Fungi decompose woody debris, an important carbon pool in forests. Fungal community structure is expected to vary according to the wood species, habitats and extent of abiotic disturbance, which have consequences for carbon cycling in tropical forests. Here we examined the effects of fungal diversity and composition on woody debris decomposition rates and sought potential mechanisms to explain an observed lack of difference in decomposition rates across a disturbance gradient in a tropical montane rainforest in Xishuangbanna, SW China. We measured wood specific gravity (WSG) loss from 280 logs of Litsea cubeba and Castanopsis mekongensis over 3 years and monitored fungal communities from 418 samples using next-generation sequencing after 0, 18 and 36 months field exposure. Wood species and termite presence determined changes in fungal diversity through time. Overall there was a peak in fungal diversity at 18 mo, suggesting an initial period of colonization followed by a period of increasingly competitive interactions leading to decreased diversity. Litsea logs, which had relatively low initial WSG and thinner bark, harbored higher fungal diversity. Shared fungal OTUs between wood species peaked at 18 mo (~50%). However, fungal diversity was not a significant predictor of WSG loss. An effect of habitat on fungal community composition suggests that functional replacement explains the similar decay rates across the disturbance gradient. In addition, the proportions of saprotroph and white-rot fungi increased through time regardless of wood species. Termite presence reduced WSG loss, but the effect was mediated via the abundance of soft rot fungi. Our results suggest that changes in functional traits, rather than fungal species diversity, may better explain variation in WSG loss. Future studies should investigate roles of fungal functional traits and rot types, particularly those of Ascomycete fungi, whose roles in wood decay are still poorly characterized.
Bibliographical noteFunding Information:
This work benefitted financial support from the National Natural Science Foundation of China (NSFC) via grant # 3181101433 to G.G.O.D., # 31470546 to R. D. H., K.E.B. and W.H. were supported by startup funds from the University of Minnesota and USDA NIFA grant # 2015-67013-23419. J.C.X. was supported by Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant # QYZDY-SSW-SMC014) and Y.P.Y. was supported by the Major Program of NSFC (# 31590820, 31590823). In addition, G.G.O.D. was supported by Yunnan provincial postdoctoral grant and young international staff Chinese Academy of Sciences (CAS) president international fellowship initiative (PIFI) grants # 2019FYB0001 and 2017PC0035 along with China postdoc foundation grant #2017M613021.This work benefitted financial support from the National Natural Science Foundation of China (NSFC) via grant # 31850410488, # 3181101433 to G.D. # 31470546 to R. D. H. Kathryn E Bushley and Weiming Hu were supported by startup funds from the University of Minnesota and USDA NIFA grant # 2015-67013-23419. Jian-Chu Xu was supported by Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant # QYZDY-SSW-SMC014) and Yong-Ping Yang was supported by the Major Program of NSFC (# 31590820, 31590823). In addition, G.G.O. Dossa was supported by Yunnan provincial postdoctoral grant and young international staff Chinese Academy of Sciences (CAS) president international fellowship initiative (PIFI) grants # 2019FYB0001 and 2017PC0035 along with China postdoc foundation grant #2017M613021, Yunnan Province Government for Talents Program. We also acknowledge the insightful discussion with Jonathan Schilling and the Biogeochemistry laboratory of Xishuangbanna Tropical Botanical Garden (XTBG) for the chemistry analysis. This work is linked to the CGIAR Research Program on Forests, Trees and Agroforestry. G.G.O. Dossa is grateful to Lulu Chen for encouragement and support throughout the redaction of the manuscript, to Atu our project local assistant in the field as well as the entire Bulong nature reserve staff for their support throughout the execution of the project. Dossa acknowledges Prof. Richard Corlett for insights and guidance and XTBG for organizing the structural equation modeling workshop. We are grateful to the two anonymous reviewers and the Chief Editor for their comments on earlier version of the manuscript.
© 2021 The Author(s)
- Carbon cycle
- Coarse woody debris
- Ecosystem function
- Tropical forest
- Wood density