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大气氮沉降不仅含有无机态氮,还含有大量有机态氮,然而目前大部分研究主要关注无机态氮沉降对土壤有机碳(SOC)矿化的影响,对于有机态氮沉降的影响关注甚少。为更全面地了解大气氮沉降对SOC矿化的影响,我们在温带落叶松(Larix gmelinii)人工林长期氮沉降试验样地中采集了对照(CK)、无机氮(IN)、有机氮(ON)及无机氮有机氮混施(IN∶ON=7∶3;MN)4种不同氮沉降处理的表层土壤(0~10 cm),然后进行室内恒温(25℃)培养62 d,测定SOC矿化速率。同时,为了研究氮沉降背景下土壤线虫在SOC矿化中的作用,我们将每个氮沉降处理的土壤分为2组,分别添加或不添加线虫抑制剂。结果显示:与CK处理相比,IN、ON及MN处理均显著降低了SOC矿化速率,其SOC累积矿化量分别降低了15.7%、23.9%和34.3%,表明无机有机氮混施处理对SOC矿化的抑制作用大于无机氮沉降和有机氮沉降。因此,单一形态的氮沉降模拟研究可能低估了大气氮沉降对SOC矿化的抑制作用。另外,添加线虫抑制剂促进了SOC矿化,且添加线虫抑制剂在IN、ON和MN处理中对SOC累积矿化量影响的效应值较CK处理分别增加了0.08%、42.40%和29.0%,该结果表明,土壤线虫对SOC矿化的影响与氮沉降形态有关。相关性分析结果显示,SOC累积矿化量与土壤C∶N、有效磷含量及真菌∶细菌呈显著正相关,与土壤硝态氮含量和革兰氏阳性细菌∶革兰氏阴性细菌比呈显著负相关。因此,在全球变化背景下,氮沉降的增加有利于降低温带森林生态系统土壤碳释放。
However, most of the current researches mainly focus on the influence of inorganic nitrogen deposition on soil organic carbon (SOC) mineralization, and pay little attention to the influence of organic nitrogen deposition. To understand more about the effect of atmospheric nitrogen deposition on SOC mineralization, we collected CK, IN, and N (ON) in long-term nitrogen deposition in Larix gmelinii plantation. ) And inorganic nitrogen (IN:ON = 7: 3; MN) were used to culture the topsoil (0-10 cm) Rate. In the meantime, in order to study the role of soil nematodes in SOC mineralization in the context of nitrogen deposition, we divided each soil for nitrogen deposition into two groups with or without addition of nematode inhibitors. The results showed that compared with CK, both IN, ON and MN treatments significantly reduced the SOC mineralization rate, and the SOC mineralization decreased by 15.7%, 23.9% and 34.3%, respectively, indicating that the combination of inorganic N The inhibition of SOC mineralization is greater than inorganic nitrogen deposition and organic nitrogen deposition. Therefore, a single form of N deposition simulation may underestimate the inhibitory effect of atmospheric N deposition on SOC mineralization. In addition, addition of nematode inhibitors promoted SOC mineralization, and effects of additive nematode inhibitors on SOC accumulation mineralization in IN, ON and MN treatments increased by 0.08%, 42.40% and 29.0%, respectively, compared with CK treatment, The results showed that soil nematodes affected the mineralization of SOC and the morphology of nitrogen deposition. Correlation analysis showed that cumulative mineralization amount of SOC was positively correlated with soil C: N, available phosphorus and fungi: bacteria, and soil nitrate nitrogen content and Gram-positive bacteria: Gram-negative bacteria ratio Negative correlation. Therefore, under the background of global change, the increase of nitrogen deposition is beneficial to reduce the soil carbon emission in temperate forest ecosystems.