Dissolved organic carbon production and flux under long-term litter manipulations in a Pacific Northwest old-growth forest
Dissolved organic carbon production and flux under long-term litter manipulations in a Pacific Northwest old-growth forest
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DOI：
10.1007/s10533-020-00667-6
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发表时间：
2020-04
期刊：
影响因子：
4
通讯作者：
L. Evans;D. Pierson;K. Lajtha
中科院分区：
文献类型：
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作者：
L. Evans;D. Pierson;K. Lajtha
溶解有机碳（DOC）通量是土壤有机碳（C）从地上部分（凋落物）向土壤深层转移的重要机制，并影响土壤稳定有机碳化合物的形成。该通量的大小取决于渗透率和DOC生产率，这是一个地区的气候，土壤，地形和生态特征的函数。通过对道格拉斯冷杉（Douglas fir）林凋落物数量和质量的连续20年的6种处理，研究了凋落物输入、DOC产生和通量以及土壤C动态之间的关系。DOC浓度测定在两个深度使用张力蒸渗仪，并创建一个水文模型，以量化水和DOC通量通过土壤剖面。30和100 cm土层DOC浓度分别为3.0-8.0和1.5-2.5 mg C/L。地面碎屑输入没有一个一致的积极影响，土壤溶液DOC，除了粗木质残体增加土壤溶液DOC的58%30 cm以下，而地上落叶层的质量增加一倍，DOC浓度下降30%。我们认为，高品质的落叶加速微生物的处理，导致“启动”效应，导致浓度较低。每年DOC流入地下水的通量很小（2.7-3.7 g C/m2/年），占该地点估计凋落物C的0.1%以下。因此，DOC从地表凋落物到地下水的直接损失对土壤C收支的影响相对可以忽略。然而，进入土壤表层的DOC通量要大得多（73-210 g C/m2/year），相当于地上凋落物C的1.4-2.4%。因此，DOC的运输是C的一个重要来源浅土壤层。
Dissolved organic carbon (DOC) flux is an important mechanism to convey soil carbon (C) from aboveground organic debris (litter) to deeper soil horizons and can influence the formation of stable soil organic C compounds. The magnitude of this flux depends on both infiltration and DOC production rates which are functions of the climatic, soil, topographic and ecological characteristics of a region. Aboveground litter quantity and quality was manipulated for 20 years in an old-growth Douglas fir forest under six treatments to study relationships among litter inputs, DOC production and flux, and soil C dynamics. DOC concentrations were measured at two depths using tension lysimeters, and a hydrologic model was created to quantify water and DOC flux through the soil profile. DOC concentrations ranged from 3.0–8.0 and 1.5–2.5 mg C/L among treatments at 30 and 100 cm below the soil surface, respectively. Aboveground detrital inputs did not have a consistent positive effect on soil solution DOC; the addition of coarse woody debris increased soil solution DOC by 58% 30 cm belowground, while doubling the mass of aboveground leaf litter decreased DOC concentrations by 30%. We suggest that high-quality leaf litter accelerated microbial processing, resulting in a “priming” effect that led to the lower concentrations. Annual DOC flux into groundwater was small (2.7–3.7 g C/m2/year) and accounts for < 0.1% of estimated litter C at the site. Therefore, direct DOC loss from surface litter to groundwater is relatively negligible to the soil C budget. However, DOC flux into the soil surface was much greater (73–210 g C/m2/year), equivalent to 1.4–2.4% of aboveground litter C. Therefore, DOC transport is an important source of C to shallow soil horizons.