Alberts Jeremy M, Fritz Ken M, Buffam Ishi
Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio 45221 USA.
Office of Research and Development, National Exposure Research Laboratory, US Environmental Protection Agency, Cincinnati, Ohio 45269 USA.
Freshw Sci. 2018 Sep;37(3):640-652. doi: 10.1086/699385. Epub 2018 Jul 13.
Riparian reforestation is a common restoration action in urban streams, but relatively little is known about the influence of local riparian vegetation in the face of watershed-scale urban land cover. Allochthonous organic matter and benthic algae are important basal energy resources in streams, but the roles of watershed urbanization vs near-stream vegetation in the availability of these resources are not well understood. Our goal was to understand how the interaction of land cover at 2 spatial scales (watershed vs reach) and seasonal dynamics shape basal resources and their effects on macroinvertebrate communities. We assessed relationships between seasonal patterns in standing stocks of particulate organic matter (POM) and benthic periphyton and macroinvertebrate community composition in openand closed-canopy reaches of 4 urban and 4 reference streams in northern Kentucky, USA. POM standing stocks were not strongly influenced by watershed or riparian condition. Benthic algal biomass was greater in urban than in reference streams in all seasons and in open than in closed riparian canopies in summer when light levels are most affected by a deciduous canopy. Relationships between macroinvertebrate functional feeding group (FFG) biomass and their primary food resources were influenced by watershed land use and season, but riparian canopy effects were minor. The proportion of collectors varied by season, whereas the proportion of shredders was higher in reference than urban streams. Scraper biomass was influenced by benthic algal biomass and varied seasonally, whereas predator biomass was driven by prey-insect biomass. Periphyton density was affected by the interaction of watershedand reach-scale land cover and was the only basal resource strongly related to consumer taxa. Watershed land use influences the stream ecosystem, but local riparian canopy may be important in limiting benthic algal accumulation.
河岸带重新造林是城市溪流中常见的恢复措施，但面对流域尺度的城市土地覆盖，当地河岸植被的影响却知之甚少。外来有机物质和底栖藻类是溪流中重要的基础能量资源，但流域城市化与近溪流植被在这些资源可利用性方面的作用尚未得到充分理解。我们的目标是了解两个空间尺度（流域与河段）的土地覆盖相互作用以及季节动态如何塑造基础资源及其对大型无脊椎动物群落的影响。我们评估了美国肯塔基州北部4条城市溪流和4条参考溪流的开阔树冠河段和封闭树冠河段中颗粒有机物质（POM）和底栖附生植物的现存生物量季节模式与大型无脊椎动物群落组成之间的关系。POM现存生物量受流域或河岸条件的影响不大。在所有季节中，城市溪流中的底栖藻类生物量均高于参考溪流，且在夏季光照水平受落叶树冠影响最大时，开阔河岸树冠下的底栖藻类生物量高于封闭河岸树冠下。大型无脊椎动物功能摄食组（FFG）生物量与其主要食物资源之间的关系受流域土地利用和季节的影响，但河岸树冠的影响较小。收集者的比例随季节变化，而碎食者在参考溪流中的比例高于城市溪流。刮食者生物量受底栖藻类生物量影响并随季节变化，而捕食者生物量则由猎物昆虫生物量驱动。附生植物密度受流域和河段尺度土地覆盖相互作用的影响，是与消费者类群密切相关的唯一基础资源。流域土地利用影响溪流生态系统，但当地河岸树冠在限制底栖藻类积累方面可能很重要。
