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Impending climate warming is expected to influence plant growth and distribution, and the distribution range limit of tree species is extremely sensitive to climate change. However, synchronous comparisons of responses of different tree species with overlapping ecological niches to climate at their distribution range limit in the same region have received little attention. In the present study, we assessed the discrepancy in radial growth responses of two dominant oak species to climate at their distribution range limit (southern range limit for Quercus mongolica, northern range limit for Quercus variabilis) in Beijing, China. Furthermore, growth-climate relationships were examined using linear mixed-effects models, and growth trends up to the year 2100 were forecast based on future climate scenarios (RCP2.6 and RCP8.5). Our results indicated that there were no significant differences in the growth response to climate between Q. variabilis at its northern limit and Q. mongolica at its southern limit, and the growth of the two tree species was positively correlated with the minimum temperature and negatively correlated with the climatic moisture deficit of autumn. However, the growth response to climate variables varied at different sites. Additionally, the model forecast showed an increase in radial growth of Q. variabilis at its northern limit and Q. mongolica at its southern limit up to the end of the present century. [ABSTRACT FROM AUTHOR]

Background and Objectives: This study explored the appropriate classification of pre-pregnancy body mass index (BMI) in women of childbearing age in Beijing, China.Methods and Study Design: Women with singleton pregnancies at more than 28 gestational weeks were retrospectively reviewed. Based on the pre-pregnancy BMI (kg/m2), these patients were divided into 7 groups: <18.5, >=18.5-22.9, >=23-23.9, >=24-24.9, >=25-27.9, >=28-29.9, and >=30. Pregnancy adverse outcomes, including gestational hypertension with or without preeclampsia, gestational diabetes mellitus, initial cesarean section, postpartum hemorrhage, macrosomia, large-for-gestational age infant and so on were recorded. Binary logistic regression analysis was used to calculate the uncorrected and corrected odds ratios and 95% confidence intervals, with the >=18.5-22.9 group serving as a reference.Results: A total of 11,136 pregnant women were analyzed. Incidences of above mentioned six adverse outcomes were greater in women with higher pre-pregnancy BMI. The risks of the abovementioned six adverse outcomes were increased significantly among the >=23-23.9, >=24-24.9, >=25-27.9 groups and substantially higher in the >=28-29.9, >=30 groups after correction. <18.5 group showed an increased risk of small-for-gestational age infants.Conclusions: For women of childbearing age in Beijing, China, the optimal pre-pregnancy BMI range was >=18.5-22.9 kg/m2, with the cutoff value for overweight status being >=23.0 kg/m2 and the cutoff value for obesity being >=28.0 kg/m2. [ABSTRACT FROM AUTHOR]

Systematic studies of hexachlorobenzene in the ambient air before and after the Beijing Olympic Games were carried out during July 2007 to March 2009. Air samples were collected around 20th monthly on the roof of a building near the Olympic center. The average concentration of hexachlorobenzene was 264 pg·m−3, which was higher in winter than other seasons. However, hexachlorobenzene concentration was decreased clearly in winter in 2008 compare with in 2007 due to the implementation of a series of “Green Olympic” policies. Gas-particle partitioning shows that the increase of hexachlorobenzene levels in winter time was mainly contributed by the high total suspended particulate from combustion processes such as coal-burning and traffic emission. [ABSTRACT FROM AUTHOR]

Abstract: The atmospheric CH[sub 4] in Beijing is still increasing, even though its increasing rate has significantly decreased from 1.76%/a during 1985--1989 to 0.50%/la during 1990--1997. The seasonal variation of CH[sub 4] concentration showed a double-peak pattern, one peak appearing in winter and the other in summer. It is evident that the annually seasonal variations of atmospheric CH[sub 4] in Beijing are different. From 1986 to 1997, the atmospheric CH[sub 4] increased by 185 pphv, 37% and 21% of which were due to the increase in winter and in summer, respectively. After 1993, the annually seasonal increasing rate of CH[sub 4] concentration in summer (due to emission from biogenic sources) is negative while the increasing rate in winter (due to emission from non-biogenic sources) is positive about 25 ppbv/a. As a result, the increase of CH[sub 4] emission from non-biogenic sources in winter is the major reason that caused the annually seasonal increasing rate from 1993 to 1997. The biogenic sources in Beijing are shrinking while the non-biogenic ones (such as fossil fuel combustion) are enlarging. [ABSTRACT FROM AUTHOR]