Leachate from fine root litter is more acidic than leaf litter leachate: A 2.5-year laboratory incubation
Leachate from fine root litter is more acidic than leaf litter leachate: A 2.5-year laboratory incubation
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DOI：
10.1016/j.scitotenv.2018.07.038
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发表时间：
2018-12-15
影响因子：
9.8
通讯作者：
Maie，Nagamitsu
中科院分区：
文献类型：
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作者：
Tanikawa，Toko;Fujii，Saori;Maie，Nagamitsu
一些树种在土壤酸化条件下增加了细根产量，从而改变了叶片和根系凋落物输入的平衡。凋落物在分解过程中会浸出大量的酸性物质，这可能会促进土壤酸化。在此背景下，我们重点研究了溶解有机物（DOM）作为酸性物质的主要成分。我们假设在凋落叶和凋落根中，DOM的质量和数量不同，而DOM的质量和数量控制着它的功能（即质子供应）。为了验证这一假设，我们以两种针叶树（Cryptomeria japonicaaecyparis obtusa）的新鲜细根和新鲜绿叶作为凋落物进行了为期2.5年的实验室培养实验，并根据光学性质研究了渗滤液的pH和DOM组成。DOM闪淋收敛分解初期后，根部浸出的溶解有机碳（DOC）再次增加，浸出液pH值下降。相反，在孵育期间，叶片渗滤液中DOC浓度持续下降，pH下降幅度不如根渗滤液明显。DOM的光学性质（紫外可见吸收和荧光）表明，DOM中的腐殖质样物质对根渗滤液的酸性pH起主要作用。从根和叶中释放的质子总量分别是叶片的13倍和18倍。这些结果表明，在酸性土壤中，细根生物量的增加可能引起植物-土壤正反馈，影响陆地生态系统土壤生物地球化学功能。
Some tree species increase fine root production under soil acidification, thus changing the balance of litter input from leaves and roots. Litter leaches a significant amount of acidic materials during its decomposition, which might facilitate soil acidification. In this context, we focused on dissolved organic matter (DOM) as the major component of acidic materials. We hypothesized that both the quality and quantity of DOM, which control its function (i.e., proton supply), differ between leaf and root litter. To test this hypothesis, we conducted a 2.5-year laboratory incubation experiment using fresh fine roots and fresh green leaves as litter of two coniferous species (Cryptomeria japonicaandChamaecyparis obtusa) and investigated the leachate pH and DOM composition based on the optical properties. After the early stage of decomposition when flash leaching of DOM converged, the amount of dissolved organic carbon (DOC) leached from roots increased again and leachate pH declined. In contrast, DOC concentrations continued to decrease in leaf leachates during the incubation period, and the pH decrease was not as striking as that of root leachates. Optical properties (ultraviolet visible absorption and fluorescence) of DOM revealed that humic-like substances in DOM played a central role in the acidic pH of root leachates. The total amount of protons released from roots ofC.japonicaandC.obtusais about 13 and 18 times higher, respectively, than that from leaves. These results imply that the increase of fine root biomass may induce a positive plant–soil feedback in acidic soils, affecting soil biogeochemical functions of terrestrial ecosystems.