Reduced precipitation neutralizes the positive impact of soil warming on soil microbial community in a temperate oak forest

Soil microfauna mediate multifunctionality under multilevel warming in a primary forest

Soil microfauna play a crucial role in maintaining multiple functions associated with soil phosphorous, nitrogen and carbon cycling. Although both soil microfauna diversity and multifunctionality are strongly affected by climate warming, it remains unclear how their relationships respond to different levels of warming. We conducted a 3-year multilevel warming experiment with five warming treatments in a subtropical primary forest. Using infrared heating systems, the soil surface temperature in plots was maintained at 0.8, 1.5, 3.0 and 4.2°C above ambient temperature (control). Our findings indicated that low-level warming (+0.8-1.5°C) increased soil multifunctionality, as well as nematode and protist diversity, compared with the control. In contrast, high-level warming (+4.2°C) significantly reduced these variables. We also identified significant positive correlations between soil multifunctionality and nematode and protist diversity in the 0-10 cm soil layer. Notably, we found that soil multifunctionality and protist diversity did not change significantly under 3.0°C warming treatment. Our results imply that a temperature increase of around 3°C may represent a critical threshold in subtropical forests, which is of great importance for identifying response measures to global warming from the perspective of microfauna in the surface soil. Our findings provide new evidence on how soil microfauna regulate multifunctionality under varying degrees of warming in primary forests.

Differential spatial responses and assembly mechanisms of soil microbial communities across region-scale Taiga ecosystems

Different soil microbial communities play distinct key roles in regulating forest ecosystem processes and functions. However, the differences in spatial variability and assembly mechanisms of various taiga forest soil microbial taxa remain poorly understood. Here, we assessed the spatial patterns of bacterial and fungal communities, their assembly processes, and the influencing factors in taiga forest ecosystems in Xinjiang, China. A significant distance decay pattern was observed in the similarity of bacterial and fungal communities, with bacterial communities exhibiting a more pronounced pattern than fungal communities. Stochastic and deterministic processes governed together to drive soil bacterial community assembly, whereas stochastic processes dominated fungal community assembly. The coexistence networks revealed that the interactions of bacterial and fungal networks in the four regions are primarily based on interspecies symbiosis, with fungal coexistence networks demonstrating greater stability than bacterial networks. Additionally, the study identified a positive relationship between the modularity of bacterial networks and dispersal limitation. Analysis of environmental factors revealed that soil pH primarily affects the characteristics and assembly mechanisms of bacterial communities, while vegetation conditions primarily affect fungal diversity and composition, with other unconsidered environmental variables influencing the fungal community assembly process. This study emphasized the distinct ways in which bacteria and fungi respond to environmental factors and interspecies interactions. Our results suggested that distinct restoration measures should be implemented for bacteria and fungi in future conservation efforts for forest soil microorganisms.

Effects of Long-Term Application of Nitrogen Fertilizer on Soil Acidification and Biological Properties in China: A Meta-Analysis

Soil acidification is a global environmental problem with significant impacts on agricultural production, environmental protection, and ecosystem health. Soil acidification is widespread in China, affecting crop yields, agricultural product quality, and biodiversity. Since the 1980s, much work has been done on acidic soils in China, but it is controversial whether excessive nitrogen fertilizer application can lead to soil acidification mechanisms. To address the above issues, we conducted a meta-analysis of 115 published papers to integrate and analyze the effects of N fertilizer application on soil acidification and biological properties from 1980 to 2024. We also quantified the effect of nitrogen fertilization on soil acidification and biological changes under different climatic conditions. The results showed that under long-term application of nitrogen fertilizers in China from 1980 to 2024, soil pH decreased by an average of 15.27%, and the activities of soil urease, nitrate reductase, nitrite reductase, catalase, glutamate dehydrogenase, and glutamate synthetase decreased by an average of 9.82-22.37%. The soil microbial community richness (Chao1 index) increased by 6.53%, but the community diversity (Shannon index) decreased by 15.42%. Among the dominant soil microorganisms, the relative abundance of bacteria decreased by an average of 9.67-29.38% and the abundance of gene expression of nifH, amoA-AOA, amoA-AOB, and qnorB decreased by 9.92-19.83%. In addition, we found that the mean annual temperature and rainfall impacted soil acidification via their effect on soil microbial diversity and community composition. This study provides a scientific basis for an in-depth understanding of the spatial and temporal variation of soil acidification and biological properties in China.

The influence of precipitation timing and amount on soil microbial community in a temperate desert ecosystem

Introduction

Global climate change may lead to changes in precipitation patterns. This may have a significant impact on the microbial communities present in the soil. However, the way these communities respond to seasonal variations in precipitation, particularly in the context of increased precipitation amounts, is not yet well understood.

Methods

To explore this issue, a five-year (2012-2016) field study was conducted at the northeast boundary of the Ulan Buh Desert, examining the effects of increased precipitation during different periods of the growing season on both bacterial and fungal communities. The study included five precipitation pattern treatments: a control group (C), as well as groups receiving 50 and 100% of the local mean annual precipitation amount (145 mm) during either the early growing season (E50 and E100) or the late growing season (L50 and L100). The taxonomic composition of the soil bacterial and fungal communities was analyzed using Illumina sequencing.

Results

After 5 years, the bacterial community composition had significantly changed in all treatment groups, with soil bacteria proving to be more sensitive to changes in precipitation timing than to increased precipitation amounts within the desert ecosystem. Specifically, the alpha diversity of bacterial communities in the late growing season plots (L50 and L100) decreased significantly, while no significant changes were observed in the early growing season plots (E50 and E100). In contrast, fungal community composition remained relatively stable in response to changes in precipitation patterns. Predictions of bacterial community function suggested that the potential functional taxa in the bacterial community associated with the cycling of carbon and nitrogen were significantly altered in the late growing season (L50 and L100).

Discussion

These findings emphasize the importance of precipitation timing in regulating microbial communities and ecosystem functions in arid regions experiencing increased precipitation amounts.

Simulating the effect of climate change on soil microbial community in an Abies georgei var. smithii forest

Qinghai-Tibet Plateau is considered a region vulnerable to the effects of climate change. Studying the effects of climate change on the structure and function of soil microbial communities will provide insight into the carbon cycle under climate change. However, to date, changes in the successional dynamics and stability of microbial communities under the combined effects of climate change (warming or cooling) remain unknown, which limits our ability to predict the consequences of future climate change. In this study, in situ soil columns of an Abies georgei var. smithii forest at 4,300 and 3,500 m elevation in the Sygera Mountains were incubated in pairs for 1 year using the PVC tube method to simulate climate warming and cooling, corresponding to a temperature change of ±4.7°C. Illumina HiSeq sequencing was applied to study alterations in soil bacterial and fungal communities of different soil layers. Results showed that warming did not significantly affect the fungal and bacterial diversity of the 0-10 cm soil layer, but the fungal and bacterial diversity of the 20-30 cm soil layer increased significantly after warming. Warming changed the structure of fungal and bacterial communities in all soil layers (0-10 cm, 10-20 cm, and 20-30 cm), and the effect increased with the increase of soil layers. Cooling had almost no significant effect on fungal and bacterial diversity in all soil layers. Cooling changed the structure of fungal communities in all soil layers, but it showed no significant effect on the structure of bacterial communities in all soil layers because fungi are more adapted than bacteria to environments with high soil water content (SWC) and low temperatures. Redundancy analysis (RDA) and hierarchical analysis showed that changes in soil bacterial community structure were primarily related to soil physical and chemical properties, whereas changes in soil fungal community structure primarily affected SWC and soil temperature (Soil Temp). The specialization ratio of fungi and bacteria increased with soil depth, and fungi were significantly higher than bacteria, indicating that climate change has a greater impact on microorganisms in deeper soil layers, and fungi are more sensitive to climate change. Furthermore, a warmer climate could create more ecological niches for microbial species to coexist and increase the strength of microbial interactions, whereas a cooler climate could have the opposite effect. However, we found differences in the intensity of microbial interactions in response to climate change in different soil layers. This study provides new insights to understand and predict future effects of climate change on soil microbes in alpine forest ecosystems.

Study of Wetland Soils of the Salar de Atacama with Different Azonal Vegetative Formations Reveals Changes in the Microbiota Associated with Hygrophile Plant Type on the Soil Surface

Salar de Atacama is located approximately 55 km south of San Pedro de Atacama in the Antofagasta region, Chile. The high UV irradiation and salt concentration and extreme drought make Salar de Atacama an ideal site to search for novel soil microorganisms with unique properties. Here, we used a metataxonomic approach (16S rRNA V3-V4) to identify and characterize the soil microbiota associated with different surface azonal vegetation formations, including strict hygrophiles (Baccharis juncea, Juncus balticus, and Schoenoplectus americanus), transitional hygrophiles (Distichlis spicata, Lycium humile, and Tessaria absinthioides), and their various combinations. We detected compositional differences among the soil surface microbiota associated with each plant formation in the sampling area. There were changes in soil microbial phylogenetic diversity from the strict to the transitional hygrophiles. Moreover, we found alterations in the abundance of bacterial phyla and genera. Halobacteriota and Actinobacteriota might have facilitated water uptake by the transitional hygrophiles. Our findings helped to elucidate the microbiota of Salar de Atacama and associate them with the strict and transitional hygrophiles indigenous to the region. These findings could be highly relevant to future research on the symbiotic relationships between microbiota and salt-tolerant plants in the face of climate change-induced desertification. IMPORTANCE The study of the composition and diversity of the wetland soil microbiota associated with hygrophilous plants in a desert ecosystem of the high Puna in northern Chile makes it an ideal approach to search for novel extremophilic microorganisms with unique properties. These microorganisms are adapted to survive in ecological niches, such as those with high UV irradiation, extreme drought, and high salt concentration; they can be applied in various fields, such as biotechnology and astrobiology, and industries, including the pharmaceutical, food, agricultural, biofuel, cosmetic, and textile industries. These microorganisms can also be used for ecological conservation and restoration. Extreme ecosystems are a unique biological resource and biodiversity hot spots that play a crucial role in maintaining environmental sustainability. The findings could be highly relevant to future research on the symbiotic relationships between microbiota and extreme-environment-tolerant plants in the face of climate change-induced desertification.

Effects of mycorrhiza and hyphae on the response of soil microbial community to warming in eastern Tibetan Plateau

The effects of mycorrhiza and its external hyphae on the response of soil microbes to global warming remain unclear. This study investigates the role of mycorrhiza and its hyphae in regulating soil microbial community under warming by examining the microbial biomass and composition in the ingrowth cores of arbuscular mycorrhiza (AM) plant, Fargesia nitida, and ectomycorrhiza (ECM) plant, Picea asperata, with/without mycorrhiza/hyphae and experimental warming. The results showed that warming significantly increased the biomass of all soil microbes (by 19.89%-137.48%) and altered the microbial composition in both plant plots without mycorrhiza/hyphae. However, this effect was weakened in the presence of mycorrhiza or hyphae. In F. nitida plots, warming did not significantly affect biomass and composition of most soil microbial groups when mycorrhiza or hyphae were present. In P. asperata plots, warming significantly increased the total and ECM fungi (ECMF) biomass in the presence of hyphae (p < 0.05) and the total, Gn, and AM fungi (AMF) biomass in the presence of mycorrhiza (p < 0.05). Meanwhile, the response of enzyme activities to warming was also altered with mycorrhiza or hyphae. Additionally, soil microbial community composition was mainly influenced by soil available phosphorus (avaP), while enzyme activities depended on soil avaP, dissolved organic carbon (DOC), and nitrate concentrations. Our results indicate that mycorrhiza and its hyphae are essential in regulating the response of microbes to warming.

Fungal communities in soils under global change

Soil fungi play indispensable roles in all ecosystems including the recycling of organic matter and interactions with plants, both as symbionts and pathogens. Past observations and experimental manipulations indicate that projected global change effects, including the increase of CO₂ concentration, temperature, change of precipitation and nitrogen (N) deposition, affect fungal species and communities in soils. Although the observed effects depend on the size and duration of change and reflect local conditions, increased N deposition seems to have the most profound effect on fungal communities. The plant-mutualistic fungal guilds - ectomycorrhizal fungi and arbuscular mycorrhizal fungi - appear to be especially responsive to global change factors with N deposition and warming seemingly having the strongest adverse effects. While global change effects on fungal biodiversity seem to be limited, multiple studies demonstrate increases in abundance and dispersal of plant pathogenic fungi. Additionally, ecosystems weakened by global change-induced phenomena, such as drought, are more vulnerable to pathogen outbreaks. The shift from mutualistic fungi to plant pathogens is likely the largest potential threat for the future functioning of natural and managed ecosystems. However, our ability to predict global change effects on fungi is still insufficient and requires further experimental work and long-term observations. Citation: Baldrian P, Bell-Dereske L, Lepinay C, Větrovský T, Kohout P (2022). Fungal communities in soils under global change. Studies in Mycology 103: 1-24. doi: 10.3114/sim.2022.103.01.