| In this study,taking throw a typical mountain apple orchard in Yan’an area of the Loess Plateau in northern Shaanxi as the research object,the soil moisture content,stem flow rate,soil saturation water conductivity and plant water conductivity of the orchard were measured in the field.And the soil water content status,stem flow variation characteristics of fruit trees,the influence of meteorological factors on stem flow,soil saturation water conductivity and plant stem flow rate change law and its influencing factors were analyzed.And the soil water content characteristics of apple orchards and the water consumption law of fruit tree growth period were clarified.It is of great significance to establish a reasonable orchard management and irrigation system in arid areas,alleviate the contradiction between water supply and demand,and to ensure the healthy and sustainable development of the mountain apple industry in the region.The main findings of this study are as follows:（1）The total rainfall during the growth period of the experimental orchard was741.17 mm,accounting for 91%of the total annual rainfall,the single-day rainfall variation ranged from 0.25 to 93.73 mm,the average daily rainfall was 11.95 mm,the maximum rainfall in September was 249.43 mm,followed by October 202.69 mm,the minimum rainfall was 24.39 mm in June,and the average rainfall in each month was108.78 mm.The soil volume moisture content of different growth stages of the orchard showed a certain lagging change with the change of rainfall,and this change weakened with the deepening of the soil layer,and the water of the 0-60 cm soil layer fluctuated significantly by the rainfall,the water content of each soil layer increased with the fluctuation of rainfall during the coloring period and maturity stage,and the soil moisture content of each layer increased significantly.During the whole growth period,the soil volume moisture content has obvious spatial variability,which is manifested by the trend of first increasing and then decreasing,and then increasing and decreasing again,and the coefficient of variation of soil volume moisture content in 0-100 cm soil layer continues to decrease with the deepening of soil layer,and the larger the coefficient of variation,the greater the change in soil volume moisture content.Soil water storage generally shows a trend of first decreasing and then increasing,which is manifested in the fact that the soil water storage from the flowering period to the expansion stage of the fruit（May to August）is decreasing,the soil moisture is in a state of deficit,and the deficit is 42.93 mm;the coloring period and the maturity period（September to October）,the soil water recharge is greater than the consumption,the soil water storage gradually increases,the water storage reaches 132.16 mm,and the surface water gradually moves to the deeper layer,and the surface water content decreases;the soil water storage during the whole growth period increases by 81.47 mm.（2）The soil saturation conductivity at different growth stages in the study area was the largest at the maturity stage,which was 0.86 mm/min,and the soil water conductivity at the young fruit stage,coloring stage and flowering stage was also large,which was0.77,0.72 and 0.65 mm/min,respectively,and the soil saturation water conductivity at the expanded fruit stage was as small as 0.47 mm/min.The plant water conductivity was at different development stages at the flowering stage>the coloring stage>the young fruit stage>the ripening stage>the fruit expansion stage,and their plant water conductivity was（8.25,6.12,4.25,3.38,3.34）×10-5 kg/s/Mpa,respectively.（3）Through correlation analysis,it can be seen that soil saturation conductivity（Ks）is significantly negatively correlated with soil bulk density and clay content,and saturated water content and organic matter are significantly positively correlated with Ks,and plant water conductivity is significantly positively correlated with soil saturation conductivity,saturated water content,organic matter and sand grain content to varying degrees,and significantly negatively correlated with soil bulk density,clay particles and silty particles to varying degrees.The transfer function of Ks and Kp is obtained by multiple stepwise regression analysis.From the path analysis,it can be seen that the organic matter content has a direct positive effect on the soil saturation water conductivity and the plant water conductivity,and the powder particle content has an indirect positive effect on the soil saturation water conductivity.（4）Apple tree stem flow rate has obvious day and night change law,the daytime stem flow rate shows a"few"character change trend,the night stem flow rate is very small,under different weather conditions,the stem flow rate change law on sunny days is single-peaked,the stem flow change law on rainy days is multi-peaked,the stem flow rate on sunny days,the opening time of stem flow are greater than on rainy days,and the stem flow closing time is later than that of rainy days.Under different weather conditions of the growth period of apple orchard,the stem flow is manifested as sunny>rainy day,under sunny conditions,the daily stem flow is the largest in the fruit expansion stage,which is 16538.9 g/h,the minimum value is 7448.5 g/h in the ripening stage,the remaining performance is the coloring period>the first fruit stage>flowering period,and the daily stem flow is 13954.1,11639.2,10514.8g/h,indicating that the water consumption of apple trees under sunny conditions is manifested as the fruit expansion stage>the coloring period>the early fruit stage>the flowering period>maturity.Under rainy weather conditions,the daily stem flow reached its peak at the expansion stage of the fruit,the maximum daily stem flow was 5473.1 g/h,and the minimum value appeared at the ripening stage,which was 2380.1 g/h,and the water consumption law of apple trees was the same as that on sunny days.The single-day stem flow rate changes in the same way as the stem flow rate and peaks at around 12:30.（5）The influencing factors of stem flow rate can be seen that the stem flow rate of apple trees in each period is significantly negatively correlated with relative humidity,and has a significant positive correlation with average temperature and average wind speed.Through the multiple stepwise regression analysis,the corresponding stem flow rate prediction model of the initial fruit stage,the fruit expansion stage and the maturity stage was established,and it can be known that relative humidity is the main factor affecting the stem flow rate,and through the test of the predicted stem flow and actual stem flow of apple trees in different periods,it was found that the prediction model is more accurate,which can well predict the stem flow changes of apple trees in different periods,and provide theoretical guidance for orchards to establish a more reasonable irrigation scheme. |
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