Adaptability Of Vertical Greenery System And Evaluation Of Its Ecological Service Function In Hot Summer And Cold Winter Region

Vertical greenery system is one of the common technical measures in the construction of"sponge cities".The technique has the ability to enrich the urban ecological functions and improve the urban environment,and is widely applied in many cities.The climatic characteristics of hot-summer and cold-winter region have significant stress on vertical greenery system,and it is of great significance to study the adaptability of vertical greenery system under such climatic conditions.Current study analyzes the stress of long-term flooding and drought on vertical greenery system,and develops a compound substrate based on organic waste which may alleviate these two types of stress.The ecological serve function value of vertical greenery system is measured and evaluated under wet cold conditions,and the predicted mean vote improvement effect of vertical greenery system is simulated by ENVI-met software.The outcomes of the study on adaptability of vertical greenery system plants under flooding stress showed that under mild flooding stress,the net photosynthetic rate of Ophiopogon japonicus reduced by 5.64%,and Gardenia jasminoides reduced by 58.31%.Under moderate and severe flooding stress,the net photosynthetic rate of Buxus sinensis dropped by 98.92%～99.83%and the net photosynthetic rate of Ophiopogon japonicus decreased by 17.07%～29.36%.Waterlogging stress caused damage of the leaf cell membrane.The MDA content of Buxus megistophylla increased by 469.25%～490.27%,indicating that its cell membrane was severely damaged.The antioxidant enzymes and osmotic regulators of the Ophiopogon bodinieri increased by 3.55%～141.52%,indicating that it adapted the stress by improving enzyme activity and osmotic balance coercion.The ranking of stress resistance to waterlogging was:Buxus sinica>Ophiopogon japonicus var.nana>Ophiopogon bodinieri Levl.>Gardenia jasminoides Ellis>Buxus megistophylla Levl.>Ligustrum quihoui Carr.The oxygen diffusion coefficient in the adventitious roots of Buxus sinica was 3.69×10^-4g/s,which showed strong waterlogging resistance.Findings on the adaptability of vertical green plants study under drought stress showed that the photosynthesis and physiological indicators of plant leaves decreased with the increase of drought time.The leaves maintained internal water balance by reducing the degree of stomata opening and closing,and the intercellular CO₂,transpiration rate and the net photosynthetic rate decreased accordingly.The net photosynthetic rate of Gardenia jasminoides reduced by 73.65%,which showed the largest decrease.Drought stress caused the leaf antioxidant content to increase,and the antioxidant enzyme activity and osmotic adjustment substance content positively correlated with drought resistance;the antioxidant enzyme activity of Buxus megistophylla increased by 4.48%,showing strong drought resistance.The drought resistance of plants was in the order of:Buxus megistophylla Levl.>Ligustrum quihoui Carr.>Buxus sinica>Ophiopogon bodinieri Levl.>Gardenia jasminoides Ellis>Ophiopogon japonicus var.nana.According to the performance of the compound substrate to relieve water stress,the compound substrate with better performance was screened out:green garbage powder,straw powder and biogas residue were mixed in a ratio of 3:1:1.The compound substrate had a bulk density of 0.45g/cm³,a total porosity of 74.53%,and a drainage capacity of 19.11mm;the use of this matrix could increase the biomass of melon seeds and boxwood by 45%,and various photosynthetic indicators by 2.7%～11.29%.Physiological indicators increased by4.08%～37.87%.The actual measurement results of the ecological service function reveal that:vertical greenery system could heat the wall by 7.5°C in the morning and night,and 3.5°C around noon in winter.Vertical greenery system has the best noise reduction ability in the range of medium and high frequency（1000～4000Hz）,and the noise reduction index can reach up to 65.13.Results also revealed that vertical greenery system can hold 3.25g of dust per square meter in winter,and it can fix 2.71g of carbon and release 2.53g of oxygen.The simulation analysis results of the winter microclimate by ENVI-met showed that vertical greenery system could effectively alleviate the impact of dampness and coldness,increasing the temperature of the study area by 7.36%～26.73%,and the relative humidity lowering by 3.04%～8.29%,making the human body thermally comfortable where the degree index increased by 2.09%～8.84%.Comprehensive evaluation of ecological service function of vertical greenery system revealed that each square meter of vertical greenery system could bring economic benefits of RMB127.48 per year and improve the thermal comfort of the human body.The findings of the current research work could provide strong theoretical support for the wide application of vertical greenery system in areas with hot summer and cold winter.