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首页> 外文期刊>Freshwater science >Leaf-litter leachate is distinct in optical properties and bioavailability to stream heterotrophs
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Leaf-litter leachate is distinct in optical properties and bioavailability to stream heterotrophs

机译：凋落叶的渗滤液在光学特性和生物利用度方面具有独特的优势

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Dissolved organic C (DOC) leached from leaf litter contributes to the C pool of stream ecosystems and affects C cycling in streams. We studied how differences in leaf-litter chemistry affect the optical properties and decomposition of DOC. We used 2 species of cottonwoods (Populus) and their naturally occurring hybrids that differ in leaf-litter phytochemistry and decomposition rate. We measured DOC and nutrient concentration in leaf leachates and determined the effect of DOC quality on heterotrophic respiration in 24-h incubations with stream sediments. Differences in DOC composition and quality were characterized with fluorescence spectroscopy. Rapidly decomposing leaves with lower tannin and lignin concentrations leached similar to 40 to 50% more DOC and total dissolved N than did slowly decomposing leaves. Rates of heterotrophic respiration were 25 to 50% higher on leachate from rapidly decomposing leaf types. Rates of heterotrophic respiration were related to metrics of aromaticity. Specifically, rates of respiration were correlated negatively with the Fluorescence Index and positively with Specific Ultraviolet Absorbance (SUVA(254)) and T280 tryptophan-like fluorescence peak. These results reveal that leaf-litter DOC is distinctly different from ambient streamwater DOC. The relationships between optical characteristics of leaf leachate and bioavailability are opposite those found in streamwater DOC. Differences in phytochemistry among leaf types can influence stream ecosystems with respect to DOC quantity, composition, and rates of stream respiration. These patterns suggest that the relationship between the chemical structure of DOC and its biogeochemistry is more complex than previously recognized. These unique properties of leaf-litter DOC will be important when assessing the effects of terrestrial C on aquatic ecosystems, especially during leaf fall.
机译：从树叶凋落物中溶出的溶解有机碳（DOC）有助于河流生态系统的碳库，并影响河流中的碳循环。我们研究了凋落物化学差异如何影响DOC的光学性质和分解。我们使用了两种杨木（杨）及其天然杂种，它们的凋落物的植物化学和分解速率不同。我们测量了叶片渗滤液中的DOC和养分浓度，并确定了DOC质量对与河流沉积物24小时孵育中异养呼吸的影响。 DOC组成和质量的差异用荧光光谱法表征。单宁和木质素浓度较低的快速分解叶片比缓慢分解的叶片沥出的DOC和总溶解氮增加了40％至50％。来自快速分解的叶片类型的沥出液的异养呼吸速率提高了25％至50％。异养呼吸的速率与芳香度有关。具体而言，呼吸速率与荧光指数呈负相关，与特定紫外线吸收率（SUVA（254））和T280色氨酸样荧光峰呈正相关。这些结果表明，凋落物DOC与周围溪水DOC明显不同。叶片浸出液的光学特性与生物利用度之间的关系与溪水DOC中发现的相反。叶片类型之间的植物化学差异可以影响溪流生态系统的DOC数量，组成和溪流呼吸速率。这些模式表明，DOC的化学结构与其生物地球化学之间的关系比以前公认的更为复杂。当评估陆地C对水生生态系统的影响时，尤其是在落叶期间，叶凋落物DOC的这些独特特性将非常重要。

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