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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Litter dominates surface fluxes of carbonyl sulfide in a Californian oak woodland
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Litter dominates surface fluxes of carbonyl sulfide in a Californian oak woodland

机译：垃圾占主导地位的加利福尼亚州橡树林的羰基硫表面通量

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Carbonyl sulfide (COS) is a promising tracer for partitioning terrestrial photosynthesis and respiration from net carbon fluxes, based on its daytime co-uptake alongside CO_2 through leaf stomata. Because ecosystem COS fluxes are the sum of plant and soil fluxes, using COS as a photosynthesis tracer requires accurate knowledge of soil COS fluxes. At an oak woodland in Southern California, we monitored below-canopy surface (soil + litter) COS and CO_2 fluxes for 40 days using chambers and laser spectroscopy. We also measured litter fluxes separately and used a depth-resolved diffusion-reaction model to quantify the role of litter uptake in surface COS fluxes. Soil and litter were primarily COS sinks, and mean surface COS uptake was small (～1 pmol m~(-2) s~(-1)). After rainfall, uptake rates were higher (6–8 pmol m~(-2) s~(-1)), and litter contributed a significant fraction (up to 90%) to surface fluxes. We observed rapid concurrent increases in COS uptake and CO_2 efflux following the onset of rain. The patterns were similar to the Birch effect widely documented for soils; however, both COS and CO_2 flux increases originated mainly in the litter. The synchronous COS-CO_2 litter Birch effect indicates that it results from a rapid increase in litter microbial activity after rainfall. We expect that the drying-rewetting cycles typical for mediterranean and other semiarid ecosystems create a pronounced seasonality in surface COS fluxes. Our results highlight that litter uptake is an important component of surface COS exchange that needs to be taken into account in ecosystem COS budgets and model simulations.
机译：羰基硫化物（COS）是一种有前景的示踪剂，可根据其白天通过叶气孔与CO_2的共同摄入量，从净碳通量中分配陆地光合作用和呼吸作用。由于生态系统COS通量是植物和土壤通量的总和，因此使用COS作为光合作用示踪剂需要对土壤COS通量有准确的了解。在南加州的一个橡树林中，我们使用室和激光光谱仪对冠层下表面（土壤+垃圾）的COS和CO_2通量进行了40天的监测。我们还分别测量了枯枝落叶通量，并使用深度分解扩散反应模型来量化枯枝落叶吸收量在表面COS通量中的作用。土壤和垃圾主要是COS汇，平均表面COS吸收量很小（〜1 pmol m〜（-2）s〜（-1））。降雨后，吸收速率更高（6-8 pmol m〜（-2）s〜（-1）），并且凋落物对表面通量的贡献很大（达90％）。我们观察到降雨开始后，COS吸收和CO_2外排迅速增加。这种模式类似于广泛记录在土壤中的桦木效应。然而，COS和CO_2通量的增加主要来源于垫料。同步的COS-CO_2凋落物桦木效应表明，它是降雨后凋落物微生物活性快速增加的结果。我们预计，地中海和其他半干旱生态系统的典型干湿循环会在表面COS通量上产生明显的季节性。我们的研究结果表明，凋落物的吸收是地表COS交换的重要组成部分，生态系统COS预算和模型模拟中必须考虑到这一点。

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