Shaw Rosalind F, Johnson Paul J, Macdonald David W, Feber Ruth E
Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Recanati-Kaplan Centre, Tubney House, Tubney, Oxon, United Kingdom.
PLoS One. 2015 Oct 7;10(10):e0138306. doi: 10.1371/journal.pone.0138306. eCollection 2015.
Drainage ditches, either seasonally flooded or permanent, are commonly found on intensively managed lowland farmland in the UK. They are potentially important for wetland biodiversity but, despite their ubiquity, information on their biodiversity and management in the wider countryside is scarce. We surveyed 175 ditches for their physical and chemical characteristics, spatial connectivity, plant communities and aquatic invertebrates in an area of intensively managed farmland in Oxfordshire, UK and collected information on ditch management from farmer interviews. Water depth and shade had a small impact on the diversity of plant and invertebrate communities in ditches. Increased shade over the ditch channel resulted in reduced taxonomic richness of both channel vegetation and aquatic invertebrates and channel vegetation cover was lower at shaded sites. Invertebrate taxonomic richness was higher when water was deeper. Spatial connectivity had no detectable impact on the aquatic invertebrate or plant communities found in ditches. The number of families within the orders Ephemeroptera, Plecoptera and Trichoptera (EPT), which contain many pollution-sensitive species, declined with decreasing pH of ditch water. As time since dredging increased, the number of EPT families increased in permanent ditches but decreased in temporary ditches. Whether or not a ditch was in an agri-environment scheme had little impact on the reported management regime or biodiversity value of the ditch. Measures for increasing the amount of water in ditches, by increasing the water depth or promoting retention of water in ditches, could increase the biodiversity value of ditches in agricultural land. Some temporary ditches for specialised species should be retained. Reducing the amount of shade over narrow ditches by managing adjacent hedgerows is also likely to increase the species diversity of plant and invertebrate communities within the ditch. We recommend that to preserve or enhance the biodiversity value of ditches, and improve their ecosystem service delivery, management prescriptions for hedgerows adjacent to ditches should differ from those aimed at hedgerows only.
在英国集约化管理的低地农田中，经常能见到季节性被水淹没或常年积水的排水沟。它们对湿地生物多样性可能具有重要意义，然而，尽管它们随处可见，但关于其在更广阔乡村地区的生物多样性和管理情况的信息却很匮乏。我们对英国牛津郡一片集约化管理农田区域内的175条排水沟的物理和化学特征、空间连通性、植物群落及水生无脊椎动物进行了调查，并通过与农民访谈收集了有关排水沟管理的信息。水深和遮荫对排水沟中植物和无脊椎动物群落的多样性影响较小。排水沟渠上方遮荫增加会导致沟渠植被和水生无脊椎动物的分类丰富度降低，且遮荫处的沟渠植被覆盖率较低。当水深增加时，无脊椎动物的分类丰富度更高。空间连通性对排水沟中发现的水生无脊椎动物或植物群落没有可检测到的影响。蜉蝣目、襀翅目和毛翅目（EPT）中的科数量，这些目中包含许多对污染敏感的物种，会随着排水沟水pH值的降低而减少。随着疏浚后的时间增加，永久性排水沟中EPT科的数量增加，而临时性排水沟中则减少。一条排水沟是否处于农业环境计划中，对所报告的管理方式或排水沟的生物多样性价值影响不大。通过增加水深或促进排水沟蓄水来增加排水沟水量的措施，可能会提高农田排水沟的生物多样性价值。应保留一些为特殊物种设置的临时性排水沟。通过管理相邻树篱来减少狭窄排水沟上方的遮荫量，也可能会增加排水沟内植物和无脊椎动物群落的物种多样性。我们建议，为了保护或提高排水沟的生物多样性价值，并改善其生态系统服务功能，与排水沟相邻的树篱的管理规定应与仅针对树篱的规定有所不同。
