中文摘要：

为了阐明土壤微生物量氮（SMBN）对土壤中氮的植物有效性及氮循环的影响,从2006年4月到2007年4月对下蜀林场次生栎林和火炬松人工林中的SMBN进行了初步研究。结果表明：（1）次生栎林与火炬松人工林SMBN均具有明显的季节动态变化,且变化规律基本一致,均表现为SMBN夏季最高,冬季最低,春秋两季居中;（2）自然情况下次生栎林SMBN显著大于火炬松人工林的（p〈0.01）,而在凋落物去除后二者之间差异消失;（3）相关分析表明,SMBN和土壤微生物量碳（SMBC）在不同林分中均表现出显著正相关关系（p〈0.05）,但是与土壤总氮、土壤湿度、凋落物输入量之间均无显著相关关系。总之,SMBN的季节变化主要受土壤微生物量季节变化的影响,其调控机理可能与土壤中碳、氮元素的供应及植物生长状况有关,但凋落物的性质对SMBN含量具有显著的影响。

英文摘要：

In order to clarify the effects of soil microbial biomass N on soil N availability of plants and N cycling,SMBN,SMBC,soil N,litterfall input,and other factors were determined in a secondary oak forest and pine plantation in Xia-shu experimental sites in Jiangsu province from April 2006 to April 2007,the results are as follows：（1）There are obvious seasonal dynamics of SMBN both in secondary oak forest and pine plantation,and the variation is consistent,which shows the highest microbial biomass N in summer,lowest in winter,spring and autumn are middle;（2）In the condition of the undisturbed natural state（control treatment）,SMBN in oak forest is significantly larger than in pine plantation（p0.01）,but the difference between the two forest types disappear after the litterfall is removed（litterfall excluding treatment）;（3）The correlation analysis shows that soil microbial biomass N is significantly and positively correlated to SMBC both in secondary oak forest and pine plantation（p0.05）,but not to soil nitrogen,soil moisture or litterfall input.Our results show that the obviously seasonal changes of SMBN mainly controlled by the seasonal changes of soil microbial biomass,which may be influenced by the soil C,N availability and the competition between soil microbial biomass and plant growth with the deeper reasons,but the properties of litterfall had a significant impact on the SMBN.