title: Elevational Variation in Soil Amino Acid and Inorganic Nitrogen Concentrations in Taibai Mountain, China.
abstract: Amino acids are important sources of soil organic nitrogen (N), which is essential for plant nutrition, but detailed information about which amino acids predominant and whether amino acid composition varies with elevation is lacking. In this study, we hypothesized that the concentrations of amino acids in soil would increase and their composition would vary along the elevational gradient of Taibai Mountain, as plant-derived organic matter accumulated and N mineralization and microbial immobilization of amino acids slowed with reduced soil temperature. Results showed that the concentrations of soil extractable total N, extractable organic N and amino acids significantly increased with elevation due to the accumulation of soil organic matter and the greater N content. Soil extractable organic N concentration was significantly greater than that of the extractable inorganic N (NO3--N + NH4+-N). On average, soil adsorbed amino acid concentration was approximately 5-fold greater than that of the free amino acids, which indicates that adsorbed amino acids extracted with the strong salt solution likely represent a potential source for the replenishment of free amino acids. We found no appreciable evidence to suggest that amino acids with simple molecular structure were dominant at low elevations, whereas amino acids with high molecular weight and complex aromatic structure dominated the high elevations. Across the elevational gradient, the amino acid pool was dominated by alanine, aspartic acid, glycine, glutamic acid, histidine, serine and threonine. These seven amino acids accounted for approximately 68.9% of the total hydrolyzable amino acid pool. The proportions of isoleucine, tyrosine and methionine varied with elevation, while soil major amino acid composition (including alanine, arginine, aspartic acid, glycine, histidine, leucine, phenylalanine, serine, threonine and valine) did not vary appreciably with elevation (p>0.10). The compositional similarity of many amino acids across the elevational gradient suggests that soil amino acids likely originate from a common source or through similar biochemical processes.
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China.
authors.forename: Xiaochuang
authors.identifier: http://orcid.org/0000-0002-9459-5919
authors.initials: X
authors.lastname: Cao
authors.affiliation: Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058 China.
authors.forename: Qingxu
authors.initials: Q
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China.
authors.forename: Chu
authors.initials: C
authors.lastname: Zhong
authors.affiliation: Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058 China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China.
authors.forename: Lianfeng
authors.initials: L
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China.
authors.forename: Junhua
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, 310006 China.
authors.forename: Qianyu
authors.initials: Q
authors.lastname: Jin
authors.affiliation: Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058 China.
authors.forename: Lianghuan
authors.initials: L
authors.lastname: Wu
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D002681:China; D017753:Ecosystem; D004777:Environment; D006868:Hydrolysis; D009584:Nitrogen / Q000032:analysis*; D012987:Soil / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D012987:Soil; D009584:Nitrogen