Soil microbes play an important role in the microbial circulation and energy flow of ecosystems. In order to understand the change in the rhizosphere soil microbial community structure and function in the heterogeneous karst habitats, the nutrient content and enzyme activity were analyzed, and Illumina MiSeq high-throughput sequencing technology was used to detect the composition, quantity and functional types of the rhizosphere soil microbial community in Rhododendron pudingense under three kinds of karst microhabitats (soil surface, rock gully and rock surface) in Wangmo Country (WM), Zhenning Country (ZN) and Qinglong Country (QL). The results showed that SS and RG microhabitats had a higher nutrient content and enzyme activity, while RS had the lowest. At the phylum level, Proteobacteria and Actinomycetes were dominant in terms of bacteria, while Ascomycota and Basidiomycotina were dominant in terms of fungi. There was no significant difference in microbial diversity among different karst microhabitats (p > 0.05). At the microbial genus level, there were some differences in species composition among the three karst microhabitats, which may lead to soil heterogeneity in karst microhabitats. WM was a little different from ZN and QL. The results of PCoA showed that the community composition of RG and RS was more similar to that of SS. There was no significant difference in microbial functional types among different microhabitats (p > 0.05). Only the abundance of pathothoph-symbiothoph fungi in RG was significantly higher than that in RS (p < 0.05). The main function of bacteria was metabolism, and saprophytic and symbiotic fungi were the dominant fungal group. In conclusion, soil organic carbon and alkaline phosphatase are important factors affecting the level distribution of microflora in different karst microhabitats. R. pudingense in the SS and RG microhabitats has better soil conditions, which may require protection for the plants in the RS microhabitat. The current study results can provide a theoretical basis for the adaptation mechanism of Rhododendron pudingense to the karst microhabitat.

Soil microbes are a crucial component of karst ecosystems, and exploring their community changes during succession can help to elucidate the mechanisms driving succession dynamics. However, the variation of soil microbial communities during vegetation succession in karst ecosystems is still poorly understood. We studied the variations in community structure and potential functions of soil microbes within the four successional stages of grassland (GL), shrubland (SL), secondary forest (SF), and primary forest (PF) for the topsoil (0–10 cm) and subsoil (10–20 cm) in a karst area using high-throughput sequencing. The research findings showed that the bacterial and fungal community diversity and composition changed more obviously in the topsoil than in the subsoil across the succession. With vegetation succession, the structural and functional characteristics of soil bacterial and fungal communities show different trends, with soil fungal communities having a greater response to successional stage changes. Actinobacteria and Acidobacteria were dominant in secondary and primary forests, respectively, while Bacteroidetes was prevalent in grassland. However, the change in Proteobacteria was not significant at both soil depths. Ascomycota was the dominant phylum of soil fungi throughout the succession. The function of soil bacteria was mainly carbohydrate metabolism, which had the highest proportion in the shrubland at different soil depths. The dominant fungal functional groups were saprotroph, pathotroph, and pathotroph–saprotroph. The soil bacterial communities were observably affected by soil organic carbon, total nitrogen, total potassium, ammonia nitrogen, nitrate nitrogen, and leucine aminopeptidase, among which soil organic carbon, ammonia nitrogen, and leucine aminopeptidase mainly influenced the bacterial community in the topsoil, while nitrate nitrogen chiefly influenced the bacterial community in the subsoil. The soil fungal community was only significantly affected by soil organic carbon. Collectively, these results indicate that the effects of vegetation succession on soil microbial communities are largely driven by successional stage and soil properties, with soil fungi being more susceptible to the vegetation successional stage and soil bacteria being more sensitive to the soil properties. During this process, soil bacterial and fungal communities follow different succession patterns.

Background: Rhododendron pudingense, firstly discovered in Puding county of Guizhou province in 2020, have adapted to living in rocky fissure habitat, which has important ornamental and economic values. However, the genetic diversity and population structure of this species have been rarely described, which seriously affects the collection and protection of wild germplasm resources. Results: In the present study, 13 pairs of primers for polymorphic microsatellite were used to investigate the genetic diversity of 65 R. pudingense accessions from six different geographic populations. A total of 254 alleles (Na) were obtained with an average of 19.5 alleles per locus. The average values of polymorphic information content (PIC), observed heterozygosity (Ho), and expected heterozygosity (He) were 0.8826, 0.4501, and 0.8993, respectively, These results indicate that the microsatellite primers adopted demonstrate good polymorphism, and the R. pudingense exhibits a high level of genetic diversity at the species level. The average genetic differentiation coefficient (Fst) was 0.1325, suggested that moderate divergence occurred in R. pudingense populations. The average values of genetic differentiation coefficient and gene flow among populations were 0.1165 and 3.1281, respectively. The analysis of molecular variance (AMOVA) indicated that most of the population differences (88%) were attributed to within-population variation. The PCoA results are consistent with the findings of the UPGMA clustering analysis, supporting the conclusion that the six populations of R. pudingense can be clearly grouped into two separate clusters. Based on Mantel analysis, we speculate that the PD population may have migrated from WM-1 and WM-2. Therefore, it is advised to protect the natural habitat of R. pudingense in situ as much as possible, in order to maximize the preservation of its genetic diversity. Conclusions: This is the first comprehensive analysis of genetic diversity and population structure of R. pudingense in Guizhou province. The research results revealed the high genetic diversity and moderate population diferentiation in this horticulture plant. This study provide a theoretical basis for the conservation of wild resources of the R. pudingense and lay the foundation for the breeding or cultivation of this new species.

The technique of stable hydrogen and oxygen isotope tracing has become an important means to study the mechanism of water movement due to its high sensitivity and traceability. In this study, four dominant tree species in the karst forest of Maolan, Guizhou Province, were selected, and their water-use strategies and the mechanism of maintenance of tree species diversity were investigated using the stable hydrogen and oxygen isotope tracing technique. The results show that: (1) The regional precipitation varied evidently with the alternation of seasons, i.e., the values of δD and δ¹⁸O in precipitation had a positive bias in spring and a negative bias in summer and autumn. The value of deuterium excess (d-excess) was between 11.67‰ and 31.02‰, with a mean value of 22.98‰. (2) The soil temperature (ST), soil water content (SWC) and precipitation, which have a significant positive correlation, imposed a joint impact on the dynamics of the soil evaporative fractionation. (3) The line-conditioned excess (LC-excess) varied seasonally in different water bodies, i.e., the relative evaporative fractionation of the rhizosphere soil of deciduous tree species was stronger than that of evergreen tree species, and the evaporative fractionation of hydrogen and oxygen isotopes in the leaf water of evergreen tree species was stronger than that of deciduous tree species in spring and summer. However, that of the latter was stronger than that of the former in autumn. (4) The soil water was the most important potential water source for dominant tree species in karst terrain (71%), followed by epikarstic water, which made up an effective supplement (29%). (5) Finally, trees of different life forms and species varied in capacity and proportion in terms of using the potential water sources in different seasons, i.e., deciduous tree species had a greater capacity for using water from potential sources and variable water-use strategies. This may be a major water-limiting mechanism that maintains photosynthesis in the leaves of evergreen tree species (leaves are evergreen and plants continue to grow via photosynthesis) and constrains photosynthesis in deciduous tree species (leaves fall and plants become dormant and stop growing). These results lead to the conclusion that the dominant tree species in karstic forests resist water stress and adjust water-use strategies towards each potential water source to adapt to the harsh karstic habitat through root plasticity and leaf defoliation.

In forests, microbial populations in the soil can directly influence the decomposition of carbon from surface plants, promoting carbon storage and stability. However, in sustainable forest management, it is still unclear how soil microorganisms under different plantation types affect organic carbon sequestration and whether the mechanisms of influence are the same. In this research, we focused on four mixed forests and pure Pinus massoniana-planted forest in the state-owned forest farm of Dushan County. Three replicated plots were set up for each model, and soil samples were collected from different layers (0–20 cm, 20–40 cm, and 40–60 cm), totaling 45 samples. We elucidated the effects of soil microorganisms on carbon sequestration under five mixed modification models of P. massoniana and further explored the mechanisms by which microbial functional communities regulate soil carbon sequestration under different mixed models through molecular sequencing and collinear network analysis. Variance analysis indicated that the soil organic carbon (SOC) of the same soil layer varied significantly, and there were also significant differences in the composition of soil bacterial and fungal microbial communities. Moreover, the bacterial community was more sensitive to changes in the vegetation environment, while the fungal community structure was more resistant to changes in the soil environment. Correlation analysis indicated that the diversity and composition of the bacterial community had more positive effects on soil organic carbon than those of the fungal community. Linear fitting and redundancy analysis (RDA) showed that particulate organic carbon (POC) in soil had the strongest correlation with SOC content. Soil microorganisms affected the storage and stability of soil carbon mainly by regulating the conversion of litter (carbon sources) into POC. The soil environment of different mixed models had different effects on soil carbon accumulation. Both correlation and collinearity network analyses indicated that soil microbial functional groups could enhance carbon storage by regulating readily oxidizable carbon (EOC) and POC content in mixed forest plantations. The results of our study provide a sound basis for replanting a reasonable forest model structure to improve forest carbon storage.

(1) Background: In managing ecological tea gardens, litter composed of pruned and fallen tea leaves from companion tree species is an important component of tea garden soil. The decomposition of litter plays a crucial role in regulating nutrient cycling in tea garden ecosystems. (2) Methods: This study employed the litterbag method to investigate chemical stoichiometry characteristics and enzyme activity changes during the decomposition process of pruned and fallen Camellia sinensis leaves from companion tree species in an ecological tea garden located in central Guizhou Province. (3) Results: With decomposition duration, the general trend of changes in the C/N and C/P ratios showed a decrease in the activity of UE (urease), AP (acid phosphatase), and PPO (polyphenol oxidase) followed by an increase, while CAT (catalase) and CEL (cellulase) activity decreased, then increased, and then decreased again. On the other hand, the N/P and the activity of SC (sucrase) first increased and then decreased. The C/N and the activities of UE, PPO, and AP generally reached their maximum values during the late decomposition stage (366–428 d), while the N/P and the CAT activity peaked during the mid-decomposition stage (305 d). In contrast, the activity of SC and CEL reached its maximum value during the early decomposition stage (123 d). The N/P ratios were significantly higher than those of the CS (C. sinensis) litter in the mixed treatment, while C/N and C/P ratios were significantly lower than those in the CS during decomposition for 184–366 days. The UE, CAT, AP, and SC activities of CBL (C. sinensis + B. luminifera) litter were significantly higher than those of the CS litter during decomposition. During the experiment, antagonistic effects were observed in the C/N and C/P ratios of the different litter types. Most mixed litter exhibited additive effects on enzyme activity, while a few showed nonadditive effects. For the nonadditive effects, most were antagonistic effects, mainly in the CPM (C. sinensis + C. glanduliferum) litter. A small portion, mainly observed in the CBL and CCG (C. sinensis + C. glanduliferum) litter, showed synergistic effects. (4) Conclusions: Selecting B. luminifera and C. glanduliferum to be part of the tree species composition in ecological tea gardens can produce positive mixed effects on enzyme activity during litter decomposition, increase nutrient return capacity, maintain tea garden fertility, and achieve the ecological development of tea gardens.