Table_1_Method for selecting ornamental species for different shading intensity in urban green spaces.pdf

In urban areas, ornamental plants face different constraints, such as the shading of buildings and trees. Therefore, the selection of suitable species and their integration or combination with pre-existing plants is very important. Trees, shrubs, and herbaceous plant species must be distributed according to plant light requirements and shading intensity. Ornamental plants are classified into two groups based on their light intensity or shade tolerance: sun and shade species. To properly position the plants, especially in the immediate vicinity of buildings, it is necessary to study the projection of shadows during the year and the most critical periods, such as July and August. The position of ornamental species with different shading tolerances can be obtained by characterizing the leaf gas exchange for each species. Among the physiological parameters, the most important is the light compensation point, which is the light intensity corresponding to a net photosynthesis equal to zero. This means that the assimilation of carbon dioxide through photosynthesis is equal to the carbon dioxide emitted by respiration. This steady state represents the most critical condition for plants to endure the summer. The distribution of species inside a green area should be determined by considering the minimum light intensity that allows sufficient photosynthesis to compensate for the respiration rate. In this context, non-destructive leaf gas exchange, chlorophyll a fluorescence, and chlorophyll content can be useful tools for selecting suitable ornamental plants under diverse shading conditions.

城市环境中，观赏植物会面临多种制约因素，例如建筑与树木带来的遮阴影响。因此，筛选适宜物种，并将其与场地原有植被进行整合或搭配，显得尤为关键。乔木、灌木与草本观赏植物的配置，需依据各物种的光照需求以及遮阴强度来开展。观赏植物可依据其光照需求或耐阴性划分为两类：喜光物种与耐阴物种。若要合理布置植物，尤其是在建筑紧邻区域，需研究全年及关键时段（如7月与8月）的阴影投射情况。针对不同耐阴特性的观赏物种，可通过测定各物种的叶片气体交换参数，确定其适宜的种植位置。在诸多生理参数中，最为核心的是光补偿点：即净光合速率为零时对应的光照强度。这意味着通过光合作用同化的二氧化碳量，与呼吸作用释放的二氧化碳量恰好相等。此种稳态是植物度过夏季的最关键临界条件。绿地内物种的配置布局，需以能够维持光合速率足以补偿呼吸消耗的最低光照强度为依据进行确定。在此研究框架下，无损叶片气体交换测定、叶绿素a荧光分析以及叶绿素含量检测，可作为不同遮阴环境下适宜观赏植物筛选的有效手段。