Impacts of wildfire and post‐fire land management on hydrological and sediment processes in a humid Mediterranean headwater catchment
Impacts of wildfire and post‐fire land management on hydrological and sediment processes in a humid Mediterranean headwater catchment
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DOI：
10.1002/hyp.13926
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发表时间：
2020-10
影响因子：
3.2
通讯作者：
J. Nunes;Léonard Bernard-Jannin;M. Rodríguez-Blanco;A. Boulet;J. M. Santos;J. Keizer
中科院分区：
文献类型：
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作者：
J. Nunes;Léonard Bernard-Jannin;M. Rodríguez-Blanco;A. Boulet;J. M. Santos;J. Keizer
近几十年来，欧洲地中海沿岸的广泛植树造林增加了野火对水文和沉积物过程的干扰，但对源头集水区的影响仍然知之甚少，特别是与以前的农业景观相比。这项工作监测了伊比利亚半岛西北部的一个农林集水区，在火灾前一年和火灾后三年，种植园林与采用土壤保持做法的传统农业相结合，在此期间，被烧毁的地区被翻耕和重新造林。在此期间，连续收集气象数据，径流和泥沙浓度在出口，侵蚀特征进行了测绘和测量后，主要降雨事件，渠道泥沙动态监测下游的农业和烧毁的森林地区。详细分析了202次10 mm以上降雨的资料。结果表明，火灾导致了显着的影响沉积物过程在火灾后的前两年，但不是对径流过程;这尽管烧毁面积小（10%的集水区）和严重干旱的发生在火灾后的第一年。在此期间，在烧毁的森林斜坡的土壤流失比大多数传统管理的领域要大得多，并最终导致沉积物耗尽。在集水区尺度上，暴雨特征是火灾前后径流量和产沙量的主导因素。然而，数据表明，从火灾前的分离限制的泥沙产量，转移到运输限制的泥沙产量之后，在径流泥沙浓度的重要增加。这表明，即使是小火灾也能暂时改变农林集水区的沉积过程，对下游水质产生潜在的负面影响。
The extensive afforestation of the Mediterranean rim of Europe in recent decades has increased the number of wildfire disturbances on hydrological and sediment processes, but the impacts on headwater catchments is still poorly understood, especially when compared with the previous agricultural landscape. This work monitored an agroforestry catchment in the north‐western Iberian Peninsula, with plantation forests mixed with traditional agriculture using soil conservation practices, for one year before the fire and for three years afterwards, during which period the burnt area was ploughed and reforested. During this period, continuous data was collected for meteorology, streamflow and sediment concentration at the outlet, erosion features were mapped and measured after major rainfall events, and channel sediment dynamics were monitored downstream from the agricultural and the burnt forest area. Data from 202 rainfall events with over 10 mm was analysed in detail. Results show that the fire led to a notable impact on sediment processes during the first two post‐fire years, but not on streamflow processes; this despite the small size of the burnt area (10% of the catchment) and the occurrence of a severe drought in the first year after the fire. During this period, soil loss at the burnt forest slopes was much larger than that at most traditionally managed fields, and, ultimately, led to sediment exhaustion. At the catchment scale, storm characteristics were the dominant factor behind streamflow and sediment yield both before and after the fire. However, the data indicated a shift from detachment‐limited sediment yield before the fire, to transport‐limited sediment yield afterwards, with important increases in streamflow sediment concentration. This indicates that even small fires can temporarily change sediment processes in agroforestry catchments, with potential negative consequences for downstream water quality.