火干扰对棋盘山油松林土壤碳氮及驱动因子的影响

Effects of fire disturbance on soil carbon,nitrogen and driving factors of Pinus tabuliformis forests in Qipan mountain

【目的】土壤碳(C)、氮(N)是陆地生态系统的重要组分,其循环过程及相互作用深刻影响生态系统的生产力和稳定性,在森林生态系统中也发挥着重要的作用,但在全球变暖的背景下,森林火灾的发生频率和强度均会增加,这将给土壤C、N库带来巨大影响。通过研究不同强度火干扰后对油松林土壤C、N的影响,探究其驱动因子,阐明火后植物多样性、微生物生物量及土壤环境因素与土壤C、N之间耦合机制。【方法】以沈阳棋盘山油松林为研究对象,采集未火烧、轻度火烧和重度火烧3种不同火烧强度的0~5 cm、5~15 cm的土壤样品,采用冗余分析、层次分割、Mantel检验和相关分析探究土壤全碳(TC)、全氮(TN)及碳氮比(C︰N)的影响因素。【结果】(1)与未火烧样地相比,轻度和重度火烧的土壤TC含量分别显著降低20.25%和27.74%,土壤TN含量分别显著降低43.11%、50.70%,而C︰N分别显著升高44.56%、46.06%。火烧、土壤深度及其交互作用对土壤TC、TN和C︰N均有显著影响。(2)轻度火烧样地的土壤pH值显著下降3.32%,重度火烧样地的土壤温度(T)显著增加9.06%,含水率(SWC)显著下降26.40%,土壤氨态氮(NH4+-N)含量显著降低43.92%,土壤微生物生物量碳(MBC)、氮(MBN)分别显著上升了113.56%和342.28%。(3)未火烧样地中土壤T和土壤SWC是土壤TC、TN和C︰N的主要驱动因子。火烧后土壤TC、TN的主要驱动因子为土壤SWC和硝态氮(NO3--N),而土壤C︰N与植被和土壤因子没有显著相关关系。【结论】轻、重度火烧导致土壤TC、TN显著降低,土壤C︰N显著升高,并且火烧改变了土壤C、N及C︰N的部分驱动因子,可为火后油松林土壤养分管理和恢复提供一定的理论支撑。

【Objective】Soil carbon(C)and nitrogen(N)are important components of the terrestrial ecosystem.Their circulation process and interaction profoundly affect the productivity and stability of the ecosystem and also play an important role in the forest ecosystem.However,under the background of global warming,the frequency and intensity of forest fires will increase,which will have a great impact on the soil C and N pools.The purpose of this paper was to study the influence of different severity fire disturbance on soil C and N of Pinus tabulaeformis forest,and explore its driving factors as well as the coupling mechanism between plant diversity,microbial biomass,soil environmental factors and soil C and N.【Method】This study took the fire burned area of Pinus tabulaeformis forest in Qipan mountain of Shenyang as the research object,and the 0-5 cm and 5-15 cm soil samples with three different fire severities of unburnt,low burn severity and high burn severity were collected.Redundancy analysis and hierarchical segmentation were used to quantify the relative contribution of fire,soil layer and environmental factors to soil carbon and nitrogen.Mantel test and correlation analysis were used to explore the mechanism of fire on soil C,N and C︰N.【Result】(1)Compared with the control stands,the soil carbon content of the low and high burn severity decreased significantly by 20.25%and 27.74%,the soil nitrogen content decreased significantly by 43.11%and 50.70%,and the carbon-nitrogen ratio increased significantly by 44.56%and 46.06%,respectively.Fire,soil depth and their interaction have significant effects on soil C,N and C︰N ratios.(2)The soil pH of the low burn severity plots decreased significantly by 3.32%,the soil temperature of the high burn severity plots increased significantly by 9.06%,the water content decreased significantly by 26.40%,the soil ammonia nitrogen content decreased significantly by 43.92%,and the soil microbial biomass carbon and nitrogen increased significantly by 113.56%and 342.28%,respectively.(3)Soil temperature and soil moisture content are the main driving factors of soil C,N and C︰N ratios.After burning,the main driving factors of soil carbon and nitrogen were soil moisture content and nitrate nitrogen,and the soil carbon-nitrogen ratio was no longer affected by environmental factors.【Conclusion】Low burn severity and high burn severity cause a significant decrease in soil TC and TN and a significant increase in soil C︰N.Moreover,fire changes some driving factors of soil C,N and C︰N,which provides theoretical support for soil nutrient management and recovery of Pinus tabuliformis forest after fire disturbance.