title: Changes of soil bacterial activities and functions after different N additions in a temperate forest.
abstract: It has been shown that different nitrogen (N) addition led to various influences on soil microbial activities in forest ecosystems; however, the changes of bacteria were still unclear. In this work, inorganic N (NH4NO3) and organic N (urea and glycine) were fertilized with different ratios (5:0, 1:4, 3:2, 2:3, and 1:4) on temperate forest soils, while fungicide (cycloheximide) was simultaneously added on half of each treatment to inhibit fungal activities (leaving only bacteria). After a 3-year field experiment, soil samples were harvested, then microbial enzymatic activities involved in carbon (C), and N and phosphorus (P) cycles were determined. Under laboratory conditions, four purified bacteria which were isolated from sample site had been inoculated in sterilized soils under different N types and enzymatic activities were assayed after 90-day incubation. The results showed that cellulase and polyphenol oxidase activities of non-fungicide-added treatments increased after N addition and greater organic N accelerated the increases. However, these enzymatic activities of fungicide-added treatments were not significantly influenced by N addition and N types. It may be due to the insufficient ability of bacteria to synthesize enough enzymes to decompose complex organic C (such as cellulose and lignin) into available compound, although N-limitation was alleviated. Alkaline phosphatase activities increased after N addition in both non-fungicide-added and fungicide-added treatments, and the acceleration on bacterial alkaline phosphatase activities was even greater. Furthermore, organic N showed at least 2.5 times promotion on bacteria alkaline phosphatase than those of inorganic N, which indicated greater alleviation of bacterial P-limitation after the addition of organic N. All the results indicated that soil bacteria may be seriously limited by soil available C but become the dominant decomposer of the complex P compounds after N addition, particularly greater organic N.
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China. guopeng.sci@gmail.com.
authors.forename: Peng
authors.identifier: http://orcid.org/0000-0001-6262-7392
authors.initials: P
authors.lastname: Guo
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China.
authors.forename: Tiwen
authors.initials: T
authors.lastname: Han
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China.
authors.forename: Shushan
authors.initials: S
authors.lastname: Li
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China.
authors.forename: Dongzhu
authors.initials: D
authors.lastname: Ma
authors.affiliation: Hebei College of Industry and Technology, Hongqi Street 626, Shijiazhuang, 050091, China.
authors.forename: Yuhan
authors.initials: Y
authors.lastname: Du
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000378:metabolism*; D002244:Carbon / Q000032:analysis / Q000378:metabolism; D065928:Forests; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D010758:Phosphorus / Q000032:analysis / Q000378:metabolism; D012987:Soil; D012988:Soil Microbiology
chemical_list: D012987:Soil; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
keywords: Bacteria; Enzymatic activity; Forest soil; Inorganic nitrogen; Nitrogen deposition; Organic nitrogen