Hydropeaking affects germination and establishment of riverbank vegetation
Hydropeaking affects germination and establishment of riverbank vegetation
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DOI：
10.1002/eap.2076
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发表时间：
2020-02-20
影响因子：
5
通讯作者：
Nilsson，Christer
中科院分区：
文献类型：
--
作者：
Bejarano，Maria D.;Sordo-Ward，Alvaro;Nilsson，Christer
水力调峰，定义为在短时间内，通常是每天到每周，在水力发电厂的调节河流中频繁和快速的流量变化，改变水力参数，如水位或流速，并对河流生态系统产生强烈影响。我们评估了水力调峰对河岸植被的影响，特别是评估了代表性状变化的植物物种的幼苗和插条的萌发和建立。我们使用不同大小的种子、幼苗和插条作为植物生长计，并将其移植到瑞典北方用于水力发电的大坝上方和下方的河岸上，选择这些河岸代表水力峰值强度的梯度，并沿着自由流动的河段。我们还分析了由水峰化修改的次日水位变量，以确定解释所观察到的植被模式的关键变量。我们发现，植物对水峰化的反应因物种而异，早在萌芽阶段，不耐洪水的物种受到的影响最大。相比之下，耐洪水物种的种子设法发芽并在早期建立阶段存活下来，尽管由水峰化引发的强烈侵蚀过程最终导致其中大多数失败。洪水不耐受物种的命运将发芽确定为最关键的生活史阶段。淹没的深度和频率是解释植物响应的主要变量，而浅淹没的持续时间解释的变化不大。水位的上升和下降速率是解释发芽成功率变化的关键。根据研究结果，我们提出了恢复措施，以加强建立河岸植物群落，同时尽量减少对水电生产的影响。由于不耐受长时间洪水和水力调峰的物种发芽率大幅下降，种植幼苗，最好是大尺寸的幼苗，同时在建立阶段限制发电厂的运行，以提高生存率，这将是最好的恢复选择。考虑到水力调峰导致植物连根拔起的可能性很高，河岸保护措施有可能增加所有物种的河岸植物存活率，包括耐洪水物种。
Hydropeaking, defined as frequent and rapid variation in flow in regulated rivers with hydropower plants over a short period of time, usually sub‐daily to weekly, alters hydraulic parameters such as water levels or flow velocity and exerts strong impacts on fluvial ecosystems. We evaluated the effects of hydropeaking on riverbank vegetation, specifically assessing the germination and establishment of seedlings and cuttings of plant species representing a variation in traits. We used seeds and seedlings and cuttings varying in size as phytometers, and transplanted them to riverbanks both above and below dams used for hydropower production in northern Sweden, selected to represent a gradient in hydropeaking intensity, and along a free‐flowing reach. We also analyzed sub‐daily water‐level variables modified by hydropeaking to identify variables key in explaining the observed vegetation patterns. We found that plant responses to hydropeaking varied with species, with flood‐intolerant species being the most strongly affected, as early as the germination stage. In contrast, seeds of flood‐tolerant species managed to germinate and survive the early establishment phase, although strong erosive processes triggered by hydropeaking eventually caused most of them to fail. The fate of flood‐intolerant species identifies germination as the most critical life‐history stage. The depth and frequency of the inundation were the leading variables explaining plant responses, while the duration of shallow inundation explained little of the variation. The rise and fall rates of water levels were key in explaining variation in germination success. Based on the results, we propose restoration measures to enhance establishment of riparian plant communities while minimizing the impact on hydropower electricity production. Given the strong decrease in the germination of species intolerant to prolonged flooding with hydropeaking, planting of seedlings, preferably of large sizes, together with restrictions in the operation of the power plant during the establishment phase to enhance survival would be the best restoration option. Given the high probability of plant uprooting with hydropeaking, bank protection measures have the potential to increase riparian plant survival of all species, including flooding‐tolerant species.