Journal
SOIL BIOLOGY & BIOCHEMISTRY
Volume 48, Issue -, Pages 51-59Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2012.01.012
Keywords
N saturation; N uptake; N/P relationships; P limitation and deficiency; P fertilization; Plant-microbe competition; Plant-soil interactions; Vector analysis of foliar nutrients
Categories
Funding
- Junta de Andalucia [PP06-RNM-02183, Egmasa-NET313926]
- FEDER-U.E.
- University of Jaen
- CEH Bangor
- Natural Environment Research Council [ceh010023] Funding Source: researchfish
Ask authors/readers for more resources
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 a N-15 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. Overall N-15 recovery from the litter, 0-15-cm soil and root-uptake components was ca. 35% higher in P-fertilized than in non-fertilized plots at both elevations. In non-fertilized plots, soil was the biggest sink for added N-15. 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 total N-15 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. (C) 2012 Elsevier Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available