Nitrogen dynamics differed among the first six root branch orders of Fraxinus mandshurica and Larix gmelinii during short-term decomposition
Nitrogen dynamics differed among the first six root branch orders of Fraxinus mandshurica and Larix gmelinii during short-term decomposition
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DOI：
10.1007/s10265-009-0303-z
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发表时间：
2010-07-01
影响因子：
2.8
通讯作者：
Jiang, Youxu
中科院分区：
文献类型：
--
作者：
Fan, Pingping;Jiang, Youxu
细根（< 2 mm）分解提供了大量维持植物生长的有效氮（N）。凋落物分解过程中的氮素释放模式一般受初始氮素浓度或C/N的控制。由于根分支顺序和菌根定殖（与分支顺序相关）与不同的初始化学物质密切相关，因此提出了一个假设，即根分解过程中的N动态在不同的分支顺序之间存在差异。采用凋落物袋法，对东北地区丛枝菌根树种水曲柳和外生菌根树种落叶松前6级根的分解进行了为期513 d的研究。结果表明，两种具有不同菌根类型的植物具有相似的模式：低级根（侧根尖），其初始C/N为17-21，持续释放N而没有任何固定，并保持一贯的低C/N（< 20），而高级根，其初始C/N为28-48，周期性固定N，导致C/N随时间推移而下降。此外，不同物种间的N动态在低级根上存在差异，而在高级根上没有差异。这些结果表明，细根N动态是异质的分支订单和物种的具体差异取决于行为的低阶根。
Fine root (< 2 mm) decomposition provides a substantial amount of available nitrogen (N) that sustains plant growth. The N release pattern during litter decomposition is generally controlled by initial N concentrations or C/N. Because root branch order and mycorrhizal colonization (related with branch order) are both highly related with different initial chemistry, a hypothesis was proposed that N dynamics during root decomposition varied among different branch orders. Using the litterbag method, decomposition of the first six order roots for Fraxinus mandshurica (an arbuscular mycorrhizal species) and Larix gmelinii (an ectomycorrhizal species) was studied in Northeast China during a 513-day period. Results showed a similar pattern for the two species with contrasting mycorrhizal type: lower-order roots (the lateral root tips), which had an initial C/N of 17-21, continuously released N without any immobilization and maintained a consistently low C/N (< 20), whereas higher-order roots, which had an initial C/N of 28-48, periodically immobilized N, leading to a declining C/N over time. In addition, the magnitude of N dynamics is different between species for lower-order roots, but no different for higher-order roots. These results suggest that fine root N dynamics are heterogeneous among branch orders and that species-specific differences depend on the behavior of lower-order roots.