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20 March 2017, Volume 38 Issue 03

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Spatiotemporal Distribution and Variation of Heat Resources in the Twenty-Four Solar Terms in North China Plain over the Period 1961-2014

DONG Bei, HU Qi,PAN Xue-biao, HE Qi-jin, JIANG Hui-fei, QIAO Yu, WANG Xiao-xiao,

2017, 38(03):  131-140.  doi:10.3969/j.issn.1000-6362.2017.03.001

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By calculating the dividing time of the twenty-four solar terms in each year, average values and climate trends for temperature (average temperature, maximum and minimum temperature) and accumulated temperature over 0℃ in each solar term were analyzed based on the observed data from 63 meteorological stations in North China Plain from 1961 to 2014. Spatial distribution of the deviation days between last / first frost date and Vernal Equinox/Autumnal Equinox date, as well as accumulated temperature over 0℃ in frost-free period and their changing rates, were also studied. Results showed that the Great Heat and Slight Heat solar terms exhibited the largest heat resources, on the contrast, the Great Cold and Slight Cold solar terms exhibited the smallest heat resources. The days of frost free period increased from north to south in the study area. The last frost date averagely occurred in the Vernal Equinox, postponed from south to north along the latitude direction, and the first frost date occurred in the Hoar-frost Falls on the average, advanced from south to north along the latitude direction. Each solar term in North China Plain in 1961-2014 showed a significant increasing trend for heat resources, and the highest warming rate occurred in the Rains solar term with average temperature, maximum and minimum temperature increasing trend values 0.63, 0.74 and 0.53℃·10y-1, respectively. The minimum temperature had greater contribution to climate warming than maximum temperature because of its higher increasing trend. Accumulated temperature over 0℃ in frost-free period in the study area increased by 442.8℃·d in recent 54 years. Climate warming has also prolonged frost free period in North China at increasing trend 3.9d·10y-1 due to the changes in both the first and last frost date, and the advanced last frost date in spring (climate tend rate 2.1d·10y-1) was more significant than the delayed first frost date in autumn (climate tend rate 1.9d·10y-1) .

Estimating Rainfed Maize Evapotranspiration Using the FAO Dual Crop Coefficient Method on the Loess Plateau

FENG Yu, GONG Dao-zhi, WANG Han-bo, HAO Wei-ping, MEI Xu-rong, CUI Ning-bo

2017, 38(03):  141-149.  doi:10.3969/j.issn.1000-6362.2017.03.002

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Evapotranspiration (ET) is the only term which appears in both land surface energy balance equation and water balance equation, accurate estimation of ET is challenging but of impotance for assessing biomass production, allocation of water resources, and improving crop water ues efficiency in rainfed agricultural ecosystem. This paper invested the applicability of FAO dual crop coefficient approach in estimating ET and its components (plant transpiration and soil evaporation) of rainfed maize in semi-arid region of the Loess Plateau. Continuous measurements of ET with eddy covariance system in 2011 and 2012 were used to validate the performances of FAO dual crop coefficient approach. The results indicated that reference evapotranspiration were 628mm in 2011 and 553mm in 2012. The FAO dual crop coefficient approach was acceptable in estimating ET compared to eddy covariance measurements, with RMSE, AAE and R2 of 0.864mm·d-1, 0.678mm·d-1 and 0.755 (P＜0.01) in 2011, 0.676mm·d-1, 0.693mm·d-1 and 0.781 (P＜0.01) in 2012, and the measured and estimated ET values were 400.3 and 492.7mm in 2011, 372.6 and 441.4mm in 2012, which confirmed the good performances of FAO dual crop coefficient for estimating ET. Soil evaporation and maize transpiration accounted for 36.4% and 63.6% of total ET in 2011, 31.7% and 68.3% in 2012, respectively, indicating that maize transpiration was the main component of ET.

Accuracy Analysis of Several Global Solar Radiation Models Based on Empirical and GRNN Methods in South China

WU Li-feng, WANG Juan, ZHANG Fu-cang, FAN Jun-liang, YAN Hui, LU Xiang-hui

2017, 38(03):  150-162.  doi:10.3969/j.issn.1000-6362.2017.03.003

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Validation of global radiation models with measured daily data based on the meteorological data (including the extraterrestrial radiation) from 15 radiation stations in South China during 1981-2009.The daily global solar radiation was estimated using five empirical models (i.e., Angstrom-Presscott model, Bahel model, Bristow-Campbell model, Chen model and Hargreaves model) and 12 generalized regression neural network models (GRNN) with different input variable combinations. The performance of these global radiation models were evaluated using observed daily global solar radiation data during 2010-2014 at the 15 radiation stations. Finally, the global radiation models were developed by meteorological data from the adjacent stations, and then evaluated the applicability of these models using the observed data from the studied station. The results showed that the Chen model had the highest accuracy among the empirical models, followed by the Bahel model. The Bristow-Campbell model performed similarly to the Hargreaves model for most radiation stations. The Bahel model had the highest accuracy at 9 of 15 radiation stations when developing models by using the meteorological data from the adjacent stations, while the Chen model was most suitable for 7 stations. The Bristow-Campbell model and Hargreaves model had higher accuracy at 13 of 15 stations. But the Hargreaves model performed better at the Wuhan station and Ganzhou station, where the RMSE was decreased by about 14%. The GRNN model had the lowest average RMSE with input variable of sunshine percentage, which was better than the Bahel model and Chen model, but the difference in average RMSE at each station was less than 2%. When using the local meteorological data, the RMSE of the GRNN model was decreased by about 14% compared to that of the Bristow-Campbell model and the Hargreaves model. When using the data from the adjacent stations, the GRNN model performed similarly to the Bristow-Campbell model and the Hargreaves model due to the large differences in the smoothing factor at each station. Therefore, the Bahel model and the Chen model were considered to be more suitable for the estimation of global solar radiation in these areas considering the complexity of GRNN model development.

Effects of Biochar Application on the Losses of Nitrogen and Phosphorus in Surface Water of Paddy Field

XIAO Jian-nan, ZHANG Ai-ping, LIU Ru-liang, YANG Zheng-li

2017, 38(03):  163-171.  doi:10.3969/j.issn.1000-6362.2017.03.004

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Applied high rates of nitrogen (N) fertilizer in rice production may result in lower N use efficiency in a paddy rice field of the Yellow River irrigation region, Ningxia. To reduce N and phosphorus (P) leaching and improve fertilizer use efficiency are important for sustainable and water quality. Thus, a field plot experiment was conducted to study the effect of exogenous biochar application on the loss risk of N and P and soil quality in a paddy field. Four biochar rates, i.e., 0, 4500, 9000, and 13500kg·ha-1 with optimum nitrogen rate (240kg·ha-1) were chosen. From May to October 2014, we determined the contents of NH4+-N, NO3--N, total N (TN) and total P (TP) in the surface water of paddy field during the whole rice growth period. The results showed that biochar amendment decreased the contents of both TN and NO3--N but increased NH4+-N content in the surface water. The contents of TN and NH4+-N reached the peak on the following day of the first top dressing and the maximum values were 34.86 and 8.28mg·L-1 respectively. The content of NO3--N reached the peak on the following day of the second top dressing and the maximum value was 3.31mg·L-1. Then TN leveled off after 10 days, but the NH4+-N and NO3--N contents approached a relatively stable level after a week. There was no significant difference in TP content in the surface water between the biochar addition and the control treatments. The content of TP peaked 3 days after fertilization and decreased rapidly afterwards, then leveled off after another 6-7 days. On the other hand, biochar amendment decreased TN leaching by 8.03%-13.36% relative to control, but the high-level biochar amendments (13500kg·ha-1) significantly (P＜0.05) increased the contents of TN and soil organic matter by 41.2% and 27.5% respectively compared with the control. There was no significant difference in TP and available P contents in soil between the biochar addition treatments and the control. Our study has revealed that biochar could positively reduce N leaching in the rice fields, while there has no significant effect on P loss.

Effects of Silicon Supply on Reflectance Spectroscopy Characteristics of Rice Canopy under Elevated UV-B Radiation

ZHU Huai-wei,LOU Yun-sheng,SHI Yi-fan,ZHANG Yi-wei,ZHAO Si-di

2017, 38(03):  172-180.  doi:10.3969/j.issn.1000-6362.2017.03.005

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A field experiment was conducted to observe the canopy spectra of rice by using ASD FieldSpec HandHeld spectrometer on typical sunny days and analyze the characteristics of red edge parameters by calculating the first derivative spectrum at tillering, jointing, heading and grain-filling stages under the conditions of elevated UV-B radiation and silicon supply. The experiment was designed with two UV-B radiation levels, i.e. ambient UV-B (ambient, A) and elevated UV-B (elevated by 20%, E)；with two silicon supply levels, i.e. control and +Si (200kgSiO2ha-1 as sodium silicate). The results indicated that LAI (leaf area index) and chlorophyll content (value of SPAD) were decreased under elevated UV-B radiation, but silicon supply increased and could alleviate the depressive effect of elevated UV-B radiation on rice growth. The differences of rice canopy spectra were mainly reflected in near-infrared band under each treatment, the reflectance of near-infrared band was decreased under elevated UV-B radiation, but increased by silicon application. The red edge position showed blue shift under elevated UV-B radiation and red shift by silicon application. The rice red edge position, red edge amplitude and red edge area showed a trend with an increase firstly and then a decrease, and reached the maximum at jointing stage.

Impacts of Quasi-biweekly Atmospheric Low Frequency Oscillation on Immigration of Nilaparvata lugens（St?l）in Cropping Area of Jiangling

DIAO Jia-min, SUN Si-si, BAO Yun-xuan, LU Ming-hong, XIE Xiao-jin

2017, 38(03):  181-195.  doi:10.3969/j.issn.1000-6362.2017.03.006

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Understanding the impacts of the atmospheric oscillation with quasi-biweekly low frequency on the immigration of brown planthopper (BPH), Nilaparvata lugens (St?l) could provide an important reference to the extended-period forecast of its occurrence. The daily BPH’s light trap data from 105 plant protection stations in China, the daily reanalyzed meteorological data from the National Center of Environment Prediction (NCEP), and the data from the National Center of Atmospheric Research (NCAR) from 1979 to 2015 were collected. It took 2010 as a typical year with occurrence characteristic of BPH, and the relationship between the amount of BPH migrated in rice-growing region from Nanling Mountain to the Yangtze River and the atmospheric oscillation with quasi-biweekly low frequency was analyzed. HYSPLIT (hybrid single particle Lagrangian integrated trajectory) model was used to analyze the backward trajectory of the brown planthopper population at the typical site. The impacts of the atmospheric oscillation on insect sources and migratory paths of BPH was discussed. The results showed that, （1）10-20d oscillation cycle of BPH amount existed significantly in the rice-growing region from the Nanling Mountain to the Yangtze River during August and September in 2010. （2）Wind fields, geo-potential height fields and vertical velocity fields on the isobaric surfaces of 850hPa and 925hPa appeared significant low-frequency cycles of 10-20d simultaneously. And the low-frequency oscillation of BPH’s immigrating amount was correlated significantly with these atmospheric physical variables. （3）Under the impacts of the low-frequency southwestern wind, the populations of BPH were transported from the rice-growing region of southwestern China to the rice-growing region, from the Nanling Mountain to the Yangtze River. In the later period, the part of BPH’s populations immigrated from the rice-growing region between the Huaihe River and the Yangtze River to the rice-growing region between the Nanling Mountain and the Yangtze River under the impacts of the low-frequency northeastern wind.（4）Results of backward trajectory analysis of Brown Planthopper Population was provided to confirm that the insect sources and migration paths of BPH’s populations that immigrated into the rice-growing region between the Nanling Mountain and the Yangtze River were consistent with the low frequency prevailing wind fields.