title: Responsiveness of soil nitrogen fractions and bacterial communities to afforestation in the Loess Hilly Region (LHR) of China.
abstract: 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.
authors.affiliation: 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.
authors.forename: Chengjie
authors.initials: C
authors.lastname: Ren
authors.affiliation: 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.
authors.forename: Pingsheng
authors.initials: P
authors.lastname: Sun
authors.affiliation: The Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling 712100 Shaanxi, China.
authors.forename: Di
authors.initials: D
authors.lastname: Kang
authors.forename: Fazhu
authors.initials: F
authors.lastname: Zhao
authors.affiliation: 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.
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Feng
authors.affiliation: 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.
authors.forename: Guangxin
authors.initials: G
authors.lastname: Ren
authors.affiliation: 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.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Han
authors.affiliation: 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.
authors.forename: Gaihe
authors.initials: G
authors.lastname: Yang
mesh_terms: D001419:Bacteria / Q000235:genetics*; D002681:China; D065928:Forests; D009584:Nitrogen / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D031301:Robinia / Q000378:metabolism / Q000382:microbiology; D012987:Soil; D012988:Soil Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; D012987:Soil; D009584:Nitrogen