Light and dissolved nutrients mediate recalcitrant organic matter decomposition via microbial priming in experimental streams
Light and dissolved nutrients mediate recalcitrant organic matter decomposition via microbial priming in experimental streams
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DOI：
10.1111/fwb.13503
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发表时间：
2020-03
影响因子：
2.7
通讯作者：
Brooke Howard‐Parker;B. White;Halvor M. Halvorson;M. Evans‐White
中科院分区：
文献类型：
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作者：
Brooke Howard‐Parker;B. White;Halvor M. Halvorson;M. Evans‐White
环境因素，如养分和光的可利用性可能在确定微生物引发和碎屑分解的幅度和方向方面发挥重要作用，因此，微生物启动效应在淡水生态系统碳动态中的相对重要性。我们将光的可利用性与现有的概念模型相结合，预测启动效应（PE）的大小，沿着溶解营养梯度（即nutrientPE模型）。我们的modifiedlight-nutrientPE模型假设光如何在任何给定的营养浓度下介导引发，并提供了一个计算PE值的定量方法（即在给定的营养浓度下的光效应大小）。我们使用循环流围隔生态系统与栎（栎后）叶凋落物作为有机质（OM）基质在150天的实验中，以测试我们的模型预测。我们在完全析因设计中操纵光照水平[环境（全光照），阴影（约19%的环境）]和磷（P）浓度（10，100，500 µg PO 4-P/L）。我们还为所有围隔生态系统提供了500 µg/L的溶解无机氮。测定了微生物生物量、水柱溶解有机碳、落叶干重和腐殖酸OM [即橡木后基质的纤维（纤维素+木质素）组分]。利用顽拗性OM（ROM）k-速率（第-1天）计算P处理内的光效应大小，作为对数响应比（ln[ambientk-速率/shadek-速率]），以确定PE的大小和方向（正或负）。光是溶解有机碳的重要驱动因素，是引发异养微生物所必需的额外不稳定有机物质的潜在来源。凋落叶干物质剩余量中存在弱的PE，但凋落叶ROM剩余量中的PE更为明显。最强的阳性PE（特定于窝ROM池）发生在最高的P处理，大概是由于营养，氮与P的变化，是一个限制因素的微生物的基础上营养比，而不是单独的P浓度。这些结果说明了在进一步的PE模型开发中考虑光照水平、营养物质比例（而不是单独的营养物质）和碎屑ROM组分的重要性。
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.We integrated light availability with an existing conceptual model predicting the magnitude of the priming effect (PE) along a dissolved nutrient gradient (i.e.nutrientPE model). Our modifiedlight‐nutrientPE 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).We used recirculating stream mesocosms withQuercus 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[ambientk‐rate/shadek‐rate]) to ascertain PE magnitude and direction (positive or negative).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.