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    20 May 2021, Volume 42 Issue 05
    Evaluation of the Ability of Statistical Downscaling Dataset from the CMIP5 Global Climate Models to Extreme Temperature Indices over Liaoning Province
    PANG Jing-yi, LIU Bu-chun, LIU Yuan, QIU Mei-juan, WANG Ke-yi
    2021, 42(05):  351-363.  doi:10.3969/j.issn.1000-6362.2021.05.001
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    Liaoning Province is one of the main grape production areas in China. Due to the increasing of temperature and the frequent occurrence of extreme temperature, it has a noticeable impact on the planting and production of grapes in Liaoning. Based on extreme temperature indices, Global Climate Models(GCM) are evaluated and the model with the best simulation effect in the study area are selected. It is helpful to improve the accuracy of future climate resource and disaster risk analysis. In this paper, the observation meteorological daily data during 1971−2010 was used, including 32 stations across Liaoning Province. 31 models in the CMIP5 climate downscaling dataset were assessed the simulation performance about the spatio-temporal variation characteristics of the extreme temperature indices in Liaoning Province (yearly and seasonally). And the locations of the meteorological stations were completely consistent with that of the model stations. After using SS/M2 indices and MR comprehensive rating, the best model was selected. Seven extreme temperature indices, including mean maximum temperature(TXm), mean minimum temperature(TNm), frost days(FD0), summer days (SU25), minimum minimum temperature(TNn), maximum maximum temperature(TXx) and the range of extreme temperatures(ETR), were adopted to investigate the change of extreme temperature. There were the following conclusions: for the indices representing the characteristics of mean temperature, the performance of all models were better and closest to the observed values; For the indices representing continuous extreme temperature events, the simulated results of all models were ordinary; And for indices representing extreme temperature, the simulation results were very different from the observation values. Since there was no consistency in the ranking of extreme temperature indices among the different time and space scales, the three models with the best simulation ability were MPI-ESM-LR, GFDL-ESM2M and MIROC-ESM-Chem introduced by MR index. The three models were the first choice in this paper. Comparing the error, the results of the preferred model ensemble averages were significantly better than that of others. It is helpful to use the selected models to predict the future change of agricultural climate resources and to analyze disaster risks across Liaoning Province. It can help seek advantages and avoid disadvantages and reduce disaster losses.
    Response of Main Phenological Periods of Two Typical Leguminosae Plants to Climate Change in Alxa Desert
    CHANG Pei-jing , LI Yong-shan , WU Nan, WANG Hai-mei, LI Zhong
    2021, 42(05):  364-376.  doi:10.3969/j.issn.1000-6362.2021.05.002
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    To explore the climate driving factors of the phenological changes of legumes in Alxa Desert, the characteristics of climate change and the temporal evolution trend of the main phenological periods of two typical leguminosae plants(Caraganabrachypoda Pojark. and Oxytropis aciphylla Ledeb.) were studied by using linear trend rate and stepwise regression methods. Based on the observation data of climate elements and vegetation phenology at Alxa Desert monitoring points in recent 40 years, that is from 1981 to 2019. The results showed that: (1)the annual average temperature of the monitoring points in the past 40 years was 8.8℃, and increased significantly with a trend of 0.46℃·10y-1(P<0.01). The average annual hours of sunlight was 3136h, decreasing at a rate of about 98h·10y-1(P<0.01). The average annual precipitation was 159mm, with an increasing trend and a precipitation variation tendency rate of 19.08mm·10y-1(P<0.05). (2) In recent 40 years, the turning green period and flowering period of Caragana microphylla and C. maotouci were significantly advanced, the yellow withered period was slightly delayed, and the whole growth season was extended over the past 40 years. The annual average turning green, the flowering and the yellow withered period from Jan.1of Caraganabrachypoda Pojark were 898, 11610 and 30810 respectively. And these three periods in Oxytropis aciphylla Ledeb 308 ± 10 and 315 ± 10, respectively. (3) From the correlation analysis between vegetation phenology and climate factors, it would be found that the phenological changes of Caraganabrachypoda Pojark and Oxytropis aciphylla Ledeb were mainly limited by air temperature. The sunshine hours had a slight effect on the green returning period of the two plants, and the precipitation only effected the yellowing period of the Caraganabrachypoda Pojark.
    Research on Downscaling and Correction of TRMM Data in the Yangtze River Basin
    DOU Shi-qing, ZHANG Han-bo, XU Yong, WEN Ying, ZHANG Nan
    2021, 42(05):  377-389.  doi:10.3969/j.issn.1000-6362.2021.05.003
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    The Yangtze River Basin has abundant rainfall, and rainfall is unevenly distributed in space and time, which is prone to flood disasters. It is of great significance to obtain precipitation information accurately and quickly. At present, remote sensing precipitation data has been widely used, but its spatial resolution and data accuracy still cannot meet actual application requirements. Therefore, based on the full consideration of the applicability of TRMM 3B43 data for 2001-2019 in the Yangtze River Basin using a geographically weighted regression model, combining NDVI, EVI, elevation, slope, and aspect, different vegetation index combinations are selected to establish low and high resolution GWR models based on pixels to achieve the downscaling of TRMM data in the Yangtze River basin from 2001 to 2019. Geographical Differential Analysis (GDA) and Geographical Ratio Analysis (GRA) corrections are then applied to the preferred TRMMNDVI data. Finally, accuracy evaluation and result analysis are performed on annual, seasonal, and monthly scales based on the actual measurement data from the meteorological stations. The results of the study showed that, (1) the R², BIAS and RMSE of the downscaled data and the measured data at the site meet the accuracy requirements, while the spatial resolution is improved from 0.25° to 1km, and the accuracy of TRMMNDVI data is higher than the TRMMEVI data. (2) The GDA calibration results are better than the GRA calibration results, and the GDA calibration results shows a higher stability and precise accuracy. Therefore, GDA calibration is more suitable for the calibration of TRMM data in the Yangtze River Basin. (3) The data have high accuracy on annual (0.91−0.986), seasonal (0.704−0.88), and monthly (0.625−0.89) scales with the site measured data R², and its detailed characteristics are better than TRMM data. (4) The downscaling and correction are better in the months with higher precipitation. The TRMM data of downscaling and correction can better reflect the real precipitation information of the Yangtze River Basin, and it provide reliable data support for agricultural production, optimal allocation of water resources, and flood prevention and disaster reduction.
    Influence of Environmental Factors on Negative Air Ion Using Random Forest Algorithm
    SHI Guang-yao, ZHOU Yu, SANG Yu-qiang, ZHANG Jin-song, MENG Ping, CAI Lu-lu, PEI Song-yi, WANG Yao
    2021, 42(05):  390-401.  doi:10.3969/j.issn.1000-6362.2021.05.004
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    Negative air ion(NAI) is an essential indicator for measuring the air cleanliness of a given area, which plays an important role in promoting the psychological and physiological functions of the human body. With the development of forest eco-tourism, NAI has attracted substantial attention, while research on NAI has become increasingly active, especially for the topics of the occurrence process and impact mechanism of NAI in related fields. Based on meteorological data and observation data of NAI during the main growing season of Quercus variabilis BI. plantation in the hilly area of North China, the random forest model in machine learning was used to analyze the environmental factors that affected NAI concentration changes from a non-linear view, and independent samples were used to simulate the random forest model to determine the prediction accuracy of the model. The estimation model of NAI was established for revealing the response mechanism and predicting the response pattern of NAI to environmental factors for further research. Results showed that the random forest model had higher accuracy and better fitting effect in analyzing the impact of environmental factors on NAI, and by verifying the fitted and measured values of the model, the root mean square error(RMSE) was 59.349, and the coefficient of determination R2 reached 0.887. While using independent test data to 10-fold cross-validation of the random forest model, the average R2 was above 0.904 and the root mean square error(RMSE) was small at 24.851. In addition, the model screened out that the main factors affecting NAI were particulate matter PM2.5(48.037), vapor pressure deficit(46.169), soil moisture(43.984), wind speed(43.779), ultraviolet radiation(41.130), soil temperature(40.107), direct radiation(36.838) and atmospheric pressure(34.532) sorted by importance scores. Among them, the three variables contributed relatively high importance to the model were particulate matter PM2.5, vapor pressure deficit and wind speed, which prove that they play a decisive role in the variations of NAI. Therefore, the random forest model is better to simulate the NAI with high accuracy and strong stability.
    Driving Influence of Environmental Factors on the Sap Flow of the Artificial Poplar Forest on Sandy Land
    WU Peng-fei, LIU Yun-qiang, LI Dong-mei, CHEN Zhi-jun, MA Chang-ming
    2021, 42(05):  402-411.  doi:10.3969/j.issn.1000-6362.2021.05.005
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    Stem sap flow is an important basis to characterize the transpiration of trees. Studying the dynamic characteristics of sap flow and the driving effects of environmental factors on it is of great significance to explore the physiological characteristics and water dynamic changes of trees. Populus×euramericana cv.‘74/76’ is one of the main fast-growing tree species widely cultivated and also a water-fertilizer-sensitive tree species. The amount of water directly affects its growth. Populus×euramericana cv.‘74/76’ in Luannan county forest farm in Tangshan city was taken as research object, the drip irrigation method was used to set the soil volumetric water content at 15%−20%, 10%−15% and 5%−10% respectively by controlling the irrigation time, the soil volumetric water content was respectively set as 15%−20%, 10%−15% and 5%−10% by drip irrigation, the sapwood flow rate of Populus×euramericana cv.‘74/76’ was measured by the thermal dissipation probe(TDP), and the solar radiation, air temperature, atmospheric humidity, atmospheric pressure, wind speed and other meteorological factors were simultaneously monitored by using the HOBO automatic weather monitoring station to explore the change rules of sap flow during day and night under different environmental conditions, establish a regression model between meteorological factors and the sap flow, analyze the water utilization of trees in different environments in order to provide guidance for the formulation of reasonable water irrigation strategies for fast-growing and high-yield plantation. Tharted earlier, peaked higher, lasted longer, and fluctuated more at night than cloudy and rainy de results showed that the sap flow was driven by different weather conditions, it on sunny days stays; The sap flow was also driven by soil moisture, under the condition of soil water shortage, the start time was late, the peak was low, the duration was short, and it changed steadily and increasingly at night. After time lag analysis, it is found that there is a "time lag effect" between the sap flow and meteorological factors, the sap flow lagged behind the solar radiation for 40 min, and was ahead of temperature, relative humidity and VPD (vapor pressure deficit) for 60min. There was a "hysteresis loop" relationship between sap flow and VPD, meteorological factors all had a significantly driving effect on the sap flow after the time lag dislocation, it had the greatest correlation with air temperature and stronger driving force during the day, while had the greatest correlation with VPD and stronger driving force at night. After time lag dislocation, the imitative effect of sap flow and meteorological factors was better than before. It can be seen that the environmental factors had an obvious driving effect on the sap flow, especially weather types, meteorological factors, and soil moisture, the regression model established between the weather factors and the sap flow after the time lag can better explain the relationship between the two mathematical relationship, meanwhile, sap flow can better reflect the water condition of sandy soil and the water consumption characteristics of trees, which provided a strong basis for the precise irrigation strategy of poplar fast-growing and high-yielding forests.
    Relationship between Walnut Fruit External Quality and Canopy Micro-climate
    ZHAO Fang-xiong, LIU Li-qiang, REN Jia-xing, LIU Guo-qing, GUO Jin-bao
    2021, 42(05):  412-425.  doi:10.3969/j.issn.1000-6362.2021.05.006
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    Using walnut variety 'Wen 185' as the test material, the changes in the surface microclimate and the external quality of the fruit in different crown positions and canopies were observed, and the correlation between the microclimate and the external quality of the fruit was analyzed. At different heights in the canopy, as the canopy area went from the lower layer to the upper layer, the average light intensity and temperature of the fruit surface during the whole development period increased, and the average humidity decreased. Nut dry weight, nut longitudinal diameter, nut transverse diameter, nut shell thickness, and kernel dry weight all increased to varying degrees, while the shell dew kernel rate decreased; within the same height canopy, the difference in the microclimate environment and fruit quality on the surface of the fruit was significantly smaller than the difference between the bottom layer and the upper layer of the canopy. The high-quality walnut fruits were mainly concentrated in the outer and upper layers of the canopy; in different positions of the canopy, the surface light intensity and temperature of the fruits on the east and south sides were higher than those on the north and west sides, but the humidity on the east side was higher than that on the west side. The light intensity was significantly different in different directions, and there was no significant difference in temperature and humidity; The external quality of fruits in different orientations and different canopies were significantly different, and had a strong correlation with the surface microclimate of the fruit. Among them, the fruit fresh weight, the thickness of the green peel, the fresh weight of the nut, the dry weight of the nut, the longitudinal diameter of the nut, the nut Horizontal diameter, shell thickness, kernel dry weight were significantly positively correlated with light intensity and temperature, and were significantly negatively correlated with humidity; the husk kernel rate was extremely significantly negatively correlated with fruit surface light intensity and temperature, and was significantly negatively correlated with fruit surface humidity, and there was a significant negative correlation. The fruit husks on the east and south canopies had the strongest negative correlation with light intensity (−0.965, −0.838) and temperature (−0.895, −0.878). The north and west canopies The strongest positive correlation was between the weight and the humidity, the correlation coefficients were 0.929 and 0.945, respectively; The fruit surface light intensity had the greatest impact on fruit quality in different orientations and canopy heights. The effect of fruit surface temperature on fruit quality was second only to light intensity, while fruit surface humidity had relatively little effect on fruit quality. The microclimate of the fruit surface in the corresponding area in the canopy significantly affects the establishment of walnut fruit structure, and its synergistic effect had a greater impact on walnut fruit quality. The east and south sides of the canopy, the upper layer and the periphery received better light intensity and temperature, which was conducive to the growth and development of the fruit. The quality of fruits in the middle and lower layers of the canopy and the middle and inside of the canopy was more strongly affected by the microclimate environment. Horticultural measures based on the leaf structure and fruit quality characteristics could improve the microclimate environment on the surface of the fruit, which was conducive to the overall improvement of walnut fruit quality.

    Effects of Elevated Atmospheric CO2 Concentration and Increased Air Temperature on Photosynthetic Characteristics and Nitrogen Metabolism of Soybean Leaves
    LIU Zhao-lin, ZONG Yu-zheng, ZHANG Dong-sheng, HAO Xing-yu, LI Ping
    2021, 42(05):  426-437.  doi:10.3969/j.issn.1000-6362.2021.05.007
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    The effects of elevated CO2 concentration and increased temperature on photosynthetic characteristics and nitrogen metabolism of soybean leaves were studied in order to provide reference for soybean production under climate change in the future. In this experiment, soybean variety‘Zhonghuang35’ was used as the test material. The experiment was carried out at four treatments: CK (the CO2 concentration and air temperature were consistent with atmosphere measurement value), EC(the CO2 concentration is the measured value in the atmosphere + 200μmol·mol–1; the air temperature was consistent with atmosphere measurement value), ET (the CO2 concentration was consistent with atmosphere measurement value; the air temperature was the measured value in the atmosphere +2℃), and ECT (the CO2 concentration was the measured value in the atmosphere +200μmol·mol–1 and the air temperature was the measured value in the atmosphere + 2℃).The soybean was planted in the artificial climate chamber throughout the growth period. At the seed filling stage of soybean, we measured the relative chlorophyll content of soybean leaves by leaf chlorophyll meter, photosynthetic parameters by portable gas exchange system, light response curves and CO2 response curves by portable photosynthesis measurement system, and measured the leaf nitrogen metabolism related indeices, through these experiment results to study the effect of CO2 concentration elevated by 200μmol·mol–1 and air temperature increased by 2℃ on photosynthetic characteristics and key indicators of nitrogen metabolism of soybean leaves at seed filling stage. The results showed that: (1) ET treatment significantly increased the relative chlorophyll content (SPAD) of soybean leaves at seed filling stage, but EC treatment and ECT treatment had no significant effect on SPAD. (2) The stomatal conductance (Gs) of soybean leaves at seed filling stage was decreased significantly in all treatments. Net photosynthetic rate (Pn) and water use efficiency (WUE) of leaves was decreased significantly in ET treatment. EC treatment had little effect on Gs of soybean leaves, but it could improve WUE of soybean leaves and alleviate the negative effect of ET treatment. (3) EC treatment and ET treatment significantly decreased the maximum net photosynthetic rate (Pnmax) of soybean leaves at seed filling stage, but ECT treatment had no significant effect on it. (4) In EC treatment, CO2 compensation point (Γ), saturated intercellular CO2 concentration (Cisat) and photorespiration rate (RP) of soybean leaves were significantly increased, but ET treatment and ECT treatment had little effect on them all treatments decreased the maximum net photosynthetic capacity (Amax) of soybean leaves at seed filling stage. (5) The nitrate reductase (NR) activity and soluble protein content of soybean leaves was decreased significantly in EC treatment, while the soluble protein content of soybean leaves was increased significantly in ET treatment and ECT treatment, but NR activity and glutamine synthetic (GS) activity was not significantly changed. In conclusion, in this experiment, elevated CO2 concentration by 200μmol·mol–1alleviated the negative effect of increased air temperature by 2℃ on photosynthesis of soybean leaves at seed filling stage, but the nitrogen metabolism was inhibited. Increased air temperature by 2℃ can alleviate the inhibition of CO2 concentration by 200μmol·mol–1 on nitrogen metabolism to a certain extent.