| Rice is one of the most important crops in China.In order to analyze the water consumption during rice growing,and clarify the hydrothermal process of rice field ecosystems and their dynamic changes,the field observation data combined with data of temperature,humidity and radiation in 2018 and 2019 were used to analyze the physiological and ecological changes of rice during the growth period.The temperature and humidity changes in the soil,water layer and canopy of the field under different irrigation treatments were studied.Energy balance was calculated,and its daily and seasonal changes was analyzed,as well as heat storage in water layer under different irrigation treatments.Path analysis was used to further study the relationship between water,heat flux and environmental factors.Finally,through the model simulation of water and heat transfer during rice growth,the following main conclusions were obtained(1)Rice growth status and microclimate characteristics under irrigationIrrigation for 5～10 cm,the photosynthetic rate of rice leaves was faster,as well as obvious increasement in yield.Irrigation of more than 10 cm will result in decreased water use efficiency(2)Microclimate characteristics of paddy field under irrigationUnder irrigation,the soil temperature of field showed that,with increasement of the irrigation,the daily maximum value of the surface soil temperature was lower and the daily minimum value was higher,that is,the temperature difference between day and night was smaller.The daily variation of deep soil temperature was not obvious.Meanwhile,the thickness of the water layer increasing,the daily maximum temperature of the water layer is lower.The water layer keep the temperature well,especially when water layer was thicker.The temperature inside the canopy was significantly affected by the seasonal variation of solar radiation(3)Water and heat transfer process in rice fieldsThe trends of latent heat flux and sensible heat flux of the field ecosystem were consistent with the change of the net radiation.Values of net radiation,latent heat,and sensible heat flux were higher in July and August.And soil heat flux was always low,with positive values in the early stage and negative values in the later stage.The existence of the water layer caused part of the heat stored in the water layer.The peak of daytime heat storage in the water layer appears about 2 hours earlier than that of the latent heat flux.The thicker the water layer,the heat storage was larger.Values of net radiation and latent heat flux on sunny days are greater than those on cloudy and rainy days.The sensible heat flux was not significantly affected by the weather,but differences in sensible heat flux on cloudy and rainy days were not significant(4)Results of water and heat flux simulationThe difference between simulating latent heat flux and observation value was generally high,which was mainly reflected at night,with a maximum difference of 59.55 W/m2.Differences during the day were also emerging.The root-mean-square error(RMSE)of the simulated latent heat flux and the observation value was 1.40,and the R2 was 0.82.Simulated value of sensible heat flux coincides with the measured value at night and was higher than the measured one during the day.The root-mean-square error(RMSE)was 0.49,and R2 was 0.77.The overall simulation effect was as expectedThe simulating leaf stomatal conductance and the measured ones were in a well correlation R2 was 0.88,which was obviously affected by solar radiation.The canopy stomatal conductance showed a common trend of diurnal variation in rice growing season with lower values in the morning and evening,and higher values at the midday.Affected by physiological effects of leaves,stomatal conductance finally decreased... |
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