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On the tracks of Nitrogen deposition effects on temperate forests at their southern European range – an observational study from Italy
Author(s) -
Ferretti Marco,
Marchetto Aldo,
Arisci Silvia,
Bussotti Filippo,
Calderisi Marco,
Carnicelli Stefano,
Cecchini Guia,
Fabbio Gianfranco,
Bertini Giada,
Matteucci Giorgio,
Cinti Bruno,
Salvati Luca,
Pompei Enrico
Publication year - 2014
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/gcb.12552
Subject(s) - throughfall , deposition (geology) , topsoil , nutrient , environmental science , nitrogen , canopy , basal area , zoology , chemistry , atmospheric sciences , environmental chemistry , soil water , soil science , botany , forestry , geography , biology , geology , paleontology , organic chemistry , sediment
We studied forest monitoring data collected at permanent plots in Italy over the period 2000–2009 to identify the possible impact of nitrogen (N) deposition on soil chemistry, tree nutrition and growth. Average N throughfall (N‐NO 3 +N‐NH 4 ) ranged between 4 and 29 kg ha −1 yr −1 , with Critical Loads (CLs) for nutrient N exceeded at several sites. Evidence is consistent in pointing out effects of N deposition on soil and tree nutrition: topsoil exchangeable base cations (BCE) and pH decreased with increasing N deposition, and foliar nutrient N ratios (especially N : P and N : K) increased. Comparison between bulk openfield and throughfall data suggested possible canopy uptake of N , levelling out for bulk deposition >4–6 kg ha −1 yr −1 . Partial Least Square (PLS) regression revealed that ‐ although stand and meteorological variables explained the largest portion of variance in relative basal area increment (BAI rel 2000–2009) ‐ N‐related predictors (topsoil BCE, C : N, pH ; foliar N‐ratios; N deposition) nearly always improved the BAI rel model in terms of variance explained (from 78.2 to 93.5%) and error (from 2.98 to 1.50%). N deposition was the strongest predictor even when stand, management and atmosphere‐related variables (meteorology and tropospheric ozone) were accounted for. The maximal annual response of BAI rel was estimated at 0.074–0.085% for every additional kgN. This corresponds to an annual maximal relative increase of 0.13–0.14% of carbon sequestered in the above‐ground woody biomass for every additional kgN, i.e. a median value of 159 kgC per kgN ha −1 yr −1 (range: 50–504 kgC per kgN, depending on the site). Positive growth response occurred also at sites where signals of possible, perhaps recent N saturation were detected. This may suggest a time lag for detrimental N effects, but also that, under continuous high N input, the reported positive growth response may be not sustainable in the long‐term.