Nitrogen Enrichment Reduces Soil Bacterial Diversity and Alters Bacterial Composition in a Seasonal Manner Within the Tidal Marsh of the Yellow River Delta, China
摘要
Since the Industrial Revolution, anthropogenic activities have significantly increased substantial nitrogen inputs into natural ecosystems, drawing considerable attention to the responses of ecosystem components to these changes. However, although a large number of studies have focused on the impact of nitrogen input on soil bacterial communities in terrestrial ecosystems, the impact on the diversity and composition of soil bacteria in coastal wetlands remains unclear. We conducted a field experiment in 2017 in a tidal marsh of the Yellow River Delta, with nitrogen addition treatments at four levels: 0 g • m−2 • year−1 (N0), 5 g • m−2 • year−1 (N1), 20 g • m−2 • year−1 (N2), and 50 g • m−2 • year−1 (N3). Urea [CO(NH2)2, containing 46% nitrogen] was uniformly applied to the experimental plots in May and July. Soil samples were collected in May and September 2018 for analysis of soil physical and chemical properties as well as soil bacterial composition. Our study demonstrated that, in both May and September samples, nitrogen treatment consistently led to a significant reduction in bacterial diversity across all taxonomic levels, ranging from phylum to species. Furthermore, seasonal fluctuations in the types and quantities of soil available nitrogen were found to substantially influence soil bacterial composition under the influence of nitrogen inputs. The phyla with the highest relative abundance were Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Cyanobacteria, Chloroflexi, Acidobacteria, Planctomycetes, Deinococcus-Thermus, and Gemmatimonadetes. Soil physical and chemical factors, particularly electrical conductivity, soil total carbon content, ammonium (NH-N) content, and nitrate (NO-N) content, significantly influenced bacterial composition in both May and September. Specifically, NH-N content was the most influential factor on bacterial composition in May, whereas NO-N content played a pivotal role in shaping bacterial composition in September. Therefore, nutrient availability is one of the important factors affecting the diversity and composition of bacteria in tidal marsh of the Yellow River Delta.