Premium
The legacy of enhanced N and S deposition as revealed by the combined analysis of δ 13 C, δ 18 O and δ 15 N in tree rings
Author(s) -
GUERRIERI R.,
MENCUCCINI M.,
SHEPPARD L. J.,
SAURER M.,
PERKS M.P.,
LEVY P.,
SUTTON M. A.,
BORGHETTI M.,
GRACE J.
Publication year - 2011
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2010.02362.x
Subject(s) - canopy , nitrogen , nutrient , δ13c , stomatal conductance , δ18o , environmental science , deposition (geology) , cycling , ecosystem , agronomy , chemistry , botany , biology , stable isotope ratio , ecology , forestry , photosynthesis , paleontology , physics , organic chemistry , quantum mechanics , sediment , geography
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 δ 13 C and δ 18 O in tree rings to evaluate the changes in CO 2 assimilation ( A ) and stomatal conductance ( g s ) and to assess their contribution to variations in the intrinsic water‐use efficiency (WUE i , i.e., the A / g s ratio). Measurements of δ 15 N 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 g s 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 WUE i 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) δ 15 N 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 WUE i 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 δ 15 N 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.