Forest ecosystem succession plays an important role in soil microbiota variation, and soil microbes will re-establish ecosystem function after disturbance events. A distinctive disturbance of the expansion of bamboo forest into the surrounding broadleaved ecosystem is the change in litter type input. We conducted a 6-month microcosm experiment to examine the effects of proportional changes in leaf litter composition due to moso bamboo (Phyllostachys edulis) invasion into a broadleaved forest on soil microbial community. A series of mixed litters were prepared with bamboo litter occupying at 0%, 33%, 50%, 67% and 100% in proportion (with a decrease in litter carbon (C)/nitrogen (N) from 36.23 to 31.35), and they were then amended into a broadleaved forest soil at a rate of 1%, respectively. Soil bacterial and fungal communities at different incubation stages were determined by high-throughput sequencing. With the increasing proportion of bamboo litter, the broadleaved forest soil exhibited strong changes in microbiome assembly, including reducing bacteria alpha-diversity, the relative abundance of Acidobacteria and Basidiomycota, while increasing the relative abundance of Actinbacteria, Proteobacteria and Ascomycota. Moreover, the increased proportion of bamboo litter (0% PP→100% PP) increased the relative abundance of membrane transport and carbohydrate metabolism of soil bacteria but decreased the relative abundance of saprotrophic soil fungi. Redundancy analysis showed that bacteria rather than fungal communities changed greatly during incubation (p < 0.05). Additionally, the activities of soil pH, NO₃⁻-N, NH₄⁺-N, dissolved nitrogen and C- and N- acquiring enzymes were the main factors affecting bacterial and fungal community structure (p < 0.05). The soil physicochemical properties were significantly correlated with the composition of microbial phyla among different litter amendment treatments. These results indicated that different proportions of bamboo litter dramatically alter the soil bacterial rather than the fungal community, most likely by changing edaphic patterns. This study has important implications for understanding the litter–soil–microbe synergy during the bamboo forest expansion and provides a basis for assessing the ecological risk of bamboo forest expansion.

Chinese hickory (Carya cathayensis Sarg.) is an important economic forest in Southeastern China. A large amount of hickory husk waste is generated every year but with a low proportion of returning. Meanwhile, intensive man-agement has resulted in soil degradation of Chinese hickory plantations. This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment, including soil acidity, soil nutrition, and microbial community. The field experiment carried out four treatments: control (CK), hickory husk mulching (HM), hickory husk biochar (BC), and hickory husk organic fertilizer (OF). The phospholipid fatty acid (PLFA) biomarker method was employed to determine the soil microbial community. After one year of treatment, the results showed that: (i) HM and BC significantly increased soil pH by 0.33 and 1.71 units, respectively; (ii) HM, BC and OF treatments significantly increased the soil organic carbon, alkaline nitrogen, available phosphorous, and available potassium. The OF treatment demonstrated the most significant improvement in the soil nutrient; (iii) The soil microbial biomass significantly increased in the HM, BC and OF treatments, and all microbial groups showed an increasing trend. HM treatment increased the fungal/bacterial ratio (F/B). The OF treatment significantly decreased the Shannon-Wiener diversity (H') and evenness index (J) of the microbial community (P < 0.05). Considering the treatments effects, costs, and ease of operation, our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.

Assessing the soil quality of coastal reclamation areas is fundamental to alleviating land resource scarcity in coastal cities and ensuring food security. However, it remains unclear how to evaluate soil quality in reclaimed areas and identify factors driving its variation. In this study, paddy soils from four typical reclaimed coastal areas in China (Yueqing, YQ; Longgang, LG; Rui’an, RA; Longwan, LW) were investigated to construct a minimum data set via principal component analysis and to calculate soil quality indices (SQIs). YQ had higher contents of soil organic carbon (SOC: 22.82 g kg⁻¹), total nitrogen (TN: 0.14 g kg⁻¹), total water-soluble salts (TWS: 3.09 g kg⁻¹), cation exchange capacity (CEC: 21.77 cmol(+) kg⁻¹), and available Fe (44.23 mg kg⁻¹), Mn (36.63 mg kg⁻¹), Cu (30.31 mg kg⁻¹), and Zn (8.79 mg kg⁻¹) than the other sites. RA exhibited significantly higher activities of β-glucosidase (BG: 32.79 nmol g⁻¹ h⁻¹), xylanase (XYL: 5.88 nmol g⁻¹ h⁻¹), N-acetyl-β-D-glucosaminidase (NAG: 18.00 nmol g⁻¹ h⁻¹), leucine aminopeptidase (LAP: 27.01 nmol g⁻¹ h⁻¹), and acid phosphatase (PHOS: 54.50 nmol g⁻¹ h⁻¹) than the other sites (p < 0.05). LW had the greatest bacterial and fungal abundances, whereas LW displayed the highest fungal diversity. RA showed the highest SQI (SQIw: 0.49; SQIa: 0.48), followed by LW (SQIw: 0.47; SQIa: 0.47), LG (SQIw: 0.43; SQIa: 0.41), and YQ (SQIw: 0.38; SQIa: 0.41). Random forest analysis indicated that soil enzyme activities (XYL, NAG, BG, CB, PHOS), nutrients (TN, SOC, AN), fungal abundance and diversity, and TWS were key SQI predictors (Welch ANOVA p = 0.016), with XYL being the strongest predictor (p < 0.05). Collectively, soil quality in coastal reclamation areas is co-regulated by microbial metabolic activity, nutrients, and salinity, with soil enzyme activity serving as an important indicator for its assessment, thereby deepening the understanding of soil quality dynamics within these areas and enabling their sustainable management. However, the microbial mechanisms underlying these patterns across broader environmental gradients remain to be explored.