Biofiltration systems can fail over time due to clogging by fine sediments in stormwater. Infiltration can be maintained by plant roots, but species selection for biofiltration to date has largely been driven by pollutant removal efficiency and tolerance of conditions. As a result, plant species diversity in biofilters is typically low and dominated by sedges and rushes. Increased use of woody species could in theory improve plant diversity, aesthetic appeal, infiltration under high sediment loads and volumetric runoff reduction via higher evapotranspiration, without jeopardising nutrient pollutant removal. We tested whether shrubs could maintain infiltration and evapotranspiration in biofiltration profiles treated with a high sediment load, by comparing them with biofilters subjected to tap water without sediment. Following sediment application, biofilter columns planted with shrubs with high total biomass and total root length showed higher infiltration and evapotranspiration than those receiving tap water. These results indicate that shrub species are likely to alleviate clogging and increase stormwater retention in biofiltration systems. However, shrubs with a high root diameter also had low total biomass and total root length and showed 33–51 % lower infiltration rates after sediment application compared with those receiving tap water. As all shrubs had higher root diameters than typical sedges and rushes, we suggest that shrubs need a combination of higher total biomass, total root length and average root diameter to effectively maintain infiltration. While shrubs which maintained infiltration had traits associated with high nutrient removal, nutrient removal efficiency of shrubs needs to be quantified. Although root traits were related to maintenance of infiltration, above-ground stems likely created flow pathways through sediment which requires further investigation. Overall, selecting shrub species with high total biomass has the potential to maintain infiltration and increase evapotranspiration in biofiltration systems impacted by high sediment loads.

中文翻译：

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较大的灌木可以在受高沉积物负荷影响的实验生物过滤系统中保持较高的渗透和蒸散速率


由于雨水中的细小沉积物堵塞，生物过滤系统可能会随着时间的推移而失效。植物根系可以维持渗透，但迄今为止，生物过滤的物种选择在很大程度上是由污染物去除效率和条件耐受性驱动的。因此，生物过滤器中的植物物种多样性通常很低，并且以莎草和灯心草为主。理论上，增加木本物种的使用可以改善植物多样性、美学吸引力、高沉积物负荷下的渗透和通过更高的蒸散量减少体积径流，而不会危及营养污染物的去除。我们通过将灌木与无沉积物的自来水处理的生物过滤器进行比较，测试了灌木在高沉积物负荷处理的生物过滤剖面中是否能保持渗透和蒸散。施用沉积物后，种植总生物量和总根长高的灌木的生物滤池柱比接受自来水的灌木柱显示出更高的渗透和蒸散。这些结果表明，灌木物种可能会缓解生物过滤系统中的堵塞并增加雨水滞留。然而，根径大的灌木的总生物量和总根长也较低，与接受自来水的灌木相比，施用沉积物后的渗透率降低了 33-51%。由于所有灌木的根径都高于典型的莎草和灯心草，因此我们建议灌木需要更高的总生物量、总根长和平均根直径的组合才能有效维持渗透。虽然保持渗透的灌木具有与高养分去除相关的特征，但灌木的养分去除效率需要量化。 尽管根性状与维持渗透有关，但地上茎可能在沉积物中创造了流动路径，这需要进一步研究。总体而言，选择总生物量高的灌木物种有可能在受高沉积物负荷影响的生物过滤系统中保持渗透并增加蒸散。