RESUMEN
Clarifying changes in the microbial community in deadwood at different stages of decomposition is crucial for comprehending the role of deadwood in the biogeochemical processes and the sustainability of forest development. However, there have been no reports on the dynamics of microbial community during the decomposition of Pinus massoniana. We used the "space-for-time" substitution to analyze the characteristics of microbial community changes and the key influencing factors in the P. massoniana deadwood during different decomposition stages by 16S and ITS rRNA gene sequencing. The results suggest that the microbial community structure of the early decomposition (decay class I) was significantly different from the other decay classes, while the diversity and richness of the microbial community were the highest in the late decomposition (decay class V). The Linear Discriminant Analysis Effect Size analysis revealed that most bacterial and fungal taxa were significantly enriched in decay classes I and V deadwood. During the initial stages of decomposition, the relative abundance of the bacterial functional group responsible for carbohydrate metabolism was greater than the later stages. As decomposition progressed, the relative abundance of saprophytic fungi gradually decreased, and there was a shift in the comparative abundance of mixed saprophytic-symbiotic fungi from low to high before eventually decreasing. Total organic carbon, total nitrogen, carbon-to-nitrogen ratio, total potassium, total phenol, condensed tannin, lignin, and cellulose were significantly correlated with microbial community structure, with the carbon-to-nitrogen ratio having the greatest effect. Our results indicate that the physicochemical properties of deadwood, microbial community structural composition and functional group changes were related to the decay class, among which the carbon-to-nitrogen ratio may be an important factor affecting the composition and diversity of microbial communities.
RESUMEN
Soilless culture has been widely used in horticultural plant production, but little research has been done on bryophyte. In this study, we selected a cultivation substrate mixed and proportioned with garden soil, granular soil, grass charcoal soil, general-purpose nutrient soil, and decomposed grade II, III, and IV fallen wood of Pinus massoniana as the raw materials of soilless substrate to investigate its effects on the growth and physiology of Plagiomnium acutum. The results showed that the total porosity, water-holding porosity, and water-holding capacity of the mixed substrate containing fallen wood of P. massoniana were significantly higher than those of other cultivated substrates. The average cover of the P. acutum was significantly and positively correlated with the substrate's total porosity and water-holding porosity. Chlorophyll content was highly significantly and positively correlated with the water holding capacity and total nitrogen content of the substrate. Among them, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate had the highest overall evaluation index and the best overall growth condition of P. acutum. In summary, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate can be the best substrate for cultivation of P. acutum. The addition of P. massoniana fallen wood to the soil substrate increased the total porosity, water-holding porosity, and water-holding capacity of the substrate, which was conducive to the growth of P. acutum and the increase of chlorophyll content.