Differential response of soil microbial and animal communities along the chronosequence of Cunninghamia lanceolata at different soil depth levels in subtropical forest ecosystem

Fungal communities in boreal soils are influenced by land use, agricultural soil management, and depth

Land use and agricultural soil management affect soil fungal communities that ultimately influence soil health. Subsoils harbor nutrient reservoir for plants and can play a significant role in plant growth and soil carbon sequestration. Typically, microbial analyses are restricted to topsoil (0-30 cm) leaving subsoil fungal communities underexplored. To address this knowledge gap, we analyzed fungal communities in the vertical profile of four boreal soil treatments: long-term (24 years) organic and conventional crop rotation, meadow, and forest. Internal transcribed spacer (ITS2) amplicon sequencing revealed soil-layer-specific land use or agricultural soil management effects on fungal communities down to the deepest measured soil layer (40-80 cm). Compared to other treatments, higher proportion of symbiotrophs, saprotrophs, and pathotrophs + plant pathogens were found in forest, meadow and crop rotations, respectively. The proportion of arbuscular mycorrhizal fungi was higher in deeper (>20 cm) soil than in topsoil. Forest soil below 20 cm was dominated by fungal functional groups with proposed interactions with plants or other soil biota, whether symbiotrophic or pathotrophic. Ferrous oxide was an important factor shaping fungal communities throughout the vertical profile of meadow and cropping systems. Our results emphasize the importance of including subsoil in microbial community analyses in differently managed soils.

Windfarm construction alters soil multinutrient cycling by destabilizing microfauna community in a mountain ecosystem

In recent decades, investors attracted to wind power's promise of zero-emission electricity have fueled the proliferation of large windfarms across the world. However, the effects of windfarm construction with different land use subtypes (i.e., wind turbine, waste slag, and construction production and living areas) on soil microfauna community stability and subsequent consequences for ecosystem functioning remains poorly understood. Here, we evaluated how these three land use types affect soil microfauna community stability relative to natural vegetation types (forest, shrubland, and grassland) in a mountain area. We found that all three windfarm land use subtypes reduced soil multinutrient cycling and microfauna community stability compared with natural ecosystems. However, among these natural ecosystems, reductions of soil multinutrient cycling were 66.36% and 79.10% lower in grassland than in forest and shrubland, respectively. Reductions of soil nematode community stability were 62.15% and 77.22% lower in grassland than in forest and shrubland; as well as soil protist community stability were 74.01% and 56.74%, respectively. Interspecific interactions and environmental filtering jointly drove variation in soil microfauna community stability. Soil microfauna community stability was significantly and positively linked to soil multinutrient cycling, which has the potential to initiate cascading ecological consequences. Our finding implies that grasslands may be more suitable than shrublands or forests for windfarm development based on the responses of soil microfauna communities.

Effects of forest age and season on soil microbial communities in Chinese fir plantations

Understanding changes in the distribution patterns and diversity of soil microbial communities from the perspectives of age-related changes, seasonal variations, and the interaction between the two factors can facilitate the management of plantations. In Chinese fir plantations, we collected soils from different depths in over-mature forests, mature forests, near-mature forests, middle-aged forests, and young forests in summer, autumn, and winter in China's subtropical regions. As the forests developed, bacterial and fungal communities' diversity changed, reached a minimum value at near-mature forests, and then increased in mature forests or over-mature forests. Near-mature forests had the lowest topological properties. The Shannon index of microbial communities varied with seasonal changes (P < 0.05). Bacterial and fungal community composition at genus level was more closely related to temperature indicators (including daily average temperature, daily maximum temperature, and daily minimum temperature) (P < 0.01, 0.5554 < R2 <0.8185) than daily average precipitation (P > 0.05, 0.0321 < R2 <0.6773). Bacteria were clustered by season and fungi were clustered by forest age. We suggested that extending the tree cultivation time of plantations could promote microbial community recovery. In addition, we found some species worthy of attention, including Bacteroidetes in autumn in over-mature forests, and Firmicutes in summer in young forests.IMPORTANCEChinese fir [Cunninghamia lanceolata (Lamb.) Hook] is an important fast-growing species with the largest artificial forest area in China, with the outstanding problems of low quality in soil. Soil microorganisms play a crucial role in soil fertility by decomposing organic matter, optimizing soil structure, and releasing essential nutrients for plant growth. In order to maintain healthy soil quality and prevent nutrient depletion and land degradation, it is crucial to understand the changes of soil microbial composition and diversity. Our study determined to reveal the change of soil microbial community from stand age, season, and the interaction between the two aspects, which is helpful to understand how interannual changes in different years and seasonal changes in one year affect soil fertility restoration and sustainable forest plantation management. It is a meaningful exploration of soil microbial communities and provides new information for further research.

Response of soil micro-food web to nutrient limitation along a subtropical forest restoration

Forest ecosystem productivity and function is strongly influenced by the interaction between soil organisms and their resource use that can be impeded by an imbalance of ecological stoichiometry. Soil microorganisms are known to have an important role in biogeochemical cycling which is strongly influenced by ecological stoichiometry. However, there is limited understanding of how soil micro-food web respond to stoichiometric imbalances during forest restoration. Here, we investigated the effect of forest restoration on soil physio-chemical properties and the structure and function of soil micro-food web along a chronosequence of transformation stages: (i) early stage monoculture plantation of Chinese fir (Cunninghamia lanceolata) comprised of three age classes (5, 10 and 20 years); (ii) mid-stage conifer-broadleaved mixed forest; and (iii) late-stage mixed species broadleaved forest in south China. Results showed that forest restoration from C. lanceolata monocultures to mixed species broadleaved forest significantly increased soil organic carbon and total nitrogen. Soil bacteria, fungi, protists and nematodes abundance increased and the co-occurrence networks of soil biota became more complex and stable along the restoration chronosequence. In contrast, soil nitrogen and phosphorus limitations, particularly phosphorus limitation, increased along the chronosequence. In addition, soil exoenzyme activity suggested that the microbial investment in resource acquisition shifted from C- to nutrient-acquiring enzymes from the earlier to the later restoration stages. Availability of soil resources (e.g., dissolved organic carbon, ammonium, and available phosphate) appeared to have an important role in regulating soil food web composition, structure and stability during forest restoration. We conclude that nutrient limitation, particularly phosphorus limitation, likely has an important role in determining the stability of soil food webs during forest restoration. These findings contribute to our understanding of the relationships between soil nutrient limitation and soil micro-food web, and have implications for carbon sequestration through forest restoration and management in southern China.

Precipitation Drives Soil Protist Diversity and Community Structure in Dry Grasslands

Protists are essential components of soil microbial communities, mediating nutrient cycling and ecosystem functions in terrestrial ecosystems. However, their distribution patterns and driving factors, particularly, the relative importance of climate, plant and soil factors, remain largely unknown. This limits our understanding of soil protist roles in ecosystem functions and their responses to climate change. This is particularly a concern in dryland ecosystems where soil microbiomes are more important for ecosystem functions because plant diversity and growth are heavily constrained by environmental stresses. Here, we explored protist diversity and their driving factors in grassland soils on the Tibetan Plateau, which is a typical dryland region with yearly low temperatures. Soil protist diversity significantly decreased along the gradient of meadow, steppe, and desert. Soil protist diversity positively correlated with precipitation, plant biomass and soil nutrients, but these correlations were changed by grazing. Structural equation and random forest models demonstrated that precipitation dominated soil protist diversity directly and indirectly by influencing plant and soil factors. Soil protist community structure gradually shifted along meadow, steppe and desert, and was driven more by precipitation than by plant and soil factors. Soil protist community compositions were dominated by Cercozoa, Ciliophora and Chlorophyta. In particular, Ciliophora increased but Chlorophyta decreased in relative abundance along the gradient of meadow, steppe and desert. These results demonstrate that precipitation plays more important roles in driving soil protist diversity and community structure than plant and soil factors, suggesting that future precipitation change profoundly alters soil protist community and functions in dry grasslands.

Sugarcane cultivar-dependent changes in assemblage of soil rhizosphere fungal communities in subtropical ecosystem

Sugarcane cultivars (Saccharum officinarum L.) are widely cultivated for both sugar and renewable energy in China. The response of rhizosphere fungal composition and diversity to different emerging sugarcane cultivars is limited. Therefore, utilizing high-throughput sequencing, we explored fungal communities' structure in soils adhering to six sugarcane cultivars' roots (Guitang 08-120, Regan14-62, Guitang 08-1180, Haizhe 22, Liucheng 05-136, Taitang 22) in Guangxi Province, China. Our results suggested that sugarcane varieties significantly altered rhizosphere soil attributes, with Haizhe 22 having substantially lower soil pH, organic matter (OM), available phosphorus (AP), and soil water contents (SWC) than others cultivars. Different sugarcane varieties did not substantially affected the Shannon fungal diversity index, but the apparent effect on fungal richness was significant. Beta diversity analysis revealed that "Haizhe 22" distinguished the fungal community from the other five cultivars. Soil pH, OM, cultivars, and soil moisture were crucial determinants in shaping soil fungal composition. The Haizhe 22 rhizosphere significantly enriched the operational taxonomic units (OTUs) assigned to two fungal genera (Cephalotheca and Sagenomella), while rhizosphere of other verities significantly enriched the OTUs assigned to four fungal genera (Chaetomium, Chaetosphaeria, Mortierella, and Talaromyces), suggesting their essential role in plant development, disease tolerance, and bioremediation. These findings may help in selecting or breeding innovative genotypes capable of supporting abundant rhizosphere fungi beneficial to plants that would likely improve crops' agronomic potential and maintain soil ecosystem sustainability.

Sugarcane cultivars manipulate rhizosphere bacterial communities' structure and composition of agriculturally important keystone taxa

Different sugarcane cultivars are grown to produce renewable energy and sugar in China. However, we have a limited awareness of the interactive influence of varying sugarcane cultivars on rhizosphere bacterial structure and diversity. Assessing cultivar choice impact on soil bacterial communities is vital since bacterial taxa are frequently impacted by planting performance. Employing high-throughput Illumina sequencing, we examined bacterial communities' assemblage in the rhizosphere of six Chinese sugarcane cultivars (Regan14-62, Guitang 08-120, Haizhe 22, Guitang 08-1180, Taitang 22 and Liucheng 05-136). Our results indicated that different sugarcane cultivars have no significant influence on the Shannon index; however, their impact on richness was substantial. There was a difference in the bacterial community structure that is also associated with a change in the community composition, as determined by the DESeq2 results, suggesting that "Haizhe 22 (HZ22)" had a completely different beta diversity as compared to other five cultivars by enriching abundance of Firmicutes, Proteobacteria, Gemmatimonadetes, Saccharibacteria and Bacteroidetes and reducing the quantity of Actinobacteria, Chloroflexi, Acidobacteria, and Planctomycetes, respectively. The HZ22 rhizosphere significantly enriched six genera (e.g., Devosia, Mizugakiibacter, Mycobacterium, Nakamurella, Rhizomicrobium, and Virgibacillus) relative to other varieties, suggesting an important role in plant disease tolerance and growth development, including soil nutrient cycling and bioremediation. Analysis of similarity (ANOSIM) and correlation analysis revealed that cultivars, soil organic matter, pH and soil moisture were central factors influencing bacterial composition. These findings may help in selection of plant cultivars capable of supporting highly abundant specific beneficial microbial groups, improving plant disease resistance, growth stimulation, and soil bioremediation capabilities, further leading to improvements in breeding strategies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03091-1.