Plastic film mulching has been applied globally in various agricultural settings and inevitably disintegrate into microplastics (MPs, less than 5 mm in size) due to a series of natural and artificial forces, emerging as a novel type of contaminant. However, the effects of MPs on the dynamics of soil microbial communities and network patterns have not been sufficiently reported.

In a study recently published in Journal of Hazardous Materials, researchers from WANG Guanghua's group at the Northeast Institute of Geography and Agroecology of Chinese Academy of Sciences (CAS) revealed that addition of conventional and biodegradable MPs significantly shifted soil bacterial community and network structures, which was not only along with the exposure duration of MPs but also MP dosages and types.

By high-throughput sequencing, this study revealed the incubation time was found to be the most dominant factor on disturbing bacterial community structure, which strongly suggests that MPs might pose a huge potential threat to the security of agricultural production, as they can easily accumulate in the soil and is predicted to continue to increase in the next few decades. Moreover, 1% MP dosage could be identified as the threshold value, over which negatively significant influences on soil bacterial diversity would occur.

Differently, biodegradable MPs caused greater community dissimilarity than that of conventional ones when compared to CK, and the two types of MPs act as distinct driving force of species selection. Biodegradable MPs tended to promote the growth of environmentally friendly and crop beneficial bacteria, while conventional ones enriched the bacterial taxa often found in contaminated or crop disease-inducing soils.

Moreover, biodegradable MPs provided more nutrients and habitats for microbes as revealed by SEM-EDS analyses, which mitigated both cooperation and competition among microbial communities. Specially, Nitrospira was not only enriched by the two types of MPs but also identified as a keystone species in microbial ecological networks, suggesting that conventional and biodegradable MPs had crucial legacy influences on soil nitrogen cycling.

The study provides new insights into the disturbances of conventional and biodegradable MPs on the dynamic patterns of soil bacterial communities, revealing the potential ecological detriments of conventional MPs and the alternatives of biodegradable plastic mulches in agricultural practices.

The influences of conventional and biodegradable microplastics on soil bacterial communities. (Image by HU Xiaojing)

Contact:

WANG Guanghua

Northeast Institute of Geography and Agroecology

E-mail: wanggh@iga.ac.cn