Spatial patterns in periphyton biomass after low-magnitude flow spates: geomorphic factors affecting patchiness across gravel–cobble riffles
Spatial patterns in periphyton biomass after low-magnitude flow spates: geomorphic factors affecting patchiness across gravel–cobble riffles
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低强度水流爆发后附生生物生物量的空间模式：影响砾石-卵石浅滩斑块状的地貌因素
DOI：
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发表时间：
2010
影响因子：
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通讯作者：
M. Lapointe
中科院分区：
文献类型：
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作者：
J. Luce;A. Cattaneo;M. Lapointe
摘要：砾石河床底栖藻类空间分布呈斑块状，可能是由于频繁小流期的物理干扰所致。在这种情况下，砾石和鹅卵石组成的河床是稳定的，但水流往往足够强大，可以通过一种被称为跃移的跳跃运动来运输大量的沙子。我们测试了一个与空间相关的避难栖息地存在于变异带边缘和河道底部之间的过渡区（TZ）的假设，在那里高水力应力和跳跃沙减少了生物量。我们记录了魁北克省一条低营养河流在3个夏季汛期后的15条河流的物理干扰和周围植物生物量。确定了潮前生长期间近床水流速度（0.25 m/s）、流期沙输运（64-180 g m−1事件−1）和流动剪切应力（15 Pa）的周围植物扰动阈值。使用广义线性模型来检验这3个干扰变量和洪水后周围植物生物量的交叉波动趋势。生物量最高的是TZ。随着沙粒输运速率的降低，离海浮游植物增加。除非受到高输沙率的干扰，否则生物量继续向该带的边缘增加，而高输沙率与一个小的近岸输沙率次峰有关。在3个干扰变量中，沙粒输运模式控制了小水期后周围植物生物量的空间分布，平均复发间隔为7 d。当整个水期通常超过干扰阈值时，在更大的洪峰（3倍平均年流量）后，没有发现跨河段的避难所。物理扰动的强度和分布，特别是河床上的沙蚀，决定了周围植物保护区的大小和排列。这些区域对于促进河流系统对土地利用变化的适应能力至关重要。
Abstract The patchy spatial distribution of benthic algae (periphyton) on gravel-bed rivers might be caused by physical disturbances during small frequent flow spates. During such spates, the gravel–cobble river bed is stable, but flows are often strong enough to transport large quantities of sand by a hopping motion called saltation. We tested the hypothesis that a spate-related refuge habitat exists in a transition zone (TZ) between the edge of the varial zone and the thalweg of the river channel where high hydraulic stress and saltating sand reduce biomass. We documented physical disturbance and periphyton biomass across 15 riffles after 3 summer spate periods in an oligomesotrophic river in Quebec. Periphyton perturbation thresholds were identified for near-bed water velocity during prespate growth (0.25 m/s) and for sand transport (64–180 g m−1event−1) and flow shear stress (15 Pa) during spates. Generalized linear models were used to examine cross-riffle trends in these 3 disturbance variables and in postspate periphyton biomass. The highest biomass occurred in the TZ. Periphyton increased away from the thalweg as sand transport rates decreased. Biomass continued to increase toward the edge of this zone unless disturbed by high rates of sand transport that were associated with a small, near-shore secondary peak in sand transport rate. Of the 3 disturbance variables, sand transport patterns controlled the spatial distribution of periphyton biomass after small spates with an average recurrence interval of 7 d. No cross-riffle refuge was found after a higher-magnitude spate (3× mean annual discharge) when disturbance thresholds were typically exceeded across the entire riffle. The intensity and distribution of physical disturbance, particularly sand abrasion, over the streambed dictated size and arrangement of periphyton refuge zones. These zones are crucial to promote stream system resilience to landuse change.