Different responses of stem and soil CO₂ efflux to pruning in a Chinese fir (Cunninghamia lanceolata) plantation

Key message: Pruning significantly reduced stem CO₂efflux, but had little effect on soil CO₂efflux and root respiration.Pruning did not alter temperature sensitivity of CO₂efflux from stem and soil. Abstract: Pruning is one of the common silvicultural practices for Chinese fir (Cunninghamia lanceolata) plantations to produce knot-free wood. However, little is known about the effects of pruning on stem and soil CO₂ efflux in Chinese fir plantations. In this study, we experimentally manipulated the canopy of Chinese fir by pruning the lower 50 % of the green crown length in a Chinese fir plantation. We monitored the effects of pruning on the stem and soil CO₂ efflux, stem radial growth, xylem sap flow, and nonstructural carbohydrate (NSC) concentrations. Our results showed that pruning resulted in the significant reduction of stem CO₂ efflux, particularly during the growing season. Despite the removal of the lower 50 % of the green crown length, we did not observe a pronounced reduction in soil CO₂ efflux and its components. Moreover, pruning had only little effect on sap flow. No significant difference was observed in the NSC concentrations between treatments in the stem cores and fine roots. We speculated that the different responses of stem and soil CO₂ efflux to pruning in the Chinese fir (sprouting species) plantation may have resulted from the different carbon allocations between aboveground and belowground tissues. However, further studies are required to confirm if our findings could be applied to other tree species or ecosystems.