College of Environment and Planning, Henan University, Kaifeng, 475004, China.
Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions (Henan University), Ministry of Education, Kaifeng, 475004, China.
New Phytol. 2021 Aug;231(4):1377-1386. doi: 10.1111/nph.17460. Epub 2021 Jun 12.
Elucidating the effects of atmospheric nitrogen (N) deposition on fine root dynamics and the potential underlying mechanisms is required to understand the changes in belowground and aboveground carbon storage. However, research on these effects in forests has mostly involved direct understory addition of N and has ignored canopy interception and processing of N. Here, we conducted a field experiment comparing the effects of canopy addition of N (CAN) with those of understory addition of N (UAN) at three N-addition rates (0, 25 and 50 kg N ha yr ) on fine root dynamics in a temperate deciduous forest. Fine root production and biomass were significantly higher with CAN than with UAN. At the same N-addition rate, increases in fine root production with CAN were at least two-fold greater than with UAN. At the high N-addition rate and relative to the control, fine root biomass was significantly increased by CAN (by 23.5%) but was significantly decreased by UAN (by 12.2%). Our results indicate that traditional UAN may underestimate the responses of fine root dynamics to atmospheric N deposition in forest ecosystems. Canopy N processes should be considered for more realistic assessments of the effects of atmospheric N deposition in forests.
阐明大气氮 (N) 沉降对细根动态的影响及其潜在的机制，对于理解地下和地上碳储存的变化是必要的。然而，森林中关于这些影响的研究大多涉及氮的直接林下添加，而忽略了树冠对氮的截留和处理。在这里，我们进行了一项野外实验，比较了在三种氮添加速率（0、25 和 50 kg N ha yr ）下，树冠添加氮 (CAN) 与林下添加氮 (UAN) 对温带落叶林细根动态的影响。与 UAN 相比，CAN 显著增加了细根的生产力和生物量。在相同的氮添加速率下，CAN 增加细根生产力的幅度至少是 UAN 的两倍。在高氮添加率下，与对照相比，CAN 显著增加了细根生物量（增加了 23.5%），而 UAN 则显著降低了细根生物量（降低了 12.2%）。我们的结果表明，传统的 UAN 可能低估了森林生态系统中大气氮沉降对细根动态的响应。为了更真实地评估大气氮沉降对森林的影响，应考虑树冠氮过程。
