Harvest shifts carbon–water dynamics and environmental controls in a managed loblolly pine plantation in the southeast United States

How carbon–water coupling reorganizes across stand development and harvest in managed plantations remains poorly quantified. We used 20 years (2005–2024) of eddy covariance measurements at a loblolly pine ( Pinus taeda L.) plantation (US-NC2, North Carolina, United States) to quantify carbon and water flux dynamics across three stand development stages spanning pre- and post-harvest periods. The harvest in 2019 triggered an abrupt sink-to-source transition (annual NEE in 2020: +991 g C m −2 yr −1 ), driven by asymmetric declines in GPP (88%) and RE (33%). Concurrently, evapotranspiration declined while residual drainage increased, consistent with a shift of water toward drainage. Flux–driver relationships reorganized following harvest, with radiation and leaf area index losing explanatory power for GPP and the leading predictor of net ecosystem exchange shifting from radiation to air temperature. Despite this disruption, NEE declined by 89% within 5 years, approaching but not yet reaching carbon neutrality by 2024. These findings demonstrate that carbon and water fluxes co-evolve via asymmetric harvest responses and reorganization of environmental driver hierarchies, informing carbon accounting and water-resource management in managed pine plantations.