【作者】 刘兰；

【导师】 宗桦；

【作者基本信息】 西南交通大学 ， 风景园林（专业学位）， 2023， 硕士

【摘要】 乔木冠层对降雨再分配是影响城市水文循环的重要环节,为探索成都市景观乔木降雨再分配规律及其穿透雨的空间异质性,定量评价成都市常用乔木的冠层雨水资源利用效率,本研究选取杜英、天竺桂、金桂、桢楠、紫叶李、水杉、垂柳和银杏,这8种成都市内常见的景观乔木作为研究对象,采用长期野外定点观测法得到林外降雨总量、冠层穿透雨量和树干茎流量,并运用水量平衡法计算获得乔木冠层截留量数据。借助统计学软件进行相关性和显著性分析,揭示了再分配三个环节的基本规律及穿透雨空间异质性规律、降雨特征和林分特征对其影响因素,明确不同景观乔木之间截留能力的差异性,为川西平原地区节水型景观乔木选择和生态水文优化提供科学依据,并进一步提出优化和提升地区植物截留效应的种植策略。具体研究成果如下:1.研究期间共收集21场林外降雨,降雨总量201.60 mm,8种景观乔木降雨再分配各分量之间存在显著差异,冠层截留量占比较高,树干茎流量占比最低。乔木的穿透雨量变化范围为4.63～6.36 mm,穿透雨率为32.98%～49.11%,穿透雨及穿透雨率大小为杜英>垂柳>紫叶李>天竺桂>银杏>水杉>桢楠>金桂。树干茎流量变化范围为0.02～0.84 mm,树干茎流率为0.26%～12.81%,树干茎流及树干茎流率大小为金桂>杜英>紫叶李>天竺桂>水杉>桢楠>银杏>垂柳;冠层截留量变化范围为2.93～4.47 mm,冠层截留率为45.84%～65.39%,冠层截留及冠层截留率大小表现为桢楠>银杏>水杉>金桂>天竺桂>垂柳>紫叶李>杜英。桢楠截留能力最强,而紫叶李、杜英、垂柳截留能力较弱。2.降雨量是影响乔木冠层对降雨再分配过程的最重要因素。各种乔木的穿透雨与降雨量之间为极显著线性正相关,穿透雨率和林外降雨之间呈幂函数关系,先随降雨量增加,后趋于平缓,乔木之间穿透雨和穿透雨率差异不显著,穿透雨率随降雨等级和降雨强度增大而增大。各乔木树干茎流和降雨量呈显著线性正相关,但金桂乔木显著大于其他乔木的树干茎流和树干茎流率,垂柳的树干茎流和树干茎流率显著低于杜英、金桂与紫叶李。除水杉,天竺桂和金桂外,其他乔木树干茎流率随降雨等级、降雨强度增加而减小。乔木间冠层截留量与降雨量为幂函数关系,冠层截留率与降雨量为指数函数关系,两者均随着降雨量的增大而增大,最终趋于平缓,乔木间冠层截留差异不显著,但桢楠的冠层截留率显著高于杜英,冠层截留率随降雨等级的增加而减少,杜英、天竺桂、金桂、桢楠、紫叶李和垂柳6种景观乔木的冠层截留率随降雨强度先增后减。3.乔木特征与降雨再分配过程部分相关。乔木的叶面积指数与穿透雨率为显著负相关,与冠层截留量、冠层截留率显著正相关。乔木树高、胸径与树干茎流、树干茎流率为显著负相关。林外降雨量对不同冠层位置下(1/3R、2/3R、3/3R)的穿透雨的影响显著,叶面积指数(LAI)仅与3/3R处穿透雨显著相关,降雨强度、降雨等级和离树干距离因子均与不同冠层位置下的穿透雨无显著相关性。4.各乔木不同冠幅位置下(1/3R、2/3R、3/3R)的穿透雨量和林外降雨量呈线性正相关。各乔木不同位置处的平均穿透雨、穿透雨率和叶面积指数值为3/3R>2/3R>1/3R,平均穿透雨、穿透雨率和叶面积指数大小由树干中心逐渐向冠幅边缘减小。5.乔木林下不同位置的穿透雨率变异系数差异显著性不同,穿透雨率变异系数范围分别为:1/3R冠幅30.27%～60.78%,2/3R冠幅48.18%～69.14%,3/3R冠幅50.43%～84.10%,观测点平均穿透雨变异系数大小为3/3R>2/3R>1/3R。各乔木穿透雨率的变异系数和林外降雨为幂函数关系,紫叶李穿透雨受林外降雨变化的影响较大,垂柳则受影响最小。林外降雨量在2.00～10.40 mm时,穿透雨变异系数较高且波动明显;降雨量在10.40～26.40 mm时,穿透雨变异系数波动较小且变化趋于平缓;林外降雨量大于26.40 mm时,穿透雨变异系数无明显波动。6.基于截留效应下提出以下植物种植策略:优化单株植物选择、提升植物群落的整体储水能力和截留效益、增强斑块的连通性来构建蓝绿生态网络等,来提高城市绿地整体的雨水再分配效应。综上所述,8类景观乔木对雨水截留的能力差异较大,桢楠、银杏、水杉和金桂冠层对雨水拦截能力较强,更能降低雨水对土壤的冲刷力和减缓城市地表径流,可作为海绵城市建设的优选乔木,而杜英、垂柳、紫叶李和天竺桂对雨水的截留作用较弱,金桂、杜英、紫叶李和天竺桂树干茎流率较大,能维持乔木体内水分平衡,提高降雨资源利用效率。更多还原

【Abstract】 The redistribution of rainfall by tree canopy is an important part of urban hydrological cycle.In order to explore the characteristic of rainfall redistribution and the spatial heterogeneity of throughfall in landscape trees in Chengdu,and to quantitatively evaluate the utilization efficiency of canopy rainwater resources of commonly used trees in Chengdu.In this study,eight common landscape trees.In this study,eight common landscape trees in Chengdu were selected as the research objects,including Elaeocarpus decipiens,Cinnamomum japonicum,Osmanthus fragrans,Phoebe zhennan,Prunus cerasifera,Metasequoia glyptostroboides,Salix babylonica,and Ginkgo biloba.The total rainfall outside the forest,canopy throughfall and stem flow were obtained by long-term field fixed-point observation method,and the canopy interception data of trees were calculated by water balance method.With the help of statistical software for correlation and significance analysis,the basic laws of the three links of redistribution and the spatial heterogeneity of throughfall,the influence factors of rainfall characteristics and tree characteristics were revealed,and the differences in interception capacity between different landscape trees were clarified,which provided scientific basis for the selection of water-saving landscape trees and eco-hydrological optimization in the Chuanxi Plain.Furthermore,the planting strategy of optimizing plant interception effect was proposed.The specific research results are as follows :1.During the study period,a total of 21 out-of-forest rainfalls were collected,with a total rainfall of 201.60 mm.There were significant differences between the components of rainfall redistribution of 8 landscape trees.The throughfall of trees ranged from 4.63 mm to6.36 mm,and throughfall rate was 32.98% to 49.11%.The order of throughfall and throughfall rate was Elaeocarpus decipiens>Salix babylonica>Prunus cerasifera>Cinnamomum japonicum>Ginkgo biloba>Metasequoia glyptostroboides>Phoebe zhennan>Osmanthus fragrans.The variation range of stem flow was 0.02 mm to 0.84 mm,and the stem flow rate was 0.26% to 12.81%.The stem flow and stem flow rate were Osmanthus fragrans >Elaeocarpus decipiens >Prunus cerasifera> Cinnamomum japonicum>Metasequoia glyptostroboides> Phoebe zhennan>Ginkgo biloba>Salix babylonica.The canopy interception ranged from 2.93 mm to 4.47 mm,and the canopy interception rate was 45.84 % to 65.39 %.The canopy interception and canopy interception rate were Phoebe zhennan>Ginkgo biloba>Metasequoia glyptostroboides>Osmanthus fragrans>Cinnamomum japonicum>Salix babylonica>Prunus cerasifera>Elaeocarpus decipiens.Phoebe zhennan had the strongest interception capacity,while Prunus cerasifera,Elaeocarpus decipiens and Salix babylonica had weak interception capacity.2.Rainfall is the most important factor affecting the redistribution of rainfall by tree canopy.There was a very significant linear positive correlation between throughfall and rainfall of various trees.There was a power function relationship between throughfall rate and rainfall outside the forest,which first increased with rainfall and then tended to be gentle.There was no significant difference between throughfall and throughfall rate among trees.Throughfall rate increased with rainfall intensity and rainfall grade.There was a significant linear positive correlation between stem flow and rainfall.The stem flow and stem flow rate of Osmanthus fragrans were significantly higher than those of other trees.The stem flow and stem flow rate of Salix babylonica were significantly lower than those of Elaeocarpus decipiens,Osmanthus fragrans and Prunus cerasifera.Except for Metasequoia glyptostroboides,Cinnamomum japonicum and Osmanthus fragrans,the stem flow rate of other trees decreased with the increase of rainfall grade and rainfall intensity.The relationship between canopy interception and rainfall outside the forest was a power function,and the relationship between canopy interception rate and rainfall was an exponential function.Both of them increased with the increase of rainfall,and finally tended to be gentle.There was no significant difference in canopy interception between trees,but the canopy interception efficiency of Phoebe zhennan was significantly higher than that of Elaeocarpus decipiens,.The canopy interception rate decreased with the increase of rainfall grade.The canopy interception rate of six landscape trees of Cinnamomum japonicum,Prunus cerasifera,Elaeocarpus decipiens,Osmanthus fragrans,Salix babylonica and Phoebe zhennan increased first and then decreased with rainfall intensity.3.The tree characteristics are partially related to the rainfall redistribution process.The leaf area index(LAI)of trees was negatively correlated with throughfall rate,and positively correlated with canopy interception and canopy interception rate.There was a significant negative correlation between tree height,DBH and stem flow,stem flow rate.Rainfall outside the forest had a significant effect on throughfall at different canopy positions(1/3R,2/3R,3/3R).Leaf area index(LAI)was only significantly correlated with throughfall at3/3R.Rainfall intensity,rainfall grade and distance from trunk were not significantly correlated with throughfall at different canopy positions.4.Under different canopy positions(1/3R,2/3R,3/3R),the throughfall was linearly positively correlated with the rainfall outside the forest.The average throughfall,throughfall rate and leaf area index(LAI)at different positions of each tree were 3/3R>2/3R>1/3R,and the average throughfall,throughfall rate and leaf area index(LAI)gradually decreased from the trunk center to the crown edge.5.There were significant differences in the coefficient of variation of throughfall rate at different locations under arbor forests.The coefficient of variation of throughfall rate ranged from30.27% to 60.78% for 1/3R crown width,48.18 % to 69.14% for 2/3R crown width,and50.43% to 84.10% for 3/3R crown width.The average coefficient of variation of throughfall rate at three observation points of arbor was 3/3R>2/3R>1/3R.The coefficient of variation of the throughfall rate of each tree and the rainfall outside the forest are power functions.The throughfall under Prunus cerasifera forest is greatly affected by the change of rainfall outside the forest,while Salix babylonica is least affected.The rainfall outside the forest is2.00<P≤10.40 mm,the coefficient of variation of the throughfall is high and the fluctuation is obvious;when 10.40<P<26.40 mm,the coefficient of variation of the throughfall fluctuates slightly and the change tends to be gentle;when P≥26.40 mm,the coefficient of of the throughfall variation did not fluctuate significantly.6.Based on the interception effect,the following plant planting strategies are proposed :optimizing the selection of individual plants,improving the overall water storage capacity and interception efficiency of plant communities,and enhancing the connectivity of patches to build a blue-green ecological network to improve the overall rainwater redistribution effect of urban green space.In summary,the ability of eight different types of trees to intercept rainwater is different.The canopy of Phoebe zhennan,Ginkgo biloba,Metasequoia glyptostroboides and Osmanthus fragrans has a strong ability to intercept rainwater,which can reduce the erosion force of rainwater on soil and slow down urban surface runoff.It can be used as a preferred tree for sponge city construction.The interception effect of Elaeocarpus decipiens,Salix babylonica,Prunus cerasifera and Cinnamomum japonicum on rainfall is weak.The stem flow rate of Osmanthus fragrans,Elaeocarpus decipiens,Prunus cerasifera,Cinnamomum japonicum is higher,which can maintain the water balance in trees and improve the effective utilization rate of rainfall resources.更多还原