Nodulated soybean enhances rhizosphere priming effects on soil organic matter decomposition more than non-nodulated soybean

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• 作者：Biao Zhu^a ; ^b ; ^{biaozhu@gmail.com} ; Weixin Cheng^a
• 关键词：Priming effect ; Rhizodeposition ; SOM decomposition ; N mineralization ; Soybean ; Nodulation ; Nitrogen fixation
• 刊名：Soil Biology & Biochemistry
• 出版年：2012
• 期刊代码：96_00380717
• 类别：abs
• 出版时间：August, 2012
• 卷：51
• 期：Complete
• 页码：56-65
• 文件大小：430 K

摘要

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 鈥渞hizodeposit quality hypothesis鈥?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 continuous ¹³C-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.