Chemical changes in organic matter after fungal colonization in a nitrogen fertilized and unfertilized Norway spruce forest.

BACKGROUND AND AIMS: Decomposition and transformation of organic matter (OM) in forest soils are conducted by the concomitant action of saprotrophic and mycorrhizal fungi. Here, we examine chemical changes in OM after fungal colonization in nitrogen fertilized and unfertilized soils from a Norway spruce forest. METHODS: Sand-filled bags amended with composted maize leaves were placed in the forest soil and harvested after 17 months. Infrared and near edge X-ray absorption fine structure spectroscopies were used to study the chemical changes in the OM. Fungal community composition of the bags was also evaluated. RESULTS: The proportion of ectomycorrhizal fungi declined in the fertilized plots, but the overall fungal community composition was similar between N treatments. Decomposition of the OM was, independently of the N level or soil horizon, accompanied by an increase of C/N ratio of the mesh-bag content. Moreover, the proportions of carboxylic compounds in the incubated OM increased in the mineral horizon, while heterocyclic-N compounds decreased, especially in unfertilized plots with higher N demand from the trees. CONCLUSIONS: Our results indicate that more oxidized organic C and less heterocyclic-N proportions in the OM remain after fungal colonization in the mineral layers, and suggest that ectomycorrhizal fungi transfer less heterocyclic-N from the mesh bags to the host trees under high N levels.

De Sitter symmetries and inflationary scalar-vector models / Simetrías en el espacio de De Sitter y modelos inflacionarios escalar-vector / Simetrias de De Sitter e modelos inflacionarios escalar-vetors

Abstract In this paper, we study the correspondence between a field theory in de Sitter space in D-dimensions and a dual conformal field theory in a euclidean space in (D-1)-dimensions. In particular, we investigate the form in which this correspondence is established for a system of interacting scalar and a vector fields propagating in de Sitter space. We analyze some necessary (but not sufficient) conditions for which conformal symmetry is preserved in the dual theory in (D - 1)-dimensions, making possible the establishment of the correspondence. The discussion that we address in this paper is framed on the context of inflationary cosmology. Thusly, the results obtained here pose some relevant possibilities of application to the calculation of the fields's correlation functions and of the primordial curvature perturbation Z, in inflationary models including coupled scalar and vector fields.

Resumen En este artículo se estudia la correspondencia entre una teoría de campos en el espacio de De Sitter en D-dimensiones y una teoría dual conforme en un espacio euclidiano en (D - 1)-dimensiones. En particular, se investiga la forma en la que se establece esta correspondencia para un sistema compuesto por un campo escalar y un campo vectorial acoplados propagándose en el espacio de De Sitter. Se analizan algunas condiciones necesarias (pero no suficientes) en las cuales la simetría conforme se preserva en la teoría dual en (D - 1)-dimensiones y hace posible el establecimiento de la correspondencia. La discusión presentada aquí se enmarca en el contexto de la cosmología inflacionaria, así que los resultados obtenidos plantean algunas posibilidades relevantes de aplicación en el cálculo de funciones de correlación de los campos y de la perturbación de ¡a curvatura primordial Z en modelos inflacionarios que incluyen campos escalares y vectoriales acoplados.

Resumen Neste artigo, é estudada a correspondencia entre uma teoria de campos no espaço de De Sitter em D-dimensões e uma teoria dual conforme num espaço euclidiano em (D - 1)-dimensões. Em particular, é pesquisado o caminho no qual se estabelece esta correspondência para um sistema de interação composto dum campo escalar e um vetorial, propagando-se no espaço de De Sitter. São analisadas algumas condições necessárias (mas não suficientes) para as quais a simetria conforme é preservada na teoria dual em (D-l)-dimensões, fazendo viável o estabelecimento da correspondência. A discussão apresentada aqui, está situada no contexto da cosmologia inflacionária. Portanto, os resultados obtidos representam algumas possibilidades relevantes para sua aplicacão no cálculo de funções de correlação dos campos e da perturbação da curvatura primordial Ç em modelos inflacionários incluindo campos acoplados escalares e vetoriais.