Responses of forest ecosystems to increasing N deposition in China: A critical review.

China has been experiencing a rapid increase in nitrogen (N) deposition due to intensified anthropogenic N emissions since the late 1970s. By synthesizing experimental and observational data taken from literature, we reviewed the responses of China's forests to increasing N deposition over time, with a focus on soil biogeochemical properties and acidification, plant nutrient stoichiometry, understory biodiversity, forest growth, and carbon (C) sequestration. Nitrogen deposition generally increased soil N availability and soil N leaching and decreased soil pH in China's forests. Consequently, microbial biomass C and microbial biomass N were both decreased, especially in subtropical forests. Nitrogen deposition increased the leaf N concentration and phosphorus resorption efficiency, which might induce nutrient imbalances in the forest ecosystems. Although experimental N addition might not affect plant species richness in the overstorey, it did significantly alter species composition of understory plants. Increased N stimulated tree growth in temperate forests, but this effect was weak in subtropical and tropical forests. Soil respiration in temperate forests was non-linearly responsive to N additions, with an increase at dosages of <60 kg N ha-1 yr-1 and a decrease at dosages of >60 kg N ha-1 yr-1. However, it was consistently decreased by increased N inputs in subtropical and tropical forests. In light of future trends in the composition (e.g., reduced N vs. oxidized N) and the loads of N deposition in China, further research on the effects of N deposition on forest ecosystems will have critical implications for the management strategies of China's forests.

Tea Consumption and Longitudinal Change in High-Density Lipoprotein Cholesterol Concentration in Chinese Adults.

BACKGROUND: The relation between tea consumption and age-related changes in high-density lipoprotein cholesterol (HDL-C) concentrations remains unclear, and longitudinal human data are limited. The aim of current study was to examine the relation between tea intake and longitudinal change in HDL-C concentrations. METHODS AND RESULTS: Baseline (2006) tea consumption was assessed via a questionnaire, and plasma HDL-C concentrations were measured in 2006, 2008, 2010, and 2012 among 80 182 individuals (49±12 years of age) who did not have cardiovascular diseases or cancer, or did not use cholesterol-lowering agents both at baseline (2006) and during the follow-up period (2006-2012). The associations between baseline tea consumption and rate of change in HDL-C concentrations were examined using generalized estimating equation models. Tea consumption was inversely associated with a decreased rate of HDL-C concentrations (P-trend <0.0001) in the fully adjusted model. The adjusted mean difference in the HDL-C decreased rate was 0.010 (95% confidence interval, 0.008, 0.012) mmol/L per year for tea consumers versus nonconsumers (never or less than once/month group). Interactions between tea consumption and age, sex, lifestyle scores, and metabolic syndrome (all P-interaction <0.0001) were identified. The associations between greater tea consumption and slower decrease in HDL-C concentrations were more pronounced in men, individuals aged 60 or older, individuals with a lower lifestyle score, and individuals with metabolic syndrome (all P-trend <0.0001). CONCLUSIONS: Tea consumption was associated with slower age-related decreases in HDL-C concentrations during 6 years of follow-up. CLINICAL TRIAL REGISTRATION: URL: www.chictr.org. Unique identifier: ChiCTR-TNRC-11001489.