Ant mound constructions reduce chemical diversity but increase network complexity of soil organic matter: A case from drained peatlands in Northeast China

Abstract

Ant mound construction is an ecologically destructive phenomenon affecting the carbon cycle in drainage peatlands. However, it remains unclear to what extent ant mound consturction alters soil organic matter (SOM) stability by changing chemical composition of SOM at the molecular scale. As such, we extended the application of graph networks established using pyrolytic products by pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS) technology analysis, so as to assess differences in molecular diversity and quantify network topologies of SOM between ant mounds and nearby soils, and then, to explore relationships between SOM thermal stability and complexity of molecular-interaction networks. Soil organic carbon contents from ant mounds, 26.8 % on average, were significantly lower than nearby soils, 31.2 % on average. Thermal stability of SOM in ant mounds was higher than that in nearby soils. SOM in ant mounds was characterized by significantly more aromatic compounds but less lignin and phenolic compounds, while SOM in ant mounds had lower molecular diversity than those in nearby soils. The beta diversity significantly differed between ant mound and nearby soils. Network analysis indicated that there were 310 nodes and 2248 edge links, 274 nodes and 648 edge links in SOM from ant mounds and nearby soils, respectively. It confirmed that ant invasion trended to create more complex and interconnected SOM networks. Molecular diversity seemed to promote SOM contents in nearby soils remarkably, but network complexity played more crucial controls in enhancing SOM stability in ant mounds. These findings indicated that ant bioturbation could reshape molecular diversity and complexity of SOM, and alter the persistence mechanism of SOM from molecular diversity to forming the more complex network.