Abstract Plants play a critical role in the carbon cycle by driving carbon uptake and release through photosynthesis and respiration, with dominant species exerting large control over these fluxes. Invasive plants can disrupt carbon cycling because of their high biomass and rapid growth, yet their influence across a growing season remains unclear. Many studies show that invasive species exhibit greater phenological plasticity than native species, which can enhance their competitive ability. Under warming, this phenological plasticity may allow invasive species to better track resource availability and capitalize on longer growing seasons, potentially disadvantaging native communities. To test how warming and an invasive species interact to alter carbon dynamics, we measured plant biomass, net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (ER) three times over the growing season in a Calluna vulgaris ‐invaded alpine community in New Zealand. We removed C. vulgaris and increased temperatures using open‐top chambers in a factorial design. With the removal of C. vulgaris, we found significantly lower community plant biomass and weakened ecosystem carbon sink strength due to lower GPP across the growing season. These responses reflect the removal of C. vulgaris itself rather than a general reduction in biomass, as biomass‐corrected NEE showed the same patterns. Surprisingly, warming increased GPP in native‐only plots, but not in C. vulgaris‐invaded plots. C. vulgaris had the strongest effects on carbon fluxes early in the season, with influence diminishing later in the season. This seasonal shift aligns with C. vulgaris phenology, as late‐season measurements coincided with peak flowering, a period likely characterized by reduced photosynthetic investment. Overall, removal of C. vulgaris decreased plot‐level biomass and productivity, while warming more strongly enhanced carbon uptake in native rather than in invaded plant communities. These findings indicate that invasive species can exert an outsized influence on ecosystem carbon dynamics, independent of warming, and these effects vary seasonally. As biological invasions and climate warming intensify, resolving their interactive and time‐dependent impacts on carbon cycling will be important for improving ecosystem and carbon models. Read the free Plain Language Summary for this article on the Journal blog.
Vought et al. (Thu,) studied this question.