Sensitivity of river ecosystems to global change: Assessing land management strategies to mitigate the combined impacts of climate warming and land use changes in cold temperate regions

气候引起的变暖将如何与未来的土地利用变化相互作用，在很大程度上仍然未知。大多数试图预测气候变化对水文和水质的影响的研究认为，流域结构不会改变。然而，在今后几十年里，土地使用可能会继续演变，并对今后的流域水文和水质产生重要影响。未来的气候变化，结合土地利用的修改和土地管理的做法，将创建复杂的相互作用和反馈的水生生态系统，本研究计划的长期目标是检查河流底栖藻类（硅藻）的敏感性，气候和土地利用变化的综合影响，并评估一套缓解策略，以保持河流生态系统的完整性的效率。为了实现这一研究计划的目标，提出了三种方法，涉及不同的研究设计和时间和空间尺度。首先，底栖硅藻和环境因素（水温和流量，沉积物和营养制度）之间的关系将进行实证研究，并在一个大的空间尺度上的基础上，从一个监测网络延伸超过800流到达加拿大东部的数据。第二，借由溪流围隔生态系统中附着生物的实验，探讨底栖矽藻与环境因子的关系。最后，全球变化情景对河流底栖硅藻的综合影响将使用流域模型（GIBSI）进行调查，其中校准的水文模型将被迫与气候输入代表几个全球变暖的情景。除了气候模拟，土地利用和减缓情景将用于测试旨在减少点或扩散营养物排放的具体社会经济措施的效果，虽然人们对气候变暖有广泛的共识，但由于区域降水和土地利用的变化，对水质和河流生态系统可能产生的影响还不太确定。这项研究计划的结果将使利益相关者能够制定战略，以更好地适应气候变化的影响，并提高加拿大东部河流的生态完整性。新的耕作方法和土地使用规划的设计必须考虑到气候变化的影响，可能需要新的操作程序。我们的研究结果将有助于确定长期土地利用分区计划，在气候变化的情况下保护水质。这项研究的结果可以迅速纳入实践，作为我们与80个农业流域的利益相关者进行藻类监测的合作的一部分。

How climate-induced warming will interact with future land use changes remains largely unknown. Most studies that have attempted to forecast the effect of climatic changes on hydrology and water quality consider that watershed configuration would not be altered. However, it is likely that land use will continue to evolve over the next decades and that it will have an important influence on future watershed hydrology and water quality. Future climatic changes, combined with land use modifications and land management practices will create complex interactions and feedbacks in aquatic ecosystems.The long-term objectives of this research program are to examine the sensitivity of river benthic algae (diatoms) to the combined impacts of climatic and land use changes and to evaluate the efficiency of a set of mitigation strategies to maintain the integrity of river ecosystems. To fulfill the objectives of this research program, three methodological approaches are proposed, involving different study designs and temporal and spatial scales. First, the relationships between benthic diatoms and environmental factors (water temperature and flow, sediment and nutrient regimes) will be investigated empirically and at a large spatial scale based on data from a monitoring network extending over more than 800 stream reaches in Eastern Canada. Second, the relationships between benthic diatoms and environmental factors will be tested by means of periphyton experiments in stream mesocosms. Finally, the combined impact of global change scenarios on river benthic diatoms will be investigated using a watershed model (GIBSI), whereby a calibrated hydrological model will be forced with climatic inputs representing several global warming scenarios. In addition to climate simulations, land use and mitigation scenarios will be applied for testing the effects of specific socio-economic measures aimed at reducing point or diffuse nutrient emissions.Although there is a wide consensus about climatic warming, there is less certainty about the likely impacts on water quality and river ecosystems due to changes in regional precipitation and land use. The results of this research program will enable stakeholders to develop strategies to better adapt to climate change impacts and enhance the ecological integrity of Eastern Canadian rivers. Designs for new farming practices and land use planning will have to incorporate climate change effects, and new operational procedures may be required. Our findings will be useful to define plans for long-term land use zoning that is protective of water quality under a changing climate. The results of this research could be quickly incorporated into practice as part of our collaborations with the stakeholders of 80 agricultural watersheds undergoing algae-based monitoring.