Contrasting responses of soil organic and inorganic carbon pools under plant invasion in tropical coral islands

Abstract Plant invasions pose significant threats to biodiversity and ecosystem functioning, but their impact on soil carbon (C) pools in island ecosystems remains underexplored. This study examined the responses of soil total C (TC), organic C (SOC), inorganic C (SIC), and microbial‐derived C (i.e., amino sugars (ASs) and glomalin‐related soil proteins (GRSP)) in tropical island forests invaded by Cassytha filiformis , Eupatorium odoratum , and Wedelia biflora . Results revealed that invasions substantially reduced aboveground and belowground biomasses of local plant communities with increasing invasion degree, yet the soil TC pool size remained nearly unaffected due to increased SIC offsetting decreased SOC. The effects on soil C pools depended on the invasive species and sampling season. E. odoratum and W. biflora invasions significantly reduced microbial‐derived C concentrations (ASs and GRSP) but increased their contribution to the SOC pool during the wet season, whereas C. filiformis invasion reduced microbial‐derived C only in the dry season. The study highlights the tradeoff between SOC and SIC in regulating soil C pools and emphasizes the need for context‐specific management strategies. Despite the stable soil TC pool, the loss of SOC's multifunctional benefits necessitates targeted strategies to mitigate invasions' adverse effects on ecosystem health and carbon storage.