The impact of warming on peak-season ecosystem carbon uptake is influenced by dominant species in warmer sites

Climatic warming affects ecosystem-scale carbon fluxes directly through
its impact on photosynthesis and respiration, and indirectly by altering
the plant community. This study reports on a 10-year factorial warming and
dominant plant species removal experiment, conducted in a high- and a
low-elevation montane meadow, to explore how dominant plants modify the
effect of warming on the carbon cycle over time and in different
locations. At the low-elevation site, warming increased peak-season net
carbon uptake in most years, primarily due to higher primary productivity.
This effect was observed only in plots where the dominant species was
present. Net ecosystem carbon uptake was generally positive, but it often
shifted from net carbon uptake to net carbon release when the dominant
species was removed, particularly in dry years. Surprisingly, the
high-elevation site showed no response to the warming or plant removal
treatments. Synthesis: These findings highlight that dominant plant
species can modify the impacts of warming on carbon fluxes. However, the
effects of warming and plant species removal on the carbon cycle vary
spatially and temporally. This study provides valuable insights into how
both abiotic and biotic factors influence ecosystem carbon cycling and
source-sink dynamics.