An in situ 15N labeling experiment unveils distinct responses to N application approaches in a mountain beech forest.

Autor:	Da Ros L; Faculty of Agricultural, Environmental and Food Sciences, Free University of Bolzano/Bozen, Piazza Università 1, 39100 Bolzano, BZ, Italy., Rodeghiero M; Agriculture Food Environment Centre (C3A), University of Trento, 38010 San Michele all'Adige, TN, Italy., Ventura M; Faculty of Agricultural, Environmental and Food Sciences, Free University of Bolzano/Bozen, Piazza Università 1, 39100 Bolzano, BZ, Italy., Tognetti R; Faculty of Agricultural, Environmental and Food Sciences, Free University of Bolzano/Bozen, Piazza Università 1, 39100 Bolzano, BZ, Italy., Tonon G; Faculty of Agricultural, Environmental and Food Sciences, Free University of Bolzano/Bozen, Piazza Università 1, 39100 Bolzano, BZ, Italy., Gianelle D; Research and Innovation Centre, Fondazione Edmund Mach, 38010 San Michele all'Adige, TN, Italy.
Jazyk:	angličtina
Zdroj:	Tree physiology [Tree Physiol] 2024 Sep 03; Vol. 44 (9).
DOI:	10.1093/treephys/tpae104
Abstrakt:	Atmospheric nitrogen (N) deposition has notably increased since the industrial revolution, doubling N inputs to terrestrial ecosystems. This could mitigate N limitations in forests, potentially enhancing productivity and carbon sequestration. However, excessive N can lead to forest N saturation, causing issues like soil acidification, nutrient imbalances, biodiversity loss, increased tree mortality and a potential net greenhouse gas emission. Traditional experiments often overlook the canopy's role in N fate, focusing instead on direct N addition to the forest floor. In our study, we applied 20 kg N ha y-1 of labeled 15NH415NO3 solution (δ15N = 30‰) both above and below the canopy, maintaining also control plots. We assessed ecosystem components before and after treatment, calculated N stocks, and used mass balance for fertilizer recovery analysis. Findings revealed that the above-canopy N addition intercepted up to 31 ± 4% of added N in foliage, a significant contrast to the negligible recovery in leaves with below-canopy treatment. Overall plant recovery was higher in the above-canopy treatment (43 ± 11%) compared with below (9 ± 24%). Post-vegetative season, about 15 ± 1% of above-canopy added N was transferred to soil via litterfall, indicating substantial N reabsorption or loss through volatilization, stemflow or throughfall. In contrast, the below-canopy approach resulted in just 4.0 ± 0.6% recovery via litterfall. These results highlight a significant difference in N fate based on the application method. Nitrogen applied to the canopy showed distinct recovery in transient compartments like foliage. However, over a few months, there was no noticeable change in N recovery in long-lived tissues across treatments. This implies that N application strategy does not significantly alter the distribution of simulated wet N deposition in high Carbon/N tissues, underscoring the complex dynamics of forest N cycling. (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)
Databáze:	MEDLINE
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