Investigation And Experiment Of Drought Resistance Of Ornamental Shrubs In Changsha

In the soil plant atmosphere continuum, the plant is in the center position, and the drought resistance is the main index of plant adaptation environment.Changsha is located in the subtropical monsoon climate zone, about 1400 mm annual rainfall, but the seasonal distribution of precipitation is not uniform. In most years in summer and autumn seasons exist periodic drought. Most widely used in garden plants are shrubs, shrubs due to shallow roots, drought tolerance than other trees, therefore, to strengthen the water management in the period of drought shrub is the urgent problems faced in the current landscape. The selection of Changsha City 5 kinds of common ornamental shrub -- Lobular gardenia、 Fatsia japonica、Semperflorens、Aucuba japonica f. variegata and Rhododendron as the research object, investigation the drought damage of 5 Shrubs under extreme dry weather conditions in 2013, followed by drought stress test, was measured in photosynthesis and transpiration under light drought stress, observe the appearance of form,5 kinds of shrub drought tolerance evaluation, to screen the drought tolerant shrub species, as well as formulating scientific and reasonable irrigation system provides guidance. The main results are as follows:(1) Experience extreme high temperature and drought in 2013,5 kinds of shrub’s deciduous rate ranking rate:Rhododendron (50.4%)> Fatsia japonica (29.1%)> Semperflorens (21.3%)> Aucuba japonica f. variegata (20.3%)> Lobular gardenia (17.0%).5 kinds of shrubs death:Fatsia japonica (39.42%)> Aucuba japonica f. variegata (31.65%)> Rhododendron (27.17%)> Lobular gardenia(6.18%)> Semperflorens (6.08%) of the four seasons.Comprehensive analysis of 5 kinds of shrubs spilled the drought resistance is:Semperflorens> Lobular gardenia> Aucuba japonica f. variegata> Fatsia japonica> Rhododendron.(2) By water control experiment found that soil moisture falling by transpiration,12 d when soil moisture content to 9.25%～10.47%, and then gradually to slow, to 18 d, fell to 5.34%～6.98%, and is only 22.9%～22.9%.To 21 d, the moisture content is only 3.38%～ 5.86%, most of the dead or dying plants at this time.Drought stress test showed that when soil moisture content to 6.41%,5 kinds of shrubs cannot absorb moisture from the soil, a large number of lower leaves withered and yellow even fall off, severe prolapse branches, leaves a permanent wilting, ornamental effect.(3) The daily transpiration rate of the 5 kinds of shrubs ranked as follows:Aucuba japonica f. variegata (1.28 mmolH2O m.-2 · s-1)> Semperflorens (1.16 mmol H2O m. 2 · s-1)> Fatsia japonica (1.06 mmol H2O m.-2 · s-1)> Rhododendron (0.94 mmol H2O m.-2 · s-1)> Lobular gardenia (0.81 mmol H2O m. -2 · s-1)(4) The daily photosynthetic rate of the 5 kinds of shrubs ranked as follows: Semperflorens (5.04 μmolCO2 m-2 · s-1)> Lobular gardenia (4.24 μ molCO2 m-2·s-1)> Aucuba japonica f. variegata (3.94 μ molCO2 m -2 · s-1)> Fatsia japonica (3.38 μ molCO2 m -2· s-1)> Rhododendron (3.17 μ molCO2 m -2 · s-1)(5) Membership function method is used to synthesis of 5 kinds of shrubs soil moisture content, Tr and Pn of three indicators ranking for the 5 kinds of shrubs ranked as follows:Semperflorens> Lobular gardenia> Aucuba chinensis>Rhododendron> Fatsia japonica, are consistent with the previous survey.