Responses and interactions of soil cadmium-PAHs and bacterial communities to ecosystems and seasons

Abstract

Soil health and stability of the microbiome are critical to ecosystem sustainability. However, the changes in pollutant concentrations and bacterial communities in diverse ecosystems during seasonal changes are unclear. This study attempted to address this gap by collecting and analyzing soil samples across spring, summer, and autumn in grassland (3 sites) and forest (5 sites). The study found that both grassland and forest ecosystems were polluted by cadmium (0.56–2.08 mg kg⁻¹) and polycyclic aromatic hydrocarbons (10.98–973.43 μg kg⁻¹). Soil pH, water content, and microbial community composition were mostly influenced by soil properties of different ecosystems, while seasonal changes mainly affected soil enzyme activity and microbial diversity. Cadmium and polycyclic aromatic hydrocarbons were key factors shaping microbial community structure, exhibiting notable correlations with Chloroflexi and Proteobacteria. Network diagram showed that in both ecosystems, the connections between bacteria were strongest in summer. Regardless of season, grassland networks are more complex and stable than forest ones. Ecosystem type had a greater influence on bacterial community interaction than seasonal variation. The structural equation model confirms that both ecosystem and season can directly or indirectly affect bacterial community diversity and structure. The study provides insights into the response of soil microbes in forest and grassland ecosystems, supporting soil health evaluation under future climate change scenarios.