| As a gardening technique,pruning of fruit trees was studied by few people associated with water consumption.In order to ease soil desiccation and prevent ecological deterioration in the Loess Plateau,preventing increasing water consumption of artificial forest in loess hil y region,the effects of different pruning intensities on reduction of jujube transpiration,raise of soil moisture were studied by continuous control and monitoring of jujube plantation for three consecutive years,suitable pruning intensity with sustainable development of dwarfed and dense forest in northern Shaanxi was explored,and theory of water-saving pruning was improved,providing theoretical basis for the development of new water-saving technology of economic forest.In order to control the size of 6-year-old jujube trees in rainfed plantation,height,crown width and total length of secondary branches were taken as pruning indexes,then,four pruning intensities(PI-I,PI-II,PI-III,PI-IV)were set from light to heavy,and specifications of jujube trees were controlled and monitored strictly during three growth periods of 2014-2016.Growth indexes was measured regularly during growth periods to calculate biomass of jujubes,sap flow of jujubes under four intensities was monitored using thermal dissipation probes(TDP),meteorological and soil moisture conditions were monitored using weather station(RR-9100)and neutron moisture gauges(CNC503B),respectively.The results could be summarized as follows:(1)Size of jujube trees could be controlled by increasing the pruning intensity,and water consumption of jujube trees could be reduced effectively at different times scales(time,day,growth stage and growth period)by increasing the pruning intensity.On small time scales(day and day),increase of jujube sap flow decreased with the increasing pruning intensities,peak value of the sap flow under PI-I,PI-II,PI-III,PI-IV were 2.67 mm,2.44 mm,1.92 mm,1.54 mm,respectively.On growth stage time scale,water consumption was mainly effected on fruitenlargement stage by increasing the pruning intensity,water consumption of fruit-enlargement stage accounted for 46.4%-53.7% of the whole growth period.On growth period time scale,transpiration of jujubes trees could be significantly reduced by increasing the pruning intensity under different annual rainfall conditions,transpiration of jujube trees under PI-II,PI-III and PI-IV decreased by 72.15 mm,157.00 mm,259.04 mm respectively compared with PI-I.Effects of pruning were different under different annual rainfall conditions,and results were more significant in the rainy years than that in dry years.(2)While transpiration of jujube decreased with the increasing pruning intensity,soil moisture conditions were improved.Average soil moisture in the 3 m soil layer of 3 years under PI-I,PI-II,PI-III,PI-IV were 7.61%,7.54%,8.00% and 8.26%,respectively.Soil water storage increment of growth period under PI-I,PI-II,PI-III,PI-IV were-15.76 mm,-5.80 mm,17.89 mm and 38.14 mm,respectively.The soil moisture of 3m soil layer in the jujube plantation under PI-I had been reducing from 2014 to 2016,while the soil moisture of 3m soil layer in the jujube plantation under PI-IV had been increasing.Increasing the pruning strength could ease soil desiccation in dry farming jujube plantation,which could be a new way to prevent and cure dry soil layer in the Loess Plateau.In years when soil moisture was higher or rainfall was heavier,the effect of pruning to improve the soil moisture would be more effective.(3)Pruning promoted the evaporation of jujube plantation while reduced transpiration of jujubes.With the increase of pruning intensity,evaporation and evaporation accounted for evapotranspiration increased in a growth period.Compared with the jujube forest under PI-I,transpiration of jujube plantation under PI-II,PI-III and PI-IV decreased by 24.05 mm,52.33 mm and 86.35 mm respectively,while evaporation of jujube plantation under PI-II,PI-III,PI-IV increased by 8.9 mm,14.36 mm and 29.54 mm respectively,evaporation accounted for evapotranspiration increased by 2.47%,4.01% and 8.22%,respectively.Pruning reduces the transpiration of water consumption of jujubes,affecting the soil moisture of the plantation,which would be conducive to the improvement of soil moisture,while pruning could also increase the evaporation of the plantation at the same time.So,combination of traditional coverage treatments and suitable pruning were recommended to improve soil moisture and protect soil environment of the Loess Plateau.(4)The average jujube transpiration efficiency in 2014,2015 and 2016 were 2.99 g / kg,3.17 g / kg,2.88 g / kg,respectively,and the transpiration efficiency in the same growth period changed little(coefficient of variation <10%).Fresh weight of jujube leaves was in accordance with the natural growth law in the growth period,indicating that the pruning standard used in this study could control the biomass of tree leaves and reduce the biomass of jujube leaves effectively,thus transpiration of jujubes were reduced,average jujube biomass dry weight of 3 years under PI-I,PI-II,PI-III,PI-IV could reach 5.79 kg,5.21 kg,4.18 kg,3.40 kg.(5)Effects of increasing pruning intensity on fruit yield were not significant in this study,there was no significant difference in yield of jujube trees during the same growth period,while water use efficiency of jujube was improved with the increase of pruning intensity.Compared with jujubes under PI-I,the average yield of jujube trees was reduced by 4.3% and water use efficiency increased by 11.99% under PI-IV,which proved that the pruning standard had strong reference meaning for local rainfed jujube plantations.(6)Considering water consumption,jujube yield and water use efficiency of jujube plantation,Compared with the jujube plantations under PI-I,PI-II,PI-III,no significant difference in the yield of jujube plantation under PI-IV from 2014 to 2016,the water consumption of jujubes under PI-IV was significantly reduced,and the water use efficiency of jujube plantation under PI-IV was significantly improved,while the soil moisture was improved obviously.Jujubes under PI-IV made full use of water efficienctly and increased the soil moisture of the plantation,while also ensuring the economic plantation production.Therefore,PI-IV was suggested as a sustainable development pruning management reference standard,while the traditional coverage measures should also be taken improve the soil moisture,to al eviate soil desiccation of dry farming jujube plantations. |
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