冻融季帽儿山森林改变有机碳输入方式对土壤活性氮含量的影响

根系与凋落物有机碳输入变化对土壤碳氮循环的影响已成为当前学界关注的热点，但冻融季不同有机碳输入方式将对土壤活性氮含量产生何种影响尚不明确。为此在春季具有明显冻融作用的温带森林设立凋落物去除、根系去除处理以代表仅根系有机碳输入方式、仅凋落物有机碳输入方式，并设置自然条件有机碳输入方式即保留根系及凋落物作为对照，多角度探究土壤微生物量氮、矿质氮动态变化。结果表明：(1)有机碳输入方式对土壤活性氮含量有重要影响：与自然条件下有机碳输入方式相比，仅根系输入处理使土壤微生物氮、总矿质氮含量升高10.5%、12.3%。(2)输入时长改变了有机碳输入方式对土壤活性氮含量的作用效果：长期单一有机碳输入使土壤微生物量氮含量下降，反应率值为0.451、0.422。(3)季节差异是影响有机碳输入方式对土壤活性氮含量作用效果的关键因素：仅根系有机碳输入在冻融季使总矿质氮含量上升，反应率值为0.404,生长季相反，呈下降趋势，其值为0.121。以上结果表明，有机碳输入方式对土壤活性氮含量有重要调控作用，且作用效果会受季节、输入时长等因素影响。

Effects of changing organic carbon input methods on soil reactive nitrogen content in the Maoershan forest during the freeze-thaw season

The effect of changes in organic carbon input from aboveground litter and belowground roots on soil active nitrogen content is currently a topical issue in academia. However, it is unclear about the influence of organic carbon input methods on soil active nitrogen content during the freeze-thaw season. The root-only organic carbon input treatment (litter removal) and the litter-only organic carbon input treatment (root removal) were measured, the root and litter retention treatment was a control group. This study investigated the dynamics of soil microbial and mineral nitrogen content. The results show that: (1) the mode of organic carbon input has a significant effect on the soil active nitrogen content. Soil microbial biomass nitrogen content in the root-only organic carbon input method and total mineral nitrogen in the root-only organic carbon input method are 10.5% and 12.3% higher than those in the control treatment, respectively. (2)The duration of input changes the effect of the organic carbon input method on the soil active nitrogen content: the long-term root-only and litter-only organic carbon input treatments decrease the soil microbial biomass nitrogen content, and the response rates are 0.451 and 0.422, respectively. (3) The seasonal difference is a key factor influencing the effect of organic carbon input methods on soil active nitrogen content: the litter removal during the freeze-thaw season increases the total mineral nitrogen content, while litter removal during the growing season decreases the total mineral nitrogen content, and the response rates are 0.404 and 0.121, respectively. The results highlight the importance and regulation of organic carbon inputs on soil active nitrogen content, which varies with the season and the input duration of the treatment.