Northern China Plain Research Articles

Reduction of wheat photosynthesis by fine particulate (PM2.5) pollution over the North China Plain

ABSTRACTThe negative impact of rapid urbanization in developing countries has led to a deterioration of urban and regional air quality. Much attention has been given to the impact of fine particulate pollution on urban public health. However, very little attention has been given to its impact on the regional ecosystem such as the agricultural ecosystem. Thus, we evaluate the direct impact of air pollution on the reduction of wheat photosynthesis by fine particulate matter (PM2.5) pollution in the world’s most heavily polluted area, the North China Plain, using remote sensing observations and ground measurements. We found the following to be true: (1) Heavy PM2.5 pollution could significantly reduce wheat photosynthesis and cause an expositional relationship between the PM2.5 concentration and wheat photosynthesis (R2 = 0.9824, P < 0.05); (2) Heavy PM2.5 pollution makes up 2% for the reduction in wheat photosynthesis at all wheat-plant farmlands in the North China Plain, approximately covering an area of 354,400 km2; (3) Increasing heavy PM2.5 pollution significantly reduced wheat photosynthesis by 87% in wheat-planted farmland during 1999–2011. We hope the results presented here could draw attention to the effect of PM2.5 pollution on the agricultural ecosystem and encourage further studies to evaluate the feedback of atmospheric pollution on the agricultural ecosystem using remote sensing.Abbreviation: Northern China Plain (NCP); normalized difference vegetation index (NDVI); The Moderate Resolution Imaging Spectroradiometer (MODIS); fine particulate matter (PM2.5)

Climate-smart management can further improve winter wheat yield in China

Climate change, genotype, and agronomic management have profound impacts on crop yield. Our goal in this study is to untangle the interrelated contributions of climate change, genetic improvements, and agronomic management on winter wheat yield in China to develop management strategies that address future nutritional needs. The Agricultural Production System Simulator (APSIM) farming systems model was used to simulated long-term (1981–2010) wheat yield for four wheat production regions under different Genotype by Environment by Management (GxExM) scenarios. Using detailed field experimental data from 1981 to 2005 in conjunction with the APSIM-wheat model, the potential for climate-smart management to improve yield on a regional scale is investigated. Results showed that when all climatic variables were considered together, winter wheat relative yield change decreased from 0.62% to 7.16% over the period 1981 to 2010, depending on cultivar and growing region. The impact of individual climatic variables varied by region. In general, winter wheat yields showed the least decline in the Northern China Plain (NC) due to climate change. Cultivar renewal combined with improvements in agronomic management boosted yields but to a different extent in each region. For cultivar renewal, yields increased 6.93%, 17.69%, 24.87%, and 52.72% in the NC, Yellow and Huai River Valleys (YH), SW and YV, respectively over the period 1981 to 2010. Agronomic management improved yields by 22.91%, 5.27%, 58.77%, and 59.20% in these regions, respectively. Overall, the observed yield improvements with agronomic management were higher than those resulting from cultivar renewal for most of China's wheat growing regions. The exception was found in YH, where improvements in winter wheat yield from cultivar renewal were greater than those from agronomic management. Regardless, there is still ample room for yield improvement in winter wheat by implementing climate-smart management. SW would benefit significantly, with a potential increase of 99% because of improved agronomic management. More moderate, but still significant increases were predicted for NC and YH (49% and 42%, respectively) while only moderate improvements were anticipated for YV (17%). Our findings highlight the extent that improvements in cultivar renewal and agronomic management have compensated for the negative impacts of climate change for different wheat growing regions of China over the past three decades. The results also indicate that advances in agronomic management outweighed the effects of cultivar renewal in most regions. Climate-smart management is still needed to further improve yields in wheat-growing regions of China.

Detection and emission estimates of NOx sources over China North Plain using OMI observations

ABSTRACTWe designed a fast procedure to detect the nitrogen oxides (NOx) sources in the China North Plain and to estimate their NOx emissions through a two-dimensional Gaussian fitting method applied to averaged Ozone Monitoring Instrument (OMI) observations of nitrogen dioxide (NO2) column concentration. The Northern China Plain is a region that has one of the highest densities of anthropogenic NOx sources in the world and therefore the sources are difficult to distinguish. With our procedure we still found 94 individual NOx emission sources. Of these sources Tangshan city has the strongest NOx emission rate (92 Gg N year–1), while the weakest that we are still able to detect is Zhangjiakou city, with a NOx emission rate of 0.4 Gg N year–1. Using the fitting results, we reconstruct the NO2 column concentration distribution map, which matches the OMI observations with an R2 = 0.85 and a slope of 0.78. The derived NOx emission rates for cities and provinces level show good agreement with former studies.

Characterizing and sourcing ambient PM2.5 over key emission regions in China III: Carbon isotope based source apportionment of black carbon

Regional haze over China has severe implications for air quality and regional climate. To effectively combat these effects the high uncertainties regarding the emissions from different sources needs to be reduced. In this paper, which is the third in a series on the sources of PM2.5 in pollution hotspot regions of China, we focus on the sources of black carbon aerosols (BC), using carbon isotope signatures. Four-season samples were collected at two key locations: Beijing-Tianjin-Hebei (BTH, part of Northern China plain), and the Pearl River Delta (PRD). We find that that fossil fuel combustion was the predominant source of BC in both BTH and PRD regions, accounting for 75 ± 5%. However, the contributions of what fossil fuel components were dominating differed significantly between BTH and PRD, and varied dramatically with seasons. Coal combustion is overall the all-important BC source in BTH, accounting for 46 ± 12% of the BC in BTH, with the maximum value (62%) found in winter. In contrast for the PRD region, liquid fossil fuel combustion (e.g., oil, diesel, and gasoline) is the dominant source of BC, with an annual mean value of 41 ± 15% and the maximum value of 55% found in winter. Region- and season-specific source apportionments are recommended to both accurately assess the climate impact of carbonaceous aerosol emissions and to effectively mitigate deteriorating air quality caused by carbonaceous aerosols.

Winter Wheat Yield Gaps and Patterns in China

Core Ideas Based on yield gap analysis, wheat yield can be improved significantly in China.Both actual and potential wheat yields showed considerable spatial variability.Winter wheat yields increased in 53% of the counties in China.Nearly half of the counties experienced impaired wheat yields.Declining solar radiation and increasing temperature reduce wheat yield. Wheat (Triticum aestivum L.) yield stagnation has been reported in some regions of the world. China is the largest producer of wheat across the globe, but the pattern of its wheat yield stagnation remains poorly addressed. Here, our goal is to examine the temporal trends and spatial patterns of wheat yields along with possible causes based on a comprehensive assessment of winter wheat yield throughout China over the 31‐yr period from 1980 to 2010. Combined with the Agricultural Production Systems Simulator (APSIM) wheat model, we assessed the winter wheat yield gaps and patterns in 1414 counties and at five physiogeographic regional scales across China to ascertain the driving factors of yield variations. Wheat yields increased in 53% of the 1414 counties, but the remaining counties experienced yields that never improved, stagnated, or collapsed from 1980 to 2010. The yield gap analysis showed that actual yields represented only 59% of the national average yield potential, indicating a substantial opportunity to improve winter wheat yields. Relatively larger yield gaps were observed in the northern China Plain (NC, 47%) and in southwestern China (SW, 45%). Although the yield gaps in these regions were accompanied by significantly progressive uptrends of actual yields, our results suggest that agronomic management could be further improved. Moreover, underperforming regions could potentially benefit from new investments and strategies to reliably increase actual yields and reverse trends in stagnation in winter wheat performance.

Optimizing the nitrogen application rate for maize and wheat based on yield and environment on the Northern China Plain

Optimizing the nitrogen (N) application rate can increase crop yield while reducing the environmental risks. However, the optimal N rates vary substantially when different targets such as maximum yield or maximum economic benefit are considered. Taking the wheat-maize rotation cropping system on the North China Plain as a case study, we quantified the variation of N application rates when targeting constraints on yield, economic performance, N uptake and N utilization, by conducting field experiments between 2011 and 2013. Results showed that the optimal N application rate was highest when targeting N uptake (240kgha−1 for maize, and 326kgha−1 for wheat), followed by crop yield (208kgha−1 for maize, and 277kgha−1 for wheat) and economic income (191kgha−1 for maize, and 253kgha−1 for wheat). If environmental costs were considered, the optimal N application rates were further reduced by 20–30% compared to those when targeting maximum economic income. However, the optimal N rate, with environmental cost included, may result in soil nutrient mining under maize, and an extra input of 43kgNha−1 was needed to make the soil N balanced and maintain soil fertility in the long term. To obtain a win-win situation for both yield and environment, the optimal N rate should be controlled at 179kgha−1 for maize, which could achieve above 99.5% of maximum yield and have a favorable N balance, and at 202kgha−1 for wheat to achieve 97.4% of maximum yield, which was about 20kgNha−1 higher than that when N surplus was nil. Although these optimal N rates vary on spatial and temporal scales, they are still effective for the North China Plain where 32% of China's total maize and 45% of China's total wheat are produced. More experiments are still needed to determine the optimal N application rates in other regions. Use of these different optimal N rates would contribute to improving the sustainability of agricultural development in China.

Characteristics of summer and winter precipitation over northern China

In this paper, the statistical properties of summer and winter precipitation over the northern China plain are investigated by using a two-dimensional video disdrometer (2DVD) and a micro-rain radar (MRR). The properties of summer precipitation presented herein are bulk properties (radar reflectivity, reflectivity-weighted fall velocity, liquid water content, and rainfall rate), raindrop fall velocity, axis ratio, and particle size distribution. Well correlations can be found among the diurnal cycles of radar reflectivity, liquid water content, and rainfall rate, whereas reflectivity-weighted fall velocity is poorly related to other bulk properties. The vertical profiles exhibit that radar reflectivity for stratiform rain is increasing with the altitude decreasing, in contrast, liquid water content and rainfall rate are reducing during the falling. These facts are useful for the radar-based rainfall rate retrieval algorithm. Axis ratio measurements are, for the first time, obtained and analyzed in northern China, which are particularly important for improving microphysical scheme in the climate models. In the constraint gamma model, the μ−Λ relation is adapted to the particle size distribution of stratiform rain, while the normalized gamma distributions for convective rain are separated to maritime-like and continental categories following the orientations and mechanisms of the storms. A new bulk-property-based algorithm is developed for the classification of convective and stratiform precipitation. For winter precipitation, radar reflectivity and snowfall rate for aggregates are calculated from the disdrometer data. The relationship of radar reflectivity and snowfall rate is obtained and validated with MRR data. The characteristics of summer and winter precipitation will be used to improve the microphysical scheme and evaluate the representation of precipitation in the climate models.

Isolating and Quantifying the Effects of Climate and CO2 Changes (1980–2014) on the Net Primary Productivity in Arid and Semiarid China

Although the net primary productivity (NPP) of arid/semiarid ecosystem is generally thought to be controlled by precipitation, other factors like CO2 fertilization effect and temperature change may also have important impacts, especially in the cold temperate areas of the northern China, where significant warming was reported in the recent decades. However, the impacts of climate and atmospheric CO2 changes to the NPP dynamics in the arid and semiarid areas of China (ASA-China) is still unclear, hindering the development of climate adaptation strategy. Based on numeric experiments and factorial analysis, this study isolated and quantified the effects of climate and CO2 changes between 1980–2014 on ASA-China’s NPP, using the Arid Ecosystem Model (AEM) that performed well in predicting ecosystems’ responses to climate/CO2 change according to our evaluation based on 21 field experiments. Our results showed that the annual variation in NPP was dominated by changes in precipitation, which reduced the regional NPP by 10.9 g·C/(m2·year). The precipitation-induced loss, however, has been compensated by the CO2 fertilization effect that increased the regional NPP by 14.9 g·C/(m2·year). The CO2 fertilization effect particularly benefited the extensive croplands in the Northern China Plain, but was weakened in the dry grassland of the central Tibetan Plateau due to suppressed plant activity as induced by a drier climate. Our study showed that the climate change in ASA-China and the ecosystem’s responses were highly heterogeneous in space and time. There were complex interactive effects among the climate factors, and different plant functional types (e.g., phreatophyte vs. non-phreatophyte) could have distinct responses to similar climate change. Therefore, effective climate-adaptive strategies should be based on careful analysis of local climate pattern and understanding of the characteristic responses of the dominant species. Particularly, China’s policy makers should pay close attention to climate change and ecosystem health in northeastern China, where significant loss in forest NPP has been triggered by drought, and carefully balance the ecological and agricultural water usage. For wildlife conservation, the drought-stressed grassland in the central Tibetan Plateau should be protected from overgrazing in the face of dramatic warming in the 21st century.

Historical variation in black carbon deposition and sources to Northern China sediments

Black carbon (BC) in fine particulate matter (PM2.5) is an important air pollutant in a large area of China. We have reconstructed a 100-year-long history of BC deposition based on analyses of sediment samples in the coastal area of the Northern China Plain (NCP). During 1900–2010, the sedimentary BC concentrations at three cores increased from 0.2 to 1.3, from 0.2 to 2.3, and from 0.2 to 1.9 mg g−1, and the ranges for the BC deposition fluxes were 0.1–4.7, 0.1–8.2, 0.2–7.4 g m−2 a−1, suggesting the increase of ten times from the pre-industrial era. The BC deposition fluxes showed abrupt variation with two peaks in the 1970s and 2010s. Residential energy consumption and biomass burning (i.e., low-temperature combustion sources; thus, large-scale wildfires with high temperature may not be included) were responsible for the BC increase in the 1970s. Fossil fuel combustion generated by the industrial sectors, including industry, power plants, and transportation, was negligible before 1990 but significantly increased during 1990–2010. The historical increase in the BC deposition was accurately predicted by climate models, specifically the Coupled Model Intercomparison Project Phase 5 (CMIP5). However, the BC fluxes in the NCP sediments were an order of magnitude greater than those of the simulated depositions, suggesting an underestimation of the BC deposition in the severely polluted area in China.

Understanding Variability of Haze in Eastern China

In recent years, there are heavy aerosol pollutions in eastern China. For example, in the Northern China Plain (NCP) and the capital city of Beijing, the concentrations of PM2.5 (particle matter <2.5 μm in diameter) often reached to the levels of more than 200-400 μg/m3. In contract, the World Health Organization (WHO) identifies a safe level of air quality as containing 10-25 μg/m3. In addition to the high levels of aerosol pollutions, there is a largely temporal variability of the concentrations. This study discusses the major factors, which control the short-term variability (days to weeks) of the aerosol pollutions in eastern China. The results suggest that the meteorological parameters, including wind direction, wind speed, and vertical diffusion in the planetary boundary layer (PBL) have important effects on the short-term variability. The secondary formation of aerosols, especially during heavy haze periods, has also important contribution to the large variability. Because the secondary aerosols (SA) have a large portion in the composition of the total aerosols during the haze period, the formation of SA amplifies the magnitude of the variation, causing significant increase in the concentrations of PM2.5 during the heavy haze periods in eastern China.

Photosynthetic production of wheat under precision planting patterns in northern china

Winter wheat ( Triticum aestivum ) is cultivated across a wide region; however, water is scarce during the growing season of wheat in the Northern Plain of China. Therefore, winter wheat should be irrigated to maintain a stable and high grain yield. The aim of this field study was to develop a water-conserving precision planting pattern for winter wheat that is grown in the Northern China Plain with the purpose of exploring the benefits in maintaining water and effects on wheat productivity. To accomplish this, several production variables and photosynthetic indexes were measured, including the number of stems, the leaf area index (LAI), photosynthetically available radiation (PAR), net photosynthetic rate, and grain yield. The study was carried out during the 2011–2012 and 2012–2013 winter wheat growing seasons. The experiment included a double-row planting pattern (DRPP) and a single-row planting pattern (SRPP), both of which were either irrigated or rainfed. The area of each plot was 9 m 2 , and the experimental design was a randomized blocks design with three replicates. All results were analyzed with an ANOVA, the F test, and the LSD (p ≤ 0.05) for means comparison. PAR capture ratios in the DRPP were higher than those in the SRPP at 50–120 cm above the ground. The photosynthetic traits of flag leaves under irrigated conditions were not significantly influenced by the respective planting pattern. However, at a growth stage of 80 under the rainfed conditions, the mean photosynthetic rate within flag leaves in the DRPP was higher than that in the SRPP. Furthermore, the DRPP under rainfed conditions was more likely to increase the apparent quantum yield (AQY) of flag leaves than the yield obtained under irrigation. These results suggest that DRPP optimizes the canopy PAR distribution in winter wheat and contributes to the maintenance of a higher photosynthetic capacity in the flag leaves under water stress (the rainfed condition). This relationship may be applied in demonstration trials to encourage winter wheat farmers to incorporate the use of DRPP in the drought-prone areas, which are subjected to insufficient precipitation during the growing stage of wheat in Northern China.

Multi-model evaluation of short-lived pollutant distributions over east Asia during summer 2008

Abstract. The ability of seven state-of-the-art chemistry–aerosol models to reproduce distributions of tropospheric ozone and its precursors, as well as aerosols over eastern Asia in summer 2008, is evaluated. The study focuses on the performance of models used to assess impacts of pollutants on climate and air quality as part of the EU ECLIPSE project. Models, run using the same ECLIPSE emissions, are compared over different spatial scales to in situ surface, vertical profiles and satellite data. Several rather clear biases are found between model results and observations, including overestimation of ozone at rural locations downwind of the main emission regions in China, as well as downwind over the Pacific. Several models produce too much ozone over polluted regions, which is then transported downwind. Analysis points to different factors related to the ability of models to simulate VOC-limited regimes over polluted regions and NOx limited regimes downwind. This may also be linked to biases compared to satellite NO2, indicating overestimation of NO2 over and to the north of the northern China Plain emission region. On the other hand, model NO2 is too low to the south and west of this region and over South Korea/Japan. Overestimation of ozone is linked to systematic underestimation of CO particularly at rural sites and downwind of the main Chinese emission regions. This is likely to be due to enhanced destruction of CO by OH. Overestimation of Asian ozone and its transport downwind implies that radiative forcing from this source may be overestimated. Model-observation discrepancies over Beijing do not appear to be due to emission controls linked to the Olympic Games in summer 2008.With regard to aerosols, most models reproduce the satellite-derived AOD patterns over eastern China. Our study nevertheless reveals an overestimation of ECLIPSE model mean surface BC and sulphate aerosols in urban China in summer 2008. The effect of the short-term emission mitigation in Beijing is too weak to explain the differences between the models. Our results rather point to an overestimation of SO2 emissions, in particular, close to the surface in Chinese urban areas. However, we also identify a clear underestimation of aerosol concentrations over northern India, suggesting that the rapid recent growth of emissions in India, as well as their spatial extension, is underestimated in emission inventories. Model deficiencies in the representation of pollution accumulation due to the Indian monsoon may also be playing a role. Comparison with vertical aerosol lidar measurements highlights a general underestimation of scattering aerosols in the boundary layer associated with overestimation in the free troposphere pointing to modelled aerosol lifetimes that are too long. This is likely linked to too strong vertical transport and/or insufficient deposition efficiency during transport or export from the boundary layer, rather than chemical processing (in the case of sulphate aerosols). Underestimation of sulphate in the boundary layer implies potentially large errors in simulated aerosol–cloud interactions, via impacts on boundary-layer clouds.This evaluation has important implications for accurate assessment of air pollutants on regional air quality and global climate based on global model calculations. Ideally, models should be run at higher resolution over source regions to better simulate urban–rural pollutant gradients and/or chemical regimes, and also to better resolve pollutant processing and loss by wet deposition as well as vertical transport. Discrepancies in vertical distributions require further quantification and improvement since these are a key factor in the determination of radiative forcing from short-lived pollutants.

Revealing the scale-specific controls of soil organic matter at large scale in Northeast and North China Plain

Soil organic matter (SOM) plays an important role in terrestrial ecosystem functioning and is closely related to soil fertility and soil health. Better understanding on the spatial distribution of SOM is vital to agriculture and C-cycle management. With the advancement of digital soil mapping framework and data mining technology, selection of environmental covariates become critical to identify the controls of SOM spatial distribution at different scales and were rarely discussed in previous studies. The objectives of this study were to separate the scale-specific variations in SOM and their dominant controls at those scales along two transects from Northeast and North China Plain. Spatial distribution of SOM was separated into seven scale components (six details, D1 through D6 and one approximation, A6) along each transect using the discrete wavelet transform. The largest variations in SOM were separated in A6 (>1280km) along the northeast transect (91.2% of the total) and D5 (320–640km) along the north transect (40.6% of the total). Unlike the northeast transect, considerable amount of variations was also separated in other scale components of the north transect. There were no significant correlations between the scale-components of SOM and terrain factors along both the transects. While a relatively stronger correlation was observed between SOM and climatic and vegetation factors along the northeast transect, no significant correlation was observed along the north transect at large scales. This may be due to the long-term cultivation in the Northern China Plain. Principal components 1 and 3 identified from the proximally sensed visible and near infrared (vis–NIR) spectra had strong correlation with SOM along the north transect while the principle component 2 was highly correlated with SOM along the northeast transect. The scale-specific controlling factors at different locations may help in selecting environmental factors in digital soil mapping at different scales for improving mapping accuracy.

American Silver Inflow and the Price Revolution in Qing China

Employing panel data from the Northern China Plain for the period 1736–1911, this paper tests the so-called price revolution hypothesis. It finds that American silver inflow played an important role in raising grain prices when factors such as weather and population are controlled. This role is verified in two dimensions: the quantity dimension of American silver inflow into China; the value dimension of silver relative to copper coin and to gold. This paper provides the first econometric test of the so-called price revolution hypothesis in the 18th and 19th century China and deepens our understanding of the role of American silver inflow in late imperial times of China.

Dynamics of soil nematode communities in wheat fields under different nitrogen management in Northern China Plain

The temporal dynamics of nematode abundance and community composition were monitored in a nitrogen (N) fertilization experiment during the main growth stages of winter wheat in Northern China Plain. A randomized complete block design was used with four levels of N fertilization (50, 100, 150 and 300 kg N ha−1 y−1 denoted as N1, N2, N3 and N4, respectively). The results showed that winter wheat aboveground biomass increased but soil pH decreased with elevating N fertilization. Total nematode abundance reached the highest values at the shooting stage of wheat, and was significantly increased by the N fertilization. On the contrary, nematode generic richness declined with increasing N fertilization. The relative abundance of bacterivores showed minor changes among different fertilization treatments whereas that of fungivores was suppressed by the N4 treatment. Plant parasites were the most abundant under the N2 treatment. The relative abundance of omnivores–predators declined with increasing N fertilization. The results indicate that trophic groups have distinctive responses to different levels of N fertilization, and N fertilization may induce an abundant but simple nematode community in the winter wheat field of North China Plain. Our findings also highlight the potential of adequate N application to reduce plant parasites and to control agriculture pests.

An effective strategy to improve grain zinc concentration of winter wheat, Aphids prevention and farmers’ income

Foliar zinc (Zn) application represents an effective way to improve grain Zn concentration of cereal crops. Spraying Zn together insecticides would be an important advantage for the growers to minimize costs. However, there is very little information about combined foliar application of Zn fertilizers together with insecticides. A field experiment was conducted to investigate how spraying Zn fertilizer in form of ZnSO4 together with commonly applied insecticides (e.g., Acetamiprid and Imidacloprid) affects the grain Zn concentration of wheat grown in the Northern China Plain. The main treatment included three levels: only insecticide applied (recorded as T1); foliar Zn fertilizer applied one day after insecticide application (recorded as T2); foliar Zn fertilizer applied together with insecticide (recorded as T3). The results showed that there was no antagonistic effect between insecticide and Zn when they were sprayed together. Compared with insecticide application only, foliar application of Zn fertilizer with insecticide increased grain yield by 3.7–4.9%, and grain Zn density by 48.2–61.6%. Grain yield and grain Zn concentration were not affected no matter Zn fertilizers were applied simultaneously with insecticide or one day after. The toxic effect of insecticide on insects was not affected when it was mixed with Zn fertilizer in the laboratory condition. Compared with application of Zn fertilizer and insecticide at different times, simultaneous combination can reduce the cost by 120 USDha−1 and increase farmers’ net income by 6.3%. Therefore the results show clearly that ZnSO4 can be mixed and sprayed together with insecticide without causing any adverse effect. This is a very useful and cost-effective approach for growers contributing both to improving grain yield and grain Zn concentration and controlling aphids as well.

The characteristics of air pollution episodes in autumn over the southern Hebei, China

In this study, the Models-3/Community Multiscale Air Quality Model (CMAQ) coupled with the Mesoscale Modeling System Generation 5 (MM5) was employed to simulate the air pollution episodes over East Asia, northern China Plain (NCP), and southern Hebei (SHB), at a grid resolution of 36, 12, and 4 km, respectively in Oct. 2012. The PM10 concentrations over SHB at 12-km are overpredicted with NMBs of 34.6% to 45.7% and also overestimated with that of 72.1% to 97.5% at 4-km which applied such a fine grid resolution over the SHB for the first time. It indicated that the simulation at 12-km performs better than the 4-km which may be related to the spatial allocation of the emissions, the lack of dust emissions and the limitations of model treatments. Five heavy episodes show the characteristics of sawtooth-shaped cycles over the NCP in fall (i.e. the maximum of PM10 was up to 885.1 µg m−3 and PM2.5 was up to 438.4 µg m−3 in Handan city) which resulting in the deterioration of visibility and periodically haze days. The concentrations of OC, EC, SO42−, NO3− and NH4+ were significantly higher in heavy episodes than non-heavy pollution episodes. In comparison with other cities ([NO3−]/[SO42−] &gt; 1) at 12-km, the monthly-mean mass ratio of [NO3−]/[SO42−] at Taiyuan (0.17−0.73), Shijiazhuang (0.28−2.34) was 0.43, 0.84 respectively, which means the stationary sources emissions were more important than the vehicle emission in the source areas. The influence of the regional transportation for pollutants compared with local emission was also an important factor for heavy pollution episodes. The regional joint framework should be established along with controlling the local emission over the SHB in China to improve the air quality.

Climate change and fiscal balance in China over the past two millennia

The relation between climate change and historical rhythms has long been discussed; however, this type of study still faces the lack of high-resolution data of long-term socio-economic processes. In this study, we collected 1101 items of direct and proffered evidence from 24 Chinese fiscal and economic history books written by leading contemporary scholars. By analysing the semantics of words, we reconstructed a 2130-year-long fiscal sequence with decadal resolution to express the phase transition of fiscal soundness for approximately 21 dynasties in China. Our reconstruction shows four relatively sufficient stages and three relatively deficient stages, with several secondary stages lasting 60 or 160 years on average within each large stage, from 220 bc to ad 1910. Then, the fiscal association with climate change was analysed. The results show that the fiscal crisis was more likely to occur in cold-dry climatic scenarios. Both temperature and precipitation displayed more significant effects on the fiscal fluctuation within the long term, particularly for temperature. In short, fiscal decline had a 10-year lag in response to decreasing precipitation, whereas influence of decreasing temperature on the fiscal balance might be through amplifying already deteriorating fiscal conditions. Regional differences existed in the influence of precipitation on the fiscal balance. The precipitation in the Northern China Plain and in the Jiang-Huai area had more significant effects on the fluctuation of the dynastic fiscal balance than on that in the Jiang-Nan area. In particular, the dynastic finance was more sensitive to the change in the precipitation in the Northern China Plain because of its special geographical, economic and social backgrounds.

Temporal change in body mass of two sympatric hamster species and implications for population dynamics

Shifting of body size distributions of animals has been a long-time focus in population ecology, but the underlying mechanism of density-dependent changes in body size and its implications for population dynamics of animals are largely unknown. In this 26-year study, we investigated intrinsic and extrinsic factors affecting body mass of the Chinese striped hamster (Cricetulus barabensis Pallas, 1773) and the greater long-tailed hamster (Tscherskia triton de Winton, 1899) in the Northern China Plain. We proposed three hypotheses to explain body mass shifts in the two hamster species: growth, survival, and reproduction hypotheses. Our results showed that mean and maximum body masses of both hamster species were positively correlated with population density, and that this density-dependent change in body mass is more likely to be caused by a change in mortality rates, not by a change in growth rates or reproduction rates. The sustained decline of body mass during the study period was probably caused by increased mortality owing to an increase in the area of agricultural irrigation. Our results suggest that, under the condition of lacking survival and growth data, the maximum body mass (which represents survival rate), minimum body mass (which represents growth rate), and mean body mass are very useful criteria in revealing intrinsic and extrinsic effects on population dynamics and the underlying mechanisms.

Effect of Traffic and Tillage on Agriculture Machine Traction and Fuel Consumption in Northern China Plain

Controlled traffic with conservation tillage can reduce soil compaction, thus to improve operation performance and fuel consumption of agricultural machine. Northern Chinese Plain is one of the main agricultural production bases with high level of agricultural mechanization. To explore the effect of wheel traffic on machine traction force and fuel consumption, three treatments were conducted: zero tillage with Controlled Traffic (NTCN), Compacted Treatment (CT) and traditional tillage system with random traffic (CK). Results showed that wheel traffic increased soil bulk density in the top soil layer in both fully compacted and random compacted plots. Controlled traffic system should certain potential on soil compaction amelioration. Controlled traffic system reduced traction force on winter wheat planting by 9.5 and 6.3%, compared with fully compacted treatment and random compacted treatment. Controlled traffic system reduced fuel consumption in both winter wheat planting and sub soiling (significantly), compared with fully compacted treatment and random compacted treatment. Results indicated that controlled traffic system had certain advantages in soil compaction and fuel consumption in this region and with high application potential.