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Interactive effects of elevated CO 2 and nitrogen deposition on fatty acid molecular and isotope composition of above‐ and belowground tree biomass and forest soil fractions
Author(s) -
Griepentrog Marco,
Eglinton Timothy I.,
Hagedorn Frank,
Schmidt Michael W. I.,
Wiesenberg Guido L. B.
Publication year - 2015
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.12666
Subject(s) - soil water , chemistry , deposition (geology) , environmental chemistry , nitrogen , beech , soil organic matter , biomass (ecology) , organic matter , soil carbon , composition (language) , botany , agronomy , biology , ecology , paleontology , linguistics , philosophy , organic chemistry , sediment
Atmospheric carbon dioxide ( CO 2 ) and reactive nitrogen (N) concentrations have been increasing due to human activities and impact the global carbon (C) cycle by affecting plant photosynthesis and decomposition processes in soil. Large amounts of C are stored in plants and soils, but the mechanisms behind the stabilization of plant‐ and microbial‐derived organic matter ( OM ) in soils are still under debate and it is not clear how N deposition affects soil OM dynamics. Here, we studied the effects of 4 years of elevated ( 13 C‐depleted) CO 2 and N deposition in forest ecosystems established in open‐top chambers on composition and turnover of fatty acids ( FA s) in plants and soils. FA s served as biomarkers for plant‐ and microbial‐derived OM in soil density fractions. We analyzed above‐ and belowground plant biomass of beech and spruce trees as well as soil density fractions for the total organic C and FA molecular and isotope ( δ 13 C) composition. FA s did not accumulate relative to total organic C in fine mineral fractions, showing that FA s are not effectively stabilized by association with soil minerals. The δ 13 C values of FA s in plant biomass increased under high N deposition. However, the N effect was only apparent under elevated CO 2 suggesting a N limitation of the system. In soil fractions, only isotope compositions of short‐chain FA s (C 16+18 ) were affected. Fractions of ‘new’ (experimental‐derived) FA s were calculated using isotope depletion in elevated CO 2 plots and decreased from free light to fine mineral fractions. ‘New’ FA s were higher in short‐chain compared to long‐chain FA s (C 20−30 ), indicating a faster turnover of short‐chain compared to long‐chain FA s. Increased N deposition did not significantly affect the quantity of ‘new’ FA s in soil fractions, but showed a tendency of increased amounts of ‘old’ (pre‐experimental) C suggesting that decomposition of ‘old’ C is retarded by high N inputs.