title: Nitrogen and phosphorus additions alter nutrient dynamics but not resorption efficiencies of Chinese fir leaves and twigs differing in age.
abstract: It is unclear how or even if phosphorus (P) input alters the influence of nitrogen (N) deposition in a forest. In theory, nutrients in leaves and twigs differing in age may show different responses to elevated nutrient input. To test this possibility, we selected Chinese fir (Cunninghamia lanceolata) for a series of N and P addition experiments using treatments of +N1 - P (50 kg N ha(-1) year(-1)), +N2 - P (100 kg N ha(-1) year(-1)), -N + P (50 kg P ha(-1) year(-1)), +N1 + P, +N2 + P and -N - P (without N and P addition). Soil samples were analyzed for mineral N and available P concentrations. Leaves and twigs in summer and their litters in winter were classified as and sorted into young and old components to measure N and P concentrations. Soil mineral N and available P increased with N and P additions, respectively. Nitrogen addition increased leaf and twig N concentrations in the second year, but not in the first year; P addition increased leaf and twig P concentrations in both years and enhanced young but not old leaf and twig N accumulations. Nitrogen and P resorption proficiencies in litters increased in response to N and P additions, but N and P resorption efficiencies were not significantly altered. Nitrogen resorption efficiency was generally higher in leaves than in twigs and in young vs old leaves and twigs. Phosphorus resorption efficiency showed a minimal variation from 26.6 to 47.0%. Therefore, P input intensified leaf and twig N enrichment with N addition, leaf and twig nutrients were both gradually resorbed with aging, and organ and age effects depended on the extent of nutrient limitation.
authors.affiliation: Collaborative Innovation Center of Jiangxi Typical Trees Cultivation and Utilization, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China chenfush@yahoo.com.
authors.forename: Fu-Sheng
authors.initials: FS
authors.lastname: Chen
authors.affiliation: Plant Biology Section, School of Integrative Plant Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Karl Joseph
authors.initials: KJ
authors.lastname: Niklas
authors.affiliation: Collaborative Innovation Center of Jiangxi Typical Trees Cultivation and Utilization, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Collaborative Innovation Center of Jiangxi Typical Trees Cultivation and Utilization, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China.
authors.forename: Xiang-Min
authors.initials: XM
authors.lastname: Fang
authors.affiliation: Collaborative Innovation Center of Jiangxi Typical Trees Cultivation and Utilization, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China.
authors.forename: Song-Ze
authors.initials: SZ
authors.lastname: Wan
authors.affiliation: Qianyanzhou Ecological Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Wang
mesh_terms: D032486:Cunninghamia / Q000378:metabolism*; D065928:Forests; D009584:Nitrogen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D012621:Seasons; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil; D010758:Phosphorus; D009584:Nitrogen
keywords: evergreen tree species; nitrogen and phosphorus interaction; nitrogen deposition; nutrient resorption; red soil region