The legacy of enhanced N and S deposition as revealed by the combined analysis of 13C, 18O and 15N in tree rings

Guerrieri, R.; Mencuccini, M.; Sheppard, L.J.; Saurer, M.; Perks, M.P.; Levy, P.; Sutton, M.A.; Borghetti, M.; Grace, J.. 2011 The legacy of enhanced N and S deposition as revealed by the combined analysis of 13C, 18O and 15N in tree rings. Global Change Biology, 17 (5). 1946-1962.

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This study aimed to evaluate the effects of long-term repeated aerial nitrogen (N) and sulphur (S) misting over tree canopies of a Sitka spruce plantation in Scotland. We combined δ13C and δ18O in tree rings to evaluate the changes in CO2 assimilation (A) and stomatal conductance (gs) and to assess their contribution to variations in the intrinsic water-use efficiency (WUEi, i.e., the A/gs ratio). Measurements of δ15N enabled shifts in the ecosystem N cycling following misting to be assessed. We found that: (i) N applications, with or without S, increased the ratio between A and gs in favour of A, thus supporting a fertilizer effect of added N. (ii) After the treatments ceased, the trees quickly adjusted to the reductions of N deposition, but not to the reduction in S deposition, which had a negative effect on WUEi by reducing A. This indicates that the beneficial role of N deposition may be negated in forests that previously received a high load of acid rain. (iii) δ15N in tree rings reflected the N dynamics caused by canopy retention, with the fingerprint also present in the litter, after the experiment stopped. (iv) Both our results (obtained using canopy applications) and a collection of published data (obtained using soil applications) showed that generally WUEi increased in response to an increase of N applications, with the magnitude of the changes related to soil conditions and the availability of other nutrients. The shifts observed in δ15N in tree rings also suggest that both the quantity of the applied N and its quality, mediated by processes occurring during canopy N retention, are important determinants of the interactions between N and C cycles. Stable isotopes are useful probes to understand these processes and to put the results of short-term experiments into context.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.3 - Quantify & attribute changes in biogeochemiical cycles ...
UKCEH and CEH Sections/Science Areas: Billett (to November 2013)
ISSN: 1354-1013
Additional Keywords: acid mist, annual tree rings, CO2 assimilation, nitrogen, Sitka spruce stable C–O–N isotopes, stomatal conductance, sulphur, WUEi
NORA Subject Terms: Ecology and Environment
Date made live: 11 Apr 2011 15:03 +0 (UTC)

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