Welcome to visit Scientia Silvae Sinicae,Today is

Scientia Silvae Sinicae ›› 2019, Vol. 55 ›› Issue (6): 1-12.doi: 10.11707/j.1001-7488.20190601

• Articles • Previous Articles     Next Articles

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

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

CLC Number: