1. Environmental factors such as nutrient and light availability may play important roles in determining the magnitude and direction of microbial priming and detrital decomposition and, therefore, the relative importance of microbial priming in carbon (C) dynamics in freshwater ecosystems.
2. We integrated light availability with an existing conceptual model predicting the magnitude of the priming effect (PE) along a dissolved nutrient gradient (i.e. nutrient PE model). Our modified light‐nutrient PE model hypothesises how light may mediate priming at any given nutrient concentration and provides a calculation method for quantitative PE values (i.e. light effect size at a given nutrient concentration).
3. We used recirculating stream mesocosms with Quercus stellata (post oak) leaf litter as an organic matter (OM) substrate in a 150‐day experiment to test our model predictions. We manipulated light levels [ambient (full light), shaded (c. 19% of ambient)] and phosphorus (P) concentration (10, 100, 500 µg PO₄‐P/L) in a fully factorial design. We also supplied all mesocosms with 500 µg/L dissolved inorganic nitrogen. Microbial biomass, water column dissolved organic C, and leaf litter dry mass and recalcitrant OM [i.e. the fibre (cellulose + lignin) component of post oak substrate] were measured. Recalcitrant OM (ROM) k‐rates (day⁻¹) were used to calculate the light effect size within P treatments as a log response ratio (ln[ambient k‐rate/shade k‐rate]) to ascertain PE magnitude and direction (positive or negative).
4. Light was an important driver of dissolved organic C, a potential source of additional labile organic matter essential for priming heterotrophic microbes. There were weak PEs in total leaf litter dry mass remaining, but PEs were more pronounced in leaf litter ROM remaining. The strongest positive PEs (specific to litter ROM pools) occur in the highest P treatment, presumably due to a change in which nutrient, nitrogen versus P, was a limiting factor for microbes based on nutrient ratios rather than P concentration alone. These results illustrate the importance of considering light levels, nutrient ratios (rather than individual nutrients), and detrital ROM components in further PE model development.

中文翻译：

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轻质和溶解性营养物通过微生物灌流在实验流中介导难降解的有机物分解

1. 营养素和光的利用率等环境因素可能在确定微生物引发和碎屑分解的程度和方向以及因此确定微生物引发在淡水生态系统碳（C）动态中的相对重要性方面起着重要作用。
2. 我们将光的可用性与现有的概念模型相结合，该模型可预测沿溶解的营养梯度的激发效应（PE）的大小（即营养PE模型）。我们修改后的光养分PE模型假设在任何给定养分浓度下光如何介导启动，并提供了定量PE值（即在给定养分浓度下光效应大小）的计算方法。
3. 在150天的实验中，我们使用了带有Quercus stellata（橡树后）枯枝落叶作为有机物（OM）底物的循环流中观，以测试我们的模型预测。我们操纵光水平[环境（全光）中，阴影（角的环境19％）]和磷（P）浓度（10，100，500微克PO ₄处于完全析因设计-P / L）。我们还为所有中观宇宙提供了500 µg / L的溶解无机氮。测量了微生物生物量，水柱中溶解的有机碳，枯枝落叶干重和顽固性OM（即橡木后基质的纤维（纤维素+木质素）成分）。顽固性OM（ROM）k速率（第^-1天））用于计算P处理内的光效应大小，以对数响应比（ln [环境k比率/阴影k比率]）确定PE的大小和方向（正或负）。
4. 光是溶解有机碳的重要驱动力，而溶解有机碳是引发异养微生物必不可少的其他不稳定有机物的潜在来源。剩余的总凋落物干质量中的PE较弱，但剩余的叶子凋落物ROM中PE更为明显。最强的阳性PE（特定于垃圾ROM池）出现在最高的P处理中，大概是由于养分（氮对P）的变化是微生物（基于养分比而不是单独的P浓度）的限制因素。这些结果说明了在进一步的PE模型开发中考虑光照水平，养分比（而不是单个养分）和碎屑ROM成分的重要性。