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20 July 2024, Volume 45 Issue 7

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Impact of Data Inhomogeneity on Analyzing Temperature Trends in Huai River Basin

LU Xiao-jing, JIANG Xiao-dong, CAO Wen, ZHOU Jian-fei, YANG Zai-qiang

2024, 45(7):  689-700.  doi:10.3969/j.issn.1000-6362.2024.07.001

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Long homogeneous meteorological data is important to study climate change. Evaluating the impact of data inhomogeneity on analyzing average temperature trends in Huai river basin is value for accurately understanding the response of agriculture, ecology and water resources to climate change. In this study, based on the homogeneous data and observation data of daily average air temperature from the National Meteorological Information Center, the trends of annual and seasonal air temperatures during 1961 to 2018 were calculated using simple linear regression at 172 meteorological stations over Huai river basin. Then the impacts of data inhomogeneity on analyzing mean air temperature trends during 1961 to 2018 were evaluated by using two terms which were inhomogeneity impacts and contribution rates. The results showed that the average air temperature series of 96 meteorological stations in Huai river basin were inhomogeneous, accounting for 55.8% of the 172 total stations. Before and after the homogenization, the regional annual average air temperature both increased significantly. But the increasing rate was underestimated due to the data heterogeneity, and the influence was −0.015℃·10y⁻¹ with a contribution of −6.6%. For each station, 35 stations (20.3%) was positively affected and the warming rate was overestimated with an average contribution of 21.3%, while 61 stations (35.5%) were negatively affected and the warming rate was underestimated with an average contribution of −43.6%. The influences of inhomogeneity for four seasons showed little difference, which were −0.016℃·10y⁻¹，−0.014℃·10y⁻¹，−0.016℃·10y⁻¹ and −0.015℃·10y⁻¹, respectively. However, because of the slowest increasing rate, the absolute value of inhomogeneity contribution was largest in summer with a contribution of −40.0%. The contributions of spring, autumn and winter were −4.7%、−8.0% and −4.3%. Inhomogeneity mostly affected the temperature rising rate at each station in spring, autumn and winter, while led to a turning of temperature trend before and after homogenization at 20 stations (11.6%) in summer.

Using Temperature Models to Estimate ET0 in Data-scarce Regions with Limited Solar Radiation Data

ZHOU Jun-wei, DONG Qin-ge

2024, 45(7):  701-714.  doi:10.3969/j.issn.1000-6362.2024.07.002

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Accurate estimation of reference crop evapotranspiration (ET₀) is essential for water resources planning and irrigation scheduling. However, the absence of solar radiation (R_s) data is a common problem affecting the estimation of ET₀. This study investigates the feasibility of employing temperature-based models to estimate R_s and proposes effective methodologies for obtaining more convenient and accurate ET₀ estimates. To evaluate the effectiveness of different approaches, authors compared nine empirical models (M1−M9) and three machine learning algorithms (RF, GRNN and ANN) for daily R_s estimation. This analysis utilized data from 339 national basic meteorological stations in China, spanning the period from 2001 to 2018. Subsequently, authors proposed two strategies for estimating daily ET₀ in regions where solar radiation data is limited or unavailable. The results showed that (1) temperature-based models exhibited satisfactory accuracy (R²> 0.6) for daily R_s estimation, with machine learning algorithms outperforming their empirical counterparts. The machine learning accuracies are ranked as follows: Artificial Neural Network (ANN) > Generalized Regression Neural Network (GRNN) > Random Forest (RF). And empirical models are ranked in descending order of accuracy: M9 > M8 > M6 > M7 > M5 > M2 > M3 > M1 > M4. The accuracies of twelve models in the four climatic zones are indicated as follows: the temperate continental zone (TCZ) > the temperate monsoon zone (TMZ) > the subtropical monsoon zone (SMZ) > the mountain plateau zone (MPZ). (2) The comprehensive assessment for nine empirical models indicates that the Hargreaves-Samani model (M1) is the most reliable for solar radiation estimation. Its estimated results are close to those of the other models, and the coefficient of variation of the parameters (0.10) is much lower than that of the other empirical models. Thus, combining the model with the nationally calibrated parameters computed by the Kriging interpolation method allows for reliable values of the daily solar radiation. (3) Machine learning techniques show variations in estimating daily ET₀ across different climate zones. The machine learning accuracies are ranked as ANN>GRNN>RF, and TCZ>TMZ>MPZ>SMZ in the four climate zones. (4) The accuracies of the two daily ET₀ estimation strategies, with or without actual Rs calibration, are very close. Both strategies provide accurate daily ET₀ estimates (R²>0.95) with an average R² improvement of only 0.39% for strategy I compared to strategy II. In conclusion, this study provides new ideas to address the scarcity of solar radiation data and highlight the potential of machine learning in ET₀ estimation. This approach can be effectively applied to reference crop evapotranspiration estimates in regions where solar radiation data is scarce.

Change of Runoff Volume in the Middle and Upper Reaches of Han River Basin under Future Climate Scenarios

YUE Zi-ying, DENG Yu, NI Fu-quan, KANG Wen-dong, XIANG Jun, WU Ming-yan, JIANG Nan

2024, 45(7):  715-728.  doi:10.3969/j.issn.1000-6362.2024.07.003

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The middle and upper reaches of the Han river are involved in the South-to-North Water Diversion Project, and the change of runoff affects the amount of adjustable water. In order to investigate the change of runoff in the middle and upper reaches of the Han river basin under climate change, based on the SWAT (Soil & Water Assessment Tool, SWAT) model, we have developed a new model, which is based on the Soil & Water Assessment Tool (SWAT), five global climate models and four Shared Socioeconomic Pathways (SSPs) scenarios are simulated under future climate scenarios (2021−2021) in the upper and middle reaches of the Han river Basin. Based on the SWAT (Soil & Water Assessment Tool) model, we applied five global climate models and four Shared Socioeconomic Pathways (SSPs) scenarios from the latest 6th Coupled Model Intercomparison Project Phase 6 (CMIP6), and simulated the temporal and spatial changes of runoff in the middle and upper reaches of the Han river basin in the near term (2021−2040), middle term (2041−2060), and long term (2061−2080) under the future changes of climate scenarios. The results showed that: (1) compared with the baseline period (2000−2014), rainfall and temperature increased significantly under all model scenarios, and under the ＂two-carbon＂ scenario, the increase in temperature and precipitation was smaller than that of the high-carbon scenario, and the watershed was developing towards wetting and warming. (2) The future runoff in the study area showed a significant increasing trend under the SSP2-4.5 and SSP5-8.5 pathways, relative to the historical period, and the runoff decreased in some years in the upstream near, middle and far periods. 8.5 pathways show a significant increasing trend, relative to the historical period, and runoff decreases in some years in the upstream near-, mid-, and far-periods. (3) Intra-annual distribution was more even, and runoff increased during the dry period from November to June of the following year, which improved the drought-resistant capacity of the basin. (4) Spatially, the increase in runoff was dominated by the central and eastern parts of the country, and runoff decreased under the high-carbon scenario in the near future, but showed an increasing trend in the long term, with an increasing trend in future runoff at the source area of the South-to-North Water Diversion Project.

Responses to Drought of Relationships between Dry Matter Partitioning and Development Process of Maize

CAI Fu, MI Na, MING Hui-qing, ZHANG Hui, ZHANG Shu-jie, ZHAO Xian-li, JIN Chen, ZHANG Yu-shu

2024, 45(7):  729-744.  doi:10.3969/j.issn.1000-6362.2024.07.004

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In order to deeply understand the variation characteristics of dry matter partitioning (DMP) of above ground organs of maize with development stage (DVS) and their response mechanisms to drought and to improve DMP parameterization scheme, based on the 4-year water stress experiments conducted in vegetative and reproductive growth stages of maize ‘Danyu405’ and ‘Xianyu335’ in Jinzhou, the above-mentioned characteristics and their responses to drought were investigated. Results showed that under the normal water supply condition, the maize ear dry matter weight (DMW) had an increasing trend with DVS which is similar with that of the total above-ground DMW, and the leaves and stalk DMWs both saw the change trend of increase and then decrease with DVS. The DMP rate (DMPR) of maize leaves decreased linearly or exponentially with DVS, and DMPR of stalk increased from emergency to florescence and silking period and then decreased gradually until maturity. However, the ear DMPR increased linearly with DVS. The dry matter partitioning rate of increment (IDMPR) of leaves decreased with DVS, and the dry matter redistribution (DMRD) for leaves occurred at about milk stage. Meanwhile, the IDMPRs of stalk and ear increased and then decreased with DVS, and the DMRD of stalk was slightly later than that of leaves. In the case of soil drought, the DMWs of the corn organ decreased with the enhancement of drought, and the DMPRs of the corn organ responded more belatedly and weakly to drought relative to the DMWs. In addition, the DMPRs of leaves and stalk of maize ‘Danyu405’ increased with the enhancement and the delay of occurrence time of drought in late growth period, which is opposite to the situation of the ear DMPR, while the responses of the DMPRs of aboveground organs for maize ‘Xianyu335’ to drought were weaker than those for maize ‘Danyu405’. Moreover, drought in different growth stages caused the IDMPRs of leaves, stalks, and ears to be smaller, larger, and larger than the normal values, respectively, and the DMRD of leaves to be ahead of time. In addition, weather conditions combined with abnormally high temperatures and drought led to a stagnation of ear growth, which severely inhibited DMRDs and resulted in the increase in DMPRs and DMWs of leaves and stalks relative to normal values. According to the results of the 4-year experiment, the changes in dry matter accumulation and DMP with DVS and their responses to drought showed clear interspecific differences, and were closely related to severity and occurrence time of drought.

Climate Change Impact on the Growth Period and Yield of Irrigation Spring Maize in Arid Region of Northwest China

CHU Chao, LEI Jun, YANG Ren-gui, QI Yue, LI Qiang, YANG Qing-yi, YAO Yu-bi, SHI Lei

2024, 45(7):  745-755.  doi:10.3969/j.issn.1000-6362.2024.07.005

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To investigate the impact of climate change on the growth period and yield of irrigated spring maize in arid region of Northwest China, the study was conducted based on located observational experiment and climatic data from 1984 to 2022. The results showed that the temperature increased significantly during the entire growth period with a climate trend rate of 0.76℃·10y⁻¹ (P<0.01), and a significant rise in active accumulated temperature above 10℃, with a climate trend rate of 135.80℃·d·10y⁻¹ (P<0.01). Although there was no significant change in precipitation during the entire growth period, it increased significantly during the milky-maturity stage, with a climate trend rate of 4.50mm·10y⁻¹ (P<0.05). The sunshine duration increased significantly from 1984 to 2004, with a climate trend rate of 126.88h·10y⁻¹ (P<0.01), but decreased significantly in the last 19 years, with a climate trend rate of −109.38h·10y⁻¹ (P<0.01). The growth days of spring maize increased from 1984 to 2004, with a climatic trend rate of 9.86d·10y⁻¹ (P<0.01), but decreased significantly in the last 19 years, with a climatic trend rate of 7.39d·10y⁻¹. The length of sowing-seedling and seventh leaf-jointing was significantly negatively correlated with temperature, respectively. The length of sowing-seeding, third leaf-seventh leaf and silking-milky was significantly positively correlated (P<0.05) with precipitation, respectively. The length of different growth periods was significantly positively correlated (P<0.01) with sunshine duration, respectively. The yield of spring maize fluctuated and climatic yield was significantly negatively correlated (P<0.05) with precipitation. In summary, climate change has been unfavorable to spring maize growth under current irrigation methods in arid region of northwest China.

Effects of Late Spring Coldness during the Anther Differentiation Period on Bacterial Community Structure in Wheat Rhizosphere

CHEN Xiang, WANG Peng-na, LIU Bing-bing, DAI Wen-ci, CAI Hong-mei, ZHENG Bao-qiang, LI Jin-cai

2024, 45(7):  756-765.  doi:10.3969/j.issn.1000-6362.2024.07.006

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Crop rhizosphere microorganisms is crucial for their growth, development and adaptability to stress. A field pot experiment was conducted using Yannong19(YN) with strong resistance to late spring coldness and Xinmai26(XM) with weak resistance to late spring coldness. 4℃(T1) and −4℃(T2) low temperature stress treatment were carried out in intelligent ultra-low temperature incubator during the anther differentiation period of young wheat spike differentiation, and 15℃ was used as control group(CK). High-throughput sequencing technology was used to determine the bacterial community in wheat rhizosphere soil, and to analyze the effects of late spring coldness during the anther differentiation period on the diversity and community structures of wheat rhizosphere bacteria. The results showed that: (1) late spring coldness decreased the ACE index of bacteria in rhizosphere soil of the two wheat varieties, and the ACE index of the variety XM with weak resistance to late spring coldness was significantly affected (P<0.05). (2) The bacterial community in rhizosphere soil of the two wheat varieties were mainly composed of 33 phyla and 819 genera, including Proteobacteria(53.20%−57.55%), Actinobacteria (13.34%−21.69%), Bacteroidetes(10.56%−12.37%), Gemmatimonadetes(6.17%−9.19%). The relative abundance of various bacterial phyla showed differences among different degrees of late spring coldness treatment. Late spring coldness increased the relative abundance of Actinobacte by 9.79%−19.11% in YN, and decreased by 26.43% −38.47% in XM. (3) Function prediction analysis indicated that that late spring coldness during the anther differentiation period increased the gene abundance of membrane transport, amino acid metabolism, carbohydrate metabolism, replication and repair in YN rhizosphere soil, and decreased their gene abundances in XM rhizosphere soil. In conclusion, late spring coldness during the anther differentiation period reduced the richness of the bacterial community in the wheat rhizosphere soil, changed the bacterial community structure, and affected the membrane transport, amino acid metabolism, carbohydrate metabolism, and replication and repair functions of the bacterial community.

Impact of Extreme Climate Change on Maize Yield in Beijing-Tianjin-Hebei Region from 1980 to 2020

LIU Bing, YANG Yang, HAO Zhuo

2024, 45(7):  766-776.  doi:10.3969/j.issn.1000-6362.2024.07.007

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 Extreme climate change, which can cause agricultural problems, has become a global hot topic. In recent decades, the Beijing-Tianjin-Hebei region has experienced several extreme climate events that have had a significant impact on grain yields. This study evaluted the impact of climate change on grain yields in the Beijing-Tianjin-Hebei region from 1980 to 2020 using meteorological data and maize yield per unit area data at eight sites and selected 25 national meteorological stations. Four types of statistical methods were selected, including linear regression, inverse distance weighting interpolation, M-K test, and Pearson correlation, to analyze the characteristics of climate change (maximum, minimum and average temperature, and growing degree days) and its impacts on maize yields. The results revealed: (1) the growing degree days (GDD) and temperature indices such as extreme maximum temperature (TXx) and high temperature days (Htd) exhibited an upward trend over time, with increase rates of 58.31℃·d·10y⁻¹, 0.39℃·10y⁻¹ and 0.96d·10y⁻¹, respectively. However, the low temperature indices (extreme minimum temperature, low temperature days) tended to decrease with decrease rates of 0.28℃·10y⁻¹ and 2.8d·10y⁻¹, respectively. Mutation analysis indicated a higher mutation rate for high temperature indices compared to low temperature indices, indicating a clear warming trend in the Beijing-Tianjin-Hebei region from 1980 to 2020. (2) The spatial distribution of extreme temperature index terms was different. High value of high temperature indices were primarily concentrated in economically developed cities such as Beijing and Tianjin, while low temperature indices were mainly concentrated in the northern (Zhangbei) and southwestern (Xingtai) areas. (3) The grain yield presented a fluctuate increase, with climate yield of maize fluctuating greatly (−1179 to 831kg·ha⁻¹). There were three climatic bumper years (2004, 2005 and 2006) and two lean years (1999, 2000) from 1990 to 2020 in the study area. Correlation analysis indicated that GDD、TXx、Htd were the primary response indices for grain yields in the Beijing-Tianjin-Hebei region, it can be seen that when TXx≥36℃, Htd≥4d, the climatic yield of maize decreases gradually. 

Effect of Biochar Addition on the Ratio of Soil Denitrification Products: A Review

GAO Shang-jie, LIU Xing-ren, XU Chun-ying, PENG Qin

2024, 45(7):  777-785.  doi:10.3969/j.issn.1000-6362.2024.07.008

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Soil denitrification is an important pathway of soil nitrogen loss. The large amount of nitrogen fertilizer applied in agricultural production leads to the increase of soil N₂O emission, and it has caused environmental problems such as the enhanced greenhouse effect. At the same time, soil denitrification is also the main way of N₂O reduction, so controlling the ratio of soil denitrification products N₂O/(N₂O+N₂) is the key to reduce soil N₂O emission. Based on a large quantity of relevant researches, this paper summarized the measurement methods and influencing factors of denitrification product ratio in soil and the mechanism of biochar addition affecting soil denitrification product ratio. The results showed that there was still existing uncertainty about the effect of biochar application on denitrification product ratio, and whether biochar addition could effectively regulate denitrification product ratio and reduce N₂O emission was affected by some influencing factors, such as soil physicochemical properties, biochar properties and application amount. Based on the above research status, the future prospects for improving the measurement methods of denitrification products and clarifying the quantitative effects of biochar addition denitrification products ratio and its key influencing factors were proposed.

Spatial and Temporal Distribution of Heat Stress during Citrus Growth Period in Jiangxi Province

ZHANG Fang-liang, JIN Guo-hua, YANG Jun, LI Xiang-xiang, LI Ying-chun

2024, 45(7):  786-797.  doi:10.3969/j.issn.1000-6362.2024.07.009

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Daily meteorological data from 1981 to 2022 and citrus growth periods data were used in this paper. The daily mean temperature, daily maximum temperature and their duration were selected as indicators of heat stress in citrus to clarify the spatial distribution characteristic and temporal variation trend of heat stress during citrus growth periods. The spatial and temporal differences of heat stress in different growing periods of citrus were compared using a paired t-test. The results show that (1) the average frequency, times and intensity of heat stress during flowering-fruit expanding stage of citrus are 87.73%, 2.23times·y⁻¹ and 5.28d·times⁻¹, respectively. High-value areas are mainly concentrated in the southeast of Jiangxi province. The average frequency, times and intensity of heat stress during the fruit expanding-fruit coloring stage of citrus are 56.43%, 1.15times·y⁻¹ and 2.74d·times⁻¹, respectively. High-value areas are mainly in the northern and central parts of Jiangxi province. (2) The station ratios, times and intensity of heat stress during the flowering-fruit expanding stage of citrus show a decreasing trend, with an average decrease of 0.90 percent points, 0.02 times and 0.06 d·time⁻¹ every 10 years, respectively. The station ratios, times and intensity of heat stress during fruit expanding-fruit coloring stage of citrus show an increasing trend, with an average increase of 6.80 percent points, 0.26times and 0.50d·times⁻¹ every 10 years, respectively. (3) The paired t-test results show that, the frequency, times and intensity of heat stress during flowering-fruit expanding stage of citrus are significantly higher than that during fruit expanding-fruit coloring stage of citrus. However, the climate tendency of times and intensity of heat stress during flowering-fruit expanding stage of citrus are significantly lower than that during fruit expanding-fruit coloring stage of citrus. The flowering-fruit expanding stage of citrus in Jiangxi province is the most frequent period of heat stress. For now, it is necessary to strengthen citrus defenses against heat stress during the flowering-fruit expanding stage. In the future, we should improve the prevention of heat stress in citrus during the fruit expanding-fruit coloring stage.

Risk Assessment of Agricultural Meteorological Disasters in North China under Warming Environment Ⅲ: Joint Return Period Analysis of the Duration and Intensity of Heat Events in Beijing-Tianjin-Hebei Region

YANG Yu-xiao, ZHAO Jun-chi, ZHANG Qi, LIU Zhong-xian, YU Xin

2024, 45(7):  798-808.  doi:10.3969/j.issn.1000-6362.2024.07.010

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Heat events were identified based on the daily maximum temperature data at 27 meteorological stations located in the Beijing-Tianjin-Hebei region from 1960 to 2019. The Copula function was introduced to fit the joint cumulative probability distribution of the two characteristics, taking into account the duration of heat events and the heat intensity (defined as ≥35℃ accumulated temperature), so as to obtain the joint return period of the heat events with arbitrary duration and heat intensity and analyze the return period characteristics of heat events in the Beijing-Tianjin-Hebei region. The results demonstrate that the distribution of the frequency and severity of heat events in the Beijing-Tianjin-Hebei region is higher in the south and lower in the north, but the increase in frequency, duration and average daily intensity is lower in the south and higher in the north; the effect of POISS function is optimal at all sites by fitting the edge distribution of the duration of heat events; when fitting the heat intensity, the GEV function works more efficiently at a greater number of station; when combining the duration and intensity of heat events in two dimensions, the Copula function used most is Symmetrised Joe-Clayton function, followed by Frank function; return period of heat events lasting more than five days in the study area exceeds once in five years, and once in 100 years in the northern region. The results of the study can provide a reference for heat disaster prevention and mitigation in the Beijing-Tianjin-Hebei region.