Effect Of Steady And Rhythm Water Supply On Biomass And Tolerant To Drought Of Platycladus Orientalis And Acer Truncatum

In order to combine stage heterogeneity of woody plant growth with rhythm of water supply,tree species for afforestation was selected in the add and semi-aded region to accelerate the artificial vegetation restoration and the built of ecological system.A simulated drought experiment was conducted in a rain-free shed to test the variation regulations of hydraulic conductivity,water potential,ultra weak luminescence and biomass of Platycladus orientalis and Acer truncatum samplings to steady or rhythm water stress during different stages.Soil moisture treatments were 7.50%,9.78%,13.13%,16.47%and 18.75% respectively.The growing season was divided into three growth stages by means of logistic curve for the height growth of two species.The main results were as follows:1.The hydraulic conductivity of plant branch was increased significantly with increasing soil water content.The contribution of the effect of water supply at fast growing stage on hydraulic conductivity of small branch of the two tree species was at greatest while that contribution at early growing stage was at least.So it is necessary to supply sufficient water at fast growing stage to decrease the embolism of conducting tissue and maintain the natural conductive function.2.The leaf-water potential was increased significantly with increasing soil water content. Restoration of leaf-water potential of Platycladus orientalis(The maximum was 94.89%)was significantly greater than that of Acer truncatum(The maximum was 85.27%).In the main weather factors,temperature was the most important factor affecting the leaf-water potential of Platycladus orientalis,while the air relative humidity was the most important factor affecting the leaf-water potential of Acer truncatum.The effect of water supply at fast growing stage on leaf-water potential of Platycladus orientalis was the least,while that on leaf-potential ofAcer truncatum was the greatest.The effect of water supply at early stage on leaf-water potential of Platycladus orientalis was greatest,while that on leaf-potential of Acer truncatum was least which could be contributed to different mechanism of Acer truncatum and Platycladus orientalis in adapting to the environment.3.As soil water content increased,the leaf UWL of Platycladus orientalis and Acer truncatum was increased significantly,the magnitude in increase of Platycladus orientalis was comparatively high when compared to Acer truncatum.The UWL of Platycladus orientalis in the early growing stage was greatest and it was decreasing with increasing time span in the treatment of the same soil water content while the same index was decreasing with increasing time span first and then showed an increase for Acer truncatum,the effect of the water supply at fast growing stage on UWL was greatest for Platycladus orientalis while that for Acer truncatum was observed at least The opposite results was concluded on water supply effect on Platycladus orientalis and Acer truncatum when at late stage.4.The proportion of fine root(＜1 mm)length to total root lenght was not significantly different,which all fell into the range between 97.25%and 99.51%.The proportion of fine root biomass of Platycladus orientalis was far greater than that of Acer truncatum which had a 47.74%excessive root biomass when the proportion was at greatest for Platycladus orientalis and at least for Acer truncatum,The proportion of coarse root(＞2mm)biomass to root total biomass was greater for Acer truncatum than that for Platycladus orientalis.The root biomass and woody plant biomass was increasing withincreasing soil water content for both Platycladus orientalis and Acer truncatum while the magnitude of the increase was greater for Platycladus orientalis than for Acer truncatum.The contribution of the effect of periodic change in water supply on root biomass and single plant biomass of Platycladus orientalis was in the order as follows:Early growing stage＞Fast growthing stage＞Late growing stage, while that contribution followed the order:Fast growing stage＞Early growing stage＞Late growing stage for Acer truncatum.