火后不同年限兴安落叶松林土壤氮的矿化速率及其影响因素

摘要

Fire disturbance has been one of the important disturbance factors of Greater Xing'an Mountains forest ecosystem in China.Nitrogen is the most important nutrient elements in the boreal forest ecosystem study,the effects of fire disturbance on soil nitrogen mineralization is of great significance for in-depth study of boreal forest ecosystem recovery mechanism after the fire disturbance.In this paper,we investigated the growing season temporal variation of Larix gmelinii forest soil nitrogen mineralization of three different restoration stages after high burning severity fire disturbance (3 year,9 year,28 year) in the Greater Xing'an Mountains.We used the in-situ cultivation method to study one growing season soil nitrogen mineralization rate and analysis the indicators of soil nitrogen mineralization.The results of this study indicated that:The average NH4+-N in three different restoration stages were 82.99,93.27,108.38 mg·kg-1,respectively.The NH4+-N shown increased trend at different restoration stages after fire disturbance.NO3--N in three different restoration stages were 4.66,10.07,3.59 mg·kg-1,respectively.The soil net nitrogen mineralization (NMR) rate of growing season after fire disturbance was achieved the largest value in May (3.55 mg·kg1),while the smallest was occurred in August (-1.96 mg·kg-1).The average NMR in three different restoration stages soils were 4.66,10.07,3.59 mg·kg-1,respectively.The soil NMR rate of growing season shown firstly increased and then decreased at different restoration stages.The pH and K+ value were significantly correlated with nitrogen mineralization,which indicated that pH and K+ are the dominant factors for the variability of net nitrogen mineralization rate in Larix gmelinii forest after fire disturbance.This study will provide the data basis for revealing the variability of forest ecosystem soil nitrogen pool after fire disturbance and the forest ecosystem restoration after fire disturbance.%火干扰一直是我国大兴安岭森林生态系统的重要干扰因子之～.氮是北方森林生态系统最重要的养分元素,研究火干扰对土壤氮矿化的影响对于深入探讨火后森林生态系统的恢复机制具有重要意义.选择大兴安岭地区兴安落叶松林火后不同年限(3年、9年、28年)的重度火烧迹地,采用原位培养法,经过1个生长季的土壤氮素矿化采样和测定分析.结果表明:火后不同年限土壤的铵态氮(NH4+-N)平均值分别为82.99、93.27、108.38 mg·kg-1,随着火后时间的增加土壤NH4+-N含量呈递增趋势.土壤硝态氮(NO2-N)含量平均值分别为4.66、10.07、3.59 mg·kg-1,火后短期内NO3--N含量随着时间推移先增加再减小.火干扰后不同年限生长季土壤氮净矿化率(NMR)呈现出显著的季节动态变化,最高值出现在5月份为3.55 mg·kg-1,最低值出现在8月份为-1.96 mg·kg-1,不同年限NMR分别为1.20、-0.07、0.76 mg·kg-1,火后土壤NMR随着恢复年限呈现出先升高再降低的变化趋势.pH值与NMR呈极显著正相关,速效钾与NMR呈显著正相关,这说明pH值和速效钾是影响火后兴安落叶松林土壤NMR的主要因子.本研究将为深入揭示火后森林土壤氮库的变化以及火后森林生态系统的恢复提供基础数据.