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The North China Plain (NCP) is the most important agricultural production area in China. Crop production in the NCP is sensitive to changes in both climate and management practices. While previous studies showed a negative impact of climatic change on crop yield since 1980s, the confounding effects of climatic and agronomic factors have not been separately investigated. This paper used 25 years of crop data from three locations (Nanyang, Zhengzhou and Luancheng) across the NCP, together with daily weather data and crop modeling, to analyse the contribution of changes in climatic and agronomic factors to changes in grain yields of wheat and maize. The results showed that the changes in climate were not uniform across the NCP and during different crop growth stages. Warming mainly occurred during the vegetative (preflowering) growth stage of wheat and maize, while there was a cooling trend or no significant change in temperatures during the postflowering stage of wheat (spring) or maize (autumn). If varietal effects were excluded, warming during vegetative stages would lead to a reduction in the length of the growing period for both crops, generally leading to a negative impact on crop production. However, autonomous adoption of new crop varieties in the NCP was able to compensate the negative impact of climatic change. For both wheat and maize, the varietal changes helped stabilize the length of preflowering period against the shortening effect of warming and, together with the slightly reduced temperature in the postflowering period, extend the length of the grain-filling period. The combined effect led to increased wheat yield at Zhengzhou and Luancheng; increased maize yield at Nanyang and Luancheng; stabilized wheat yield at Nanyang, and a slight reduction in maize yield at Zhengzhou, compared with the yield change caused entirely by climatic change. [ABSTRACT FROM AUTHOR]

Soil denitrification fluxes and nitrous oxide (N2O) emissions from the soil surface simulated by a Water and Nitrogen Management Model (WNMM), with three different gas modules, are compared to measurement data sets from two irrigated wheat-maize systems at two locations in the North China Plain (NCP) (2 years of measurement at the Luancheng site and 1 year of measurement at the Fengqiu site). The three gas modules are the WNMM gas module, the DAYCENT gas module, and the DNDC gas module. The term gas module used in this paper refers to the model component which simulates N2O emission from the processes of soil nitrification and denitrification. Soil water, temperature, organic matter decomposition, other nitrogen (N) transformations, such as mineralization and immobilization, and crop growth are simulated by the WNMM platform. For the 2-year data set from Luancheng, the three gas modules generate similar soil mineral N dynamics in the 0-20 cm topsoil. The daily time step, simply structured WNMM gas module consistently performs the best among the three gas modules for predicting soil denitrification fluxes (R² = 0.28, n = 39, p = 0.0006) and N2O emissions (R² = 0.45, n = 36, p < 0.0001). Up to 73, 43, and 22% of total N2O emissions are nitrification-induced as simulated by the DNDC, DAYCENT, and WNMM gas modules respectively, in this well-drained loam soil during the 2-year simulation. When applied to the 1-year data set at the Fengqiu site, the WNMM gas module consistently performs better in estimating N2O emissions (R² = 0.54, n = 35, p < 0.0001) compared to the other two modules. Simulations using the DNDC and DAYCENT gas modules explain over 40% of the temporal variation of N2O emission from the soil. Further testing on different soils and different agroecosystems is needed to confirm the superior performance of the WNMM gas module observed in this simulation study. [ABSTRACT FROM AUTHOR]

Winter wheat (Triticum aestivum L.) is the major crop in the North China Plain (NCP). The monsoon climate in this region causes most rain to fall in the summer season, but during the winter?wheat growing season (October–May) the rainfall is far less than the water requirements for the crop. The efficiency of soil water use by winter wheat needs to be improved to reduce the need for irrigation. In this paper, we report the results of two seasons'' work on soil water utilization, root growth and distribution, root water uptake by the crop under different irrigation treatments, and possible ways to improve soil water?use efficiency. The field experiments were carried out at Luancheng Station (37° 53?N, 114° 41?E) from 1996 to 1997 and 1998 to 1999, two growing seasons of winter wheat. Five treatments for each season: rain?fed and irrigated winter wheat with different irrigation numbers from 1 up to 4, were set up in a randomized plot design. Soil available water?holding capacity at the experimental site was about 454 mm for the top 2 m soil profile. Root sampling results showed that winter wheat had a prolific root system with an average maximum rooting depth of 2 m. Most of the root system was concentrated in the upper 40 cm of soil. Root length density in the top layer of soil (0–20 cm) was very high, with values over 5 cm cm?3. The distribution of water uptake from the soil profile under high soil moisture conditions was the same as the distribution of root length density. The roots in the top layer of soil played an important role in soil water uptake. When root length density was less than 0 · 8 cm cm?3, the root was the main factor limiting the complete utilization of soil water by crops. The scarcity of roots in the deep soil layers restricted the full utilization of soil water by the crops. Thus, at maturity, over 100 mm of available water remained in the root zone for the rain?fed treatment, although the upper layers had already entered water deficit. The crop took up 80% of the total available soil water in the treatment without irrigation in a dry season. For irrigated wheat, from 40 to 50% of crop water uptake was from the stored soil water. Available stored soil water played an important role in the higher production of wheat crops in the NCP. Effective measures to increase the utilization of stored soil water could improve crop performance under conditions of limited water supply. Results showed that deep tillage to break the soil pan improved root growth in the deeper soil layers, and sowing the crop evenly also enhanced water uptake from the top soil layer to compete with soil evaporation. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In China, croplands account for a relatively large form of vegetation cover. Quantifying carbon dioxide exchange and understanding the environmental controls on carbon fluxes over croplands are critical in understanding regional carbon budgets and ecosystem behaviors. In this study, the net ecosystem exchange (NEE) at a winter wheat/summer maize rotation cropping site, representative of the main cropping system in the North China Plain, was continuously measured using the eddy covariance technique from 2005 to 2009. In order to interpret the abiotic factors regulating NEE, NEE was partitioned into gross primary production (GPP) and ecosystem respiration ( Reco). Daytime Reco was extrapolated from the relationship between nighttime NEE and soil temperature under high turbulent conditions. GPP was then estimated by subtracting daytime NEE from the daytime estimates of Reco. Results show that the seasonal patterns of the temperature responses of Reco and light-response parameters are closely related to the crop phenology. Daily Reco was highly dependent on both daily GPP and air temperature. Interannual variability showed that GPP and Reco were mainly controlled by temperature. Water availability also exerted a limit on Reco. The annual NEE was −585 and −533 g C m−2 for two seasons of 2006-2007 and 2007-2008, respectively, and the wheat field absorbed more carbon than the maize field. Thus, we concluded that this cropland was a strong carbon sink. However, when the grain harvest was taken into account, the wheat field was diminished into a weak carbon sink, whereas the maize field was converted into a weak carbon source. The observations showed that severe drought occurring during winter did not reduce wheat yield (or integrated NEE) when sufficient irrigation was carried out during spring. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the soil water movement in shallow groundwater areas in Cangzhou (CZ) and Hengshui (HS) of Hebei province in the North China Plain, China. It states that North China Plain is considered as the center of politics, economics, and culture in the country. However, it faces great difficulties in water supply and water pollution. It mentions that in the shallow groundwater areas, precipitation infiltration and evaporates are the major processes for the water cycle. The study suggests that although the two sites shared the same climate, there are noted differences in the infiltration process, soil water movement, and groundwater recharge sources.

The article reports on the study using climatic variables for the estimation of the evapotranspiration which is important for detecting crop water status and proper irrigation scheduling in the wheat field in the North China Plain in China. The method is simplified from the Penman-Monteith equation which requires canopy resistance which is used to calculate sensible heat flux and then the latent heat flux as the residual of the surface energy balance. The result reveals that original modified Todorovic model underestimates the canopy temperature and the sensible heat flux and overestimates the latent heat flux.

Focuses on silt loading and development of the Yellow River in China. Background information on the Yellow River basin; Information on the North China Plain; Environmental degradation in the Yellow River watershed.

Growing demand on groundwater resources and the semi-arid climate in the North China Plain (NCP) highlight the need for improved understanding of connections between regional climate change and groundwater recharge. Hydrologic time series of precipitation and groundwater levels were analyzed in three representative geographical zones throughout the NCP for the period of 1960-2008 using trend analysis and spectral analysis methods. A significant change point around 1975 is followed by a long-term decline trend in precipitation time series, which coincides with the Pacific Decadal Oscillation positive phase. However, the magnitudes of groundwater level variability due to heavy pumping overwhelm the low-frequency signal of groundwater levels. Nonlinear trends that related to long-term climatic variability and anthropogenic activities are removed by using the Singular Spectrum Analysis method. Spectral analyses of the detrended residuals demonstrate significant short-term oscillations at the frequencies of 2-7 years, which have strong correlations with the El Niño-Southern Oscillation modes. This study contributes to improved understanding of dynamic relationship between groundwater and climate variability modes in the NCP and demonstrates the importance of reliable detrending methods for groundwater levels that are affected greatly by pumping. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]