Objective This study aims to reveal the fundamental role of woody debris in the carbon cycle within the Tsuga longibracteata communities in Tianbaoyan National Nature Reserve (TNNR). The findings will provide a basis for the conservation and sustainable management of the Tsuga Longibracteata community.

MethodsFour forest types of Tsuga longibracteata communities in TNNR were investigated, including T. longibracteata pure forest, T. longibracteata + broadleaf mixed forest, T. longibracteata + Rhododendron simiarum mixed forest and T. longibracteata + Phyllostachys edulis mixed forest. The study conducted a dynamic investigation of different tree species and forms of woody debris (fine woody debris, log, snag, and stump) in the forest from 2012 to 2016. The biomass and carbon storage of woody debris were estimated, and their dynamic changes were analyzed.

ResultsThe results showed that: (1) Woody debris biomass accounted for the largest proportion (31.57%-77.77%) among the four population colonies and different tree species.; (2) The differences in the same form of woody debris types within the same forest type in different years were not significant in the four T. longibracteata communities (p>0.05). Log had the highest biomass in different years (T. longibracteata pure forest: 5.82-9.48 t·hm⁻²; T. longibracteata + broadleaf mixed forest: 10.90-17.83 t·hm⁻²; T. longibracteata + R. simiarum mixed forest: 7.20-10.37 t·hm⁻²; T. longibracteata + P. edulis mixed forest: 6.11-9.77 t·hm⁻²). There were significant differences in stump biomass between the T. longibracteata pure forest and the other three populations across the three surveys (p<0.05). (3) T. longibracteata communities had the largest carbon storage, which showed an overall growth trend with increasing year (T. longibracteata pure forest: 3.64-4.62 t·hm⁻²; T. longibracteata + broadleaf mixed forest: 4.67-4.71 t·hm⁻²; T. longibracteata + R. simiarum mixed forest: 2.29-2.53 t·hm⁻²; T. longibracteata + P. edulis mixed forest: 3.10-4.79 t·hm⁻²).; (4) Log had the highest carbon storage among the four types of T. longibracteata communities woody debris, except for T. longibracteata + P. edulis mixed forest. The carbon storage of log increased in the other three T. longibracteata communities. Among the four populations, the carbon storage of the T. longibracteata + broadleaf mixed forest was the highest, ranging from 4.91-7.68 t·hm⁻². The carbon storage of snag significantly differed between the pure forest of T. longibracteata and the other three mixed forests (p<0.05).

Conclusion Among the four T. longibracteata communities, log has the highest biomass and carbon storage among different forms of woody debris. Woody debris from different tree types has the highest biomass and carbon storage in T. longibracteata. The biomass and carbon storage of snag in the T. longibracteata pure forest are significantly different from those in other communities (p<0.05).