Enhanced understory carbon flux components and robustness of net CO2 exchange after thinning in a larch forest in central Japan

•Influence of thinning on understory flux components was assessed comprehensively.•Twelve-year long-term monitoring data were used for the assessment.•Thinning increased understory light intensity, soil temperature, and soil moisture.•Increased understory respiration was offset by increased photosynthesis.•Net understory CO2 exchange was relatively robust compared with each flux component.