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首页> 外文期刊>River research and applications >ASSOCIATIONS OF WATERSHED VEGETATION AND ENVIRONMENTAL VARIABLES WITH FISH AND CRAYFISH ASSEMBLAGES IN HEADWATER STREAMS OF THE PEDERNALES RIVER, TEXAS
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ASSOCIATIONS OF WATERSHED VEGETATION AND ENVIRONMENTAL VARIABLES WITH FISH AND CRAYFISH ASSEMBLAGES IN HEADWATER STREAMS OF THE PEDERNALES RIVER, TEXAS

机译：德克萨斯州河流上游流域水体植被与环境变量与鱼类和小龙虾组合的关系

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Intermittent headwater streams serve important functions for humans and wildlife in semi-arid rangelands. Increases in ashe juniper coverage in central Texas over recent decades are believed to have negatively impacted stream flows. Few studies have examined relationships between aquatic species and environmental factors in these systems as well as the influence of juniper coverage on assemblage structure. During summer 2003 and spring 2004, we examined species-environment relationships to infer potential effects of juniper cover on aquatic ecology relative to local-scale and watershed-scale environmental variables. Fish and crayfish species assemblages and physicochemical variables were investigated in spring-fed headwater tributaries of the Pedernales River, Texas. Fish abundance was much higher in summer 2003, whereas crayfish abundance was higher in spring 2004. Fish species richness was lower during spring 2004, possibly due to below average precipitation during spring 2004 that reduced deep-water refugia. Higher abundance of crayfish in spring 2004 samples was probably due to their ability to survive low-flow conditions, and a release from fish predation pressure. Fish assemblage structure was more strongly associated with local abiotic factors during spring 2004 when flow was reduced, whereas structure during summer 2003 samples suggested a relatively greater influence of predation. In general, juniper cover was weakly associated with fish and crayfish assemblages, although it tended to be positively associated with relatively high-quality habitat for sensitive taxa (flowing runs with coarse substrate; deep, connected pools). We suggest that intermediate levels of juniper cover in the region provide indirect benefits to aquatic organisms. However, short-term, local environmental factors appear to have a much greater influence than watershed vegetation on fish and crayfish assemblages in these intermittent streams.
机译：间歇性源头水流对半干旱牧场的人类和野生生物具有重要作用。据信，近几十年来，得克萨斯州中部的杜松杜松覆盖率增加，对溪流产生了负面影响。很少有研究检查这些系统中水生物种与环境因素之间的关系以及杜松覆盖度对组合结构的影响。在2003年夏季和2004年春季，我们检查了物种与环境之间的关系，以推断杜松覆盖物对当地生态和分水岭尺度环境变量的潜在影响。在得克萨斯州Pedernales河的春季喂养的上游支流中调查了鱼类和小龙虾的种类组合以及理化变量。 2003年夏季鱼的丰度大大提高，而小龙虾的丰度在2004年春季更高。2004年春季鱼的物种丰富度较低，这可能是由于2004年春季降水低于平均水平而减少了深水避难所。 2004年春季样本中小龙虾的丰度较高，可能是由于它们能够在低流量条件下生存，并且能够从鱼类捕食压力中释放出来。鱼群结构在2004年春季水流减少时与当地的非生物因子有更强的联系，而2003年夏季样品的结构表明对捕食的影响相对较大。总的来说，杜松的覆盖与鱼类和小龙虾的组合关系不大，尽管它与敏感分类单元的相对高质量的栖息地（与粗基质的流动；深水相连的水池）呈正相关。我们建议该地区杜松的中间水平为水生生物提供间接利益。但是，对于这些间歇流中的鱼类和小龙虾组合，短期的局部环境因素似乎比分水岭植被具有更大的影响。

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