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20 December 2020, Volume 41 Issue 12

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Effects of Shading on the Carbon Emission Intensity of CH4 and N2O from Rice- Wheat Rotated Soil in Southern China

MA Li , LOU Yun-sheng , YANG Xiao-jun, GOU Shang, LI Jun,  LI Rui , ZHANG Zhen

2020, 41(12):  747-760.  doi:10.3969/j.issn.1000-6362.2020.12.001

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The solar radiation weakening is one of the main characteristics of climate change. It is still unclear concerning the impact of the solar radiation weakening on the emissionsof greenhouse gas (CH4 and N2O) and carbon emission intensity in rice-wheat soils. A field simulation experiment was conducted to investigate the emissions of greenhouse gases in rice-winter wheat rotation ecosystem and the changes in carbon emission intensity with field managements under shading conditions. The two-factorial experiment was adopted with 3 levels of shading intensities, i.e. control (CK, no shading), light shading (S1, 61.26% of shading rate) and heavy shading (S2, 83.65% of shading rate). The shading treatment was performed by covering the crop canopy with black sunshade net and periodically adjust the net hight to maintain the distance at 30 cm between the net and crop canopy. Field managements (water management/planting date) were set 2 levels, i.e. traditional flooding irrigation/conventional planting date (F/P; rice F, water depth 5cm; winter wheat P, planting time November 6, 2017) and moistening irrigation/late planting (M/L; rice M, anhydrous layer; winter wheat L, planting time November 13, 2017). The closed chamber method was used to measure the emission fluxes of CH4 and N2O from 8:00 am to 11:00 am at one-week interval. The tested soil was a hydromorphic paddy soil. The tested cultivars of rice and winter wheat were Nanjing 5055 and Sumai 188, respectively. The field experiment was performed at the Station of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing, Jiangsu prov., China. The results showed that, shading (S1, S2) significantly reduced the cumulative CH4 emission in rice-winter wheat rotation ecosystem under traditional flooding irrigation/conventional planting by 68.08% and 42.22%, and slightly increased the CH4 emission under moistening irrigation/late planting. Moistening irrigation /late planting significantly reduced the cumulative CH4 emissions by 15.6% to 86.61%. The shading significantly increased the cumulative N2O emissions from rice-winter wheat rotation ecosystem by 63.59% to 111.40% (P<0.05), and the cumulative N2O emissions were slightly reduced under traditional flooding irrigation/conventional planting. In terms of global warming potential, compared with no shading, shading significantly reduced the contribution of CH4 and N2O to the global warming potential in rice-winter wheat rotation ecosystem under traditional flooding irrigation/conventional planting date by 36.32% to 62.51%, but slightly increased under moistening irrigation/late planting. The global warming potential of CH4 and N2O under the moistening irrigation/late planting was reduced by 12.1% to 83.22%, compared with the traditional flooding/conventional planting. This study indicates that shading significantly increased the carbon emission intensity of CH4 and N2O in rice-winter wheat rotated soil, while moistening irrigation/late planting without shading significantly reduced the carbon emission intensity of CH4 and N2O, which ensured the yield and improved the ecological benefits.

CLDAS Drive Land Surface Model to Simulate Latent Heat Flux in China

WANG Zhi-hui , SHI Chun-xiang , SHEN Run-ping , SUN Shuai, SHAN Shuai, HAN Shuai

2020, 41(12):  761-773.  doi:10.3969/j.issn.1000-6362.2020.12.002

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The correlation coefficient (R), the average deviation between (ME), root mean square error (RMSE), and coefficient of Nash (NSE) were calculated between the three land surface model from the land data assimilation system of the China Meteorological Administration (CLDAS CLM, CLDAS Noah and CLDAS-Noah-MP) and global land surface assimilation system (GLDAS-Noah) and the flux tower standing observation data, and the accuracy evaluation in terms of different time scales and the different underlying surface were given. The results show that the diurnal variation and annual variation trends and peak time of the single peak can be simulated according to the simulation results of the four models. The peak of diurnal variation generally occurs at 14：00, the annual variation peak occurs in summer, and the numerical simulation effect is slightly worse in irrigated or freezing-thawing farmland and wetland in spring. On the scale of the hour, day, and month, the simulation of models driven by CLDAS is generally better than that of GLDAS. The mean R-value of simulation by models driven by CLDAS is higher than that of GLDAS-NOAH, which is 0.07, 0.08, and 0.02, respectively. The mean value of RMSE is lower than that of GLDAS -NOAH, and the errors are reduced by 6.6, 5.5, and 2.3W·m−2, respectively. The simulation of the model will change along with the time scale and the underlying surface properties. From the hour to the day to the month scale, the simulation goes through a process of first getting worse and then getting better. The simulation on the month scale is the best, in which Noah-MP performs well, with R value of 0.88, RMSE of 20.8 W·m−2, and NSE of 0.58. Four model simulation results under different performance have the same certain commonality that simulation in mixed forest and coniferous forest were overestimated and that in the rest underlying surface are underestimated. Although no models work well for all underlying surfaces, CLM performs best in stations covered by Gobi, mixed forest, and coniferous forest, Noah performs best in desert and cropland, and Noah-MP performs best in meadow, grassland, and wetland.

Mechanism of High Temperature Affecting Carbon and Nitrogen Metabolism of Rice Grain at the Early Stage of Grain Filling

WANG Jun-ke , WANG Ya-liang, CHEN Hui-zhe, XIANG Jing , ZHANG Yi-kai, ZHU De-feng, ZHANG Yu-ping

2020, 41(12):  774-784.  doi:10.3969/j.issn.1000-6362.2020.12.003

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Global temperature increase caused by climate warming is an obvious feature of climate change in recent years. With the global temperature rising, high temperature and heat damage of rice occur frequently. Especially in southern China, high temperature during grain filling has become an important factor restricting rice quality. The optimumaverage temperature for the grain-filling stage of rice is about 21℃. High temperature above 35℃ will significantly reduce the yield and quality of rice. The physiological process of carbon and nitrogen metabolism plays a key role in grain filling. As an important component of grain dry weight, the metabolism of starch and protein is affected by the physiological processes of carbon and nitrogen metabolismIn order to clarify the effect of high temperature on the physiological characteristics of carbon and nitrogen metabolism of rice grains during the early stage of filling, In this experiment,“Zhehexiang2”, a Japonica rice with good quality, was used as material. Two temperature gradients (31℃ / 24℃ (NT) and 35℃ / 28℃ (HT) were set up at the early stage of grain filling. After 5 days, 10 days and 15 days, and at harvest, the activities of key enzymes and related gene expression of starch, protein and adenosine triphosphate (ATP) formation in rice grain were observed and analyzed to determine the high temperature at the early stage of grain filling mechanism of effects on carbon, nitrogen and energy metabolism in rice grain. The results showed that, (1)compared with NT, HT treatment significantly reduced grain weight and starch content, while protein content increased. (2)Under HT treatment, the relative expression of sucrose transport genes OsSUT1 and OsSUT2 decreased significantly, while the activity of sucrose catabolic enzymes increased first and then decreased with the extension of the treatment time, resulting in the inhibition of sucrose supply under high temperature. (3)Compared with NT, the activities of key glycolytic enzymes hexokinase and pyruvate kinase decreased significantlyunder HT conditions; however the changes of key enzymes in the tricarboxylic acid cycle pathway showed significant differences under high temperature, citrate synthase. The activities of ɑ-ketoglutarate dehydrogenase and succinate dehydrogenase decreased significantly, while the activities of isocitrate dehydrogenase and malate dehydrogenase increased significantly.There was no significant difference in ATP and ADP between HT and NT. (4)Compared with NT, HT treatment significantly reduced the activity of ADPG pyrophosphorylase, and at the same time reduces the activity of granule-bound starch synthase and soluble starch synthase, resulting in the hindrance of amylose synthesis; the activity of starch hydrolysis-related enzymes has an upward trend. It showed that high temperature promotes the hydrolysis of grain starch. (5)Compared with NT, the total nitrogen content of grains under HT treatment had a rising trend, but the difference was not significant, the amino acid content had a significant rising trend, and the content of glutamic acid and ɑ-ketoglutarate increases significantly. The activities of nitrate reductase and nitrite reductase showed a downward trend, while the effect of high temperature on the activities of glutamate synthase and glutamine synthetase was not significantly different from that of optimum temperature. The test results showed that, the main reason for the hindrance of grain development at high temperature was that sucrose transport is hindered rather than sucrose utilization. At the same time, high temperature led to disorder of glycolysis and tricarboxylic acid cycle; grain starch synthesis was hindered at high temperature, while starch hydrolysis was enhanced; Process disorder and increased accumulation of ɑ-ketoglutarate are one of the reasons for the increase in protein content.Related research on energy metabolism involving ɑ-ketoglutarate can provide new ideas for the improvement of rice quality under high temperature.

Fuzzy Comprehensive Evaluation and Model Establishment of the Effect of High Temperature in the Seedling Stage on the Nutritional Quality of Strawberry Fruit

XU Chao, GAO Rui, WANG Ming-tian, YANG Zai-qiang , HAN Wei, ZHENG Sheng-hua

2020, 41(12):  785-793.  doi:10.3969/j.issn.1000-6362.2020.12.004

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In order to study the effect of high temperature at seedling stage on the intrinsic quality of strawberry fruits in the greenhouse, and then to conduct comprehensive evaluation of different experimental treatments to establish a comprehensive evaluation model of intrinsic quality of strawberry fruits. In 2018 and 2019, strawberry seedlings were stressed with different high temperature (32, 35, 38 and 41℃) and different stress days (2, 5, 8 and 11d), and then transplanted to Venlo glass greenhouse for normal cultivation experiments, with normal greenhouse cultivation as a control. Based on the differences in fruit intrinsic quality indicators under each treatment, the comprehensive score of each experimental treatment determined by the fuzzy comprehensive evaluation method, and by analyzing the relationship between the comprehensive score and different stress temperatures and stress days, a comprehensive evaluation model of fruit intrinsic quality was constructed. Among them, the data obtained in 2018 were used for model construction, and in 2019 were used for model verification. The results showed that the effects of different stress days on the vitamin C, soluble sugar content, titratable acid content and anthocyanin of strawberry fruits were different under high temperature. The weights of the four intrinsic qualities of strawberries are titratable acid (0.33)> anthocyanin (0.25)> vitamin C (0.23)> soluble sugar (0.19). The score of the fuzzy comprehensive evaluation showed that the comprehensive score of the intrinsic quality of the fruit was highest at 8 days and 11 days at 35℃, and 2 days and 5 days at 38℃ (all greater than 0.8). The comprehensive fruit quality scores were medium (between 0.6 and 0.8) at 2d and 5d at 35℃ and 32℃ treatment, and the lowest comprehensive fruit quality scores (between 0 and 0.6) under 38℃ treatments for 8 days and 11 days and 41℃ treatment. The determination coefficients (R2) of the built-in comprehensive quality model for the simulated and measured values ​​of greenhouse strawberry comprehensive quality were 0.86, the root mean square error (RMSE) was 0.01, and the relative error (RE) was 0.06%. Therefore, a certain degree of high temperature treatment (within 11 days at 35℃ or within 5 days at 38℃) in the greenhouse strawberry seedling stage will help to improve the comprehensive intrinsic quality and the model established can predict the comprehensive intrinsic quality of the greenhouse strawberry under high temperature at the seedling stage, which has a guiding significance for the regulation of the strawberry greenhouse temperature environment.

Risk Analysis of Chilling Injury of Morchella in Middle and Upper Reaches of Qu River in Sichuan Province

ZHANG Li-ping, ZHOU Ze-ying, PENG Yun, WANG Qing-li, LAI-Zhi-li, WANG Ming-tian

2020, 41(12):  794-806.  doi:10.3969/j.issn.1000-6362.2020.12.005

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Chilling injury is one of the main climatic problems affecting the cultivation and production of Morchella. However, there are few reports about the mechanism of chilling injury, meteorological index and climate risk zoning of Morchella, and there is lack of necessary technical support to carry out the weather services for Morchella chilling injury. It provides scientific basis for the production planning of Morchella in the study area, the dynamic assessment of the risk of chilling injury and the meteorological service of disaster prevention and reduction, and facilitates the development of agricultural industry in mountainous areas. Taking the upper and middle reaches of the Qu River below 600m above sea level as the study area, DEM data of this area and climatic data of 21 stations in and around the basin from 1991 to 2020, and experimental data of Morchella production from 2018 to 2019 were used, based on the chilling injury types and disaster-causing factors of Morchella, extreme minimum air temperature and accumulated cold were selected as zoning indices to analyze the relationship between air temperature and ground temperature from February and March in the study area, to determine the threshold of extreme minimum air temperature; to statistically analyze the temporal and spatial distributions of extreme minimum air temperature, cold accumulation, chilling injury frequency and its lasting days. The spatial distribution data of index factors were standardized by establishing the spatial distribution model of chilling damage index. Analytic hierarchy process and natural breakpoint method were used to determine the influence weight and risk level thresholds of chilling injury indexes respectively. Based on the principle of comprehensive meteorological disaster risk assessment, ArcGIS10.1 was used to make a classification in Morchella chilling risk. The results showed that: (1) the average difference between air and ground temperature from February and March was about 1.0℃(0.7~1.4℃) in the study area, smaller in the south and larger in the north. The risk index of chilling injury of Morchella was the daily minimum temperature that was less than or equal to 2.0℃, and the basic index of early-warning of chilling injury risk was daily average temperature that was less than 6.0℃. (2) The chilling injury frequency of Morchella was more than 7 times in 10 years, mainly occurred from early February to early March, and the occurrence frequency and intensity decreased every 10 days, among which 70% occurred in early and middle February. The duration of chilling injury process was 1−3 days, accounting for 82%−89% of the total number of processes, the longest duration was 6−8 days, and the maximum accumulated cold was 3.64℃·d. (3) The risk levels of chilling injury of Morchella increased from south to north and from low altitude to high altitude, mainly in the middle and low risk areas. The middle and low risk areas are mainly distributed in the shallow hills and valleys below 520m above sea level in the middle and upper reaches of the Qu River, accounting for about 2/3 of the total area. The secondary high and high risk areas were scattered, mainly distributed in the low-mountain valley area with an altitude of 520−600m in the central and northern part, accounting for about 1/3 of the area. (4) After controlling the differentiation stage of Morchella to late February, the chilling injury frequency was reduced to about 2 times in 3 years, the chilling injury intensity was significantly reduced, and the harm was significantly reduced. (5) The planting site selection and the establishment of greenhouses had different effects on the chilling injury of Morchella. the influence of local topography on microclimate can be judged comprehensively according to the altitude and whether it is conducive to the southward cold air flow and aggregation, the cultivation facilities built with black sunshade net can reduce the environmental minimum temperature by about 0.3℃ and aggravate the chilling damage to Morchella. In the study area, the suitable season cultivation of Morchella should be controlled below 520m above sea level. According to the weather conditions, the primary basal differentiation period should be adjusted after late February. Attention should be paid to the adverse effects of local microclimate and black hollowed-out greenhouse in the process of chilling injury, so as to avoid or reduce the risk and harm of chilling injury.

Investigation of the Effects of Cold Weather on Fruit Setting Rate of Red Cartridge Kiwifruit in Western Guizhou

CHI Zai-xiang, LUO Pei-fu, SUN Xiang, ZENG Xiao-shan, HU Qiu-ling, LI Xiu-ya , LONG Ru-yong

2020, 41(12):  807-813.  doi:10.3969/j.issn.1000-6362.2020.12.006

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In the first ten days of April 2020, a long-term low temperature weather process occurred in western Guizhou, which led to a large number of flower and fruit drop of red cartridge kiwifruit which was in the period of flowering and fruit setting. In view of this to ascertain the effects of low temperature on fruit setting of red cartridge kiwifruit in early April 2020, we investigated the fruit setting rate of red cartridge kiwifruit in nineteen main planting areas of Western Guizhou from April 10th to 17th. And, combined with the data of the daily average temperature and minimum temperature from April 3th to 9th, the study analyzed the effects of cold weather on flowering and fruit setting of red cartridge kiwifruit in western Guizhou. In order to provide scientific basis for prevention and mitigation of low temperature disaster and take reasonable countermeasures, the low temperature conditions affecting the flower and fruit drop of red cartridge kiwifruit in Guizhou Province were found out. The results showed that the cold weather from April 3th to 8th caused serious flower and fruit drop of red cartridge kiwifruit during their flowering, pollination, fertilization and fruit setting stage. The highest rate of flower and fruit drop was 70% in Shunchang, Xinyao and Pugu, and the second is 64.5% in Shaomi, and the third is 63.3% in Houchang. The lowest rate of flower and fruit drop was 10% in Mugang, and the second is 29.5% in Dayong. Through analysing the first-flowering dates and the time of flowering and pollination, it was found that the earlier first-flowering dates, the longer time of flowering and pollination, the rate of flower and fruit drop was higher. Besides, it was found that the rate of flower and fruit drop of Hongyang varieties was higher than that of Donghong varieties. In the period of flowering, pollination, fertilization and fruit setting stage of red cartridge kiwifruit, it was found that when the daily average temperature＜12℃ and the daily minimum temperature＜10℃ last 3 days or more, or when the daily average temperature＜15℃ and the daily minimum temperature＜13℃ last 5 days or more, it would cause flower and fruit to fall. In production, spraying antifreeze, smoking and other measures can prevent low-temperature freezing injury, and reduce the impact of low-temperature weather on the flowering, pollination and fruit setting of red cartridge kiwifruit trees.