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20 December 2018, Volume 39 Issue 12

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Trend Evaluation on Changes of Maize Yield in China under Global Warming by 1.5℃ and 2.0℃

LI Kuo, XIONG Wei, PAN Jie, LIN Er-da, LI Ying-chun, HAN Xue

2018, 39(12):  765-777.  doi:10.3969/j.issn.1000-6362.2018.12.001

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Based on the simulation results from 5 climate models recommended by ISI-MIP under 4 RCP scenarios, the future climate situations were selected which are the approximate scenarios with global warming by 1.5℃ and 2.0℃. Applying DSSAT, the per unit yield changes of maize in China under global warming by 1.5℃ and 2.0℃ were analyzed and the spatial distributions of changes of maize yield were revealed relative to the baseline from 1985 to 2006. The results showed that, the yield reduction area under global warming by 2.0℃ was 6.2% more than that under global warming by 1.5℃; the ratios of yield reduction were separately 3.7% and 11.5% under global warming by 1.5℃ and 2.0℃; the risk of global warming by 2.0℃ was obviously higher than 1.5℃. The spatial distributions of yield changes were similar between 1.5℃ and 2.0℃ global warming, under which the area and magnitude of yield reduction were different. There were some regions with yield increasing under global warming by 1.5℃ and 2.0℃ in maize planting area of North China and Southwest China; most of the other regions in China would be mainly suffering to yield reduction; the largest reduction of maize yield would break out in Northwest China. Especially it was advantageous under global warming by 1.5℃ for maize production in North China; there was no distinct negative effect under global warming by 2.0℃ for maize production in North China. In other words, in the near future, there would be yield increasing potential for maize in North China with global warming.

Effect of Smash Ridging Conservation Tillage with Green Manure on Rice Field Soil Infiltration and Its Delayed Action

CHEN Sheng-nan, HU Jun-ming, XU Xian-li, WEI Xiang-hua, HE Tie-guang

2018, 39(12):  778-785.  doi:10.3969/j.issn.1000-6362.2018.12.002

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Studying the smash riding conservation tillage with green manure on rice filed soil infiltration is playing an importance role in improving the conservation tillage systems on rice field. In order to find out the effect of smash ridging conservation tillage with green manure on rice field soil infiltration in first season and its delayed action, a field experiment was carried out under 2 tillage modes and 4 manuring modes in Guangxi Academy of Agricultural Sciences from 2016 to 2017. The study measured the soil compaction and soil infiltration by SC-900 and single ring after early and late rice harvesting, and used cutting ring to measure the soil bulk density after late rice harvesting. The results showed that smash ridging conservation tillage with green manure had no significant effect on 0-15cm soil compaction, and can reduce plough layer soil compaction. At the same time, smash ridging conservation tillage with green manure can reduce soil stable infiltration rate in first season and second season, which result to soil infiltration capacity fell. Smash ridging conservation tillage with green manure increased soil bulk density and reduced soil porosity, which made soil ramming. Smash ridging conservation tillage with green manure had significantly effect on soil infiltration and soil structure in second season.

Estimation and Distribution of Minimum Air Temperature within Winter Wheat Canopy in Prone Period of Late Frost

LIU Hong-jie, NI Yong-jing, REN De-chao, DU Ke-ming, GE Jun, ZHU Pei-pei, ZHAO Jing-ling,

2018, 39(12):  786-795.  doi:10.3969/j.issn.1000-6362.2018.12.003

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Using the hourly meteorological observation data at different heights within winter wheat canopy in 2016 and 2017, the height and variation of minimum air temperature within winter wheat canopy during the prone period of late frost were analyzed. An estimation model for canopy minimum air temperature was established based on the meteorological factors at the 150cm height and soil temperature at 0cm depth. The results indicated that: (1) the air temperature below 0℃ appeared earlier and lasted longer near the canopy. (2) The minimum air temperature appeared mostly at about 4/5 of the highest canopy and between AM 2:00 and AM 6:00, especially at AM 5:00. (3) Correlation of the canopy minimum air temperature with relative humidity and wind speed at 150cm height reaches P＜0.01 significant level, and correlation with air temperature at different heights and soil temperature at different depths reaches P＜0.001 significance level, and correlation with soil temperature decreases as the soil depth increases. (4) The value of partial correlation coefficient of the canopy minimum air temperature with air temperature, wind speed, relative humidity at 150cm height, and soil temperature at 0cm depth, were listed as temperature＞wind speed＞soil temperature＞relative humidity. An estimation model for canopy minimum air temperature was established by multiple linear regression function. The coefficient of determination (Adj.R2) reached 0.967 and the root mean square error (RMSE) was 0.915. It was feasible to establish the estimation model for canopy minimum air temperature based on the conventional observation data of meteorological stations. The model could provide valuable information on monitoring and predicting for late frost in winter wheat.

Effect of Source Size on Rice Pollen Diffusion under Field Experiments

ZHANG Jie, WANG Yong-qun, HU Ning, JIANG Xiao-dong, LIU Zi-he, PEI Xin-wu

2018, 39(12):  796-804.  doi:10.3969/j.issn.1000-6362.2018.12.004

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Pollen-mediated gene flow from rice is one of the main ways of transgenic escape. Therefore, it is great significance to master the rule of pollen diffusion for the study of gene flow. In this study, three treatments with different source size of 5m×5m(TR1), 10m×10m(TR2) and 15m×15m(TR3) were designed. Rice panicles per unit area, flowering spikelets per panicle, pollen grains for each spikelet and pollen depositions along the main wind direction were observed to calculate pollen source strength per unit area and effective source strength ratio. The effect of source size on pollen source strength, pollen deposition, effective source strength ratio and pollen diffusion distance was studied. The results showed that: (1) source size did not affect the pollen source strength per unit area, while it could only change the total source strength. The proportion of total source strength between TR1, TR2 and TR3 was 1:4:9. (2) Source size did not change the characteristic of pollen deposition along the main wind direction. The pollen deposition first had a rapid increase and then declined after the peaks within the source area. In the downwind, pollen deposition could be expressed as the negative exponential function of distance. (3) The pollen source size was larger, the pollen deposition at different distances was greater, and the pollen diffusion distance was increased accordingly. However, this effect would levelled off with a larger pollen source size. (4) 27.9%?33.4% of the effective source strength ratio for three treatments meant that only about 30 percent pollen could escape and dropped down out of the source area, which might lead to gene flow. But, the effective source strength ratio would gradually decrease, when the pollen source size was increasing. (5) There were similar effects of wind on pollen diffusion between different treatments. The effective source strength ratio was larger and the pollen diffusion distance was farther at higher wind speed. Wind direction mainly affects the effective source strength ratio. It should be noted that the wind had a more significant influence on the larger pollen source.

Effects of Low Temperature on Physiological Characteristics of Rice Seedlings with Different Cold Tolerance and Anatomical Structure of Root Tip

WU Li-qun, CAI Zhi-huan, ZHANG Gui-lian, LIU Yi-tong, ZHAO Rui

2018, 39(12):  805-813.  doi:10.3969/j.issn.1000-6362.2018.12.005

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In order to explore the influence mechanism of low temperature on rice seedlings, a hydroponics experiment was conducted using 2 rice varieties with different cold tolerance at seedling stage including the cold-tolerant cultivar Sanqishiluo and cold sensitive cultivar Xiangzaoxian45, cultivated in light incubator under two different temperature treatments, the two temperature treatments were optimal temperature treatment (25℃,taken as control，CK) and low temperature treatment(10℃), respectively. The effects of low temperature on the physiological characteristics of rice seedlings and anatomical structure of root apex were studied. The results showed that compared with the control, total root number, longest root length, root fresh weight, root dry weight, root total absorption area, root active absorption area,and root activity decreased under low temperature treatment, and the decrease extent was increased with the increase of treatment time, the reduced range of cold-sensitive cultivar Xiangzaoxian45 was greater than that of cold-tolerant cultivar Sanqishiluo. The activity of SOD and POD increased first and then decreased, and relative conductivity and MDA content increased. The change range of SOD activity, POD activity, relative conductivity and MDA content in cold-tolerant cultivar Sanqishiluo was less than that of cold sensitive cultivar Xiangzaoxian45. The contents of free amino acids and soluble sugar in root increased first and then decreased under low temperature, the change range of cold-tolerant cultivar Sanqishiluo was higher than that of cold sensitive cultivar Xiangzaoxian45. Under low temperature, epidern cell of root tip wall in cold-sensitive cultivar Xiangzaoxian45 arranged irregularly and untightly, vascular bundle of connective tissue was seriously destroyed, and vascular bundle sheath cell arranged irregularly, xylem and phloem were unclear. While epidern cell of root tip wall in vascular bundle of connective tissue in cold-tolerant cultivar Sanqishiluo arranged regularly and tightly, vascular bundle sheath cell and parenchyma cells arranged regularly, xylem and phloem were clear. Results showed that the different physiological and morphological changes were inspired and induced by low temperature, and by applying physiological and morphologica changes to reply synthetically the influence of low temperature on rice seedlings.

Variation Characteristics of Vegetation Coverage Based on Terrain Factors in the Manas River Basin

WEI Hong, XU Li-ping, LI Xiao-lei, XUE Kai

2018, 39(12):  814-824.  doi:10.3969/j.issn.1000-6362.2018.12.006

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Based on MODIS NDVI data from 2000 to 2016, the distribution pattern and dynamic change characteristics of vegetation coverage in the Manas River Basin of Xinjiang were studied by using the dimidiate pixel model and the spatial analysis of ArcGIS, and the spatial distribution differences of vegetation cover change in elevation, slope and aspect were analyzed. The results showed that: (1) the Manas River Basin was dominated by low vegetation cover, the area of high-level vegetation coverage was significantly increased, and the other levels were less volatile. The area ratio of vegetation cover improvement (31.17%) was much larger than the proportion of degraded area (16.1%) during the study period, the overall vegetation coverage of the study area increased, and the ecological environment improved. (2)In the area of elevation <800m and slope <8°, the vegetation coverage was obviously improved. The vegetation significantly degraded areas were mainly distributed in the elevation of 1300-3400m, the slope was >25°, and the area where the vegetation coverage had not changed was mainly concentrated in the elevation > 3600m. (3)When the elevation was >2100m, the vegetation coverage tended to decrease with the increase of elevation. In the area below 2100m, the vegetation coverage fluctuated greatly with the increase of elevation. (4)With the increase of slope, the vegetation coverage gradually decreased. The vegetation coverage was the largest (42.69%) in the 0?5 degree slope of the whole basin. (5)The difference of vegetation coverage was not significant in all aspects. The vegetation coverage on the flat ground was the largest (44.21%), and the vegetation coverage on the shade aspect was better than the sunny aspect. There was no obvious difference of the vegetation coverage change except in the flat ground.