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Xu J.W.,Chinese Academy of Agricultural Sciences | Xu J.W.,Key Laboratory of Agricultural Environment | Ju H.,Chinese Academy of Agricultural Sciences | Ju H.,Key Laboratory of Agricultural Environment | And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

It is widely recognized that the frequency and intensity of extreme weather events and climate disasters have strongly increased with global warming. The area of influence of climate disasters has also increased, which has had adverse effects on sustainable social and economic development. Drought is a recurring natural phenomenon, and is associated with a deficit of water resources over a large geographic area and long duration. Drought is attracting increased attention from scholars, with a focus on its intensity, duration and areal extent in northern China within the context of global change. Investigation of the variation of drought and regional response to climate change is very important to agricultural production, and can provide a reference fordeveloping appropriate measures to reduce droughts on the Huang-Huai-Hai(3H) Plain. At present, relevant research is more inclined to study meteorological drought itself, without consideration of drought characteristics in different phases in crop-growing seasons and the climate background of global change. In this paper, we determine drought characteristics in all four seasons and the winter wheat growing season on the 3H Plain, together with the effects of climate change. Based on data of 34 meteorological stations from 1961 to 2011, a relative moisture index was calculated to investigate the spatial pattern and temporal variability of drought characteristics on the 3H Plain. The results show varying degrees of drought in spring, winter and the winter wheat growing season. Drought frequency exceeded 90% over the past 50 years on the plain, with spring and winter the driest seasons. There were high-frequency drought areas in central and northern parts of the plain during spring, winter and the winter wheat growing season. The regional distribution of drought intensity and frequency showed an increasing tendency from south to north. A wet trend was detected on the plain in the winter wheat growing season over the last 50 years. However, the relative moisture index changed since 1978. That is to say, the index had an increasing trend from 1961 to 1980 when the plain was wetter; the index decreased from 1980 to 2011 when it was drier. Overall, although drought eased over the entire analysis period, a serious drought tendency has emerged over the last 20 years. In addition, temporal variability of the relative moisture index was significantly correlated with precipitation, solar radiation and relative humidity. This indicates that drought characteristics of the plain were more sensitive to these three climate variables. This has received increased attention in recent years with respect to addressing climate change. The results of our study indicate an arid trend, with increase of temperature in spring and summer on the 3H Plain. Therefore, relevant agencies should create an early warning system of extreme weather events and natural disasters, toward improvement of future regional agricultural scientific management and decision support systems in agricultural production. These agencies should also adapt to climate change by selecting strongly drought-resistant crop varieties and by adjusting cultivation methods and management measures, especially irrigation measures aimed at spring drought on the 3H Plain. Source

Xu J.W.,Chinese Academy of Agricultural Sciences | Ju H.,Chinese Academy of Agricultural Sciences | Ju H.,Key Laboratory of Agricultural Environment | Liu Q.,Chinese Academy of Agricultural Sciences | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

With the purpose of probing the drought characteristic in growth stages and its possible climate factors of winter wheat in Huang-Huai-Hai plain (3H plain) under climate change,based on meteorology data of 5 selected meteorological stations from 1981 to 2010, relative moist index has been calculated to investigate the temporal variability of drought characteristic in five growth stages of winter wheat in 3H Plain in recent 30 years.The results indicated that on the temporal variation, an increasing drought trend was detected in sowing to seeding stage in southern of 3H plain while a contrary trend was found in northern of 3H plain, and the same slight tendency was detected in whole growth period. The drought of growth stages except seedling stage was reduced from north to south. The most severe drought occurred in the seeding to jointing stage and a slight increasing drought trend was detected in north while a decreasing drought trend in south in this stage. A drought trend was detected in heading to maturity, with higher magnitude in south than in north. Tianjin and Shijiazhuang stations were observed to be medium drought and serious drought primarily in whole growth period, the frequency of varying degrees of droughts in Shenxian station was equivalent while Xuzhou and Zhumadian stations were observed to be primarily slight drought from 1981 to 2009. Continuous drought of Tianjin and Shijiazhuang station was serious while sustained drought was not found in Zhumadian station in recent 30 years. With the temperature increasing, aridification might be enhanced in Tianjin and Shijiazhuang stations while a contrary trend was found in Shenxian, Xuzhou and Zhumadian stations in whole growth period of winter wheat. The trend of drought will be alleviated with the temperature decreasing in jointing to heading stage and heading to maturity statge. Drought in sowing to seeding stage will be more obvious in Tianjin and Xuzhou stations with the solar radiation increasing. There was a drought trend detected in Shijiazhuang and Zhumadian stations with the relative humidity decreasing in growth stages. Besides, with the wind speed decreasing, moisture tendency will be found in whole growth period and heading to maturity in southern of 3H Plain. The research results can provide a reference for the simulation study on the impact of drought on yield of winter wheat and developing appropriate measures to reduce droughts in the 3H plain. Source

Hu W.,Chinese Academy of Agricultural Sciences | Hu W.,Key laboratory of Dryland Agriculture | Yan C.R.,Chinese Academy of Agricultural Sciences | Yan C.R.,Key laboratory of Dryland Agriculture | And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

This paper investigated impacts of climate change on irrigation water requirement for winter wheat with consideration to growing period in the North China Plain(NCP), benefitting to make irrigation scheduling and adaptive strategy. Based on data from 4 typical meteorology stations including Beijing Miyun and Shijiazhuang Nangong stations in the west and Tianjin Baodi and Xingtai Nangong stations in the east and phenology data of winter wheat during 1981 to 2010, the objective of this study is to investigate impacts of climate change on winter wheat irrigation water requirements in growth stages. The results showed that the dates of sowing stage and seeding stage delayed and the more variation of trend was at high latitudes, while the others showed an advanced trend. Then the spatial variation of irrigation water requirement in the NCP was decreasing from south to north in the past 30 years. And in temporal distribution study, there was a marked increase in east, but it was opposite in west area. The irrigation water requirement during the different growth stages made a different change with time. Except for a slight rise during the seeding to jointing stage in two stations and milky to maturity, the irrigation water requirements were reduced during the other growth periods. In the whole growth stages, the west sites were decreased by 6. 72 mm/ 10a and 8. 3 mm/ 10a, respectively. However, in the east sites, there was an increasing tendency of irrigation water requirements with 2. 6 mm/ 10a and 7. 08 mm/ 10a, respectively. Besides the order of annual fluctuation was: sowing to seeding stage>milky to maturity>heading to milk stage>jointing to heading stage>seeding to jointing stage > sowing to maturity. The influence of different meteorological elements on irrigation water requirement was relatively various. The relationship between irrigation water requirement and effective precipitation and related humidity was negative significant, to the contrary, the impact of wind speed, sunshine duration and mean temperature was positive. And correlation was slightly negative between irrigation water requirement and growth period length. The consequence would be more precise if growth period length was taken into consideration in the formula. Therefore, the main climatic factors influencing the irrigation water requirements were different in each growth stage. The prior impact factor was related humidity in jointing to heading stage, while the main factors were different between Beijing Miyun station and others even during the same period of heading to milky stage due to the different districts, which were mean temperature and related humidity, respectively. But for other growth stages, the influence of effective precipitation on irrigation water requirement was more important than other factors. Thus the results could become more realistic, which provided theoretical basis for the reasonable irrigation system and strategies of adapting to climate change. Source

Liu X.,Key laboratory of Dryland Agriculture | Liu X.,Chinese Academy of Agricultural Sciences | Xu Y.,Key laboratory of Dryland Agriculture | Xu Y.,Chinese Academy of Agricultural Sciences | And 6 more authors.
Applied Energy | Year: 2012

Application of the ångström-Prescott (A-P) model, one of the best rated global solar irradiation (. Rs) models based on sunshine, is often limited by the lack of model parameters. Increasing the availability of its parameters in the absence of . Rs measurement provides an effective way to overcome this problem. Although some models relating the A-P parameters to other variables have been developed, they generally lack worldwide validity test. Using data from 80 sites covering three agro-climatic zones in China, we evaluated seven models that relate the parameters to annual average of relative sunshine (. n/N) (models 1-2), altitude (model 7), altitude and . n/N (model 3), altitude, . n/N and latitude (model 4), altitude and latitude (model 5) and annual average air temperature (model 6). It was found that model 7 performed best, followed by models 6, 1, 3, 2 and 4. The better performance of models 7 and 6 and the fact that they used fewer sites and variables in their establishment demonstrated that using a large dataset in developing the A-P parameter model or having more variables included is no guarantee of wider applicability, and that the local climatic regime may override other factors in the parameter modeling. This also suggests that applicability of a . Rs model is not proportional to its complexity. The common feature of the better performing models suggests that accurate modeling of parameter . a is more important than that of . b. Therefore, priority should be given to parameter models having higher accuracy for . a. Comparison of predicted against the calibrated A-P parameters revealed many unrealistic predictions by model 5, with which it was possible to obtain meaningful . Rs estimates. To ensure that a parameter model is conceptually consistent and related to reality, it is necessary to check the modeled parameters against the calibrated ones. Models 1, 6 and 7 showed an advantage in keeping the physical meaning of their modeled parameters due to the small magnitude of . n/N and the use of the relation of (. a+. b) versus other variables as a constraint, respectively. All models tended to perform best in zone II and poorest in zone I in predicting . Rs, indicating larger errors in humid climates. Since most productive agricultural areas in China are located in zone I, developing parameter models tailored to this zone would be valuable to improve . Rs accuracy. © 2012 Elsevier Ltd. Source

Yan C.,Chinese Academy of Agricultural Sciences | Yan C.,Key laboratory of Dryland Agriculture | He W.,Chinese Academy of Agricultural Sciences | He W.,Key laboratory of Dryland Agriculture | And 8 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Plastic mulching film plays an important role in development of agriculture. However, a series of problems such as pollution of plastic film residue left in the field occur. It is required to make a reasonable assessment on film mulching and rationally utilize it. Based on its application, this study proposed a concept of crop safety period of plastic film mulching, and its estimation methods. Crop safety period through plastic film mulching means the appropriate choice of a photo-selective mulch film according to the transplant season, to the pedoclimatic conditions of the area under cultivation and, finally, to the type of crop. In the days before the transplant, the plastic mulching film should be basic whole, and it works to decrease soil moisture evaporation, to warm soil and to prevent weeds. Successively, these functions almost reduce. The selection of crop safety period of plastic film mulching is helpful to manage agricultural activities efficiently; guiding film makers to produce both meet the demand of production and lower cost of plastic products; to help farmers due to the types of crop and production conditions choosing appropriate plastic mulch film. Based on measurement of function of plastic film mulching, and crop canopy density, 2 kinds of method were established. The first one is to continuously monitor soil moisture,temperature and weed control, to build relationship between the function of soil temperature, moisture, weed suppression and mulching treatments, with that to seek the intersection of them. The coincidence point means functions disappear of plastic mulching and the days from starting mulching to this date is a certain crop safety period in a certain site. The second is crop canopy density to determine crop safety of plastic film mulching period, which includes 2 steps: to measure the change of crop canopy density, and the functions (soil temperature and moisture etc.) of mulching under no mulching and mulching at same time, to establish the curve of crop canopy density and the main function of plastic film in order to cross the best condition between crop canopy density and the contribute of mulch films aimed to the determination of the ideal crop safeguard period. All in all, plastic mulching film has been widely used in global, especially in China, in the past 30 years, and its application area and efficacy works better than any other agronomic practices. Concept of crop safety period of plastic film mulching has been firstly proposed in this paper, and further research in the connotation and extension of its definition still need to be developed. Moreover, the mentioned estimation methods around crop safety period of plastic film mulching showed some usefulness in cotton in Xinjiang, corn in Northeast and tobacco in southwest planting, but more extensive research, application and improvement were needed by far. The findings from this research provide an important information base for improving adaptability evaluation system of plastic mulching film, investigating the spatial pattern of plastic mulching film utilization, and biodegradable plastic film production and application. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved. Source

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