Winter mulching practice alters soil bacterial communities and networks in lei bamboo (Phyllostachys praecox) forests

Winter mulching is widely used to raise soil temperature and promote earlier harvesting in agroforestry, but successive years of mulching can lead to soil degradation. The effect of winter mulch on soil bacterial community composition and co-occurrence patterns is not clear. The influence of different mulches (a defatted seed cake of Camellia oleifera, DS; a mixture of wheat straw and chicken manure, MWC; and wheat straw, WS) on soil bacterial communities and networks in lei bamboo (Phyllostachys praecox) forests over a four-month mulching period was studied using Illumina sequencing of the 16S rRNA gene. The results showed that mulching time and mulching material treatment significantly influenced bacterial community composition and diversity, mainly driven by nutrient availability. MWC and WS mulching treatments decreased alpha-diversity of the bacterial communities, whereas the DS treatment had no significant impact. The oligotrophs, Gryllotalpicola, Granulicella, and Verrucomicrobia, were enriched before and at the end of mulching, while the copiotrophs, Deltaproteobacteria, were enriched in the middle of the mulching period (Jan). Comparing the three mulching treatments, Proteobacteria were enriched in DS mulching soils in Jan. The complexity of the four networks decreased with pre-mulching, DS mulching, WS mulching, and MWC mulching networks, with a reduction in the number of edges and average degree observed. The results suggested that winter mulching practices adversely affected soil bacterial community diversity and interactions, which may be detrimental to the resistance of bacterial communities to environmental changes and soil sustainability. Mulching MWC and WS has a greater risk of loss of soil bacterial biodiversity than DS.