 1 738 were valid, accounting for 98.03%. The level of health literacy in the junior high school students in Jiaxing was 22.84% ( 95%CI: 20.87%-24.82% ), The levels of basic knowledge and concept, healthy lifestyle and behaviors, and basic skills were 55.29% ( 95%CI: 52.95%-57.63% ), 21.75% ( 95%CI: 19.81%-23.69% ), 53.05% ( 95%CI: 50.70%-55.40%), respectively. Multivariate logistic regression analysis showed that the second grade and above ( OR: 1.609-1.835, 95%CI: 1.195-2.459 ), mother's educational level of technical secondary school/senior high school and above ( OR: 1.965-1.976, 95%CI: 1.276-3.357 ), and self-rated academic achievement of medium and above ( OR: 1.881-2.441, 95%CI: 1.359-3.335 ) were the promoting factors for health literacy level of junior high school students; self rated health status as unhealthy ( OR=0.254, 95%CI: 0.089-0.721 ) was an obstructive factor.@*Conclusions@#The health literacy level of the junior high school students in Jiaxing was 22.84%. The level of healthy lifestyle and behaviors was the lowest in three aspects. Grade, mother's educational level, self-rated academic performance and self-rated health status may have impacts on health literacy level of junior high school students.