The Dynamics Of Nitrogen Mineralization And Driving Factors In A Querqus Aliena Var.acuteserrata Forest In Baotianman,Henan

Studying nitrogen mineralization dynamics and the influencing factors not only can reveal the function of the ecosystems,but also help understand the underlying processes of biogeochemical cycles.This study was conducted between April 2016 and April 2017,making use an existing soil displacement and litter input manipulation experimental in a warm temperate Quercus aliena var.acuteserrata forest in Baotianman,Henan province.The seasonal dynamics of soil nitrogen mineralization was measured by resin-core technique and the physicochemical and biological factors that affect the nitrogen mineralization process were also studied.The study tried to answer two questions:(1)what would be the effects of surface litter and roots as well as the interaction between the two on soil nitrogen mineralization?and(2)what would be the main driving factors of soil nitrogen mineralization in the Q.aliena var.acuteserrata forest?The main findings are summarized below:(1)Soil pH,microbial biomass nitrogen,microbial biomass C:N ratio,microbial activity,and the activities of ?-glucosidase,N-acetyl-?-glucosidase,and protease all varied significantly with sampling time(P<0.001).Litter and roots had significant interactive effects on soil pH and protease activity(P<0.05).Normal litter input effectively increased soil total nitrogen and microbial nitrogen(P<0.001),and normal root input significantly increased microbial activity(P<0.01).(2)There were significant seasonal differences in the contents of soil ammonium nitrogen(NH4+-N)and nitrate nitrogen(NO3--N)and the rate of nitrogen mineralization(P<0.01).The contents of NH4+-N and NO3--N were highest in April and June,and the nitrogen mineralization rate was greatest in the period from June through August.Litter input highly significantly increased NO3--N content(P<0.001),and roots had a significant effect on the nitrogen mineralization rate.(3)The nitrogen mineralization rate in the original forest soil had significant negative correlations with the soil water content and ?-glucosidase actrivity,and significant positive correlations with soil pH,organic carbon,total nitrogen,microbial nitrogen,microbial activity,and activities of N-acetyl-?-glucosidase and protease(P<0.05).The soil nitrogen mineralization rate had a significant negative correlation with the ratio of microbial carbon to nitrogen,and significant positive correlations with soil moisture,pH,total nitrogen,microbial nitrogen,and N-acetyl-?-glucosidase(P<0.05).In summary,the litter input increased the content of NH4+-N,and roots facilated nitrogen fixation.The nitrogen mineralization rate was mainly influenced by physicochemical factors including soil moisture,pH,organic carbon,and total nitrogen,and biotic factors including microbial biomass nitrogen,microbial biomass C:N ratio,microbial activity,and activities of N-acetyl-beta-glucosidase and protease.