1. Riparian forests are commonly advocated as a key management option to mitigate the effects of agriculture on headwater stream biodiversity and ecosystem functions. However, the benefits of riparian forests might be reduced by uninterrupted catchment‐scale pollution.
2. We studied the effects of riparian land use on multiple ecological endpoints in headwater streams in an agricultural landscape. We studied stream habitat characteristics, water temperature and algal accrual, and macrophyte, benthic macroinvertebrate and fish communities in 11 paired forested and open agricultural headwater stream reaches that differed in their extent of riparian forest cover but had similar water quality.
3. Hydromorphological habitat quality was higher in forested reaches than in open reaches. Riparian forest had a strong effect on the summer water temperature regime, with maximum and mean water temperatures and temperature variation in forested reaches substantially lower than in open reaches.
4. Macrophyte communities differed between forested and open reaches. The mean abundance of bryophytes was higher in forested reaches but the difference to open reaches was only marginally significant, whereas graminoids were significantly more abundant in open reaches. Within‐stream dissimilarity of benthic macroinvertebrate community structure was significantly related to the difference in riparian land use between reach pairs. The relative DNA sequence abundance of pollution‐sensitive Ephemeroptera, Plecoptera, and Trichoptera species tended to be higher in forested reaches than in open reaches. Finally, fish densities were not significantly different between forested and open reaches, although densities were higher in forested reaches.
5. This unequivocal evidence for the ecological benefits of forested riparian reaches in agricultural headwater streams suggests that riparian forest can partly mitigate the adverse impacts of agricultural diffuse pollution on biota. The strong effect of forests on stream water temperature suggest that riparian forest could also mitigate harmful effects on headwater stream biodiversity and ecosystem functions of the predicted more frequent high summer temperatures.

中文翻译：

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河岸森林可以减轻农业源头河水的变暖和生态退化

1. 人们普遍提倡沿岸森林作为减轻农业对源头河水生物多样性和生态系统功能的影响的主要管理选择。但是，不间断的流域规模的污染可能会减少沿岸森林的利益。
2. 我们研究了河岸土地利用对农业景观中源头水流中多个生态终点的影响。我们研究了11个成对的森林和开放式农业源头河段河岸生境特征，水温和藻类累积以及大型植物，底栖大型无脊椎动物和鱼类群落，这些河段的河岸森林覆盖程度不同，但水质相似。
3. 森林河段的水文生境质量高于开放河段。沿岸森林对夏季水温状况有很大影响，最高和平均水温以及森林河段的温度变化远低于开放河段。
4. 森林植被和开放河流域的大型植物群落不同。在森林带，苔藓植物的平均丰度较高，但与开放带的差异仅在边缘上显着，而类粉动物在开放带则明显丰富得多。底栖大型无脊椎动物群落结构的河内差异与河岸对之间河岸土地利用的差异显着相关。污染敏感的星翅目，鞘翅目和毛鳞翅目物种的相对DNA序列丰度在林木河段比开阔河段更高。最后，尽管密林和开放林的鱼类密度较高，但密林和开放林之间的鱼类密度没有显着差异。
5. 明确的证据表明森林河岸带在农业上游水源中具有生态效益，这表明河岸带森林可以部分减轻农业扩散污染对生物区系的不利影响。森林对溪流水温的强烈影响表明，沿岸森林还可以减轻对预计的夏季高温更为频繁的源头溪流生物多样性和生态系统功能的有害影响。