Comparison of the carbon, water, and energy balances of mature stand and clear-fell stages in a British Sitka spruce forest and the impact of the 2018 drought

•Clear-felling an upland Sitka spruce resulted in a strong annual CO2 emission.•The magnitude of the CO2 source was similar to the sink of a mature stand.•Two years after replanting the clear-fell was a weak source.•Drought in 2018 reduced net CO2 uptake of the mature stand by 30%.•Drought turned the clear-fell into a CO2 source due to increase in respiration.