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Using data from Yushu Agricultural Meteorological Station of Jilin from 2018 to 2023, the impact of different sowing dates of corn is investigated focusing on its growth and yield composition as well as grain quality under global warming. It is also debated whether adjusting the sowing date of corn could be a measure for agriculture to adapt to climate change. Results show that the utilization efficiency of accumulated temperature during the growing season of corn varies with different sowing dates. The accumulated temperature is the highest in the first sowing date and lowest in the fourth sowing date, with an average decrease of 8.3% compared to the first sowing date. Different sowing dates of corn have an impact on the growing period. The duration of the first sowing date for corn is extended by an average of 7.5 days compared to the normal sowing date, while durations of the third and fourth sowing dates are shortened by 5.7 days and 13.8 days, respectively. Different sowing dates have an impact on the yield structure of corn. In the first sowing date, there is an increase in the weight of 100 grains of corn in 2 years during 6 years, while a decrease by 4.8% and 8.7% in the third and fourth sowing dates compared to the normal sowing date. The average number of grains per plant in the first sowing date increases by 0.2%, while decreases by 6.0% and 9.3% in the third and fourth sowing date. Overall, delaying the corn sowing date by 10 days and 20 days results in an average yield reduction of 10.9% and 17.1%. Sowing corn 10 days earlier could increase the yield in some years. The change in sowing dates has little effect on the quality of grains. Therefore, an early corn sowing date can be utilized as a strategy to adapt to climate change in certain regions of Northeast China.

To study the impact of global warming on the yield and quality of winter wheat, field scientific experiments are carried out at Xuzhou Agro-meteorological Station of Jiangsu from 2017 to 2022. There are four sowing dates each year with different temperature during the growing season of winter wheat, while the winter wheat variety, soil physical and chemical properties, and agriculture measures are all the same. Therefore, the yield structure and quality of winter wheat are mainly influenced by climate change. It shows that the average temperature increases 0.1℃ to 1.7℃ during the growing season of winter wheat at different sowing dates during 5-year field experiments. The increasing temperature has an impact on the yield structure, and there is a significant negative influence on the number of grains per ear of winter wheat, with a correlation coefficient of -0.49 (P

Understanding the influence of meteorological conditions on maize yield is an important basis for ensuring stable and high yield. The effects of meteorological conditions on the yield of Lianyu No.1 maize in North China are analyzed, based on the four-year field experimental data of different sowing dates (8 June(S1), 18 June(S2), 28 June(S3) and 8 July(S4)) conducted at Hebei Gucheng Agricultural Meteorological National Field Scientific Observation and Research Station from 2018 to 2021. The results show that the delay of sowing dates leads to the extension of growing period and changes in the meteorological conditions during the growing period. When the sowing date is delayed by 20 days, the average growth period is 2.5 days longer compared with sowed 10 days earlier, and the average air temperature from emergence to jointing stages increases by 0.7℃, while the average air temperature from milk-ripening to maturity stage decreases by 5.9℃. The average yield of Lianyu No.1 maize decreases with the delay of sowing dates, and the highest yield would be achieved when the sowing date is during 8-18 June. The key meteorological factors affecting maize yield per unit area are the daily temperature range from seedling emergence to jointing stage and the average temperature from tasseling to milk-ripening stage. The results provide a reference for scientific sowing date of Lianyu No.1 maize to ensure stable and high yield.

Sowing date adjustments have been widely used for crop adaptation to climate change, but its impact on crop growth and development is still unclear. Based on field sowing date adjustment experiment of winter wheat Tanmai 98 in the northern part of North China Plain from 2017 to 2022, the responses of growth and development, yield formation and quality of Tanmai 98 are analyzed. The results show that delaying sowing date has no significant effect on the growth stage of overwintering stage and regreening stage of winter wheat. The total growth period is 256 days and 228 days for early sowing and late sowing based on the field experiment, and shortening 10 days to 8 days in turn, which is basically consistent with the interval of 10 d during sowing period. The shortening of whole growth period is mainly caused by the shortening of seedling growth period before overwintering. Late sowing date reduces effective panicles number and grain yield of Tanmai 98. The decrease rate of grain yield is 569.71 kg·hm-2·(10 d)-1 during the sowing date from 30 September to 30 October, but few significant effects are found on grain number and weight per spike. The delay of sowing date also affects the aboveground dry matter distribution of Tanmai 98 during maturity stage. The stem weight decreases with the delay of sowing date by 2.44%·(10 d)-1, but the spike of wheat increases by 2.44%·(10 d)-1. The harvest index increases with the delay of sowing date. The harvest index of S2, S3 and CK are all higher than 0.5000, while the harvest index of S1 is 0.4878. There is no significant effect on leaf photosynthetic characteristics and grain quality of Tanmai 98 by sowing date adjustments. Therefore, under the background of climate change, the winter wheat sowing date should be postponed in the northern part of the North China Plain from 1 October to 15 October. At the same time, the planting amount should be increased in steps, and basic seedlings should be increased, so as to offset the adverse effects of late sowing of wheat seedlings with fewer tillers and fewer panicle number, ensuring high yield. However, very late sowing date would still lead to yield reduction. The results provide information for the decision-making of winter wheat to climate change adaptation in the northern part of the North China Plain.

Under the background of global warming, whether freezing injury is still the main meteorological disaster in northern winter wheat growing region of China becomes uncertain, and whether delaying sowing date is an effective measurement to adapt to climate change becomes an urgent scientific problem to solve. It is found that the correlation coefficient between winter freezing injury index and winter wheat yield reduction rate is 0.62 in the northern winter wheat region from 1981 to 2000, which indicates that winter freezing injury is one of the main disasters before the year of 2000. However, this correlation becomes very low after the year of 2000, indicating that winter freezing injury is no longer the main factor for yield reduction of winter wheat. Experiments are carried out at Taian and Xianyang stations, showing that the accumulated temperature before winter and the accumulated temperature of the whole growth season of winter wheat are significantly reduced. The plant height, total aboveground dry weight and leaf area index will decrease when sowing date of winter wheat is delayed for 10 days and 20 days. Furthermore, the delay of sowing date has an adverse impact on the yield structure, the effective panicles and grains per panicle are decreased by 5% and 10.2% respectively when the sowing date of winter wheat is delayed for 10 days from 2018 to 2021 at Taian Station, and they are decreased by 17.2% and 11.9% respectively when the sowing date is delayed for 10 days at Xianyang Station. Overall, the average yield of winter wheat is reduced by 22% and 40% when sowing dates are delayed for 10 days and 20 days respectively, which indicates that the delayed sowing date of winter wheat have no positive effects. The possible cause is that the local winter wheat varieties have changed at Xianyang and Taian, and farmers have appropriately adjusted the sowing date according to experience. The current winter wheat sowing date and the main winter wheat varieties have adapted to local climate change.

The accurate simulation of leaf photosynthesis is of great significance to the study of terrestrial ecosystem model and understanding the impact of global change on vegetation. To improve the description of photosynthesis from phenomenon to mechanism, empirical model is gradually replaced by photosynthetic biochemical mechanism model, in which the photosynthetic biochemical mechanism model proposed by Farquhar is widely recognized and used. The effect of CO2 concentration on plant photosynthesis is considered by the model, but the response of plant photosynthetic parameters to temperature and light intensity is studied without considering water stress. Water is one of the important raw materials of photosynthesis, which directly affects leaf stomatal conductance, transpiration rate and photosynthetic rate, and then affects plant photosynthesis. Therefore, many experiments are carried out and the water response function is gradually established. However, these studies mostly focus on soil water content rather than leaf water content that directly affects photosynthesis, limiting the accurate simulation of photosynthesis.Taking maize from North China as the research object, drought simulation data are studied based on six water gradient tests which are carried out at Gucheng Ecological and Agro-meteorological Experimental Station of Chinese Academy of Meteorological Sciences from June to October in 2014. Different from the previous empirical model of photosynthesis, a C4 plant photosynthetic biochemical mechanism model developed from the biochemical mechanism model proposed by Farquhar and modified by von Caemmerer is applied. The sampling blades and the environmental factors such as temperature, CO2, relative humidity, and light intensity are kept consistent, and the temperature difference between different observation times are adjusted to quantitatively study the relationship between leaf water content and maximum carboxylation rate accurately. The results show that the relationship between them can be expressed in a quadratic curve significantly (passing the test of 0.01 level), and the determination coefficient of the fitting equation is up to 0.88. With different parameters, the values of the maximum carboxylation rate are different, but the normalized leaf water content correction function is independent of the parameters. Through calculation, when the leaf water content is about 80%, the value of correction function is 1, and when the leaf water content drops to about 70%, the value is 0. This result perfects the photosynthetic biochemical mechanism model of C4 plant from the perspective of leaf water content, which provides a reference for further improving the accuracy of photosynthesis simulation, drought monitoring and early warning of maize.

Climate change has a substantial influence on the end of the growing season (EOS). The time-lag and cumulative effects are non-negligible phenomena when studying the interactions between climate and vegetation. However, quantification of the temporal effects of climatic factors on the EOS in the context of changing hydrothermal patterns remains scarce. Based on the Moderate Resolution Imaging Spectroradiometer (MODIS) fraction of absorbed photosynthetically active radiation (FPAR), this study first inverted the EOS of typical steppe vegetation in a semi-arid region of China and then quantified the time-lag and cumulative effects of monthly total precipitation (PRE) and monthly average temperature (TEM) on the EOS during 2003–2022. The results showed that a turning point occurred in 2011, when the EOS displayed an advancing trend until 2011, followed by a delayed trend. Accordingly, the climatic background has changed from warming and drying conditions during 2003–2011 to warming and wetting conditions during 2011–2022. The time-lag scales of PRE and TEM on the EOS decreased from 2- and 4-month scales during 2003–2011, respectively, to 1- and 2-month scales during 2011–2022, respectively. The time-lag degree of the hydrothermal factors on the EOS weakened with increased precipitation. The cumulative time scales of the EOS response to PRE and TEM were mainly concentrated within 1-month during different time periods, but the EOS was more sensitive to short-term precipitation. The time lag and cumulative partial correlation coefficient of PRE to EOS changed from mainly negative regulation during 2003–2011 (39.2% and 50.0%, respectively) to mainly positive regulation during 2011–2022 (67.8% and 93.7%, respectively). The time-lag and cumulative effects of TEM on the EOS were positive with the precipitation and temperature gradient under a warming and wetting climate, which indicated that increased precipitation was a prerequisite for temperature to induce a delayed EOS in the semi-arid study region. This study emphasizes the important role of precipitation in regulating the EOS response to hydrothermal factors in semi-arid regions. [ABSTRACT FROM AUTHOR]

Ozone (O3) deposition is the main sink of surface O3 , exerting great influences on air quality and ecosystems. Due to instrument limitations and method shortages, O3 deposition was less observed and investigated in China, where O3 has been reported to be continuously and significantly rising. Here, we conducted comprehensive measurements of O3 deposition over a wheat canopy at a typical polluted agricultural site in the North China Plain using a newly developed relaxed eddy accumulation system. For the main wheat growing season in 2023, O3 deposition flux and velocity (Vd) averaged -0.25 ± 0.39 µgm-2s-1 and 0.29 ± 0.33 cms-1 , respectively. Daytime Vd (0.40 ± 0.38 cms-1) was obviously higher than in the nighttime (0.17 ± 0.26 cms-1). The temporal changes in Vd were mainly determined by crop growth, and Vd significantly increased with decreasing relative humidity and increasing friction velocity and soil water content, enhanced by a higher leaf area index. With rapid increases in soil moisture, simultaneous and following overall increments in Vd were detected, attributed to remarkably strengthening O3 stomatal uptake under increased stomatal conductance and extended opening into the night, and more non-stomatal O3 removal at night resulted from strengthened soil NO emission in moist conditions. This study confirms the leading effects of crop growth on O3 deposition modulated by environmental conditions and the non-negligible influences of nocturnal plant activities, and it emphasizes the need for O3 deposition observation over different surfaces and accurate evaluation of O3 agricultural impacts based on deposition fluxes. [ABSTRACT FROM AUTHOR]