Water And Heat Transfer Characteristics And Simulation Of Solar Greenhouse In Grapevine Growth Period In Northeast Cold Region

In recent years,the proportion of fruit trees planted in facilities in northeast China has increased year by year,and the precise management of fruit tree irrigation in greenhouses can improve water use efficiency and fruit production quality.Therefore,it is necessary to establish efficient water-saving and energy-saving facilities for solar greenhouses,optimize the irrigation system of greenhouse fruit trees,improve the efficiency of water and heat utilization,and provide a theoretical basis for ensuring the high-quality and stable yield of fruit tree agriculture.Taking greenhouse grapevine as the research object,using water balance method,energy balance method,sap flow meter,Li-6400 photosynthetic instrument,meteorological automatic monitoring system and other theories and methods to study the variations of water heat flux,water consumption law,energy distribution and its influencing factors in the greenhouse from2017 to 2019 and 2021,and the water consumption of grapevine was quantitatively simulated to explore the hydrothermal transport process of greenhouse soil-plant system in Northeast Cold Region.The results obtained were as follows:（1）The energy distribution and its influencing factors were clarified in grapevine greenhouse.Latent heat flux（LE）accounted for most part of the net radiation（R_n）,with the value of55.13%and 73.62%,H accounted for 16.42-22.80%of R_n,and G/R_n was small（-7.3-16.5%）during the four growing seasons.The order of LE/R_n in different growth stages（Ⅰ,Ⅱ,Ⅲ）of grapevine was ranked as:Ⅱ>Ⅲ>Ⅰ.The average value of Bowen ratio（β=H/LE）in the whole growth period was 0.34-0.44.The close relationship betweenβand leaf area index（LAI）showed that LAI had a vital impact on the energy distribution in the greenhouse,and the impact in stageⅠwas greater than that in stagesⅡandⅢ（R² at 0.19-0.50）.The high values of the Priestley-Taylor coefficient（α,0.90-1.02）and the decoupling coefficient（Ω,0.69-0.82）indicated that LE was principally determined by R_n as far as the whole the growing seasons.However,in stageⅠandⅢ,LE was mainly governed by vapor pressure deficit（VPD）and crop surface conductance（G_c）,and the controlling effect of R_n on LE relatively was weakened.G_cwas closely related toα（R²=0.59-0.90）,suggesting that daily ET was significantly affected by G_c.In addition,changes in NVPD（normalization of VPD by photosynthetic active radiation,PAR）and LAI affected G_c,which in turn affected LE and energy distribution in the greenhouse.（2）The evapotranspiration and crop coefficient of grapevine in greenhouse were quantitatively described.There is a significant seasonal change in evapotranspiration（ET）and transpiration（T）in the greenhouse,with a daily average of 1.55-1.83 mm d^-1,1.28-1.55 mm d^-1.Daily average soil evaporation（E）was 1.28-1.55 mm d^-1.The change of T/ET within the day is 32%-98%.The cumulative amount of ET during the whole period was 269.65-335.64 mm.The cumulative amount of T was 222.19-283.48mm,and the range of T/ET was 82.40-84.46%.The cumulative amount of E was 47.45-52.60 mm,and the range of T/ET was 15.54-17.60%.R_nis the most significant environmental factor that affect ET distribution（E/ET）.The physiological factor（LAI）had a significant negative effect on E/ET,which had a good secondary curve relationship between E/ET（R² is 0.61-0.78）.In the four growth seasons of grapevine,the basic crop coefficients(K_cb)were in the initial stage,middle and late stages of0.22,0.63 and 0.40,respectively;The crop coefficient（K_c）was 0.35,0.70,0.52,respectively.Both the basic crop coefficient and crop coefficient are lower than the value recommended by FAO56 in the middle of grapevine growth.In addition,the single crop coefficient method can be more reasonable to estimate the greenhouse grapevine ET,and R²and slope are 0.93-0.98,0.78-1.07,respectively.（3）The heat convection type of grapevine greenhouse was clarified and the Penman-Monteith model modified by heat transfer coefficient method were determined to be the best model to simulate the transpiration of grape in greenhouse in northeast China.The daytime canopy resistance（r_c）of grapevines was basically maintained between 200and 250 s m^-1during the two growing seasons.The main convection type in the greenhouse was free convection（68.8–87.5%）and supplemented by mixed convection（12.5–31.3%）.The intensity of free convection gradually increased with the growth stage.r_a1 and r_a2 calculated under the free and mixed convection conditions had no noticeable difference and the variation trend was the same,but both were higher than r_a′calculated by the Perrier logarithmic method.The modified P-M models based on the three aerodynamic resistance methods all overestimated transpiration at the early growth stage and underestimated transpiration at the middle and late growth stages to different degrees.Overall,the P-M model under the three methods could accurately simulate hourly transpiration with a determination coefficient（R²）and root mean squared error（RSME）greater than 0.89 and 23.4 W m^-2.r_a based on the heat transfer coefficient correction improved the accuracy of daily transpiration simulation,and the P–M_ra1 model based on the free convection condition had the highest precision(R²≥0.97,RSME≤17.4 W m^-2).The P-M model with r_a calculated under free convection is recommended to simulate grapevine transpiration in greenhouse in cold regions of Northeast China.（4）Considering the difference of soil resistance under greenhouse drip irrigation,the modified Shuttleworth-Wallace could accurately simulate greenhouse evapotranspirationThe dual crop coefficient（DK）and Shuttleworth-Wallace（SW）models were applied to simulate evaporation（E）,transpiration（T）and ET,and a modified SW model（SW_m）was proposed considering the effect of the surface resistance difference between wet and dry soil under drip irrigation.Both the SW and SW_m models overestimated T（overestimation rate was3–11%）,while the DK method significantly underestimated T（underestimation rate was 9–18%）.The model simulation accuracy of T was SW=SW_m>DK.The simulation accuracy of three models for E was in the order of SW_m>SW>DK.Compared with the SW model,SW_mmodel could significantly reduce the simulation error of E and improved the simulation accuracy（R² is increased from 0.75–0.81 to 0.92–0.94）,while DK method had a poor simulation effect on E(R² is 0.74–0.89,RMSE is 0.16–0.23 mm d^-1).ET was underestimated by DK method（underestimation rate was 4–38%）,but overestimated by SW and SW_m models（overestimation rate was 3-33%）.All three models had high simulation accuracy for grapevine ET(R²>0.97,RMSE is 0.25–0.50 mm d^-1),and simulation accuracy of ET was in the order of SW_m>SW>DK.Therefore,the SW_m model is recommended to simulate ET and its components of greenhouse grapevines in the cold region of northeast China.