University of Namur, Department of Geography, 61 Rue de Bruxelles, 5000 Namur, Belgium.
University of Liège, Gembloux Agro-Bio Tech, UR TERRA, Biodiversity and Landscape Group, 2 Passage des Déportés, 5030 Gembloux, Belgium.
J Environ Manage. 2018 Apr 1;211:9-21. doi: 10.1016/j.jenvman.2018.01.017. Epub 2018 Jan 23.
Forested catchments are generally assumed to provide higher quality water in opposition to agricultural and urban catchments. However, this should be tested in various ecological contexts and through the study of multiple variables describing water quality. Indeed, interactions between ecological variables, multiple land use and land cover (LULC) types, and water quality variables render the relationship between forest cover and water quality highly complex. Furthermore, the question of the scale at which land use within stream catchments most influences stream water quality and ecosystem health remains only partially answered. This paper quantifies, at the regional scale and across five natural ecoregions of Wallonia (Belgium), the forest cover effect on biological water quality indices (based on diatoms and macroinvertebrates) at the riparian and catchment scales. Main results show that forest cover - considered alone - explains around one third of the biological water quality at the regional scale and from 15 to 70% depending on the ecoregion studied. Forest cover is systematically positively correlated with higher biological water quality. When removing spatial, local morphological variations, or population density effect, forest cover still accounts for over 10% of the total biological water quality variation. Partitioning variance shows that physico-chemical water quality is one of the main drivers of biological water quality and that anthropogenic pressures often explain an important part of it (shared or not with forest cover). The proportion of forest cover in each catchment at the regional scale and across all ecoregions but the Loam region is more positively correlated with high water quality than when considering the proportion of forest cover in the riparian zones only. This suggests that catchment-wide impacts and a fortiori catchment-wide protection measures are the main drivers of river ecological water quality. However, distinctive results from the agricultural and highly human impacted Loam region show that riparian forests are positively linked to water quality and should therefore be preserved.
森林流域通常被认为提供更高质量的水，与农业和城市流域相对立。然而，这应该在各种生态背景下进行测试，并通过研究描述水质的多个变量来进行。事实上，生态变量、多种土地利用和土地覆盖（LULC）类型以及水质变量之间的相互作用，使得森林覆盖与水质之间的关系非常复杂。此外，土地利用在溪流流域内对溪流水质和生态系统健康影响最大的尺度问题仍然没有得到充分回答。本文在区域尺度上，并跨越比利时瓦隆地区的五个自然生态区，量化了森林覆盖对沿河流域和流域尺度上的生物水质指数（基于藻类和大型无脊椎动物）的影响。主要结果表明，仅考虑森林覆盖，在区域尺度上可以解释生物水质的约三分之一，而在不同的生态区，这一比例从 15%到 70%不等。森林覆盖与较高的生物水质呈系统正相关。当去除空间、局部形态变化或人口密度效应时，森林覆盖仍占总生物水质变化的 10%以上。方差分解表明，理化水质是生物水质的主要驱动因素之一，人为压力通常解释了其中的重要部分（与森林覆盖共享或不共享）。在整个生态区，但不包括壤土区，区域尺度上每个流域的森林覆盖比例与高水质的相关性比仅考虑沿河流域的森林覆盖比例时更为积极。这表明流域范围的影响，更确切地说，流域范围的保护措施是河流生态水质的主要驱动因素。然而，来自农业和高度人为影响的壤土区的独特结果表明，河岸森林与水质呈正相关，因此应该加以保护。
