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林业科学 ›› 2019, Vol. 55 ›› Issue (6): 1-12.doi: 10.11707/j.1001-7488.20190601

• 论文与研究报告 • 上一篇    下一篇

西南酸雨区重庆缙云山常绿阔叶林土壤氮矿化特征

李一凡1,2, 王玉杰1,2, 王彬1,2, 李通1   

  1. 1. 北京林业大学水土保持学院 重庆缙云山森林生态系统国家定位观测研究站 北京 100083;
    2. 北京市水土保持工程技术研究中心 北京 100083
  • 收稿日期:2017-06-09 修回日期:2019-05-08 出版日期:2019-06-25 发布日期:2019-07-11
  • 基金资助:
    北京林业大学中央高校基本科研业务费专项资金项目(2017PT10)。

Soil Nitrogen Mineralization Characteristics of Evergreen Broad-Leaved Forest in Jinyun Mountain in Chongqing in the Acid Rain Zone, Southwest China

Li Yifan1,2, Wang Yujie1,2, Wang Bin1,2, Li Tong1   

  1. 1. National Forest Ecosystem Positioning Observation and Research Station at the Jinyun Mountain in Chongqing School of Soil and Water Conservation, Beijing Forestry University Beijing 100083;
    2. Beijing Engineering Research Center of Soil and Water Conservation Beijing 100083
  • Received:2017-06-09 Revised:2019-05-08 Online:2019-06-25 Published:2019-07-11

摘要: [目的]探讨重庆缙云山2012-2014年土壤矿质氮(铵态氮和硝态氮)变化规律、输入来源与氮矿化特征,明确土壤氮矿化的驱动因素,以期为深入研究该地区土壤养分循环提供理论依据。[方法]在重庆缙云山选择能代表中亚热带森林生态系统的常绿阔叶林,设置1块20 m×20 m样地,内部布设5个4 m×4 m样方,于2012-2014年每年4-9月每月月末,采集上、中、下层(0~15,15~30和30~60 cm)土壤样品,同步观测样地内土壤呼吸速率,并收集穿透雨与干流;在实验室内测定土壤铵态氮(NH4+-N)、硝态氮(NO3--N)和全氮(TN)含量;并用原位培养法测定土壤氮素矿化速率。[结果]土壤铵态氮和硝态氮含量在年际、月际(除2012年铵态氮含量)及各土层间均差异显著(P<0.05),4-9月土壤铵态氮和硝态氮含量均呈递增趋势,上层土壤的铵态氮与硝态氮含量均表现为2013年 > 2012年 > 2014年,各土层间铵态氮含量表现为中层 > 下层 > 上层,硝态氮含量表现为随土层加深而递减趋势;土壤氨化速率和硝化速率的月际变化为单峰或先升后降再上升的趋势,年际变化均表现为2013年 > 2014年 > 2012年;土壤铵态氮含量与硝态氮含量在各土层间极显著(P<0.05)或显著(P<0.01)正相关,但与穿透雨和干流输入量相关性不显著;土壤氨化速率与硝化速率均与土壤呼吸速率极显著(P<0.01)正相关,而与土壤pH值极显著(P<0.01)负相关;土壤呼吸速率大于4 μmol·m-2s-1时,土壤氨化速率和硝化速率明显随pH上升而下降,土壤呼吸速率小于4 μmol·m-2s-1且土壤pH值为3.70~3.75时,氨化速率与硝化速率开始出现小幅上升,之后下降。[结论]重庆缙云山常绿阔叶林土壤矿质氮含量具有年际、月际及土层间差异;土壤矿质氮含量受穿透雨和干流氮(包括铵态氮和硝态氮)输入量的影响较小,而与相邻土层氮含量相关更紧密;土壤pH值升高对土壤的氨化和硝化速率有抑制作用,且其抑制作用大小随土壤呼吸速率大小不同而变。

关键词: 常绿阔叶林, 酸雨, 矿质氮, 氨化与硝化过程, pH, 土壤呼吸

Abstract: [Objective] To clarify the driving factors of soil nitrogen mineralization in the acid rain region, a systematic experiment was conducted at the Jinyun Forest Ecosystem Research Station, Chongqing. The variation of soil mineral nitrogen (ammonium-and nitrate-nitrogen) content, input sources and nitrogen mineralization was explored based on the field data measured during 2012-2014. The results will provide the theoretical basis for in-depth study of soil nutrient cycling in the similar region, and improve forest management.[Method]A 20 m×20 m plot with five 4 m×4 m sub-plots inside was set up in the evergreen broad-leaved forest in the middle subtropical forest ecosystem in Jinyun Mountain in Chongqing. Samples in upper, middle and lower layers of the soil (0-15, 15-30 and 30-60 cm, respectively) were collected at the end of each month from April to September during the period of 2012-2014. Water samples of throughfall and stemflow were collected and soil respiration rates were measured simultaneously. The contents of ammonium-(NH4+-N), nitrate-nitrogen (NO3--N) and total nitrogen (TN) were measured in the laboratory subsequently. Soil nitrogen mineralization rate was quantified using incubation experiment in situ.[Result] The contents of ammonium-and nitrate-nitrogen were significantly different among years, months (except in 2012) and soil layers(P<0.05). There was an increasing trend for the monthly variation in both ammonium-and nitrate-nitrogen content, which increased from April to September. The annual variation in ammonium-and nitrate-nitrogen content in the top soil layer was in the order:2013 > 2012 > 2014. The variation in ammonium nitrogen content among soil layers showed a order in middle > lower > upper, and the variation of nitrate nitrogen content among soil layers showed a decreasing trend with increasing soil depth. The monthly variation of soil ammonification and nitrification rates was unimodal or bimodal. The annual variation showed an order in 2013 > 2014 > 2012 generally. The soil ammonium-and nitrate-nitrogen content were significantly (P < 0.05) or extremely significantly (P< 0.01) correlated with each other among soil layers, but not correlated with the nitrogen input in the rainfall. There was extremely positive correlation (P< 0.01) between soil ammonification/nitrification rate and soil respiration rate, while pH was extremely negatively (P< 0.01) correlated with both soil ammonification and nitrification rates. When soil respiration was greater than 4 μmol·m-2s-1, soil ammonification and nitrification rates decreased obviously with the increasing pH. However, when soil respiration was less than 4 μmol·m-2s-1 and pH ranged between 3.70-3.75, soil ammonification and nitrification rates showed a slightly rising trend first and then followed by a decrease.[Conclusion] The soil mineral nitrogen content was significantly different among years, months and soil layers. The soil mineral nitrogen content was lightly affected by the nitrogen input (including ammonium nitrogen and nitrate nitrogen) in the rainfall, but more closely related to the nitrogen content in adjacent soil layers. The increase of soil pH value inhibited the soil ammonification and nitrification rates, and the degree of inhibition varied with the soil respiration rate. Therefore, in order to maintain soil fertility, it is necessary to pay attention to the variation of soil pH and understand the status of soil nitrogen mineralization in the forest ecosystem of acid rain zone in Southwestern China.

Key words: evergreen broad-leaved forest, acid rain, mineral nitrogen, ammonification and nitrification, pH, soil respiration

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