Cropland-To-Miscanthus Conversion Increases Sulfur Availability and Shifts Microbial Pattern Enhancing Sulfur Cycle in Northern China

Abstract

Miscanthus spp. are increasingly cultivated in agricultural fields worldwide due to their potential for bioenergy production and the various ecological benefits they offer. However, the long-term impacts of cropland conversion to harvested Miscanthus without sulfur fertilizer on soil microorganisms and the sulfur cycle remain poorly understood. This study aimed to investigate the effects of Miscanthus transformation on soil microorganisms and the sulfur cycle over a 15-year period. We evaluated the influence of long-term Miscanthus planting on the diversity, relative abundance, functions, and correlations of soil sulfur-cycling microbial communities, as well as how changes in soil properties affect the sulfur conversion process. The results indicated that Miscanthus planting significantly increased the concentrations of soil sulfate (SO₄²⁻, 47.39%, p < 0.05), total sulfur (TS, 13.26%, p < 0.05), and available sulfur (AS, 156.37%, p < 0.05), while decreasing soil pH (8.83%). Sulfur exhibited a positive correlation with the abundance of Acidobacteria, Proteobacteria, unclassified_d_unclassified, and Actinobacteria, while total nitrogen (TN) content was positively correlated with sulfur metabolism. The activity of oxidoreductase in Miscanthus was significantly higher (p < 0.05) than in other land use types, facilitating the conversion of organic sulfur into plant-available inorganic sulfur (SO₄²⁻). Analysis of the microbial community based on 16S rRNA gene sequences revealed that the diversity and richness of the microbial community in Miscanthus planting areas were greater, and the microbial community structure was significantly different from that of bare soil and cultivated land. Actinobacteria and Proteobacteria were identified as the dominant microbial taxa. Redundancy analysis indicated that TN was the primary factor influencing the microbial community. These findings provide theoretical support and practical guidance for farmers to promote large-scale cultivation of Miscanthus on marginal croplands in Northern China.