title: Effects of pre-treatment on the nitrogen isotope composition of Japanese black pine (Pinus thunbergii) tree-rings as affected by high N input.
abstract: Temporal changes in the acquisition of nitrogen (N) are recorded in tree-rings together with unique N isotopic values. Some debate continues regarding the importance of wood pre-treatment in isotope analysis and, thus, this study focuses on the removal of labile components to determine the intrinsic nature of N in tree-rings. The total concentration and stable isotopic value of N in annual tree-rings were determined for two cores from Japanese black pine (Pinus thunbergii) from areas colonized by black cormorant (Phalacrocorax carbo). One core sample was also collected from a control site, without cormorants. Sharp increases in tree-ring δ(15)N values associated with migration of the cormorant population indicate positive incorporation of N from soils, whereas a less pronounced trend was observed for ring samples for periods without or substantially less migration, and for those obtained from the control site. All labile N components were removed by repeated extraction with toluene/ethanol (1:1) solution. Radial translocation of labile N is limited in tree-rings from Japanese black pine, providing intrinsic records on N acquisition. The difference in N isotopic values (up to 7.0‰) following pre-treatment was statistically significant for trees affected by the avian colony, whereas the pre-treatment of the control samples did not influence N values. The implication is that in agreement with previous studies pre-treatment is not necessary when trees are exposed to natural N concentrations in the soil but the removal of enriched δ(15)N labile components is necessary when woody plants are exposed to unusually high inputs of N into soils. However, the temporal trend in tree-ring δ(15)N series of the avian N affected trees did not change. Thus, if the priority is not the value but the trend then pre-treatment is not necessary.
authors: Faculty of Agriculture, Yamagata University, Wakabamachi 1-26, Tsuruoka 997-8555, Japan. larry@tds1.tr.yamagata-u.ac.jp
authors: M Larry Lopez
authors: ML
authors: Caceres
authors: Chitoshi
authors: C
authors: Mizota
authors: Toshiro
authors: T
authors: Yamanaka
authors: Yoshihiro
authors: Y
authors: Nobori
mesh_terms: D025041:Animal Migration; D000818:Animals; D001717:Birds; D007564:Japan; D013058:Mass Spectrometry; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis*; D028223:Pinus / Q000737:chemistry* / Q000378:metabolism; D012987:Soil; D014934:Wood / Q000737:chemistry*
chemical_list: D009587:Nitrogen Isotopes; D012987:Soil; D009584:Nitrogen