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氮添加对华北落叶松根际与非养分的影响

Effects of Nitrogen Addition on Soil Nutrients in the Rhizosphere and non Rhizosphere of Larix principis-rupprechtii Plantation

    摘要
  • 摘要:
    目的 大气氮沉降对森林根际与非根际土壤养分有重要影响。华北地区是我国氮沉降高值区之一，然而目前关于氮沉降对该地区森林土壤养分影响的阈值及其是否引起其它养分限制还不清楚。
    方法 本研究以河北省木兰林场国有林场的华北落叶松人工林为研究对象，通过多水平氮添加实验(0、5、10、20、40、80、160 kg N·ha−1·yr−1)，分析氮添加对根际和非根际土壤在全量养分、速效养分及其生态化学计量的差异影响，旨在揭示氮添加对华北落叶松人工林根际效应的影响。
    结果 研究表明：1）根际土壤有机碳（SOC）、总氮（TN）、硝态氮（NO3−-N）和有效氮（AN）含量随氮添加水平呈上升趋势，且都在氮添加为80 kg N·ha−1·yr−1时达到最高值，与对照组相比增加了39.55%、36.27%、56.69%、44.02%。2）非根际土壤 NO3−-N 在氮添加为160 kg N·ha−1·yr−1时达到最大，与对照组存在显著性差异，不同氮添加水平下SOC、TN、TP含量等均无显著变化。3）随着氮添加水平的增加，根际土壤的C∶P、N∶P呈上升趋势，非根际土壤的 C∶P、N∶P呈下降趋势。4）相对于对照组，氮添加后土壤SOC、TN 、NO3−-N 、AN、AP、C∶P、N∶P 的根际效应呈增加趋势。
    结论 本研究表明，氮添加会增强根际效应，提高华北落叶松人工林根际土壤SOC、TN、NO3−-N、AN的含量，且阈值均在80 kg N·ha−1·yr−1，而且氮添加会改变土壤磷元素平衡，华北落叶松人工林生长未来可能会面临土壤磷限制。本研究可为大气氮沉降或施肥措施下华北落叶松人工林的养分调控提供理论和科学依据。

     

    Abstract:
    Objective Atmospheric nitrogen deposition has an important effect on forest rhizosphere and non-rhizosphere soil nutrients. North China is one of the regions with high nitrogen deposition in China. However, the threshold value of nitrogen deposition on forest soil nutrients in this region and whether it causes other nutrient limitations are still unclear.
    Method Based on Larix principis-rupprechtii plantation in a state-owned forest in Mulan Forestry, Hebei Province, China, the differential effects of nitrogen addition on rhizosphere and non-rhizosphere soils in terms of total nutrients, fast-acting nutrients and their ecological stoichiometry were analyzed through a multi-gradient nitrogen addition experiment.
    Result The results showed that: 1) The contents of organic carbon (SOC), total nitrogen (TN), nitrate nitrogen (NO3−-N) and available nitrogen (AN) in rhizosphere soil increased with the nitrogen addition level. The highest value was reached when the nitrogen addition was 80 kg N·ha-1·yr-1, which increased by 39.55%, 36.27%, 56.69% and 44.02% compared with the control group. 2) In non-rhizosphere soil, NO3−-N reached its maximum when nitrogen addition was 160 kg N·ha−1·yr−1, which showed a significant difference from the control group. There were no significant differences in SOC, TN, TP contents under different nitrogen addition levels. 3) With the increase of nitrogen addition level, C∶P and N∶P in rhizosphere soil showed an increasing trend, while C∶P and N∶P in non-rhizosphere soil showed a decreasing trend. 4) Compared with the control group, the rhizosphere effects of SOC, TN, NO3−-N, AN, AP, C∶P, N∶P showed an increasing trend after nitrogen addition.
    Conclusion This study shows that nitrogen addition can enhance the rhizosphere effect and increase the contents of SOC, TN, NO3−-N and AN in rhizosphere soil of Larix principis-rupprechtii plantation and the threshold values are all at 80 kg N·ha−1·yr−1. In addition, nitrogen addition will change the soil phosphorus element balance, and the growth of Larix principis-rupprechtii plantation may face soil phosphorus restriction in the future. This study can provide theoretical and scientific basis for nutrient regulation of Larix principis-rupprechtii plantation under atmospheric nitrogen deposition or fertilization measures.

     

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