鼎湖山马尾松针阔叶混交林土壤有效氮动态的初步研究

用离子交换树脂袋法测定了鼎湖山生物圈保护区马尾松针阔叶混交林土壤有效氮变化情况。鼎湖山马尾松针阔叶混交林土壤各季节平均总有效氮(铵态氮+硝态氮)在18.87～93.20μg/d*g干树脂之间，且具有明显的季节性变化特点。然而，这些季节性变化根据土层和有效氮组分的不同而异。总有效氮主要由铵态氮组成(>90%)。总有效氮和铵态氮在土层0～10cm和10～20cm之间各个季节均无显著的差异，但硝态氮在春、夏两季差异较大，尤其在夏季两土层之间的差异达显著水平(P<0.05)。在本研究样地中，硝化速率受铵态氮供应的影响不甚明显。与同一地区的马尾松纯林和阔叶混交林比较，硝态氮为针叶纯林<针阔叶混交林<阔叶混交林；铵态氮则为针阔叶混交林〉针叶纯林＞阔叶混交林。

A preliminary study on the dynamics of bio-available nitrogen in soils of pine-broadleaf mixed forest in Dinghuashan Biosphere Reserve

The dynamics of bio-available nitrogen in soils of pine-broadleaf mixed forest in Dinghushan Biosphere Reserve were studied using the ion exchange resin bag method.The total available nitrogen (NO3--N+NH4--N) in different seasons ranged from 18.87 to 93.20μg/d*g dry resin and showed significantly seasonal variation depending on different components of available nitrogen and at different depth of soil.It was the highest in the spring season.The available nitrogen in soil was mostly composed of ammonium nitrogen (>90%).No significant differences in soil ammonium N concentrations between the two studied soil layers (0～10cm,10～20cm).However,there were significant differences in nitrate N concentrations in summer between the two layers.The positive correlation between ammonium N and nitrate N in this forest was significant only in one season.