The Research of Plants Transpiration and the Sifting of Water-conserving Green Model in Dalian City

Abstract: Urban water-conserving afforestation deserves to be attached importance to in water scarced area.This paper focused on the transpiration of one kind of mixed lawn,five bush species and four arbor species at the Laodong park,using Micro-lysimeter,Drainage lysimeters and thermal dissipation probe(TDP) for transpiration observations respectively. The environmental factors and the dynamic change of soil water content of varied layers were observed simultaneously.The paper analysed the transpiration patterns of different seasons,weather and phases of a day(diurnal-nocturnal change).The change process of the plants under various water conditions were disscussed along with the water distribution features,also investigated was how the transpiration responsed to dominant environment variables.The dissimilarities in water consumption capabilities of trees were studied, contributing to the formation of transpiration-environment response model and the scaling up.Thererfore,water-conserving composition of urban greenland would be available.The diurnal water consumption of mixed lawn accounted 80%of the total in clear and semi-clear days,70%in cloudy days.The lawn consumed more water in June,July,August and Septemberthan in May and October.Summer provided the most obvious demonstration that bushes transpired most on clear days,then semi-clear days and then cloudy days across the board,which was also similar in other seasons only in a slighter way.We ranked the species based on daily sapflow volume.The results are as following:Ligustrum lucidum transpired most in spring,Euonymus japonicus and Syringa oblata in summer,Forsythia suspensa and Hibiscus syriacus in autumn,and Forsythia suspensa>Syringa oblata>Euonymus japonicus>Ligustrum lucidum>Hibiscus syriacus in terms of volume amount.Nighttime sapflow of four arbor species accounted 4.0%~15.0%daily water consumption on clear and cloudy days,and more on rainy days to about 21%~30%.We ranked the significance of the impact of environment variables on sapflow:Radiation>temperature>vapour pressure deficit>wind speed on clear days,Radiation>vapour pressure deficit>humidity>temperature>wind speed on cloudy days and vapour pressure deficit>humidity>radiation>temperature>wind speed on rainy days.The transpiration rankings across the whole growing season are as following:Euonymus bungeanus>Zelkova serrata within the 10cm diameter class,Euonymus bungeanus> Zelkova serrata>Cedrus deodara>Metasequoia glyptostroboides within the 14cm diameter class,Cedrus deodara>Euonymus bungeanus>Zelkova serrata>Metasequoia glyptostroboides within the 18cm diameter class,and Cedrus deodara>Metasequoia glyptostroboides within 24cm diameter class.The approaches of scaling up included:LAI for bushes and the relationship between radial profile and sapflow in individual arbors.We offered suggestions for urban afforestation after the modeling of greenland arrangement pattern and sifting the water-conserving species:the pure stand of mono-species is not favorable,so is the combination of similar type plants.It’s ideal to diverse the group by setting arbors,bushes and grasses together.The same theory applys for mixed coniferous and broad-leaved trees.What’s of especial interest is more employment of water-conserving species and the pure lawn should not spread out…
Key words: Dalian; Waters-conserving green model; Transpiration; Sifting motion; Scaling up

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