《风景园林》2024-06刊首语 | 郑曦：碳中和背景下的城市绿地植物规划设计

全文刊登于《风景园林》2024年第6期 P8-9

碳中和背景下的城市绿地植物规划设计

Plant Planning and Design of Green Space in the Context of Carbon Neutrality

植物通过光合作用将二氧化碳固定为有机物质，并在生长过程中储存碳。不同生长阶段和环境条件下，乔木、灌木和草本植物的碳吸收和储存能力有所不同。在气候变化背景下，城市绿地作为城市建成区范围内唯一的近自然生态空间，具有固碳增汇能力；同时，可以通过合理的规划设计来缓解城市热岛效应，促进绿色低碳的出行方式，进而发挥其间接减排效益。因此，城市绿地成为实现碳中和目标的重要载体，合理选择和配置植物种类，是提高绿地碳汇能力的关键。

在城市复杂用地限制和高密度人口条件下，通过直接增汇和间接减排相结合的方式提高绿地的碳汇效益，是推动城市高质量发展的必然要求。低碳绿地系统空间结构如何布局？低碳绿地系统能产出多少碳汇？如何营造不同碳汇功能的植物群落结构？如何合理配置具有高碳绩效的植物种类？这些问题的研究和解决，有助于制定科学且完善的城市绿地植物规划设计体系，提升绿地碳汇效益。

绿地植物的选择需要考虑固碳能力、适应性和生态效益。松树和栎树等光合作用效率高，能够全年持续吸收二氧化碳；而梧桐和柳树等树种虽然在冬季叶片会脱落，但其较快的生长速度和较大的生物量，使其在生长期内具有显著的碳吸收效果。灌木和草本植物如紫薇、月季和芦苇等，个体碳储量虽小，但采取多层次的种植方式可以显著提高整体固碳能力。群落尺度的植物设计强调乔木、灌木和草本植物的合理搭配，形成稳定的复合群落结构，不仅能提高固碳能力，还能增强绿地的生态稳定性和抗逆性。美国纽约市通过“百万树木”项目，成功种植了100万棵树木，不仅显著提升了城市的碳汇效益，还极大改善了城市空气质量，同时为市民提供了更多休闲绿地。

在绿地规划中，需关注绿地质量提升，而非单纯追求数量。城市绿地布局应顺应“存量发展”的时代背景，通过完善绿地系统、绿道和公园体系，增加绿色出行比例，引导城市通风从而打造城市冷岛等措施，实现间接减排。丹麦哥本哈根致力于提高公共交通使用率和加强自行车道建设，以减少交通碳排放。结合“见缝插针”的方式，充分利用城市中的边角零碎空间，建设小型绿地和口袋公园，提升城市绿地整体碳汇效益。新加坡注重将绿化与建筑融合，增加垂直绿化和屋顶花园比例，不仅扩大了绿地面积，还能通过植物蒸腾作用调节城市小气候，缓解热岛效应，促进生物多样性提升。同时，这些方式可以提高建筑物的隔热性能，降低能耗。此外，通过建设生态廊道来强化不同绿地之间的联系，有利于提高生态系统整体的稳定性和适应性，为绿地植被创造更加适宜的生存环境，巩固其碳汇能力。

全生命周期的过程维护与管理是确保绿地植物长期健康发展的关键。采用可持续的管理方法，不仅能降低维护成本，还能强化减排增汇的双重功效，具体涉及施肥、灌溉、修剪等各个方面。通过有机种植和生物防治方法，减少化肥和农药使用，保护土壤；采用滴灌和雨水收集系统，减少水资源浪费，确保植物在干旱季节也能健康生长；将修剪下的植物残枝、枯叶等生物质进行堆肥处理成有机肥料，形成资源循环利用，减少碳排放。北京正在积极推进绿地中的自然带、本杰士堆、留野区、公园废弃物碳循环利用等措施，以营造低碳绿地。

碳中和背景下的绿地植物规划设计不仅是一项生态工程，更是一项关乎未来的可持续发展战略。通过科学合理的植物选择、多层次的群落营造和可持续的维护管理，能够有效提升城市绿地的碳汇能力，为实现碳中和目标贡献力量。同时，这一过程也将改善城市生态环境，提高居民生活质量。

Plant can fix carbon dioxide into organic substances through photosynthesis, hence storing carbon during its growing process. During different growing stages or under different environmental conditions, arbor, shrub and herbaceous plants will perform different carbon absorption and storage abilities. Under the background of climate change, as the only near-natural ecological space in cities, urban green space has the ability to sequester carbon and increase sinks; Meanwhile, reasonable planning and design can alleviate the urban heat island effect and promote green and low-carbon travel modes, thereby exerting its function of indirect emission reduction. Therefore, urban green space has become an important carrier for achieving the goal of carbon neutrality. Reasonable selection and configuration of plant species is the key to improve carbon sink capacity.

Facing the complex land constraints and the high-density population in cities, combining direct carbon sink enhancement and indirect emissions reduction to improve the carbon sink benefits of green spaces has become an inevitable requirement for promoting high-quality urban development. How to arrange the spatial structure layouts of low-carbon green space system? How much carbon sink can the systems produce? How to formulate the structures of plant community with different carbon performance and functions? How to allocate the plants with high carbon performance reasonably? The research and resolution of these issues will help to formulate a reasonable and comprehensive urban green space plant planning and design system, and enhance the carbon sink benefits of green spaces.

 The carbon sequestration capacity, adaptability and ecological benefits of green plants should be taken into consideration during the selecting process. Plants with efficient photosynthesis, such as pine trees and oak trees, are able to absorb carbon dioxide throughout the year continuously. Although the leaves of plants like Chinese parasol trees and willows will fall off in winter, their relatively rapid growth rate and large biomass enable themselves to perform significant effect of carbon absorption during their growth stage. Despite the relatively small individual carbon storage, shrubs and herbaceous plants such as crape myrtle, roses, and reeds can significantly improve their overall carbon sequestration capacity through multi-level planting. Plants design at the community scale emphasize the reasonable combination of arbors, shrubs, and herbaceous plants. Stable and composite community structure can not only improve carbon sequestration capacity, but also enhance the ecological stability and stress resistance of green spaces. New York City of the United States has successfully planted one million trees through the “Million Trees” Project. This large-scale tree-planting campaign has not only promoted the carbon sink benefits of cities significantly, but also improved the city’s air quality, providing the citizens more leisure green spaces.

 Rather than simply focusing on quantity, green space planning needs to improve the quality of green spaces. The layout of urban green spaces should conform to the historical background of “stock development” by improving green space systems as well as greenway and park systems, advocating green travel, planning urban ventilation, and realizing indirect emission reduction by forming urban cold islands via measures such as cooling. Copenhagen, Denmark is committed to increasing the usage of public transportation and building bicycle lanes, so as to reduce traffic emissions. By taking advantage of every opportunity, the fragmented and corner spaces in cities should be fully utilized for building small green spaces and pocket parks, so as to enhance the overall carbon sink benefits of urban green spaces. Attaching great importance to the integration of greenery and architecture, Singapore maximizes its urban green space by increasing the proportion of vertical greening and rooftop gardens, which not only expanded the green space area, but also regulated the urban microclimate through plant transpiration, thus alleviating the heat island effect and improving biodiversity. Meanwhile, these methods can also improve the insulation performance of buildings and reduce energy consumption. In addition, building ecological corridors connecting different green spaces in cities will be conducive to improving the overall stability and adaptability of the ecosystem, creating a more suitable living environment for green plants, and consolidating its carbon sink capacity.

 The key to ensuing the long-term and healthy development of green spaces is the lifecycle maintenance and management. Covering aspects such as fertilization, irrigation, and pruning, sustainable management can not only reduce the costs of maintenance, but also further strengthen the dual effects of emission reduction and sink enhancement. Organic cultivation and biological control can reduce the use of fertilizers and pesticides and protect soil. Adopting drip irrigation and rainwater collection systems will reduce water loss and ensure healthy growth of plants during dry seasons. Collecting the trimmed plant residues, dead leaves, and other biomass as organic fertilizer is a great way for resource recycling and emission reduction. Beijing is actively promoting measures such as natural belts, artificial shrubs, reserve areas, and carbon recycling of park wastes to create low-carbon and low-intervention green spaces.

 The planning and design of green plants under the background of carbon neutrality is not only an ecological project, but also a sustainable development strategy related to the future. By selecting plants rationally, planning multi-level plants communities, and sustainable maintenance and management, we can effectively enhance the carbon sink capacity of urban green spaces, thereby making contributions to achieve the goal of carbon neutrality. Besides, this process will also help to improve urban ecological environment, enhance the quality of life for residents.

主编：郑曦教授

Editor-in-Chief: ZHENG Xi

2024年6月4日

June 4, 2024

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