Beyond vegetation classes toward a trait-based understanding of tundra CO2 fluxes
Chattopadhyay, G., H. Mod, M. Luoto, P. Niittynen and A.- M. Virkkala. 2026.
Abstract
Ongoing shifts in tundra vegetation are reshaping Arctic ecosystems, but their impact on carbon
exchange remains poorly captured by coarse vegetation classifications. Consequently, it remains
unclear how CO2 fluxes relate to continuous metrics describing vegetation structure. Here,
we quantified fine-scale variation in summertime ecosystem respiration (ER20), gross primary
productivity (GPP600), and net ecosystem exchange (NEE600) across a heterogeneous tundra
landscape and tested how 21 different vegetation structure and functional traits in comparison
to vegetation classes explain flux variability. CO2 fluxes, measured using chamber observations,
and vegetation and environmental parameters were collected from multiple plots (n = 211) over
multiple field campaigns (2017–2025). CO2 exchange varied widely among the plots, with
GPP600 showing greater variation than ER20 and NEE600 ranging from net CO2 uptake to minor
net CO2 release. Coarse vegetation classes captured community-level differences in CO2 exchange,
explaining 27%, 34%, and 25% of variation in ER20, GPP600, and NEE600, respectively, with
deciduous tall shrub communities showing the highest carbon uptake and respiration, while
evergreen dwarf shrubs showed the lowest fluxes. Continuous vegetation properties, however,
explained plot-level flux variation more effectively, with the best predictors (e.g. green fraction,
maximum vegetation height and leaf nitrogen) accounting for 60% of variation in ER20, 77%
of GPP600, and 56% of NEE600. Vegetation variables explained most of the flux variance, with
soil temperature and moisture adding ≤4% to marginal R². These findings highlight the
importance of continuous vegetation properties for capturing and understanding spatial variation
in plot-level CO2 exchange.
