Alleviation of P limitation makes tree roots competitive for N against microbes in a N-saturated conifer forest: A test through P fertilization and15N labelling

  • Blanes M
  • Emmett B
  • Viñegla B
 et al. 
  • 52

    Readers

    Mendeley users who have this article in their library.
  • 16

    Citations

    Citations of this article.

Abstract

Chronic N deposition to forests may induce N saturation and stand decline, leading to reduced ecosystem N retention capacity, triggered by a shift from N limitation of trees to limitation by another nutrient. We conducted a15N soil labelling experiment in non-fertilized and P-fertilized plots at two elevations in an N-saturated Mediterranean-fir (Abies pinsapo) forest in southern Spain which shows P limitation symptoms. Root-exclusion was applied to identify the relative contributions of roots (plus mycorrhizal fungi) uptake, and heterotrophic immobilization by free-living microbes, to N retention. Overall15N recovery from the litter, 0-15-cm soil and root-uptake components was c.a. 35% higher in P-fertilized than in non-fertilized plots at both elevations. In non-fertilized plots, soil was the biggest sink for added15N. Phosphorus fertilization increased the competitive ability of tree roots for soil N resulting in equal importance of the autotrophic (roots plus associated mycorhizal fungi) and heterotrophic (free-living microbes) components with respect to total15N recovery in P-fertilized plots. Phosphorus addition increased litter and soil N immobilization only if roots had been excluded. By combining in situ fertilization, root-exclusion and isotope labelling we have demonstrated that reduced N retention capacity and dominance of soil microbial over plant immobilization in a N-saturated forest results from a shift from N to P limitation of trees, while alleviation of P limitation makes tree roots and associated mycorrhizal fungi competitive for N against free soil microorganisms. © 2012 Elsevier Ltd.

Author-supplied keywords

  • N saturation
  • N uptake
  • N/P relationships
  • P fertilization
  • P limitation and deficiency
  • Plant-microbe competition
  • Plant-soil interactions
  • Vector analysis of foliar nutrients

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free