Decomposition nitrogen is better retained than simulated deposition from mineral amendments in a temperate forest.

Autor: Nair RK; School of Geosciences, University of Edinburgh, Crew Building, Edinburgh, EH9 3FF, Midlothian, UK., Perks MP; Forest Research, Northern Research Station, Roslin, EH25 9SY, Midlothian, UK., Mencuccini M; School of Geosciences, University of Edinburgh, Crew Building, Edinburgh, EH9 3FF, Midlothian, UK.; ICREA at CREAF, Campus de UAB, Cerdanyola del Vallés, Bellaterra, Barcelona, Spain.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2017 Apr; Vol. 23 (4), pp. 1711-1724. Date of Electronic Publication: 2016 Aug 23.
DOI: 10.1111/gcb.13450
Abstrakt: Nitrogen (N) deposition (N DEP ) drives forest carbon (C) sequestration but the size of this effect is still uncertain. In the field, an estimate of these effects can be obtained by applying mineral N fertilizers over the soil or forest canopy. A 15 N label in the fertilizer can be then used to trace the movement of the added N into ecosystem pools and deduce a C effect. However, N recycling via litter decomposition provides most of the nutrition for trees, even under heavy N DEP inputs. If this recycled litter nitrogen is retained in ecosystem pools differently to added mineral N, then estimates of the effects of N DEP on the relative change in C (∆C/∆N) based on short-term isotope-labelled mineral fertilizer additions should be questioned. We used 15 N labelled litter to track decomposed N in the soil system (litter, soils, microbes, and roots) over 18 months in a Sitka spruce plantation and directly compared the fate of this 15 N to an equivalent amount in simulated N DEP treatments. By the end of the experiment, three times as much 15 N was retained in the O and A soil layers when N was derived from litter decomposition than from mineral N additions (60% and 20%, respectively), primarily because of increased recovery in the O layer. Roots expressed slightly more 15 N tracer from litter decomposition than from simulated mineral N DEP (7.5% and 4.5%) and compared to soil recovery, expressed proportionally more 15 N in the A layer than the O layer, potentially indicating uptake of organic N from decomposition. These results suggest effects of N DEP on forest ∆C/∆N may not be apparent from mineral 15 N tracer experiments alone. Given the importance of N recycling, an important but underestimated effect of N DEP is its influence on the rate of N release from litter.
(© 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
Externí odkaz: