Abstract Forest harvesting could induce diverse responses of terrestrial-derived coarse particulate organic matter (CPOM) quantity in small streams. Understanding the basis of such variation requires the assessment of the independent and interactive effects of the controlling processes of stream CPOM quantity. Here we simulated post-harvest responses of leaf litter-derived CPOM quantity in a coastal rainforest stream in British Columbia, Canada, using a published process-based model. We compared the relative importance of major biophysical controls of CPOM quantity, including riparian litterfall, discharge, and stream temperature, across a range of severity of forest harvesting disturbance, using a sensitivity analysis. This range represented published post-harvest responses of these model drivers in temperate North America. We then varied the values of model drivers to examine possible changes in CPOM quantity (within ˜4 years post-harvest) under different harvesting scenarios, and to characterise the interactions among pairs of drivers. The effects of litterfall reductions due to forest harvesting on depleting CPOM quantity were at least an order of magnitude greater than those of elevated peak flows. Summer stream warming of 4 °C or more could lead to a smaller magnitude of CPOM reductions, possibly due to decreases in CPOM consumption and shredder biomass that lasted until fall. Warming-induced CPOM increases could counteract the effects of reduced litterfall and elevated peak flows on lowering CPOM quantity, depending on disturbance severity. CPOM depletions were highly likely when litterfall was below 50% of that in undisturbed conditions. Our heuristic modelling revealed that non-additive, antagonistic interactions between paired model drivers could emerge at higher severity levels of disturbance. We suggest that establishing riparian buffer zones would more likely mitigate post-harvest changes in CPOM quantity through minimising alterations in litter inputs and stream summer temperature. Our study illustrates the utility of process-based simulations and scenario analysis in evaluating the ecological impacts of biophysical processes operating at reach to catchment scales. A wider adoption of these modelling approaches can improve the predictions of stream ecological responses to watershed disturbances.

中文翻译：

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模拟在一系列森林采伐影响下对河流有机物质常备库存的生物物理控制

摘要 森林采伐可引起小溪流中陆源粗颗粒有机物（CPOM）数量的不同响应。了解这种变化的基础需要评估流 CPOM 数量控制过程的独立和交互影响。在这里，我们使用已发布的基于过程的模型模拟了加拿大不列颠哥伦比亚省沿海雨林溪流中落叶衍生的 CPOM 数量的收获后响应。我们使用敏感性分析比较了 CPOM 数量的主要生物物理控制的相对重要性，包括河岸凋落物、流量和溪流温度，在森林采伐干扰的严重程度范围内。该范围代表了这些模型驱动因素在北美温带地区发布的收获后反应。然后，我们改变模型驱动程序的值，以检查不同收获场景下 CPOM 数量（收获后约 4 年内）的可能变化，并表征驱动程序对之间的相互作用。森林砍伐造成的凋落物减少对消耗 CPOM 数量的影响至少比峰值流量升高的影响大一个数量级。夏季河流升温 4 °C 或更高可能导致 CPOM 减少幅度较小，这可能是由于 CPOM 消耗量减少和持续到秋季的粉碎机生物量减少。变暖引起的 CPOM 增加可以抵消凋落物减少和峰值流量升高对降低 CPOM 数量的影响，这取决于干扰的严重程度。当凋落物低于未受干扰条件下的 50% 时，CPOM 耗尽的可能性很大。我们的启发式模型显示，配对模型驱动程序之间的非可加性、对抗性相互作用可能会出现在更高严重程度的干扰下。我们建议建立河岸缓冲区更有可能通过最小化凋落物输入和夏季河流温度的变化来减轻收获后 CPOM 数量的变化。我们的研究说明了基于过程的模拟和情景分析在评估流域范围内运行的生物物理过程的生态影响方面的效用。更广泛地采用这些建模方法可以改进对流域干扰的河流生态响应的预测。我们建议建立河岸缓冲区更有可能通过最小化凋落物输入和夏季河流温度的变化来减轻收获后 CPOM 数量的变化。我们的研究说明了基于过程的模拟和情景分析在评估流域范围内运行的生物物理过程的生态影响方面的效用。更广泛地采用这些建模方法可以改进对流域干扰的河流生态响应的预测。我们建议建立河岸缓冲区更有可能通过最小化凋落物输入和夏季河流温度的变化来减轻收获后 CPOM 数量的变化。我们的研究说明了基于过程的模拟和情景分析在评估流域范围内运行的生物物理过程的生态影响方面的效用。更广泛地采用这些建模方法可以改进对流域干扰的河流生态响应的预测。