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20 October 2015, Volume 36 Issue 05

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Characteristic Analysis of the Climatic Revolution in the Yellow River Extreme Temperature Index

WU Can, ZHAO Jing-bo, WANG Ge-hui

2015, 36(05):  525-535.  doi:10.3969/j.issn.1000-6362.2015.05.001

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In this paper, the spatiotemporal variation of extreme temperature events were investigated based on the daily maximum and minimum temperature data observed by 59 meteorological stations for the period 1963-2013 in the Yellow River Basin(YRB), with the help of liner regression, Mann-Kendall test, wavelet analysis, principal component analysis and correlation analysis. The results showed that, (1)cool days, cool nights, ice days, frost days and cold speel duration days displayed significant negative trend at rates of 1.06, 1.93, 2.40, 3.36 and1.12d·10y-1, respectively(P＜0.001), while warm days, warm nights, summer days, tropical nights, warm speel duration days and growing season length exhibited significant positive trend at rates of 1.56, 2.22, 2.66, 1.56, 1.48 and 3.47d·10y-1 (P＜0.001), respectively. Furthermore, the trends for annual minimum value of daily minimum (maximum) temperature, annual maximum value of daily minimum (maximum) and diurnal temperature range were 0.25(0.4), 0.18(0.27) and -0.09℃·10y-1 (P＜0.05), respectively. (2)The six sub-region’s extreme temperature indices remained same variation tendency, while the extreme temperature events of north-central Ningxia and south–central Inner Mongolia were more significant. (3)The change range of night indices(warm nights, cold night) were larger than those day indices (warm days, cold days), the range of variation in cold indices (annual minimum value of daily minimum/maximum) were smaller than warm indices (annual maximum value of daily minimum/maximum). (4)The upper-middle of Yellow River were more sensitive than downstream for the extreme temperatures change. (5)All of 16 indices had short cycles of 3 and 7 years, and had long cycles of 26 years, while warm/cold spell duration days, diurnal temperature range and growing season length also had another cycle of 16 years. (6)Besides, annual minimum value of daily minimum, diurnal temperature range and cold spell duration days, the time points of abrupt change for others were concentrated in 1990s.

Soil Water Threshold and its Dynamics of Winter Wheat Aiming Water-saving and High Yield

ZHAO Ye-meng, LI Yu-zhong, LIU Xiao-ying, ZHONG Xiu-li, CAO Jin-feng

2015, 36(05):  536-543.  doi:10.3969/j.issn.1000-6362.2015. 05.002

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It is important to determine soil water threshold affecting crop yield for diagnosis of crop water stress and practice of deficit irrigation. To achieve this, field experiment of winter wheat with seven treatments, irrigated at different growth stages and supplied with varying irrigation amount to maintain their variation in soil water, was conducted in 2011/2012 at a site in Hengshui, Hebei Province. Relations between yield and soil water of different depth at seven growth stages were examined. Soil water threshold based on yield was explored and its dynamics was revealed. Results showed that the largest difference in soil water between the six deficient treatments and the well watered control occurred at shallow soil depth, and it decreased with deepening of soil layer. The difference was respectively 19.7%-36.5%, 9.3%-21.7% and 2.9%-9.7% at the soil layer of 0.4, 0.8 and 1.2m. In addition, variability of soil water decreased as soil depth increases. Relationship between grain yield of winter wheat and soil water of different depth at varying growth stages was parabolic functions of downward opening, but correlation significance changed with both growth stage and soil depth, being most significant for soil layer of 0. 4m. Soil water threshold based on yield diminished with progression of growth stages, from 83.1%-95% to 72.3%-90.0% of the field water capacity from jointing-booting to milk maturing at soil depth of 0.4, 0.6, 1.0, 1.2 and 1.6m. We recommended 0.4m being the most appropriate soil depth for detecting water deficit based on analysis in four aspects: difference in soil water dynamic and its average over the whole growing season between treatments, soil water variability at different soil depth, significance of the relations between soil water and yield at different growth stage. The corresponding water threshold at jointing-booting, heading, flowering, beginning-, middle -, later of grain filling and milk maturing was respectively 95.0%, 98.4%, 79.9%, 73.7%, 88.6%, 79.6% and 75.7%.

Temperature Properties within Plastic Greenhouses for American Ginseng Growth in Liuba County, Shaanxi, China

ZHAO Li-min, ZHANG Bin

2015, 36(05):  544-552.  doi:10.3969/j.issn.1000-6362.2015. 05.003

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In order to determine and reveal temperature properties in areas adapted for American ginseng (Panax quinquefolium) growth, the authors measured both air temperatures at 15cm height aboveground, where canopies of two-year-old seedlings were distributed, and soil temperatures at 10cm depth underground, where roots of the plant extended, within 4 plastic greenhouses of the plant located in Zaomulan (alt. 1236m) and Zhakoushi (alt. 1722m) villages, Liuhou Township, Liuba County, Shaanxi Province, China, both from May to October 2012 and from March 2013 to April 2014. The valid observational dates were categorized into a data set, and all the valid daily temperatures into 8 data sets such as air mean (AMT), air minimum (AMIN), air maximum (AMAX), range of air temperature (RAT), soil mean (SMT), soil minimum (SMIN), soil maximum (SMAX), and range of soil temperature(RST), which were each designated as a dependent variable (Y). Ordinal dates were coded from observational ones and then calculated into sine and cosine values of their 1- to 4-fold radian angles by Fourier’s transform, with each of the 8 sets designated as an independent variable (X). Each Y was regressed against the 8 sets of X through stepwise regression analysis, and a total of 16 polynomial regression equations were established. The simulation effect of AMT, AMIN, SMT, SMIN and SMAX against Xs retained was excellent, with their compound correlation coefficients high, R= 0.933 - 0.985 (P＜0.001); and valleys and peaks of the periodic temperature curves obtained appeared mostly in January and July. Estimated by AMT equations, values of annual mean temperature (℃), valley (℃), peak (℃), accumulated temperatures above 10 and 6℃ (℃?d) in the greenhouses were respectively: Zaomulan, 11.2, -0.9, 21.1, 1475, 2403; Zhakoushi, 8.3, -3.5, 18.7, 957, 1736. Corresponding values estimated by SMT equations were: Zaomulan, 11.2, 0.1, 20.3, 1338, 2292; Zhakoushi, 8.8, -1.7, 17.8, 872, 1710. Average low of daily air temperature and the lower limit of daily minimum in winter were: Zaomulan, -5.6, -10.3; Zhakoushi, -8.8, -14.5. Average high of daily air temperature and the upper limit of daily maximum in summer were: Zaomulan, 27.6, 37.8; Zhakoushi, 25.3, 34.3. Average low of daily soil temperature and the lower limit of daily minimum in winter were: Zaomulan, 0.1, -2.1; Zhakoushi, -2.2, -4.4. Average high of daily soil temperature and the upper limit of daily maximum in summer were: Zaomulan, 21.3, 24.8; Zhakoushi, 18.9, 22.1. The study establishes regression models that match periodically changing trends of annual temperatures inside local plastic greenhouses for the plant, and reveals many temperature eigenvalues, which will benefit practices directing plantations of American ginseng, and provide other scientific studies and applications dealing with field temperatures with parameters.

Effects of Different Water Depth on Leaf Physiological Characteristics of Early Rice During Panicle Primordium Suffered to Low Temperature

TAN Meng-xiang, JING Yuan-shu, XUE Yang,ZENG Wen-quan

2015, 36(05):  553-560.  doi:10.3969/j.issn.1000-6362.2015. 05.004

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Taking early rice Lingliangyou 268 as a material, a field experiment with 3 water layer treatments was conducted in Nanjing University of Information Science and Technology during panicle primordium stage under low temperature damage (15-19 May) in 2014, which included water layer 0-1cm (CK), water layer 3-4cm (ZH), and water layer 8-10cm (SH). The leaf temperature, content of photosynthetic pigment, net photosynthetic rate, transpiration rate and leaf antioxidant of different treatments were measured every two days, to explore the effect of low temperature on leaf physiological and biochemical characters. The results showed that the leaf temperature of all treatments was lower than the air temperature, and much more obvious with time extension, in which, ZH and SH were higher than CK. This indicated that proper depth water layer was helpful to maintain the leaf temperature. All of the leaf chlorophyll content decreased significantly, with a maximum drop for SH. The net photosynthetic rate (Pn), transpiration rate (Tr) and water use efficiency (WUE) decreased significantly, with slightly for ZH. Net photosynthetic rate and transpiration rate of CK were higher than others, while the water use efficiency of leaf of ZH was highest. Net photosynthetic rate of SH decreased and its water use efficiency and transpiration rate increased. The content of catalase (CAT) and malondialdehyde (MDA) in leaves of all treatments decreased significantly, with the rate of ZH＞CK＞SH, while the superoxide dismutase (SOD) activity increased slightly and the peroxidase (POD) activity increased significantly. All these treatments could resistance to low temperature damage and slow the effect of early rice leaf antioxidant enzyme activity change, in which ZH was most effectively.

Effects of Station Density on the Spatial-Temporal Distribution of Water Deficit in the North China Plain

FENG Yu-duan, WANG Shi-li, WU Ding-rong, LIU Ling, LIU Jian-dong

2015, 36(05):  561-569.  doi:10.3969/j.issn.1000-6362.2015. 05.005

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The possible difference of temporal-spatial variation characteristics of soil moisture conditions caused by calculating with different meteorological data sets was explored in this study, to identify the effect of two type of data sets, one from all of the meteorological stations and another only the standard stations, on the calculation results of temporal and spatial rainfall amount, crop evapotranspiration and crop water deficit during growth periods of winter wheat in the North China Plain. The results showed that, (1) annual average precipitation in growth period of winter wheat in North China Plain showed an unobvious trend from 1960s to 2010s, and reference crop evapotranspiration showed a trend of decrease, while the crop water deficit rate declined and had a larger difference in inter-decadal variation; (2)The precipitation, reference crop evapotranspiration and crop water deficit rate were in obviously latitudinal distribution. The precipitation decreased with the increase in latitude, accordingly, the referencecrop evapotranspiration increased as well as the crop water deficit rate due to low precipitation. Compared with the results based on data from the standard stations, in terms of time variation, the change trend is relatively consistent. However, from the point of value, the average precipitation and reference crop evapotranspiration of standard stations were higher than all stations. Generally speaking, the spatial distributions based on both are consistent, but there is large difference in some terrain areas, which have bigger variability.

Variation in Potential Evapotranspiration and Its Sensitivity Coefficients to Climatic Factors in the Huang-Huai-Hai Plain

ZHAO Cai-xia, MEI Xu-rong, JU Hui, LIU Qin, ZHEN Wen-chao

2015, 36(05):  570-577.  doi:10.3969/j.issn.1000-6362.2015.05.006

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Potential evapotranspiration (ET0) is generally accepted to be an important element of the hydrological cycle, and changes in sensitivity coefficients of ET0 are of great significance for agricultural water use planning, irrigation system design and management. Potential evapotranspiration and their sensitivity coefficients in four seasons and entire year were calculated by the Penman-Monteith methods and partial derivative equation across six agricultural sub-zones of the Huang-Huai-Hai plain (3H plain) from a data set of daily climate variables in 40 meteorological stations during the period from 1961 to 2013. The highest value of ET0 was found in summer, whilein autumn and winter in the fourth zone. A decreasing trend for ET0 was detected in summer in these six sub-zones in recent 53 years and maximum amplitude was found in fifth zone. However, an increasing trend for ET0 was detected in second and sixth zone during spring and in second zone during winter. Relative humidity was considered to be the most sensitive variable for ET0 in spring, autumn, winter and whole year and solar radiation was the most sensitive variable for ET0 in summer. Moreover, the positive and negative values of sensitivity coefficients were recognized as solar radiation and relative humidity respectively for ET0 with a decreasing trend, similarly for wind speed and air temperature with an increasing trend. Moreover, the high value of sensitivity coefficients to relative humidity and wind speed was found in the first zone of study area, while the high value of sensitivity coefficients to solar radiation and air temperature was in fourth zone of south region. The findings from this research provide important information for crop planting adjustment, ecological engineering planning and water-soil resource management in 3H plain in an attempt to improving the healthy development of agriculture and ecological environment.

Comprehensive Effects of CO2 Concentration and Temperature Increasing on Rice Seedling

LIU Shuo, WANG Song-he, YOU Song-cai, Li Yu-e, WAN Yun-fan, QIN Xiao-bo

2015, 36(05):  578-585.  doi:10.3969/j.issn.1000-6362.2015.05.007

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Future climate change tends to be with features of CO2 concentration and temperature increasing, which will produce significant influence on agriculture. This paper mainly focused on the effect of CO2 concentration and temperature increasing on rice seedling physiological characteristics of rice in southern China by simulating 3 climate scenarios, i.e., CO2 concentration 400molmol?1 and increasing 0℃ as control treatment (CK), 550molmol?1 and increasing 2℃ compared with CK as middle treatment (M), 700molmol?1 and increasing 4℃ compared with CK as high treatment (H). The seeds were placed into different treatments about 10 days after soaking and accelerating germination, then monitored relevant indexes of seed germination and physiological characteristics. The results showed that (1) as CO2 concentration and temperature increasing simultaneously, the height of seedling, the length of root, the number of root longer than 1cm, and dry weight of root and seedling and vigor index increased. Compared with CK, under H, height of rice seedling was higher 5.78cm, root length was 12.91% longer, dry weight of root and seedling was 2.6 times than CK, vigor index was 3.1 times than CK; germination vigor, germination rate and germination index achieved highest in medium treatment; (2)Along with CO2 concentration and temperature increasing simultaneously, malonicdial dehyde (MDA) content and soluble sugars (SS) content were gradually decreasing, proline (Pro) content was highest in medium treatment, soluble protein (SP) content and catalase (CAT) activity were increasing. In general, the future climatic change characteristics of CO2 concentration and temperature increasing simultaneously had no obvious adverse effect on rice germination and seedling growth with CO2 concentration increasing to 550molmol?1 and 700molmol?1, temperature increasing 2-4℃. But the nutrient elements would be limited in germination and seedling period.

Impacts of Drip Irrigation Amount on Physiological Characteristics of Summer Soybean and Filed Micro-climate

ZHANG Yong-qiang, ZHANG Na, LI Ya-jie, SU Li-li, XU Wen-xiu, PENG Jiang-long, HU Chun-hui

2015, 36(05):  586-593.  doi:10.3969/j.issn.1000-6362. 2015.05.008

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The impacts of different drip irrigation amount on physiological characteristics of summer soybean and its filed micro-climate were studied from July to October in 2013, with radomized block design method. Four treatments were conducted in this field experiment, which were named as W1 (3000m3·ha1), W2 (3600m3·ha1), W3 (4200m3·ha1), W4 (4800m3·ha1), respectively. The results showed that the different levers of transmittance were decreased significantly with the increasing of drip irrigation amount at flowering stage and podding stage, with the minimum value at 20cm from bottom of summer soybean in different treatments. Furthermore, there was a significant negative correlation（R=-0.98, P＜0.01）between plant height and population transmittance. The relative humidity inside canopy at 40cm height increased while canopy temperature decreased with the irrigation amount increasing, and the tend of the daily variation of temperature and humidity was conversely. The net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and stomatal limitation (Ls) increased shortly and then decreased with the irrigation amount increasing at flowering stage and podding stage. The treatment W3 had the highest yield of 3741.23kg·ha1, which was higher 30.42%, 13.98% and 8.44% than treatment W1, W2 and W4 with a significant difference in level P<0.05. The irrigation water use efficiency decreased with the irrigation amount increasing. There was no significant difference between treatment W1, W2 and W3, but W3 was the best choice forsummer soybean in local natural condition, with the better population ecological environment, high photosynthetic efficiency, and high yield.

Cotton-Planting Zoning Change in Southern Xinjiang Under the Background of Global Warming

ZHANG Shan-qing, PU Zong-chao, LI Jing-lin, LI Xin-jian, JI Chun-rong, WANG Ming-quan, LI Yue

2015, 36(05):  594-601.  doi:10.3969/j.issn.1000-6362. 2015.05.009

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Based on climatic data from 52 meteorological stations in southern Xinjiang during 1961-2013, the fundamental spatial-temporal change characteristic of annual accumulated temperature of ≥10℃, frost-free period and mean temperature in July were analyzed by using the methods of linear regression, accumulative anomaly, T-test and mixed spatial interpolation technology based on ArcGIS. And the change of cotton-planting zoning was studied by combining with the cotton-planting climate division index. The main results are as the follows: heat resource was very obviously different in different regions of southern Xinjiang, generally, annual accumulated temperature of ≥10℃, frost-free period and mean temperature in July were higher or more in plain areas than in mountain areas. In the background of global warming, the three indicators showed an increasing trend at the rates of 56.63℃·d·10y1, 3.15d·10y1 and 0.15℃·10y1 in recent 53 years, and they had mutation in 1997, 1997 and 1994, respectively. Under the joint effects of the above-mentioned climate factors, the areas of middle maturing cotton and early-middle maturing cotton expanded 17682km2 and 43033km2 respectively, early maturing cotton areas did not change significantly, but the areas of special early maturing cotton and unsuitable cotton planting areas decreased by 4940km2 and 56589km2 after 1997 than before in southern Xinjiang.

Effects of Drought Stress on Photosynthetic, Osmotic Adjustment Substance and Antioxidase Activities of Winter Wheat Level

HU Cheng-da, LIU Rong-hua, WANG Xiu-ping, LIU Zhong-yang, LI Tong-xiao

2015, 36(05):  602-611.  doi:10.3969/j.issn.1000-6362. 2015.05.010

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Sufficient water supply (CK, soil relative water content, SRWC, 80%) with two drought stress treatments (T1, SRWC 40% and T2, SRWC 60%) was set under field conditions by using large moving waterproof canopy. The effects of drought stress on photosynthetic physiology, osmotic adjustment substance content, membrane lipid peroxidation, and the activities of antioxidase were investigated. The result showed that gas exchange parameters and chlorophyll contents dramatically decreased after a slightly increased along with winter wheat development stage of T1 treatment. Then the protection mechanism of winter wheat was booted as the content of soluble sugar and malondialdehyde kept increasing under T1 treatment, and the content of soluble protein, free proline content, and the activity of superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD) decreased after a first rose under T1 treatment. The performances of T2 treatment were similar to T1 with a more slight variation. The results indicated that although by increased osmotic adjustment substance content could mitigate water loss under different water deficit conditions. Water still can’t meet wheat’s demand at the late growth stage. The increasing of antioxidase activities could quench more reactive oxygen but the reactive oxygen still increased, which lead membrane lipid peroxidation and membrane permeability increased. The chlorophyll degraded, photosynthesis rate decreased and the leaf senescence aggravated.

Modeling the Impact of “Double-Delay” Technology on Yield of Wheat-Maize Cropping System in the North China Plain

WANG Na, WANG Jing, FENG Li-ping, PAN Xue-biao, YU Wei-dong

2015, 36(05):  611-618.  doi:10.3969/j.issn.1000-6362. 2015.05.011

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“Double-Delay” technology, i.e., delaying both the sowing time of wheat and the harvesting time of maize, is an effective option for wheat and maize cropping system adapting to climate change in the North China Plain (NCP). To study the impact of “Double-Delay” technology on the yield of wheat-maize cropping system as well as the spatial variability of yield changes, APSIM model was used to simulate the impact of “Double-Delay” technology on wheat and maize yield under rain-fed and sufficient irrigation conditions in the NCP. The simulated results averaged from 2000 to 2009 showed that “Double-Delay” technology could lead to the reduction in wheat yield, but increase substantially maize yield and total yields of wheat-maize cropping system under rain-fed and sufficient irrigation conditions compared with the traditional planting pattern. Under rain-fed condition, the averaged increase rates of maize yield were 19.8%, 14.5% and 13.4%, respectively in Hebei, Shandong, and Henan provinceswith the total increase rates of wheat-maize cropping system by 10.7%, 3.2% and 4.8%, respectively. Under sufficient irrigation condition, the averaged increase rates of maize were 14.2%, 8.0% and 8.5% in Hebei, Shandong, and Henan provinces, respectively with the total increase rates of wheat-maize cropping system were 4.5%, 3.4% and 2.8%, respectively. The increase in maize yield was attributed to the lengthened growth period of maize resulting from the delayed harvested time and the reduced field preparation time. The study results showed that “Double-Delay” technology increased the yield of wheat-maize system by adapting to climate change with higher increase rate in northern regions than in southern regions of NCP, especially in the Northern part of Hebei province. In general, “Double-Delay” technology is most suitable to apply in Hebei province. The study implied that adaptation options of agriculture to climate change should varied geographically.

A Preliminary Study on Modelling Winter Wheat GPP of Farm Shelterbelts in Huang-Huai-Hai Plain of China

YIN Chang-jun, LI Yan-quan ，ZHANG Jin-song ,WANG He-song，ZHENG Ning, LI Chun-you

2015, 36(05):  619-624.  doi:10.3969/j.issn.1000-6362. 2015.05.012

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The effects of shelterbelt system on farmland productivity are complex, which need an integrated monitoring of multiple shelternets. Remote sensing provided a promising tool for monitoring those effects in multiple shelternets synchronously. In case of Huang-Huai-Hai plain, multi-source remote sensing images were fused based on enhenced spatial and temporal adaptive reflectance fusion model (ESTARFM) to inverse gross primary productivity (GPP) of winter wheat with light use efficiency model in farmland shelterbelt. Results indicated that: (1) based on the light use efficiency model and images fusion, simulated GPP had signaficant linear correlation with measurements. The determination coefficient of measured and simulated values of wheat GPP is 0.8596 with an average relative error of 15.62%. As a result, the light use efficiency model had higher calculation accuracy. (2) We found highly spatial heterogeneity in GPP which modeled in 10 nets of Shelterbelts. This study preliminary revealed the feasibility of quantitative estimation of the GPP in farmland shelterbelts based on the remote sensing image fusion. Our work provided an important tool to further investigate the effecst of shelterbelts on farmland productivity.

Analysis on Meteorological Disasters Risk of Tobacco Planting Based on GIS in Western Hubei Province

MENG Dan, CHEN Zheng-hong, LI Jian-ping, YANG Wei, HE Fei, CHEN Zhen-guo

2015, 36(05):  625-630.  doi:10.3969/j.issn.1000-6362. 2015.05.013

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Based on conventional observed data at 65 meteorological stations from 1961 to 2010 in western Hubei province, the regional distribution of meteorological disasters risk of tobacco planting in this region was analyzed, by using expert estimation model, the AHP and disaster risk assessment model and the platform of GIS. The results showed that drought, chilling damage, continuous rain, rainstorm and heat injury were the major meteorological disaster in the process of tobacco growing. Drought risk was higher in the north than that of in the south, and eastern area was higher than the west. The risk of continuous rain and rainstorm were both higher in the south than the north. The chilling damage risk distributed relatively uniform from the south to the north, but lower in the east than in the west. The heat injury risk was higher in the north than that of in the south. Overall, the meteorological disaster risk in the north of this region, was higher in the east than that of in the west, which had no obvious regularity from south to north. nevertheless, the meteorological disaster risk in the south of this region was higher in the south than that of in the north. These results could provide the basis references for rational distribution and disaster prevention and mitigation of tobacco planting in western Hubei Province.

Occurrence Grade Index Model of Dynamic Early Warning for Wheat Powdery Mildew in Typical Region

ZHANG Lei1, HUO Zhi-guo, JIANG Yan, WANG Li

2015, 36(05):  631-639.  doi:10.3969/j.issn.1000-6362. 2015.05.014

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As being prone to wheat powdery mildew, Henan and Hebei province are affected severely by wheat powdery mildew. Through analysis on variable characteristic of disease index for winter powdery mildew, the disease index data in Nanyang city was interpolated at week scale and interpolated at pentad scale in Zhengding, Xinji, Guantao and Cixian. Based on disease observation data for wheat powdery mildew from 2001 to 2010 and daily meteorological data for corresponding period, the key factors and key period affecting occurrence grade for wheat powdery mildew were selected using rank correlation analysis and path analysis. Occurrence grade index model of dynamic warning for wheat powdery mildew was built based on Bayes criterion. The results elucidated that the variation of disease index for winter powdery mildew conformed to Logistic curve, and interpolation effect was well. The key factors for wheat powdery mildew occurrence grade in Nanyang were actual occurrence grade of previous week, humidity from the previous one week to current week, sunshine hours from the previous two week to current week and rain coefficient from the previous three week to current week. Which for wheat powdery mildewoccurrence grade in Hebei were actual occurrence grade of previous pentad, mean temperature from the previous three pentad to current pentad, precipitation from the previous three pentad to current pentad, rain coefficient from the previous three pentad to current pentad. The entirely accurate rate of occurrence grade index model of dynamic warning for wheat powdery mildew was above 85%, and accurate rate of nearly same grade exceeded 90%. The model can be well applied in early warning for wheat powdery mildew at the short time scale. The results can provide useful information that contributes to a better understanding of occurrence grade for wheat powdery mildew in Nanyang and Hebei region and help for the policy formation of disease protection management.

Drought Variation in Songnen Plain and Its Response to Climate Change

ZHENG Sheng-hua, QIN Zhi-hao, ZHANG Wen-bo

2015, 36(05):  640-649.  doi:10.3969/j.issn.1000-6362. 2015.05.015

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Based on observed data from 36 meteorological stations from 1961 to 2013, taking relative moisture index as a drought index, the temporal and spatial distribution of drought was analyzed by using Kriging method. The results showed that the annual index decreased significantly (P＜0.01) from 1961 to 2013, drought severity was steadily increased, and the drought grades also showed an increasing trend. The index decreased significantly in spring and autumn (P＜0.01), and more obviously in autumn. While the index in winter increased significantly, but the range was narrowed. The index in all seasons increased from southwest to northeast, with the southwest region as high risk region. There was negative correlation between the index and temperature, solar radiation, respectively, and positive correlation between the index and relative humidity, wind speed and precipitation, respectively.