Abstract.To study the influence of particulate matter (PM) transported from surrounding regions on the high PM 2.5 pollution levels in Beijing, the GRAPES-CUACE model was used to simulate a serious haze episode that occurred on 6-7 December 2013. The results demonstrate the model's suitability for describing haze episodes throughout China, especially in the Beijing-Tianjin-Hebei (Jing-Jin-Ji) region. A very close positive correlation was found between the southerly wind speed over the plain to the south of Beijing and changes in PM 2.5 in Beijing, both reaching maximum values at about 900 hPa, suggesting that the lower atmosphere

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To investigate the potential use of n-alkanes (alkanes), long-chain alcohols (alcohols) and long-chain fatty acids (acids) for estimating the diet composition of sheep, in a feeding trial. A total of 18 sheep were assigned randomly to three different diets (diet A, diet B and diet C) containing up to eight herbage species (Leymus chinensis, Leymus dasystachys, Elymus sibiricum, Chenopodium album, Puccinellia chinampoensis, Medicago sativa, Saussurea sinuata and Bromus inermis). Faecal recoveries of alkanes, alcohols and acids were determined, and diet compositions were estimated using different combinations of alkanes, alcohols and acids. The faecal concentrations of individual alkanes, alcohols and acids were corrected using the mean recovery of the dietary treatment that the respective animal belonged to (diet recovery), or the mean recovery across all dietary treatments (general recovery). In general, diets did not affect the faecal recovery values for alkanes, alcohols and acids, and no difference in accuracy was found between diet composition estimates based on dietary recovery and general recovery. The accuracy of diet composition estimates declined as the number of dietary components increased from four to eight herbage species (P , 0.001). Better (P , 0.05) estimates of diet composition were obtained with the combinations of two or three marker types instead of alkanes alone. Moreover, results showed that excluding minor diet components from the calculations decreased (P , 0.05) the accuracy of diet composition estimates, whereas including extra non-grazed herbage species did not reduce (P . 0.05) the quality of diet composition estimates. These results confirmed the usefulness of alkanes, alcohols and acids as markers for determining complex diet composition of sheep. However, a negative impact on the accuracy of diet composition estimates, caused by missing minor diet components from the calculation of diet composition, could happen when plant wax markers are used to estimate the diet composition of free-ranging animals.

In this study, three schemes [Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), and Bougeault-Lacarrère (Boulac)] were employed in the Weather Research and Forecasting/Chemistry (WRF-Chem) model to simulate the severe haze that occurred in February 2014 in the Jing-Jin-Ji region and its surroundings. The PM2.5concentration simulated using the three schemes, together with the meteorological factors closely related to PM2.5(wind speed, local vertical diffusivity, and PBL height), was evaluated through comparison with observations. The results indicated that the eastern plain cities produced better simulation results than the western cities, and the cities under the eastern root of Taihang Mountain produced the worst results in simulating high PM2.5concentration in haze. All three schemes simulated very similar variation trends of the surface PM2.5concentration compared with observations. The diurnal variations of simulated surface PM2.5were not as reasonable as their reflection of daily averaged variation. The simulated concentrations of surface PM2.5using the YSU, MYJ, and Boulac schemes all showed large negative errors during daytime in polluted days due to their inefficient descriptions of local atmospheric stability or diffusion processes in haze. The lower ability of PBL schemes in distinguishing the diffusion between haze and clean days in the complex topography areas in China is an important problem for PM2.5forecasting, which is worthy of being studied in detail.

Background: Forests are increasingly valued for non-timber ecosystem services in place of conventional wood fiber production. Biomass carbon sequestration is one of the key ecosystem services forests are relied upon for mitigating global climate change. However, planning for large-scale tree planting and managing established forest stands for carbon sequestration require careful consideration of the gain in biomass production and tradeoff for other regulatory services. How a tradeoff between forest production and conservation of water resources is shaped by the condition of forest stand and environmental factors remains a question of broad interest in sustainable forest ecosystem management. Methods: We studied the spatiotemporal patterns of net primary productivity (NPP), evapotranspiration (ET), and water use efficiency (WUE), and their relationships with local climatic and forest stand factors over a temperate forest landscape in Changbai Mountain, Northeast China. The time series of spatial data on NPP and ET were extracted from the global remote sensing datasets for the MOD16A3 and MOD17A3 products for the period 2000-2014. The time series of spatial patterns of annual precipitation and annual mean temperature were obtained as grid maps for regional meteorological variables. Stand patches were categorized into the types of conifers, broadleaves, and mixed-wood, as well as age-classes of young, mid-age, near mature, mature, and oldgrowth stands, and by establishment into natural and planted. Information on stands and selective site variables were compiled from the Forest Inventory Datasets of China. Analyses were performed with Arc-GIS. Results: Over the study period of 2000-2014, the landscape-level annual NPP varied between 311.7 and 573.6 gC•m − 2 •a − 1 , ET between 559.9 and 603.0 mm•a − 1 , and WUE between 0.54 and 1.01 gC•m − 2 •mm − 1 . Across the forest landscape, the mean annual NPP varied between 205.0 and 639.4 gC•m − 2 •a − 1 , ET between 441.5 and 784.0 mm•a − 1 , and WUE in the range of 0.46-1.10 gC•m − 2 •mm − 1 . The spatial variations in NPP, ET, and WUE were commonly attributable to forest type, stand age class and density, establishment mode, and temperature variables, with some effects of other selective factors on ET and WUE. The three forest types were significantly (p < 0.05) differentiated in the mean annual NPP, ET, and WUE: the coniferous forests were highest in NPP (505.3 ± 1.4 gC•m − 2 •a − 1 ; n = 1041) and WUE (0.872 ± 0.004 gC•m − 2 •mm − 1 ; n = 1041), and lowest in ET (584.1 ± 1.6 mm•a − 1 ; n = 1041), followed by the mixed-wood forests (NPP: 500.5 ± 0.8 gC•m − 2 •a − 1 ; WUE: 0.856 ± 0.02 gC•m − 2 •mm − 1 ; ET: 589.3 ± 0.9 mm•a − 1 ; n = 2156); whereas the broadleaved forests were lowest in NPP (491.6 ± 0.6 gC•m − 2 •a − 1 ; n = 4428) and WUE (0.832 ± 0.02 gC•m − 2 •mm − 1 ; n = 4428), and highest in ET (594.7 ± 0.6 mm•a − 1 ; n = 4428). The mean annual NPP, ET and WUE increased with stand age typically in coniferous forests, and weakly in mixed-wood forests. The natural sta...

Euwallacea fornicatus (Eichhoff) is an important forest pest that has caused serious damage in America and Vietnam. In 2014, it attacked forests of Acer trialatum in the Yunnan province of China, creating concern in China’s Forestry Bureau. We used the CLIMEX model to predict and compare the potential distribution for E. fornicates in China under current (1981–2010) and projected climate conditions (2011–2040) using one scenario (RCP8.5) and one global climate model (GCM), CSIRO-Mk3-6-0. Under both current and future climate conditions, the model predicted E. fornicates to be mainly distributed in the south of China. Comparing distributions under both climate conditions showed that the area of potential distribution was projected to increase (mainly because of an increase in favourable habitat) and shift to the north. Our results help clarify the potential effect of climate change on the range of this forest pest and provide a reference and guide to facilitate its control in China.

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