South china botanical garden unveils mechanisms of plant invasion influencing soil carbon pools in tropical coral islands

Soil carbon pools consist of organic carbon and inorganic carbon components. While research predominantly focuses on soil organic carbon due to its shorter turnover times, greater sensitivity to environmental changes, and higher regulatory potential. This often overlooks the crucial role of soil inorganic carbon, known for its stability in alkaline environments and long turnover times. Soil organic and inorganic carbon pools can influence and transform into one another, with inorganic carbon accumulation playing an equally important role in terrestrial carbon cycles and global carbon balance. Tropical coral islands, characterized by their inorganic carbon-rich soils, present unique opportunities to study how plant invasions affect the dynamics of organic and inorganic soil carbon. Although plant invasions are known to significantly impact soil carbon inputs and outputs, their effects on interactions between organic and inorganic carbon remain unclear. Understanding the mechanisms underlying these interactions is vital for the conservation and restoration of tropical coral island ecosystems.

A restoration ecology research team from the South China Botanical Garden focused on tropical coral islands in the Xisha Archipelago (Dong and Yongxing islands) to investigate how three invasive plant species—Cassytha filiformis, Eupatorium odoratum, and Wedelia biflora—impact soil organic and inorganic carbon pools. The main findings include: (1) Invasive plant species significantly reduced the above- and belowground biomass of native vegetation. However, total soil carbon storage remained unchanged, as increases in soil inorganic carbon offset decreases in soil organic carbon. (2) Invasive plants lowered the concentrations of microbial-derived carbon components such as amino sugars and glomalin-related soil proteins. Despite this, the contribution of microbial carbon to soil organic carbon increased during the wet season. (3) Plant invasion effects on soil carbon pools were jointly influenced by invasive species identity and sampling season, with total soil nitrogen and phosphorus contents identified as key factors. This study elucidates how invasive plants alter soil carbon pool components, highlighting that increases in inorganic carbon can counteract organic carbon losses. However, the multifunctionality of soil organic carbon—especially its roles in nutrient cycling and water retention—cannot be replaced by inorganic carbon. These findings provide new scientific evidence for managing invasive plant impacts and conserving tropical coral islands. Future research should monitor the long-term dynamics of organic and inorganic soil carbon under varying environmental conditions and further explore plant-microbe interactions' role in soil carbon stabilization, offering technological support for tropical island restoration and management.

This research, recently published in the journal Biological Diversity. Dr. LI Tengteng, a postdoctoral researcher, is the first author, and Dr. LIU Zhanfeng is the corresponding author. The work was supported by the National Key Research and Development Program and the National Natural Science Foundation of China. Paper Link:http://doi.org/10.1002/bod2.12024

Fig. 1 Effects of invasive plants on vegetation biomass and soil carbon pools in tropical coral islands.(Image by LI et al)

Fig.2 Effects of invasive plants on soil organic and inorganic carbon pools in tropical coral islands.(Image by LI et al)