Dissolved organic carbon mobilized from organic horizons of mature and harvested black spruce plots in a mesic boreal region
Dissolved organic carbon mobilized from organic horizons of mature and harvested black spruce plots in a mesic boreal region
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DOI：
10.5194/bg-17-581-2020
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发表时间：
2020-02-05
期刊：
影响因子：
4.9
通讯作者：
Ziegler, Susan E.
中科院分区：
文献类型：
--
作者：
Bowering, Keri L.;Edwards, Kate A.;Ziegler, Susan E.
北方森林受季节、气候和森林采伐和气候变化等干扰的影响，在时间和空间上都有很大变化。我们捕获溶解有机碳（DOC）从表面有机（O）的视野在北方森林山坡上使用被动锅蒸渗仪，以确定控制和热时刻DOC动员从这个关键的C源。我们具体解决了（1）如何从O视野DOC通量变化的每周到季节的基础上，森林和配对收获的地块和（2）如何土壤温度，土壤湿度，和水输入与DOC通量的趋势，在这些地块随着时间的推移。来自O层的总DOC年通量包含垂直流和侧向流的贡献，收获地块比森林地块高30%（分别为54 g C m（-2）vs. 38 g C m（-2）; p = 0.008）。这是尽管较小的地上C输入和较小的土壤有机碳储量在收获的地块，但类似于较大的年度O层水通量测量收获的地块。水输入，测量为雨，穿透，和/或融雪取决于季节和地块类型，正相关的O层水通量和DOC通量的变化在研究年。土壤温度与土壤水DOC浓度（[DOC]）的时间变化呈正相关，与水通量呈负相关，但在周至月尺度上，土壤温度与DOC通量之间不存在相关关系。在夏季，DOC通量的水限制存在每周期间的无通量与高DOC浓度下的大通量期间交替。这表明，DOC通量的水限制，在此期间增加水通量的DOC通量的比例增加。相反，冲洗DOC从O层（观察到DOC浓度下降）发生在增加水输入和降低土壤温度在秋季，积雪发展之前。这两个地块类型的土壤保持积雪覆盖整个冬天，保护土壤免受霜冻和有限的渗透。最大的水输入和土壤水通量发生在春季融雪，但没有导致DOC的最大通量，这表明DOC通量在湿秋和融雪期的生产限制。虽然未来年降水量的增加可能会导致DOC通量增加，但这种响应的幅度将取决于这种增加的降水量的类型和年内分布。
Boreal forests are subject to a wide range of temporally and spatially variable environmental conditions driven by season, climate, and disturbances such as forest harvesting and climate change. We captured dissolved organic carbon (DOC) from surface organic (O) horizons in a boreal forest hillslope using passive pan lysimeters in order to identify controls and hot moments of DOC mobilization from this key C source. We specifically addressed (1) how DOC fluxes from O horizons vary on a weekly to seasonal basis in forest and paired harvested plots and (2) how soil temperature, soil moisture, and water input relate to DOC flux trends in these plots over time. The total annual DOC flux from O horizons contain contributions from both vertical and lateral flow and was 30% greater in the harvested plots than in the forest plots (54 g C m(-2) vs. 38 g C m(-2), respectively; p = 0.008). This was despite smaller aboveground C inputs and smaller soil organic carbon stocks in the harvested plots but analogous to larger annual O horizon water fluxes measured in the harvested plots. Water input, measured as rain, throughfall, and/or snowmelt depending on season and plot type, was positively correlated to variations in O horizon water fluxes and DOC fluxes within the study year. Soil temperature was positively correlated to temporal variations of DOC concentration ([DOC]) of soil water and negatively correlated with water fluxes, but no relationship existed between soil temperature and DOC fluxes at the weekly to monthly scale.The relationship between water input to soil and DOC fluxes was seasonally dependent in both plot types. In summer, a water limitation on DOC flux existed where weekly periods of no flux alternated with periods of large fluxes at high DOC concentrations. This suggests that DOC fluxes were water-limited and that increased water fluxes over this period result in proportional increases in DOC fluxes. In contrast, a flushing of DOC from O horizons (observed as decreasing DOC concentrations) occurred during increasing water input and decreasing soil temperature in autumn, prior to snowpack development. Soils of both plot types remained snow-covered all winter, which protected soils from frost and limited percolation. The largest water input and soil water fluxes occurred during spring snowmelt but did not result in the largest fluxes of DOC, suggesting a production limitation on DOC fluxes over both the wet autumn and snowmelt periods. While future increases in annual precipitation could lead to increased DOC fluxes, the magnitude of this response will be dependent on the type and intra-annual distribution of this increased precipitation.