School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia; Cooperative Research Centre for Water Sensitive Cities, Clayton, VIC 3168, Australia; Ooid Scientific, White Gum Valley, WA 6162, Australia.
School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia.
Sci Total Environ. 2020 Jun 10;720:137373. doi: 10.1016/j.scitotenv.2020.137373. Epub 2020 Feb 20.
Managers tasked with repairing degraded stream ecosystems require restoration strategies that are tailored to local and regional characteristics. Emerging evidence suggests that local reach-scale approaches may be as effective, if not more so, than catchment-scale actions in highly permeable coastal landscapes, particularly if there is hydraulic connectivity to shallow groundwater and where recharge is strongly seasonal. This study assessed the relative influence of catchment-scale land use and reach-scale vegetation structure on the distribution of carbon and nutrient concentrations of streams within urban and agricultural catchments of the Perth region of south-western Australia. We used linear mixed-effects models to evaluate the extent to which phosphorus, nitrogen and carbon concentrations in different stream zones (streamwater, and fluvial and parafluvial sediments) were explained by catchment and reach-scale attributes and moderated by high versus low-flow periods, i.e., in wet versus dry months. We found that reach-scale vegetation (woody plant cover, annual plant cover) was a better predictor of nutrient concentrations than catchment-scale land use, particularly total imperviousness, a common measure of urbanisation. Flow was also important, with carbon and nutrient concentrations better described by reach- or catchment-scale attributes during the low flow period. The extent to which individual catchment and reach attributes influenced the distribution of nutrients in different stream zones was complex. However, our results suggest that planting woody vegetation can reduce nitrogen concentrations in surface water and fluvial sediments. Reducing the abundance of weedy annual species and restoring woody perennial species may further reduce phosphorus concentrations in surface water. We conclude that local riparian restoration can be a cost-effective strategy for managing excess nutrients and carbon in flat and permeable urban landscapes, particularly during low flow periods.
管理者在修复退化的溪流生态系统时，需要采用适合当地和区域特点的恢复策略。新出现的证据表明，在高度渗透的沿海景观中，局部河道尺度的方法可能与集水区尺度的方法一样有效（如果不是更有效的话），特别是如果与浅层地下水有水力连通性，并且补给强烈受季节性影响。本研究评估了集水区尺度的土地利用和局部河道尺度的植被结构对澳大利亚西南部珀斯地区城市和农业集水区内溪流的碳和养分浓度分布的相对影响。我们使用线性混合效应模型来评估不同溪流区域（地表水、河流和河岸沉积物）中的磷、氮和碳浓度在多大程度上受到集水区和河道尺度属性的解释，并受到高流量和低流量时期的调节，即湿月和干月。我们发现，与集水区尺度土地利用相比，局部河道尺度的植被（木本植物覆盖度、一年生植物覆盖度）是养分浓度更好的预测因子，尤其是总不透水率，这是城市化的常见衡量标准。流量也很重要，在低流量期，碳和养分浓度更能通过河道或集水区尺度的属性来描述。个别集水区和河道属性对不同溪流区域养分分布的影响程度很复杂。然而，我们的结果表明，种植木本植被可以降低地表水中的氮浓度和河流沉积物中的氮浓度。减少杂草一年生物种的丰度和恢复木本多年生物种可能会进一步降低地表水中的磷浓度。我们得出结论，在平坦和渗透性强的城市景观中，特别是在低流量期，当地的河岸恢复可以成为管理过多养分和碳的一种具有成本效益的策略。
