Chinese Journal of Agrometeorology

Impact of Climate Warming on the Threshold Temperature in Tibet under Global Climate Change

DU Jun, HUANG Zhi-cheng, Tsewangthondup, Dechendolkar, ZHOU Kan-she

2024, 45(02): 111-123. doi:10.3969/j.issn.1000-6362.2024.02.001

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Under the influence of global climate change, agricultural and livestock production is facing greater risks. It is important to study the spatio-temporal changes of the threshold temperature, in order to provide the informative scientific foundation for adjusting the agricultural cultivation structure to achieve sustainable agricultural development. Based on the daily average temperature observed at 38 meteorological stations over Tibet from 1981 to 2020, the spatial and temporal variation characteristics of ≥0℃,≥5℃ & ≥10℃ threshold temperatures[initial date(ID), final date(FD), duration days(DD) and active accumulated temperature(ATT)] over Tibet in the recent 40 years in the context of global warming were analyzed by various statistic methods, including linear tendency estimation, Person coefficient, Mann-Kendall, and dominance analysis. The results showed that: (1) the distribution of ≥0℃,≥5℃ & ≥10℃ threshold temperatures in Tibet generally presented the characteristics of delayed ID, earlier FD, shortened DD and reduced ATT from southeast to northwest, without significant vertical zonal characteristics of altitude. Generally, the accumulated temperature of ≥0℃, ≥5℃ & ≥10℃ decreased by 143.0, 136.1, 141.5℃·d, respectively, with an increase of 100m in altitude. The average values for all three types of ATT in Tibetan stations have increased respectively in the period of 1991−2020, compared with those in the period of 1981−2020, especially ≥10℃. The majority of stations were featured by an earlier ID, a later FD, and a more DD. (2)In the past 40 years, the amplitude of the ID, FD and DD of the threshold temperature in Tibet was the largest at ≥0℃, with an average prolonging rate of 5.4d·10y⁻¹, caused by an advancing rate of 3.2d·10y⁻¹ and a postponing rate of 3.5d·10y⁻¹, respectively. The maximum increase of ATT for ≥10℃ was 86.1℃·d·10y⁻¹. The increase of DD for ≥0℃ and ≥5℃ was caused by the significantly advanced ID, while the increase of DD for ≥10℃ can be attributed to the significantly postponed FD. (3)The linear trend(LTR) of ≥0℃ threshold temperature were significantly greater in lower elevation area than in higher elevation. The maximum LTR of the ID and ATT for ≥5℃ were in lower altitude area, and the maximum LTR of FD and DD were in middle and high altitude area(3500−4000m). The LTR of ID for ≥10℃ was the largest in middle and high elevation area, and the maximum LTR of FD, DD and ATT for ≥10℃ appeared in the altitude range of 4000−4500m. (4) In the 1980s, ≥0℃, ≥5℃ & ≥10℃ exhibited later ID, earlier FD, shorter DD and lower ATT. In the 1990s, the ID, FD and DD did not change much, which was normal, and ATT was still lower. After entering the 21st century, the threshold temperature presented the characteristics of earlier ID, later FD, longer DD and higher ATT, especially in the 2010s. (5)The mutation of FD for ≥5℃ occurred earliest in the early 1990s, while the mutation of FD at ≥10℃ was the latest in the middle of the 21st century. The abrupt changes of ID and ATT happened in the mid-late 1990s and the early 21st century, respectively. In contrast, the abrupt change of DD occurred during the late 1990s and the mid-early 21st century.

Effects of Ground-covered Plants in Jujube Orchard on Soil Carbon Sequestration Capacity in Shandong

LI Qing-jun, GAI Zhi-jun, ZHENG Xiao-ning, LIU Yun-fen, GAO Jing, XU Ke-jun, LIU Meng-jun

2024, 45(02): 124-134. doi:10.3969/j.issn.1000-6362.2024.02.002

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The process of CO2 entering the plant through photosynthesis was divided into two phases: plant absorption and soil fixation. It had been studied that the capacities of these four samples, which were Vulpiamyuros, Vicia villosa Roth, rapeseed and natural grass, absorbing CO2 through photosynthesis and that the variation of organic carbon amount in soil. And we also did some work on loss of biomass, carbon amount in early and last resudue decomposition. The result showed that Vicia villosa Roth had the most powerful capacity in carbon absorbing, which reached 3596.7-4822.3kg·ha⁻¹·y⁻¹. The remaining carbon should be the most after three months of cutting, clustering and decomposing and could reach a value of 1164.55-2529.97kg·ha⁻¹. Rapeseed had the highest value of carbon emission in the four plants, which reached the average of 5679.75kg·ha⁻¹ and the highest of 6316.67kg·ha⁻¹ which was 1.56 times as much as the CK. The quantity of fixed carbon in the soil covered by rapeseed was the highest of 4790.75kg·ha⁻¹·y⁻¹, which was 1.4 times more than the CK. This thesis can be used as an instruction for selecting right ground plants in jujube orchard and also be useful for decreasing carbon dioxide from air to come to the carbon neutral.

Based on Four Methods to Compare the Seasonal Temperature Forecasting Model for Venlo-type Glass Greenhouse

WU Hui-zhen, LI Dong-sheng, YANG Zai-qiang, ZHANG Feng-yin, CHEN Yang

2024, 45(02): 135-146. doi:10.3969/j.issn.1000-6362.2024.02.003

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The seasonal temperature forecasting models in greenhouse based on multiple regression (MR), BP artificial neural networks (BPANN), random forest (RF) and support vector machine (SVM) were constructed using meteorological observations inside and outside the Venlo-type glass greenhouses from 27th February 2021 to 4th March 2023 at Nanjing University of Information Science & Technology, and then to validate all the models. The results showed that the fitting accuracy of the seasonal forecasting models for daily average and minimum air temperatures in the greenhouse was significantly higher than that of the seasonal forecasting models for daily maximum air temperature; the fitting accuracy of each model for air temperature inside the greenhouse in spring, summer and autumn was higher than that for winter. For the seasonal forecasting models of daily average air temperature and minimum air temperature, the fitting accuracy of the spring, summer and autumn forecasting models constructed by the four algorithms was higher, but the simulation effect of the RF model was more stable, and the coefficient of determination (R2) of the simulated values and the actual observed values were above 0.94, and the root mean square error (RMSE) and absolute error (MAE) were within 1.5℃. For the seasonal forecast models of daily maximum temperature, the fitting accuracy of RF model for spring, summer and autumn was higher than other models in general, and its R2 value was above 0.75. The MR model had higher accuracy for winter indoor air temperature and was more suitable for predicting winter greenhouse air temperature. The study concluded that it is feasible to choose the RF model to forecast the air temperature inside the glass greenhouse in spring, summer and autumn and the MR model to forecast the air temperature inside the glass greenhouse in winter, and this study can provide an important reference for the seasonal forecast of air temperature in Venlo-type glass greenhouse.

Comparative Analysis of Heat Damage Index for Early Rice by Temperature from Rice Field and National Meteorological Station in Jiangxi Province

YU Yan-wen, CHEN Kun, CAI Zhe, LI Shan, SUN Hui-tian

2024, 45(02): 147-158. doi:10.3969/j.issn.1000-6362.2024.02.004

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Data from national meteorological stations in 90 counties of Jiangxi province during 2012−2021 and 8 microclimate stations in rice fields during 2017−2021 were used to analyze the differences in temperature between rice fields and stations, and the statistical results based on H1 (NS)(daily max temperature of national stations ≥35℃), H1 (RS)(daily max temperature of rice fields ≥35℃), H2 (NS)(daily max temperature of national stations ≥37℃) and H2 (RS) (daily max temperature of rice fields ≥37℃) were compared. Furthermore, proposing high-temperature damage indicators more suitable for early rice in Jiangxi, which would promoting capabilities of high-temperature monitoring and defense. The results showed that: (1) compared with the national stations, the rice fields had a cooling effect, and the Tmax(daily maximum temperature), T(daily average temperature), and Tmin(daily minimum temperature) were 0.6℃, 0.4℃, and 0.3℃ lower than national stations. What’s more, the cooling effect increased with the growth of early rice, which showed as heading-maturity period>transplanting-booting period>sowing-transplanting period. (2) The cooling effect was higher in sunny days than in cloudy and rainy days during the high temperature period, and T, Tmax and Tmin of early rice field were 0.7℃, 0.8℃ and 0.6℃ lower than that of the national stations. On cloudy and rainy days, the decrease in temperature of rice fields was similar. (3) There were significant differences in daily and hourly air temperature between 6 rice fields and the corresponding national stations during H1 (NS) heat damage occurred, and the cooling intensity of the rice field was greater at night than in the daytime. The Tmax, T and Tmin of the 6 fields were generally about 1.2℃ lower, which was strongest in Jinxi filed with T, Tmax and Tmin was 1.5℃, 1.1℃ and 2.6℃ lower. (4) H1 (NS) was the largest and H2 (RS) was the smallest in terms of the number of counties affected by heat damage, the average duration, the average yield reduction simulation value of affected counties and the simulation value of the whole in recent 10 years based on different heat damage index. There was no significant difference in the result of average duration, the simulated average yield reduction rate of affected counties, and the simulated yield reduction rate of the whole based on H2 (NS) and H1 (RS), while they were all different with the result based on H1 (NS) or H2 (RS). And the simulated value of the reduction rate of the whole calculated by H2 (NS) was closer to the actual value. Therefore, national stations Tmax≥37℃ was more suitable as an index of heat damage for early rice in Jiangxi.

Effect of Short-Term Low Temperature on Seedling Growth and Nodule Nitrogen Fixation in Soybean

LI Tian, YU Jie, QIAO Yun-fa, MIAO Shu-jie

2024, 45(02): 159-169. doi:10.3969/j.issn.1000-6362.2024.02.005

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In this study, potted experiments were conducted using the early-maturing soybean variety "Heihe 43" and the late-maturing soybean variety "Dongnong 53" under low temperature treatment (LT). The shoot and root dry weights, nodule biomass, total nitrogen content, and nodule nitrogen fixation were measured in the 28-49 days after soybean emergence. The results showed that: (1) low-temperature stress encountered by soybeans in the first week after emergence would delay soybean growth and development. From the 28d to 42d after emergence, soybean biomass was significantly lower than that of the CK treatment under low-temperature stress, but no significant difference was observed in the biomass of the two soybean varieties until the 49d after emergence. (2)In comparison to CK, significant inhibition of nodule formation in "Dongnong 53" and "Heihe 43" by low temperature occurred in the 42d and 35d after emergence, and the number of nodules decreased by 58.8% and 72.0%, respectively. During the 49d after emergence, low temperature decreased the dry weight of nodules of "Dongnong 53" and "Heihe 43" by 48.9% and 48.5%, respectively. (3) Low temperature stimulated the nitrogen fixation ability of two soybean varieties. At 49d after seedling emergence, the biological nitrogen fixation, nitrogen fixation per unit nodule biomass and nitrogen fixation per individual nodule of "Dongnong 53" and "Heihe 43" at low temperature increased by 89.9%, 118.9%; 249.3%, 172.6% and 150.6%, 114.2%, respectively. The percentages of biological nitrogen fixation increased by 26.4 and 24.5 percentage points, respectively. Collectively, low temperature stress after soybean emergence can slow down growth and development, and inhibit the formation and growth of nodules. However, soybean growth will gradually recover after the release of low temperature stress. Short-term low temperature stress has a stimulating effect on the nitrogen fixation of soybean nodules and their nitrogen fixation ability, and the stimulating effect is more pronounced for the early-maturing variety "Heihe 43". Therefore, it is recommended choosing early-maturing soybean varieties to better adapt the early spring low temperature environment in the soybean production area of Northeast China.

Research Progress on the Mechanisms of Controlling Poplar Canker by Antagonistic Microbes

CHEN Yi-fan, XIE Ke-xin, FAN Xue-qi, LIU Xi-zi, ZHANG Ping-dong, DING Chang-jun, GUO Hui, GENG Bing

2024, 45(02): 170-177. doi:10.3969/j.issn.1000-6362.2024.02.006

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Poplar is a major afforestation species which is widely planted worldwide. With the continuous expansion of poplar plant areas, the occurrence of poplar canker disease increased rapidly, causing serious damage to the trees. Currently, the major controlling method for poplar canker is chemical agents, but side effects such as environmental pollution and pathogen resistance are becoming more and more serious. There is an urgent need for developing effective non-polluting means to control the canker disease. By using microbiomes as a research tool, beneficial microorganisms that enhance plant disease resistance can be obtained. These antagonistic bacteria can inhibit the growth of canker pathogens without environmental pollution, and have good biological-control potential. This review mainly explores the role and mechanisms of antagonistic bacteria in the control of poplar canker, including inhibiting the growth of pathogenic bacteria through nutrient and water competition, secreting bacteriostatic substances, improving plant disease resistance to resist pathogen infection, and improving the host's own reactive oxygen species tolerance, in order to provide a theoretical basis for the development of efficient and specific bacterial agents, and scientific prevention and control technology.

Effect of Low Temperature at Anthesis on the Fluorescence Properties of Photosystem and Protective Enzyme Activity of Strawberry Leaves

XU Jia-qing, YANG Zai-qiang, YUAN Chang-hong, LUO Jing, WANG Can-yue, ZHANG Han-qi, JIANG Nan

2024, 45(02): 178-188. doi:10.3969/j.issn.1000-6362.2024.02.007

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The artificial environment control experiment was conducted at Nanjing University of Information Science and Technology from November to December 2022 using strawberry "Selva" (Fragaria ananassa) as the test material, and the strawberry seedlings were selected and placed in the artificial climate chamber for low-temperature treatment in mid-November when they reached the flowering stage. Three levels of temperature were set: 5℃(daily minimum)/15℃ (daily maximum), 10℃/20℃ and 15℃/25℃ (CK). The treatment duration was 3d, 6d and 9d. The kinetic parameters of photosystem fluorescence induction and protease activity of strawberry leaves were measured under different days of low-temperature to understand the effect of low-temperature on photosystem fluorescence and protease activity of strawberry leaves. The effects of low-temperature on the fluorescence properties of strawberry leaves and the activity of protease were measured. The results showed that (1) the light energy absorbed per reaction center (ABS/RC), the energy dissipated per reaction center (DIo/RC) and the energy captured per reaction center for QA reduction (TRo/RC) of strawberry leaves increased with decreasing temperature and increasing duration in the range of daily minimum temperature from 5℃ to 15℃, but the energy captured per reaction center for QA reduction (ETo/RC) increased with increasing duration. The energy captured per reaction center for electron transfer (ETo/RC) decreased. ABS/RC and DIo/RC were 1.367 and 1.718 times higher than those of CK for the treatment with daily minimum temperature of 5℃ for 9d, respectively. TRo/RC increased by 7.42%, 14.66%, 25.27%, and 30.48% for daily minimum temperature of 10°C for 3d, 6d, 9d and daily minimum temperature of 5°C for 9d, respectively, compared to CK, while ETo/RC decreased by 1.71%, 20.39%, 26.65%, and 28.32%, respectively, compared to CK. The quantum ratio for thermal dissipation (φDo) increased significantly with the duration of low-temperature, 12.34% and 25.32% higher than CK at a daily minimum temperature of 5℃ for 3d and 9d, respectively. However, the quantum yield for electron transfer (φEo) decreased with the prolongation of low-temperature, and decreased by 27.92% and 43.02% compared with CK for 3d and 9d, respectively. (2) The activities of superoxide dismutase (SOD),catalase (CAT), peroxidase (POD), and malondialdehyde (MDA) of strawberry leaves gradually increased with the decrease of temperature and the extension of the duration of low-temperature. The activities of SOD and POD reached the maximum at the daily minimum temperature of 5℃ for 6d, which were 1.39 and 2.03 times higher than those of CK, respectively, while CAT was less affected by low temperature. The MDA content was the highest at the minimum daily temperature of 5°C for 9d, which was 2.10 times higher than that of CK. The study showed that low temperatures will damage the structure and function of the photosystem of strawberry leaves, the photochemical efficiency decreases, the energy dissipated by heat increases, resulting in a decrease in the ability of PSⅡ donor side to provide electrons, and the electron transfer efficiency decreases, strawberry leaves will stimulate the antioxidant system in the body, and produce a certain resistance to the environment, which shows that the activities of SOD, POD and CAT have different degrees of increase compared with CK. However, the cell membrane structure was still damaged and the membrane permeability increased.

Determination Forecast Index of Low-temperature before Flowering of Orange Osmanthus in Nanyang by Stepwise Approach Method

WANG Yu-xiang, XUE Meng

2024, 45(02): 189-200. doi:10.3969/j.issn.1000-6362.2024.02.008

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From 2016 to 2022, the flowering phenomenon of a orange Osmanthus tree in the courtyard Nanyang Meteorological Bureau had observed for 7 consecutive years. The observing was according to the "Agricultural Meteorological Observation Code and Natural Phenology Volume" woody plant flowering period observation standard, i.e. when "the petals of one or several flowers on the observation tree begin to fully open, it is the beginning of flowering", and when "the petals on the observation tree wither and fall off, leaving a very small number of flowers" is recorded as the end of flowering. The first flowering period of Osmanthus fragrans in autumn is recorded as the first batch of flowering. The phenomenon of a second flowering after the first batch of orange Osmanthus blossomed is recorded as the second batch of orange Osmanthus blossoming, just like the first flowering period. After the second flowering of orange Osmanthus, it was observed that in some years, one or several flowers on the observed orange Osmanthus tree had fully opened petals and withered and shed was recorded as the third batch of flowering. Seldomly, the fourth batch of flowering was observed and recorded until no further flowering occurred. From 2016 to 2022, the flowering number of batches of orange Osmanthus flowering in the autumn of Nanyang every year and the initial flowering period and attributes of each batch of flowering were totally different. First, from the aspects of number and attributes of flowering batches, only one batch of flowers was bloomed per year from 2016 to 2019, which was completed at one time, and the 1st batch was also the last batch. From 2020 to 2022, 2-4 batches was bloomed every year, of which the 2nd batch in 2020, the 4th batch in 2021, and the 3rd batch in 2022 are the last batch. The 1st batch in 2020, the 1st to 3rd batch in 2021, the 1st and 2nd batches in 2022 are not the last batch. From the beginning of each batch of flowering, the earliest is August 25 and the latest is October 19. According to previous studies, as a plant that blooms in autumn, the flowering of Osmanthus is caused by the gradual decrease in temperature to a certain limit. Then, each batch of Osmanthus flowers has at least 1 day of low-temperature process that temperature below this limit, Osmanthus blooming cannot be completed at one time must be the previous low-temperature process did not meet all the conditions that should be achieved, and there is at least 1 day of low-temperature process that temperature below this limit again, and it blooms again. As long as the temperature values of each batch before flowering are statistically analyzed in turn, we can gradually approach to finding this limit. With this boundary, the low-temperature process can be counted, so as to find out the conditions that should be met when all flowers bloom compared with the flowering situation of Osmanthus. Daily temperature values include daily average temperature, daily minimum temperature and daily maximum temperature, which respectively express the average situation and range of daily temperature fluctuation, and should be analyzed to identify their respective functions. This article is based on years of continuous observation records of the multiple batches flowering phenomenon of orange Osmanthus in Nanyang, the minimum temperature values with daily maximum temperature, daily average temperature, daily minimum temperature before the first batch of flowering each year be counted in sequence, the minimum temperature values with daily maximum temperature, daily average temperature, daily minimum temperature between the previous batch of flowering and the current batch of flowering be calculated in sequence when the second and subsequent batches of flowering each year. Their respective maximum values selected as that daily index of low-temperature in each expression form of temperature, statistics of natural low-temperature process according to daily index of low-temperature, merge the discontinuous natural low-temperature process with short intervals into one combined low-temperature process, after the start date and negative effective accumulated temperature of the combined low-temperature process are calculated, analyze the relationship between the beginning of flowering of orange Osmanthus and the start date of the combined low-temperature process, as well as the relationship between the attributes of each batch of flowering and the negative effective accumulated temperature during the combined low-temperature process, the index of low-temperature before flowering which can be used for forecasting the flowering period of each batch of orange Osmanthus to be determined. Tested by correlation coefficients and univariate linear regression methods, the results showed that:(1)the method of stepwise approach method is used to determine the index of low-temperature before flowering of orange Osmanthus in Nanyang, the best effect is to use the daily maximum temperature, which is better than using the daily average temperature and daily minimum temperature. (2) The daily index of low-temperature before flowering of orange Osmanthus is the daily maximum temperature <22.3℃. (3) The process index of low-temperature before flowering of orange Osmanthus is the daily maximum temperature <22.3℃ natural low-temperature process interval days ≤1d merged into one combined low-temperature process, when the negative effective accumulated temperature during the daily maximum temperature <22.3℃ combined low-temperature process >3.4℃·d, the orange Osmanthus flowering once completed, when the negative effective accumulated temperature during the daily maximum temperature <22.3℃ combined low-temperature process ≤3.4℃·d, the 1st batch of orange Osmanthus flowering is not the last batch, if the daily maximum temperature <22.3℃ again, orange Osmanthus will bloom again, until the negative effective accumulated temperature during the daily maximum temperature <22.3℃ combined low-temperature process >3.4℃·d, the orange Osmanthus flowering is the last batch. (4)The relationship between the beginning of flowering of orange Osmanthus and the low-temperature process is as follows: the sequence of daily maximum temperature <22.3℃ combined low-temperature process corresponds to the batch sequence of flowering of orange Osmanthus, the beginning of flowering of orange Osmanthus was 4-13d after the start date of the combined low-temperature process, the specific flowering date Y is predicted by the univariate regression equation that the factor X be the start date of each combined low-temperature process with daily maximum temperature <22.3℃, and Y=1.1255X+1.4683, which is a very significant positive correlation linear relationship.

Risk Assessment of Delayed Chilling Injury of Rice and the Determination of Insurance Premium Rate in Northeast China Based on High-resolution Meteorological Grid Data

QIU Mei-juan, LIU Bu-chun, LIU Yuan, PEI Zhong-you, LI Zhi-bin, SONG Xiao-hui

2024, 45(02): 201-211. doi:10.3969/j.issn.1000-6362.2024.02.009

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The 5km×5km meteorological dataset from 1981 to 2010 is used in this study to analyze the delayed chilling injury risk of rice in Northeast China and the pure premium ratemaking thereof. The availability of the grid dataset is evaluated by calculating the correlation coefficients and root mean square errors (RMSE) between the grid database of average temperature from May to September from 1981 to 2010 in Northeast China and the data observed from 99 meteorological stations. The number of days with daily average temperature stably higher than 10°C and 18°C is taken as an indicator for defining climatologically safe rice-growing areas, within which the temporal and spatial change characteristics of chilling injury of rice in Northeast China are analyzed to determine the pure premium rate thereof. The results show a strong correlation coefficient and low RMSEs between the grid data and the observed May to September mean temperatures in Northeast China from 1981 to 2010, indicating that grid data is available in Northeast China. The climatologically safe rice-growing areas, which occupied 56.5% of Northeast China, are mainly distributed in Liaoning, central and western Jilin, southwestern and northeastern Heilongjiang, the western region in eastern Inner Mongolia and the eastern regions bordering Liaoning and Jilin. In climatologically safe rice growing areas, the frequency of delayed chilling injury in rice is typically characterized by a distribution pattern of low in the south and higher in the north, and low in the middle and elevated in the east and west. Moreover, severe delayed chilling injuries were the most frequent. The spatial distribution of the risk index of delayed chilling injury is similar to the distribution of the frequency, with high value areas in the western and northeastern parts of Inner Mongolia, northern Heilongjiang, and western Jilin. The spatial distribution of the pure premium rate of delayed chilling injury for rice in Northeast China from 1981 to 2010 is similar to its risk index distribution, i.e., low in the south, high in the north, low in the center, and high in the east and west. The pure premium rate is between 0.010 and 0.094, which can be regarded as a reference for insurance companies in making specific rates.

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