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Fate of atmospherically deposited NH4+ and NO3− in two temperate forests in China: temporal pattern and redistribution.
- Source :
- Ecological Applications; Sep2019, Vol. 29 Issue 6, pN.PAG-N.PAG, 1p
- Publication Year :
- 2019
-
Abstract
- The impacts of anthropogenic nitrogen (N) deposition on forest ecosystems depend in large part on its fate. However, our understanding of the fates of different forms of deposited N as well as the redistribution over time within different ecosystems is limited. In this study, we used the 15N‐tracer method to investigate both the short‐term (1 week to 3 months) and long‐term (1–3 yr) fates of deposited NH4+ or NO3− by following the recovery of the 15N in different ecosystem compartments in a larch plantation forest and a mixed forest located in northeastern China. The results showed similar total ecosystem retention for deposited NH4+ and NO3−, but their distribution within the ecosystems (plants vs. soil) differed distinctly particularly in the short‐term, with higher 15NO3− recoveries in plants (while lower recoveries in organic layer) than found for 15NH4+. The different short‐term fate was likely related to the higher mobility of 15NO3− than 15NH4+ in soils instead of plant uptake preferences for NO3− over NH4+. In the long‐term, differences between N forms became less prevalent but higher recoveries in trees (particularly in the larch forest) of 15NO3− than 15NH4+ tracer persisted, suggesting that incoming NO3− may contribute more to plant biomass increment and forest carbon sequestration than incoming NH4+. Differences between the two forests in recoveries were largely driven by a higher 15N recovery in the organic layer (both N forms) and in trees (for 15NO3−) in the larch forest compared to the mixed forest. This was due to a more abundant organic layer and possibly higher tree N demand in the larch forest than in the mixed forest. Leachate 15N loss was minor (<1% of the added 15N) for both N forms and in both forests. Total 15N recovery averaged 78% in the short‐term and decreased to 55% in the long‐term but with increasing amount of 15N label (re)‐redistributed into slow turn‐over pools (e.g., trees and mineral soil). The different retention dynamics of deposited NH4+ and NO3− may have implications in environmental policy related to the anthropogenic emissions of the two N forms. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 10510761
- Volume :
- 29
- Issue :
- 6
- Database :
- Supplemental Index
- Journal :
- Ecological Applications
- Publication Type :
- Academic Journal
- Accession number :
- 138413871
- Full Text :
- https://doi.org/10.1002/eap.1920