Nitrogen cycle
Nitrogen deposition is slowing forest respiration
Open access · cc by · source: Europe PMC
At Loobos, TER fell while GPP rose over 26 years; acid soils (pH 2.9) and N deposition appear to throttle decomposition.
Key findings
TER fell from 1350 to 1015 g C m−2 year−1 (1997–2021) while GPP rose from 1567 to 1904. Soil respiration is ~69% of TER. The organic layer doubled in mass (about 4.7 to 9.4 kg C m−2). R10 declined (36% implied TER drop); soil warmed 1.25°C. Incubations showed an active but pH-inhibited microbiome (pH 2.9). N deposition was 38 kg N ha−1 year−1 in 1990 and 21 in 2023.
Methodology
Authors analyzed 1997–2021 eddy-covariance fluxes at the Loobos Scots pine site in the Netherlands, compared other long FLUXNET forests, inventoried the organic layer, and incubated acidic topsoil with glucose and lime to test substrate and pH limits on CO2 release.
Limitations
A second, taller tower after 2021 raised TER estimates, so some instrumental contribution cannot be ruled out. 2024 C and N analyses were incomplete. There is no continuous soil-pH time series. NEE sustainability remains an open ecosystem-health question.
How this study connects
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At Loobos, TER fell while GPP rose over 26 years; acid soils (pH 2.9) and N deposition appear to throttle decomposition.
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