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Woody buffer effects on water temperature: The role of spatial configuration and daily temperature fluctuations
Hydrological Processes ( IF 3.2 ) Pub Date : 2020-12-13 , DOI: 10.1002/hyp.14008
Jochem Kail 1 , Martin Palt 1 , Armin Lorenz 1, 2 , Daniel Hering 1, 2
Affiliation  

Water temperature is a key driver for riverine biota and strongly depends on shading by woody riparian vegetation in summer. While the general effects of shading on daily maximum water temperature Tmax are well understood, knowledge gaps on the role of the spatial configuration still exist. In this study, the effect of riparian buffer length, width, and canopy cover (percentage of buffer area covered by woody vegetation) on Tmax was investigated during summer baseflow using data measured in seven small lowland streams in western Germany (wetted width 0.8–3.7 m). The effect of buffer length on Tmax differed between downstream cooling and heating: Tmax approached cooler equilibrium conditions after a distance of 0.4 km (~45 min travel‐time) downstream of a sharp increase in canopy cover. In contrast, Tmax continued to rise downstream of a sharp decrease in canopy cover along the whole 1.6 km stream length investigated. The effect of woody vegetation on Tmax depended on buffer width, with changes in canopy cover in a 10 m wide buffer being a better predictor for changes in Tmax compared to a 30 m buffer. The effect of woody vegetation on Tmax was linearly related to canopy cover but also depended on daily temperature range Trange, which itself was governed by cloudiness, upstream canopy cover, and season. The derived empirical relationship indicated that Tmax was reduced by −4.6°C and increased by +2.7°C downstream of a change from unshaded to fully shaded conditions and vice versa. This maximum effect was predicted for a 10 m wide buffer at sunny days in early summer, in streams with large diel fluctuations (large Trange). Therefore, even narrow woody riparian buffers may substantially reduce the increase in Tmax due to climate change, especially in small shallow headwater streams with low baseflow discharge and large daily temperature fluctuations.

中文翻译:

木质缓冲液对水温的影响:空间配置和每日温度波动的作用

水温是河流生物区系的主要驱动力,在夏季强烈依赖木质河岸植被的遮荫。尽管人们已经充分了解了遮阳对每日最高水温T max的一般影响,但仍然存在关于空间配置作用的知识空白。在这项研究中,使用德国西部7条低地小溪(湿润宽度0.8-–)测量的数据,研究了夏季底流期间河岸缓冲带长度,宽度和冠层覆盖(木质植被覆盖的缓冲区域的百分比)对T max的影响。 3.7 m)。缓冲长度对T max的影响在下游冷却和加热之间有所不同:T max在冠层覆盖率急剧增加的下游0.4 km(约45分钟的行进时间)之后达到了较凉的平衡条件。相反,在研究的整个1.6 km河流长度中,在树冠覆盖率急剧下降的下游,T max继续上升。木本植被对T max的影响取决于缓冲区的宽度,与30 m缓冲区相比,10 m宽缓冲区的冠层覆盖变化更能预测T max的变化。木本植物对T max的影响与冠层覆盖率线性相关,但也取决于日温度范围T范围,其本身受多云,上游树冠覆盖和季节的影响。推导的经验关系表明,在从无阴影条件变为完全阴影条件的变化的下游,T max降低了-4.6°C,而在下游增加了+ 2.7°C,反之亦然。预计在初夏阳光充足的10d宽的缓冲区中,这种最大影响将发生在diel波动较大(T范围较大)的溪流中。因此,即使是狭窄的木质河岸缓冲带,也可能大大降低由于气候变化而引起的T max的增加,特别是在基流流量低且日温度波动大的小型浅水源河中。
更新日期:2021-01-19
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