氮添加对蚯蚓粪有机碳矿化特征的影响

Effect of Nitrogen Addition on the Organic Carbon Mineralization Characteristics of Earthworm Cast

    摘要
  • 摘要:
    目的 探究氮素添加对蚯蚓粪有机碳矿化特征的影响，为农田蚯蚓碳源碳汇效应调控提供科学依据。
    方法 以玉米地、撂荒地和苹果园地表蚯蚓粪为研究对象，设计不同氮素添加处理（N0，0 mg kg−1；N1，5 mg kg−1；N2，50 mg kg−1；N3，250 mg kg−1），开展室内矿化培养实验，通过定时测定蚯蚓粪理化性质与微生物多样性特征揭示氮添加对蚯蚓粪有机碳矿化特征的影响机制。
    结果 农田蚯蚓粪有机碳和全氮含量显著高于土壤，铵态氮和硝态氮含量显著低于土壤（P < 0.05）。氮添加显著提高了蚯蚓粪全氮、铵态氮、硝态氮含量，降低了碳氮比、总有机碳含量。与N0处理相比，氮添加处理下蚯蚓粪全氮、铵态氮和硝态氮含量分别平均提高了25.51%、1270.62%和52.97%。其中，N3处理下铵态氮含量极显著提高3705.28%（P < 0.01），硝态氮含量显著降低（P < 0.05），N2处理下硝态氮含量提高幅度最大；氮添加使蚯蚓粪碳氮比极显著降低37.65% ~ 56.63%（P < 0.01）。适量氮添加提高了蚯蚓粪微生物量碳和微生物多样性，N3处理下微生物多样性显著降低（P < 0.05）。氮添加显著加快了蚯蚓粪有机碳矿化过程，蚯蚓粪有机碳矿化累积量增加22.98% ~ 159.83%，其中N2处理增幅最大。氮添加处理下蚯蚓粪有机碳矿化主要驱动因素为碳氮比、微生物量碳和微生物多样性，有机碳矿化累积量与碳氮比呈负相关，与微生物量碳和微生物多样性呈正相关。
    结论 农田地表蚯蚓粪在受到氮添加的强烈影响下有机碳矿化速率显著提高，导致蚯蚓粪对有机碳的保护作用降低，削弱了蚯蚓的碳汇效应。研究结果可为深入认识农田蚯蚓的生态功能和化肥施用的生态环境效应提供科学支撑。

     

    Abstract:
    Objective The aims were to investigate the effect of nitrogen (N) addition on the mineralization characteristics of organic carbon (C) in earthworm cast, in order to provide a scientific basis for regulating the C sink effect of earthworms in farmland.
    Method The earthworm casts were collected from cornfields, fallow land and apple orchards. Different N addition treatments included (N0, 0 mg kg−1; N1, 5 mg kg−1; N2, 50 mg kg−1; N3, 250 mg kg−1) and conducted indoor mineralization cultivation experiments. By periodically measuring the physical and chemical properties and microbial diversity characteristics of earthworm cast, the study aimed to reveal the mechanisms of N addition affecting the mineralization characteristics of organic C in earthworm cast.
    Result The contents of organic C and total N in earthworm cast were significantly higher than othose in soil, and the contents of ammonium N and nitrate N were significantly lower than those in soil (P < 0.05). Nitrogen addition significantly increased the total N, ammonium N and nitrate N contents of earthworm cast and decreased C/N ratio and organic C contents. Compared with the N0 treatment, the earthworm cast total N, ammonium N and nitrate N contents were increased by an average of 25.51%,1270.62% and 52.97%, respectively. Under the N addition treatment, the ammonium N content was extremely significantly increasing by 3705.28% (P < 0.01), and the nitrate N content was significantly decreased (P < 0.05) under the N3 treatment. The nitrate N content was most significantly increased under the N2 treatment. The N addition made the earthworm cast C/N ratio highly significantly reduced by 37.65% - 56.63% (P < 0.01). Nitrogen addition increased the microbial biomass C and microbial diversity of earthworm cast, and the microbial diversity was significantly reduced under N3 treatment (P < 0.05). Nitrogen addition significantly accelerated the process of earthworm cast organic C mineralization, and the cumulative mineralized amount of earthworm cast organic C increased by 22.98% to 159.83%, with the greatest increase in the N2 treatment. The main driving factors of organic C mineralization in earthworm cast under N addition treatments were C/N nitrogen ratio, microbial biomass C and microbial diversity, and the accumulation of mineralized organic C was negatively correlated with C/N ratio and positively correlated with microbial biomass C and microbes diversity.
    Conclusion The rate of organic C mineralization of earthworm cast on farmland surface was significantly increased under the strong influence of N addition, which led to the reduction of the protective effect of earthworm cast on organic C and weakened the C sink effect of earthworms. The results can provide scientific support for a deeper understanding of the ecological functions of earthworms in agricultural fields and the ecological and environmental effects of fertilizer application.

     

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