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施氮对落叶松人工林凋落物分解及土壤有机碳矿化的影响

Effects of Nitrogen Fertilization on Litter Decomposition and Soil Carbon Mineralization in Larix olgensis Plantation

  • 摘要: 为了解施氮对落叶松人工林凋落物分解及土壤碳矿化的影响,采集经过3 a不同施肥处理(0 g/(m2·a)(对照);5 g/(m2·a)(低氮);20 g/(m2·a)(高氮))的长白落叶松(Larix olgensis)人工林凋落物及土壤,在室内进行140 d的培养,并测定凋落物分解速率、土壤碳矿化速率等指标。结果表明,培养结束时不同施氮处理凋落物质量损失率为33.0%~41.6%,凋落物有机碳损失率为34.1%~42.9%,二者均表现随施氮量的增加而增大,且高氮处理显著高于低氮处理和对照(P<0.05)。低氮和高氮处理的最终土壤CO2累积矿化量分别比对照降低7.6%和3.2%,低氮处理与对照差异显著(P<0.05)。培养过程中,土壤硝态氮、总有效氮(NH+4-N+NO-3-N)质量分数及土壤微生物量碳和氮均表现随施氮量增加而增大的趋势。相关分析表明,凋落物质量损失率与土壤NO-3-N和总有效氮质量分数呈极显著正相关(P<0.01),而与凋落物C/N呈显著负相关(P<0.05),土壤CO2累积矿化量与土壤NH+4-N质量分数呈显著正相关(P<0.05)。施氮提高了土壤供氮能力,降低了凋落物C/N,进而导致落叶松人工林凋落物分解加快,土壤有机碳矿化量减少,故施氮有利于增加土壤有机碳储量。

     

    Abstract: To investigate the effects of nitrogen fertilization on litter decomposition and soil carbon mineralization, the litters and soil were collected in the Larix olgensis plantation which were fertilized for 3 years with different nitrogen fertilization(0 g/(m~2·a)(Control); 5 g/(m~2·a)(low nitrogen); 20 g/(m~2·a))(high nitrogen). After being incubated for 140 days in laboratory, the rates of litter mass and organic carbon mineralization were measured. The results showed that, at the end of incubation, the loss rates of litter mass and litter organic carbon with different nitrogen fertilization were 33.0%-41.6% and 34.1%-42.9%, respectively. They both increased with the increase of nitrogen fertilization levels, and those in the high nitrogen treatment were significantly higher(P<0.05) than those in the low nitrogen treatment and control. Compared with the control, the cumulative CO2 effluxes of soil under low nitrogen and high nitrogen treatments decreased by 7.6% and 3.2% respectively, and the difference between low nitrogen treatment and control was significant(P<0.05). During the incubation, the concentrations of soil, available nitrogen(NH■-N+NO■-N), soil microbial biomass carbon and nitrogen all increased with the increase of nitrogen fertilization levels. Correlation analysis showed that the loss rates of litter mass was significantly positively correlated with the concentrations of soil NO■-N and available nitrogen(P<0.01), while it was significantly negatively correlated with litter C/N(P<0.05). The cumulative CO2 efflux of soil was significantly positively correlated with NH■-N concentration(P<0.05). By increasing soil nitrogen supply capacity, nitrogen fertilization could reduce litter C/N, which further accelerated litter decomposition and reduced soil organic carbon mineralization. Thus, nitrogen fertilization can increase soil organic carbon storage in Larix olgensis plantation.

     

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