Nodulated soybean enhances rhizosphere priming effects on soil organic matter decomposition more than non-nodulated soybean
Nodulated soybean enhances rhizosphere priming effects on soil organic matter decomposition more than non-nodulated soybean
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DOI：
10.1016/j.soilbio.2012.04.016
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发表时间：
2012-08
影响因子：
9.7
通讯作者：
B. Zhu;W. Cheng
中科院分区：
文献类型：
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作者：
B. Zhu;W. Cheng
根际过程对土壤有机质（SOM）分解具有显著的控制作用，也被称为根际启动效应（RPE）。然而，导致RPE的确切机制在很大程度上仍然未知。特别是，一些报告表明，根沉积物的质量可能在不同植物物种中引起不同水平的RPE中起重要作用。然而，“根沉积质量假说”的直接证据一直缺乏。本文通过研究RPE对两种大豆（Glycine max L.）梅尔）隔离带的差异仅在于它们形成结节和固定N2的能力，因此组织N浓度和根沉积质量也不同。我们使用了一个连续的13 C-标记的方法来测量RPE对土壤有机C分解，并采用了N-预算方法来量化RPE对土壤净氮矿化。我们发现，大豆根沉积物产生了更强的RPE，（53%对26%），而在成熟期，大豆植株组织N浓度显著高于非大豆，但生物量与非大豆相近，而在营养生长期，两个大豆等株系的RPE相似（33-34%），而植物组织中的N浓度或植物生物量没有差异。两条等值线上的RPE对土壤净氮矿化的影响相似，从营养生长期的25%到成熟期的38-46%。RPE对土壤有机碳分解的影响与RPE对土壤净氮矿化的影响不成线性关系。这些结果表明，较高的根沉积物质量是最可能的原因之一，较高的RPE的大豆相比，非膨化大豆膨化。为了进一步验证这一假说，有必要对两个大豆等株系的根沉积质量和数量进行进一步的研究。
The phenomenon that rhizosphere processes significantly control soil organic matter (SOM) decomposition, also termed rhizosphere priming effect (RPE), is now increasingly recognized as significant as the effects of soil temperature and moisture on SOM decomposition. However, the exact mechanisms responsible for RPE remain largely unknown. Particularly, some reports have suggested that the quality of rhizodeposits may play a significant role in causing different levels of RPE among various plant species. However, direct evidence for the “rhizodeposit quality hypothesis” has been lacking. Here we tested the hypothesis by investigating RPE on soil carbon (C) and nitrogen (N) mineralization of two soybean (Glycine max L. Merr.) isolines differing only in their ability to form nodules and to fix N2, and thus differing in tissue N concentration and rhizodeposit quality. We used a continuous13C-labeling method for measuring RPE on soil organic C decomposition, and employed an N-budgeting method for quantifying RPE on soil net N mineralization. We found that the rhizodeposits from nodulated soybean produced a stronger RPE (53% vs. 26%) on soil organic C decomposition than the rhizodeposits from non-nodulated soybean at the maturity stage when nodulated soybean had significantly higher plant tissue N concentration but similar plant biomass, while both soybean isolines produced a similar RPE (33–34%) at the vegetative stage when there was no difference in plant tissue N concentration or plant biomass. The levels of RPE on soil net N mineralization were similar between the two isolines, ranging from 25% at the vegetative stage to 38–46% at the maturity stage. Moreover, RPE on soil organic C decomposition was not linearly proportional to RPE on soil net N mineralization. These results indicate that higher rhizodeposit quality is one of the most likely causes to the higher RPE of the nodulated soybean compared to the non-nodulated soybean. Further investigations of rhizodeposit quality and quantity between the two soybean isolines are warranted to further test this rhizodeposit quality hypothesis.