冻融对长白山森林土壤碳氮矿化的影响

长白山地区秋末春初常常存在冻融过程,冻融过程影响土壤水分分布而改变土壤理化性质。通过室内模拟实验,研究了冻融过程（-20~15℃）对长白山阔叶红松（Pinus koraiensis）林和白桦（Betula platyphylla）林土壤有机碳和氮矿化过程的影响。结果表明,经过3次冻融循环,冻融处理土壤矿化速率显著高于对照处理,但经过多次冻融循环过程,冻融处理抑制土壤有机碳矿化过程,对照处理土壤有机碳矿化速率高于冻融处理（P=0.019）。在培养结束后,冻融处理的阔叶红松林和白桦林土壤无机氮质量分数,分别是对照处理的1.88倍和1.96倍;冻融次数也是影响土壤有机氮矿化的一个重要因素,35次冻融循环后,阔叶红松林和白桦林土壤中无机氮分别提高了2.10倍和2.81倍。冻融循环促进了土壤有机氮的矿化,有利于土壤中有效氮的累积,为春季植物生长提供足够的氮素,但也潜在增加了土壤中无机氮流失的风险。

Effect of freezing-thawing on the carbon and nitrogen mineralization in Changbai Mountain

There are many freezing-thawing cycles（FTC） during the late autumn and early spring in ChangbaiMoutain.Freezing-thawing cycles affected the availability of soil water significantly,which would influence the soil physical,chemical and biological characteristics.A laboratory incubation experiment was conducted to investigate the effect of freezing-thawing cycles（-20-15℃）on the carbon and nitrogen mineralization of Broadleaved-Korean pine mixed forests（HS） and Birch forest（BH） soils.The results showed that the carbon mineralization rate of freezing-thawing treatment was higher than control treatment after the third freezing-thawing cycles.But,with the numbers of freezing-thawing increasing,the freezing-thawing restrained the carbon mineralization,and the carbon mineralization rate of control treatment was higher than freezing-thawing（P=0.019）.The inorganic nitrogen concentration in soil of HS and BH were 1.88 and 1.96 times as that of the control treatment after incubation reciprocally.The nitrogen mineralization of soils was affected by numbers of freezing-thawing significantly.The results indicated freezing-thawing process was benefited to the improvement of soil inorganic nitrogen content.That could provide abundant nutrient for the growth of plants in spring,on the other hand,might improve the possibility of nutrient loss from soil.