Soil structure degradation is a major obstacle to vegetation growth in urban roadside greenery, particularly under drought conditions. Biochar application can improve soil structure and water retention; however, the mechanisms linking changes in soil aggregation with those in pore size distribution, and how they interactively influence plant growth remain unclear. In this study, we investigated the role of biochar in improving soil structure and water retention under drought stress in urban roadside greenery. In a field study, plots (2 m × 2 m) were established on roadside greenery in Suwon, Korea, in which 2.5% wt bochar was mixed with surface soil (<10 cm depth) (BC_field). During the eight-month experiment, drought conditions prolonged, and soil water content was continuously higher in BC_field than in CON_field. For a more mechanistic understanding, a 100-day greenhouse experiment was conducted on Rudbeckia hirta planted in sandy soil, either mixed with 4% wt biochar (BC_greenhouse) or without biochar (CON_greenhouse). Drought conditions were simulated by maintaining soil water content below 40% of the water-holding capacity. In the biochar-added soil, macro-aggregates (250–1000 μm) increased significantly after 60 days, probably due to biochar particles themselves acting as the same-sized aggregates. In addition, biochar can act as a binding agent for forming macro-aggregates, thereby preventing their disintegration into smaller-sized aggregates. Enhanced macro-aggregation in biochar-added soil, therefore, is a potential mechanism for the increased formation of meso-pores. These pores could retain more soil water for plant uptake, eventually increasing plant biomass and water use efficiency in the BC_greenhouse, by 39%, when compared with that in the CON_greenhouse under drought conditions. Our results indicate that biochar application is a potential management strategy for improving soil physical structure in urban roadside greenery, which would, in turn increase plant resistance and resilience to drought stress.

土壤结构退化是城市路边绿地植被生长的主要障碍，尤其是在干旱条件下。生物炭的应用可以改善土壤结构和保水能力；然而，将土壤团聚变化与孔径分布变化联系起来的机制，以及它们如何相互作用影响植物生长仍不清楚。在这项研究中，我们研究了生物炭在干旱胁迫下改善城市路边绿化土壤结构和保水的作用。在一项实地研究中，在韩国水原的路边绿地上建立了一块地块（2 m × 2 m），其中 2.5% wt 的 bochar 与表层土壤（<10 cm 深度）混合（BC_场）。8个月的试验期间，干旱条件延长，BC_田土壤含水量不断升高比在 CON_领域。为了更机械地理解，对种植在沙质土壤中的Rudbeckia hirta进行了为期 100 天的温室试验，该试验与 4% wt biochar（BC_温室）或不与 biochar（CON_{温室）混合}）。通过将土壤含水量保持在持水量的 40% 以下来模拟干旱条件。在添加生物炭的土壤中，60 天后大团聚体（250-1000 μm）显着增加，这可能是由于生物炭颗粒本身充当相同大小的团聚体。此外，生物炭可以作为形成大聚集体的粘合剂，从而防止它们分解成较小尺寸的聚集体。因此，添加生物炭的土壤中增强的宏观聚集是增加中孔形成的潜在机制。这些孔隙可以保留更多的土壤水分供植物吸收，最终使 BC_温室的植物生物量和水分利用效率比 CON_温室提高 39%。在干旱条件下。我们的研究结果表明，生物炭的应用是改善城市路边绿化土壤物理结构的潜在管理策略，这反过来又会增加植物的抗旱能力和对干旱胁迫的恢复能力。