College of Agronomy, Northwest A&F University, Yangling, 712100 Shaanxi, China.
The Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling 712100 Shaanxi, China.
Sci Rep. 2016 Jun 23;6:28469. doi: 10.1038/srep28469.
In the present paper, we investigated the effects of afforestation on nitrogen fractions and microbial communities. A total of 24 soil samples were collected from farmland (FL) and three afforested lands, namely Robinia pseudoacacia L (RP), Caragana korshinskii Kom (CK), and abandoned land (AL), which have been arable for the past 40 years. Quantitative PCR and Illumina sequencing of 16S rRNA genes were used to analyze soil bacterial abundance, diversity, and composition. Additionally, soil nitrogen (N) stocks and fractions were estimated. The results showed that soil N stock, N fractions, and bacterial abundance and diversity increased following afforestation. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla of soil bacterial compositions. Overall, soil bacterial compositions generally changed from Actinobacteria (Acidobacteria)-dominant to Proteobacteria-dominant following afforestation. Soil N fractions, especially for dissolved organic nitrogen (DON), were significantly correlated with most bacterial groups and bacterial diversity, while potential competitive interactions between Proteobacteria (order Rhizobiales) and Cyanobacteria were suggested. In contrast, nitrate nitrogen (NO3(-)-N) influenced soil bacterial compositions less than other N fractions. Therefore, the present study demonstrated that bacterial diversity and specific species respond to farmland-to-forest conversion and hence have the potential to affect N dynamic processes in the Loess Plateau.
在本研究中，我们调查了造林对氮素形态和微生物群落的影响。共采集了 24 个土壤样本，分别来自农田（FL）和三种人工林，即刺槐（RP）、柠条（CK）和撂荒地（AL），这些林地已经耕种了 40 年。采用定量 PCR 和 Illumina 测序 16S rRNA 基因分析土壤细菌丰度、多样性和组成。此外，还估算了土壤氮储量和氮素形态。结果表明，造林后土壤氮储量、氮素形态、细菌丰度和多样性增加。变形菌门、酸杆菌门和放线菌门是土壤细菌组成的主要门。总的来说，土壤细菌组成通常从放线菌门（酸杆菌门）优势演变为变形菌门优势。土壤氮素形态，特别是溶解有机氮（DON），与大多数细菌类群和细菌多样性显著相关，而变形菌门（根瘤菌目）和蓝细菌之间可能存在潜在的竞争相互作用。相比之下，硝态氮（NO3--N）对土壤细菌组成的影响小于其他氮素形态。因此，本研究表明，细菌多样性和特定物种对农田向森林的转化有响应，因此有可能影响黄土高原的氮动态过程。
