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What's under the Christmas Tree? A Soil Sulfur Amendment Lowers Soil pH and Alters Fir Tree Rhizosphere Bacterial and Eukaryotic Communities, Their Interactions, and Functional Traits.

ABSTRACT: In this study, we describe the legacy effects of a soil sulfur amendment experiment performed 6 years prior and the resulting alterations to the rhizosphere communities of fir trees on a Christmas tree plantation. The pH of bulk soil was ∼1.4 pH units lower than that of untreated soils and was associated with reduced Ca, Mg, and organic matter contents. Similarly, root chemistry differed due to the treatment, with roots in sulfur-amended soils showing significantly higher Al, Mn, and Zn contents and reduced levels of B and Ca. 16S rRNA and 18S rRNA gene sequencing was pursued to characterize the bacterial/archaeal and eukaryotic communities in the rhizosphere soils. The treatment induced dramatic and significant changes in the microbial populations, with thousands of 16S rRNA gene sequence variants and hundreds of 18S rRNA gene variants being significantly different in relative abundances between the treatments. Additionally, co-occurrence networks showed that bacterial and eukaryotic interactions, network topology, and hub taxa were significantly different when constructed from the control and treated soil 16S and 18S rRNA gene amplicon libraries. Metagenome sequencing identified several genes related to transport proteins that differentiated the functional potentials of the communities between treatments, pointing to physiological adaptations in the microbial communities for living at altered pH. These data show that a legacy of soil acidification increased the heterogeneity of the soil communities as well as decreasing taxon connections, pointing to a state of ecosystem instability that has potentially persisted for 6 years. IMPORTANCE We used sulfur incorporation to investigate the legacy effects of lowered soil pH on the bacterial and eukaryotic populations in the rhizosphere of Christmas trees. Acidification of the soils drove alterations of fir tree root chemistry and large shifts in the taxonomic and functional compositions of the communities. These data demonstrate that soil pH influences are manifest across all organisms inhabiting the soil, from the host plant to the microorganisms inhabiting the rhizosphere soils. Thus, this study highlights the long-lasting influence of altering soil pH on soil and plant health as well as the status of the microbiome.

SUBMITTER: Steven B

PROVIDER: S-EPMC8552644 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Near-natural forest management plays an important role in the maintenance of the long-term productivity and soil fertility of plantations. We conducted high-throughput absolute quantitative sequencing of 16S rRNA genes to compare the structures and diversity of rhizosphere soil bacterial communities among a pure Chinese fir (Cunninghamia lanceolata) plantation (S), a Cunninghamia lanceolata-Castanopsis hystrix-Michelia hedyosperma mixed plantation (SHX), and a Cunninghamia lanceolata-Castanopsis fissa mixed plantation (SD). The results revealed that near-natural forest management improved the rhizosphere soil properties of Chinese fir, especially the phosphorus content. Rhizosphere soil bacterial communities of Chinese fir in SHX and SD contained higher total absolute abundances and more unique operational taxonomic units (OTUs) than the pure plantation forest. Planctomycetes and Actinobacteria were abundant in SD, and Actinobacteria were enriched in SHX. The tree species also had an impact on the rhizosphere soil bacterial communities. For the rhizosphere soils of different tree species of SHX, the available phosphorus (AP) content of the rhizosphere of Chinese fir significantly surpassed those of Castanopsis hystrix and Michelia hedyosperma. Bacteria related to nitrogen fixing, such as Burkholderiales and Rhizobiales, were more abundant in Chinese fir in SD than in Castanopsis fissa. Acdiobacteria and Proteobacteria underpinned the differences found in the compositions of soil bacteria. The pH and soil organic matter were key variables influencing the rhizosphere soil bacterial communities. Our results demonstrated that in Chinese fir plantations, 12 years of near-natural management of introduced broad-leaved tree species can drive alterations of the physicochemical characteristics, bacterial community structure, and composition of rhizosphere soil, with tree species identity further influencing the rhizosphere soil bacterial community. IMPORTANCE Near-natural forest management is an important way to change the soil fertility decline and productivity reduction of pure Chinese fir plantations. At present, many detailed studies have been carried out on the impact of near-natural forest management on Chinese fir plantations at home and abroad. However, there are still few studies on the response of rhizosphere bacterial communities to near-natural forest management. Our study determined absolute quantities of Chinese fir rhizosphere bacterial communities in different mixed patterns. The results underscore the importance of near-natural forest management for Chinese fir plantation rhizosphere bacterial communities and provide new information on soil factors that affect rhizosphere bacterial communities in South China.

Project description:Successive planting and monoculture, as common forest management methods, are widely used globally, especially in Chinese fir plantations in the subtropical areas of southern China. Although soil fertility depletion and productivity decline caused by successive planting have been widely reported, the underlying mechanism is still ambiguous. In this study, the composition and diversity of soil microorganisms (rhizosphere and bulk soils) in Chinese fir seedlings exposed to successive planting soils (first-generation Chinese fir seedings, FCP. second-generation Chinese fir seedings, SCP. third-generation Chinese fir seedings, TCP) and broadleaf tree species soil (Phoebe zhennan S. Lee et F. N. Wei, CK) were examined with high-throughput sequencing technology. Our findings revealed that the diversity and richness of bacterial and fungal communities were remarkably reduced in TCP than FCP and SCP, and were remarkably different between FCP and SCP. At the phylum level, the fungi with greatest relative abundance were Basidiomycota (5.74-32.88%) and Ascomycota (57.63-87.38%), while the bacteria with the greatest relative abundance were Acidobacteria (23.16-31.17%) and Proteobacteria (24.71-29.32%) for all treatments in both soil types. Additionally, the relative abundance of some pathogens (Penicillium and Burkholderia) was significantly higher in TCP than in FCP and SCP, suggesting that the presence of pathogens is an important factor in increasing the incidence of soil-borne sickness. Moreover, changes in fungal and bacterial communities were predominantly driven by soil dissolved organic carbon (DOC), DOC/DON ratio (DOCN), NO3 --N, microbial biomass carbon (MBC), and MBC/MBN ratio (MBCN). Overall, the long-term monoculture of Chinese fir promotes the microecological imbalance of rhizosphere and bulk soil, and remarkably reduced soil microbial community diversity. These results can provide a scientific support for the implementation of future management measures for fir plantations (e.g., fertilization, addition of microbial fungicides, and construction of mixed forests).

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Project description:Acidification can seriously affect the growth of tea trees and the yield and quality of tea leaves. In this study, we analyzed the effects of acidification on the physicochemical properties, microorganisms and metabolites of tea rhizosphere soils with different pH values, and the results showed that with the increase of soil pH, the organic matter content, cation exchange capacity, microbial biomass carbon, microbial biomass nitrogen, microbial respiration intensity, bacterial number and actinomyces number in tea rhizosphere soil all showed an increasing trend, while the fungi number decreased. The results of soil metabolite analysis showed that 2376, 2377 and 2359 metabolites were detected in tea rhizosphere soil with pH values of 3.29, 4.74 and 5.32, respectively, and the number of similar compounds reached 2331, accounting for more than 98%. The results of soil metabolite content analysis showed that with the increase of soil pH, the total contents of metabolite of tea rhizosphere soil increased significantly. The results of correlation analysis between physicochemical indexes of soil and microorganisms and soil metabolites showed that physicochemical indexes of soil and microorganisms were significantly correlated with 221 soil metabolites, among which 55 were significantly positively correlated and 166 were significantly negatively correlated. Based on correlation interaction network analysis, 59 characteristic compounds were obtained and divided into 22 categories, among which 7 categories compounds showed a significant increasing trend with the increase of soil pH, while the other 15 categories compounds showed the opposite trend. Based on the functional analysis of characteristic metabolites, this study found that with the increase of soil pH in tea rhizosphere, the diversity and number of soil microorganisms increased, and the cyclic ability of C and N of tea rhizosphere soil was enhanced, which in turn might lead to the enhancement of resistance of tea tree and promote the growth of tea tree.

Dataset Information

What's under the Christmas Tree? A Soil Sulfur Amendment Lowers Soil pH and Alters Fir Tree Rhizosphere Bacterial and Eukaryotic Communities, Their Interactions, and Functional Traits.

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