title: Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization.
abstract: A recent review concluded that earthworm presence increases CO₂ emissions by 33% but does not affect soil organic carbon stocks. However, the findings are controversial and raise new questions. Here we hypothesize that neither an increase in CO₂ emission nor in stabilized carbon would entirely reflect the earthworms' contribution to net carbon sequestration. We show how two widespread earthworm invaders affect net carbon sequestration through impacts on the balance of carbon mineralization and carbon stabilization. Earthworms accelerate carbon activation and induce unequal amplification of carbon stabilization compared with carbon mineralization, which generates an earthworm-mediated 'carbon trap'. We introduce the new concept of sequestration quotient to quantify the unequal processes. The patterns of CO₂ emission and net carbon sequestration are predictable by comparing sequestration quotient values between treatments with and without earthworms. This study clarifies an ecological mechanism by which earthworms may regulate the terrestrial carbon sink.
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystem, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
authors.forename: Weixin
authors.initials: W
authors.lastname: Zhang
authors.forename: Paul F
authors.initials: PF
authors.lastname: Hendrix
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Dame
authors.forename: Roger A
authors.initials: RA
authors.lastname: Burke
authors.forename: Jianping
authors.initials: J
authors.lastname: Wu
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Neher
authors.forename: Jianxiong
authors.initials: J
authors.lastname: Li
authors.forename: Yuanhu
authors.initials: Y
authors.lastname: Shao
authors.forename: Shenglei
authors.initials: S
authors.lastname: Fu
mesh_terms: D000383:Agriculture; D000818:Animals; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D057965:Carbon Sequestration / Q000502:physiology*; D017753:Ecosystem; D009835:Oligochaeta / Q000378:metabolism*; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon