Soil microbes are the key to revealing the mechanisms driving variation in soil biogeochemical processes. In recent decades, forests in Southeast China have been widely transformed into tea plantations due to the drivers of economic benefits. However, the changes in the soil microbial community and their potential function during the transition from a typical forest ecosystem to tea plantations remain poorly understood. This study investigated the soil microbial community in tea plantation soils with different planting ages, i.e., 6, 12, 23 and 35 years, and in an adjacent woodland control. We discovered that tea planting significantly increased soil bacterial richness (ACE and Chao1) and decreased fungal richness, the diversity of bacteria (Simpson and Shannon) show a trend of initially decreasing and then increasing while there was no significant effect on fungal diversity. After tea planting, the relative abundances of Actinobacteria and Proteobacteria increased by 180.9%–386.6% and 62.3%–97.5%, respectively; the relative abundances of Acidobacteria decreased by 11.4%–66.8%. However, the fungal phyla were not significantly different among different aged tea plantations and woodlands. FAPROTAX and FUNGuild revealed that the transition of natural woodland to tea plantations significantly increased the relative abundances of aerobic_chemoheterotrophy (14.66%–22.69%), chemoheterotrophy (34.36%–37.04%), ureolysis (0.68%–1.35%) and pathogenic fungi (26.17%–37.02%). db-RDA proved that the bacterial community structure was more strongly related to soil pH and available nitrogen (AN), while the main determinants of the fungal community composition were soil pH and soil organic matter (SOM). These findings indicate that tea planting has a strong effect on the soil microbial community and potential function. The change in soil pH during tea planting was the most important factor affecting the soil microbial community, while soil bacteria were more sensitive to tea planting than fungi.

Seleniferous red soils cover a large area in the southern part of China. These agricultural soils are enriched in selenium (Se), heavy metals, and rare earth elements and have been cultivated for more than 1000 years for rice production without any consideration of the effects of selenium, heavy metals, and rare earth element bioaccumulation in the food plants produced. To address this knowledge gap, this study focuses on the investigation of Se, heavy metals, and rare earth elements within soils and plants in the region. The rice (Oryza spp.) plants studied were grown in the Gutian (GT), Gechuan (GC), and Pengkou (PK) villages in Lianchen (LC) County, Fujian Province. The surface soils and harvested rice tissues were collected to determine the Se, Cd, Zn, Pb, La, Ce, and Nd concentrations in the soils and plant tissues. Different rice cultivars possessed various potentials for elemental accumulation. Generally, rice plant tissues accumulated certain amounts of these elements; however, the elemental concentrations found in rice grain were within the acceptable ranges stipulated by the National Security Standard of Food. The Hongbaoshi (HBS) Indica red rice produced in the PK village accumulated more selenium, heavy metals, and rare earth elements than those in the plant tissues of the Xinyinzhan (XYZ) and Wushansimiao (WSSM) rice cultivars because HBS had more root hairs and finer root distribution. Thus, in the interest of food safety, increased attention needs to be given to the careful selection of the optimum crop species planted in these types of seleniferous red soils.

The dynamic response of soil bacterial communities to fertilization throughout the entire crop growth cycle remains inadequately characterized. To address this, we conducted a long-term field experiment in Jiangle County, Fujian Province, China, and collected soil samples across four rice growth stages (tillering, elongation, filling and maturity) under five fertilization regimes: no fertilization (CK); chemical fertilizer (NPK); and NPK supplemented with extra nitrogen (NPKN), extra phosphorus (NPKP) and rice straw (NPKS). Bacterial communities were analyzed by high-throughput sequencing. Our results revealed that soil bacterial diversity decreased progressively throughout the growth stages, with fertilization exerting only a minor influence. Structural equation modeling (SEM) identified daily mean temperature (DMT) as the factor with the strongest direct and total effects on the diversity. In contrast, fertilization regimes were the primary determinant of the community structure. Mantel test and redundancy analysis (RDA) indicated that soil pH was the most important factor shaping the community structure. Soil bacterial network attributes also varied mainly with fertilization: fertilizer addition reduced the complexity but enhanced stability, with NPK and NPKS showing the greatest stability. Regarding rice yields, all fertilized treatments were comparable but considerably higher than CK. In conclusion, rice growth stages primarily influenced soil bacterial diversity, while fertilization regimes predominantly shaped the community structure and network attributes. Further, we recommend NPK and NPKS as optimal strategies for balancing crop production, agroecosystem sustainability and environmental health.

Long-term tea cultivation alters soil nitrogen forms and microbial communities, yet the coupling relationships between soil nitrogen fractions and microbial functions remain poorly understood. Because long-term tea cultivation is accompanied by sustained nitrogen enrichment and progressive acidification that continuously reshape the chemical composition of soil organic nitrogen, resolving this gap is essential for predicting soil nitrogen supply and turnover in intensively managed tea plantations of different ages. A space-for-time chronosequence was established within a large state-owned tea plantation in Shouning County, Fujian Province, China, comprising interspersed stands of 3- (T3), 15- (T15), and 40-year-old (T40) tea plants and adjacent uncultivated secondary forestland (CK). We combined the Bremner acid-hydrolysis method with Illumina high-throughput sequencing to investigate variations in soil organic nitrogen (SON) fractions, microbial community structure, and associated potential functions. The results showed that tea cultivation significantly reduced soil pH. Compared with CK, the concentrations of amino acid nitrogen (AAN) and acid-hydrolyzable ammonium nitrogen (AN) in T40 increased by 223.03% and 137.83%, respectively. Meanwhile, the proportions of acid-hydrolyzable unidentified nitrogen (HUN) and non-hydrolyzable nitrogen (NHN) to total nitrogen (TN) decreased from 27.18% and 51.70% under CK to 23.22% and 40.84% under T40, respectively, indicating a remarkable restructuring of the soil nitrogen pool. For bacterial communities, the relative abundance of Proteobacteria increased from 17.76% in CK to 23.96–44.46% in tea plantations, whereas that of Acidobacteriota declined from 37.80% to 34.47–22.31%, accompanied by a significant enrichment of copiotrophic taxa. Redundancy analysis revealed that AAN and AN were the dominant drivers shaping bacterial community structure. FAPROTAX analysis showed that, compared with forest soils, tea plantations exhibited a significantly lower nitrogen fixation abundance (from 14.35% to 6.81%, p < 0.001) and an enhanced relative abundance of nitrate reduction (p < 0.05). FUNGuild analysis revealed that the dominant forest multi-trophic group (Pathotroph–Saprotroph–Symbiotroph) dropped sharply from 44.53% to 17.12–18.62% in tea plantations (p < 0.01), whereas the Pathotroph group increased from 0.61% to 2.22–2.78% (p < 0.05). Collectively, long-term tea cultivation elevates the supply of soil labile organic nitrogen, selectively enriches copiotrophic microbial communities, and reshapes the functional profiles of soil microbial communities.