Comparison of the impacts of acid and nitrogen additions on carbon fluxes in European conifer and broadleaf forests

Oulehle, Filip; Tahovská, Karolina; Chuman, Tomáš; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X; Hruška, Jakub; Růžek, Michal; Bárta, Jiří. 2018 Comparison of the impacts of acid and nitrogen additions on carbon fluxes in European conifer and broadleaf forests. Environmental Pollution, 238. 884-893. 10.1016/j.envpol.2018.03.081

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Official URL: http://dx.doi.org/10.1016/j.envpol.2018.03.081

Abstract/Summary

Increased reactive nitrogen (N) loadings to terrestrial ecosystems are believed to have positive effects on ecosystem carbon (C) sequestration. Global “hot spots” of N deposition are often associated with currently or formerly high deposition of sulphur (S); C fluxes in these regions might therefore not be responding solely to N loading, and could be undergoing transient change as S inputs change. In a four-year, two-forest stand (mature Norway spruce and European beech) replicated field experiment involving acidity manipulation (sulphuric acid addition), N addition (NH4NO3) and combined treatments, we tested the extent to which altered soil solution acidity or/and soil N availability affected the concentration of soil dissolved organic carbon (DOC), soil respiration (Rs), microbial community characteristics (respiration, biomass, fungi and bacteria abundances) and enzyme activity. We demonstrated a large and consistent suppression of soil water DOC concentration driven by chemical changes associated with increased hydrogen ion concentrations under acid treatments, independent of forest type. Soil respiration was suppressed by sulphuric acid addition in the spruce forest, accompanied by reduced microbial biomass, increased fungal:bacterial ratios and increased C to N enzyme ratios. We did not observe equivalent effects of sulphuric acid treatments on Rs in the beech forest, where microbial activity appeared to be more tightly linked to N acquisition. The only changes in C cycling following N addition were increased C to N enzyme ratios, with no impact on C fluxes (either Rs or DOC). We conclude that C accumulation previously attributed solely to N deposition could be partly attributable to their simultaneous acidification.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.envpol.2018.03.081
UKCEH and CEH Sections/Science Areas:	Soils and Land Use (Science Area 2017-)
ISSN:	0269-7491
Additional Keywords:	nitrogen, fertilization, acidity, sulphur, organic carbon, respiration, DOC, hydrolytic enzymes, fungi, bacteria
NORA Subject Terms:	Ecology and Environment
Date made live:	11 May 2018 09:50 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/520024

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.envpol.2018.03.081

UKCEH and CEH Sections/Science Areas:

Soils and Land Use (Science Area 2017-)

ISSN:

0269-7491

Additional Keywords:

nitrogen, fertilization, acidity, sulphur, organic carbon, respiration, DOC, hydrolytic enzymes, fungi, bacteria

NORA Subject Terms:

Ecology and Environment