Long-term elevated precipitation induces grassland soil carbon loss via microbe-plant-soil interplay

Core microbes regulate plant-soil resilience by maintaining network resilience during long-term restoration of alpine grasslands

The alpine grasslands of the Qinghai-Tibetan Plateau (QTP), the world's highest plateau, have been severely degraded. To address this degradation, human-involved restoration efforts, including grassland cultivation, have been implemented. However, the impact of these practices on soil microbial community stability and its relationship with plant-soil system resilience has not been explored. In this study, we evaluate the effects of grassland restoration on microbial communities. We show that bacteria demonstrate higher composition resistance and resilience during the restoration process, when compared to fungi. The changes we observe in microbial community interactions support the stress gradient hypothesis. Our results emphasize the synergistic role of network resilience and the restoration of the plant-soil system. Importantly, we find that core microbial species significantly influence the resilience of the plant-soil system by sustaining the co-occurrence networks. These insights underscore the critical roles of microbial communities in grassland restoration and suggest new strategies for boosting grassland resilience by safeguarding core microbes.

Decoupled response of aboveground and belowground ecosystem multifunctionality to shrub encroachment in a semiarid grassland

Large-scale shrub encroachment poses significant challenges for the preservation and enhancement of ecosystem functions and services in grassland ecosystems. However, the impacts of shrub encroachment on grassland ecosystem multifunctionality (EMF) remain poorly understood. This study assessed the impact of shrub encroachment on 23 key ecosystem functions in a semiarid grassland, as well as the influence of plant, soil, and microbial factors on both aboveground and belowground EMF. Compared with areas with slight shrub encroachment, most individual aboveground ecosystem functions increased by 62.24%-251.05% with moderate shrub encroachment (p < 0.05). However, these functions significantly decreased (42.96-96.91%) under severe and extremely severe shrub encroachment. In contrast, individual belowground ecosystem functions consistently decreased across all stages of shrub encroachment, with reductions between 29.27% and 94.85% (p < 0.05). Shrub encroachment caused a decoupled response pattern, with the aboveground EMF initially increasing but then decreasing (R2 = 0.83, p < 0.001), whereas the belowground EMF decreased linearly (R2 = 0.86, p < 0.001). Soil bulk density and bacterial community composition were identified as the primary drivers of variations in aboveground EMF, whereas plant community composition and soil pH were crucial for regulating belowground EMF. Moreover, plant diversity was essential for maintaining both aboveground and belowground EMF. This study highlights the importance of considering both the stage of shrub encroachment and the specific ecosystem functions affected. These results emphasize the pivotal role of soil and microbial factors in shaping EMF, which is critical for predicting ecosystem responses to extensive changes in vegetation driven by intensifying climate change and human activities.

Differential responses of plant and microbial respiration to extreme precipitation and drought during spring and summer in the Eurasian meadow steppe

Increasing extreme precipitation and drought events along changes in their seasonal patterns due to climate change are expected to have profound consequences for carbon cycling. However, how these climate extremes impact ecosystem respiration (Reco) and whether these impacts differ between seasons remain unclear. Here, we reveal the responses of Reco and its components to extreme precipitation and drought in spring and summer by conducting a five-year manipulative experiment in a temperate meadow steppe. Based on a 5-year average, the seasonal mean values (±SE) of Reco, Rh, Rroot, Rabg and Rplant significantly increased (p < 0.01) under both extreme precipitation treatments: wet spring (WSP) and wet summer (WSU), and significantly decreased (p < 0.01) under both extreme drought treatments: dry spring (DSP) and dry summer (DSU), except in Rabg under DSU, which remained comparable to the control. The sensitivity of Reco, Rh, Rroot and Rplant to extreme precipitation was significantly higher in spring than in summer. On average, Rplant was the primary contributor of Reco, accounting for 37.18% and 38.31% of the total across all its components under WSP and WSU, respectively during the growing season over the five study years. Moreover, linear models revealed Rplant explained 87% of the variance in Reco. Our findings indicate that future changes in precipitation events, particularly extreme precipitation may lead to increased carbon release from ecosystems, largely driven by enhanced plant respiration rather than microbial respiration. However, due to this study focused solely on respiration and did not measure photosynthesis, the findings represent only the carbon release processes and do not account for potential carbon uptake by plants during the same conditions. These emergent identified contribution to ecosystem respiration provide valuable insights for improving model benchmarks to better predict ecosystem respiration responses to extreme climate in specified season.

Woody plant reduces soil organic carbon controlled by precipitation

Woody plant is a significant ecological challenge for grassland ecosystems worldwide. However, changes in soil organic carbon (SOC) fraction contents due to woody plant along a precipitation gradient are poorly understood. This study investigated the characteristics of SOC fractions in shrub-covered grasslands and native grasslands along a precipitation gradient in northern China using a "space-for-time" method, and explored the key factors influencing SOC fractions. The results showed that woody plant decreased total organic carbon (TOC), mineral-associated organic carbon (MAOC) contents and increased dissolved organic carbon (DOC) of grasslands. Mean annual precipitation (MAP) was the main controlling factor influencing SOC fractions, with an explanation proportion of 71.6% (p < 0.01), and the precipitation amount of 112-130 mm was the turning point influencing the direction of variation in SOC fractions due to woody plant of grasslands. With increasing precipitation, the variations in TOC contents of grasslands showed a first increasing and then decreasing trend (R2 = 0.52), and variations in POC contents showed an opposite trend to those in TOC content (R2 = 0.59). RDA and PLSPM analyses showed that from native grasslands to shrub-covered grasslands, the main controlling factors for SOC fractions were changed from MAP to a combination of plant properties and MAP, with an explanation of 84.74% and 82.57%, respectively. This study revealed the negative effects of woody plant on SOC of grasslands, and provides new perspectives on the potential dynamics of shrub -precipitation-SOC interactions.

Climate-Influenced Ecological Memory Modulates Microbial Responses to Soil Moisture

Long-term climatic differences shape the ecological memory of soil bacterial communities, which refers to the ability of past events to influence current environmental responses. However, their ecological mechanisms and consequences for bacterial responses to current environmental changes remain largely unknown, particularly in terms of temporal dynamics. Therefore, soil bacterial communities in the arid (Lhasa River Basin) and humid (Nyang River Basin) grasslands of the Qinghai-Tibet Plateau were compared to explore their temporal dynamics in response to current soil moisture and the resulting ecological consequences. Our results indicate that the differences between current and historical soil moisture determine the degree of divergence in bacterial community composition and potential function. The temporal dynamics of bacterial community composition, life strategies, and potential functions differed with environmental history, even under comparable moisture conditions. In contrast, bacterial communities with the same environmental history exhibited similar temporal dynamics, suggesting that environmental history has an important influence on bacterial community dynamics. This phenomenon may be caused by the continuous accumulation of bacterial community life strategies as an informational legacy, regulating future response patterns to soil moisture changes and thereby affecting biogeochemical cycles in the soil. For example, soil bacterial communities in relatively arid regions may increase their potential for dormancy, even when the current soil environment is moist, thereby enhancing ecosystem resilience by improving their capacity to respond to future drought events. This study provides new insights into the ecological memory of soil bacteria, emphasizing its critical role in influencing the compositional and functional changes of bacterial communities in response to current environmental changes. It highlights the significance of understanding the effect of environmental history in predicting the future responses of bacterial communities to disturbances and environmental changes.

Long-term climate establishes functional legacies by altering microbial traits

Long-term climate history can influence rates of soil carbon cycling but the microbial traits underlying these legacy effects are not well understood. Legacies may result if historical climate differences alter the traits of soil microbial communities, particularly those associated with carbon cycling and stress tolerance. However, it is also possible that contemporary conditions can overcome the influence of historical climate, particularly under extreme conditions. Using shotgun metagenomics, we assessed the composition of soil microbial functional genes across a mean annual precipitation gradient that previously showed evidence of strong climate legacies in soil carbon flux and extracellular enzyme activity. Sampling coincided with recovery from a regional, multi-year severe drought, allowing us to document how the strength of climate legacies varied with contemporary conditions. We found increased investment in genes associated with resource cycling with historically higher precipitation across the gradient, particularly in traits related to resource transport and complex carbon degradation. This legacy effect was strongest in seasons with the lowest soil moisture, suggesting that contemporary conditions-particularly, resource stress under water limitation-influences the strength of legacy effects. In contrast, investment in stress tolerance did not vary with historical precipitation, likely due to frequent periodic drought throughout the gradient. Differences in the relative abundance of functional genes explained over half of variation in microbial functional capacity-potential enzyme activity-more so than historical precipitation or current moisture conditions. Together, these results suggest that long-term climate can alter the functional potential of soil microbial communities, leading to legacies in carbon cycling.

The Response Mechanism of the cbbM Carbon Sequestration Microbial Community in the Alpine Wetlands of Qinghai Lake to Changes in Precipitation

The dramatic changes in precipitation patterns on the Tibetan Plateau affected the carbon-sequestering microbial communities within wetland ecosystems, which were closely related to the responses and adaptation mechanisms of alpine wetland ecosystems to climate change. This study focused on wetland soils subjected to different precipitation gradient treatments and employed high-throughput sequencing technology to analyze the soil cbbM carbon-sequestering microbial communities. The results indicated that Proteobacteria were the dominant microbial community responsible for carbon sequestration in the Wayan Mountain wetland. A 50% increase in precipitation significantly raised the soil moisture content, while a 50% reduction and a 25% increase in precipitation notably enhanced the total soil carbon content. The 25% reduction in precipitation increased the differences in microbial community composition, whereas both the 50% increase and the 50% reduction in precipitation decreased these differences. The soil pH and temperature had the most significant impact on the carbon-sequestering microbial communities. In conclusion, changes in precipitation affect the cbbM carbon sequestration characteristics of soil microbial communities, and a moderate reduction in water input benefited carbon sequestration in wetlands.

Effect of 9-year water and nitrogen additions on microbial necromass carbon content at different soil depths and its main influencing factors

Microbial necromass carbon (MNC) is a major source of soil organic carbon (SOC) pool, significantly influencing soil carbon sequestration. The effects of long-term water and nitrogen addition on MNC in soils at different depths, as well as their interactions, remain poorly understood. In this study, we examined the influence of water addition (+51.67 mm), nitrogen addition (25, 50, 100 kg N ha-1 yr-1), and their interactions on MNC accumulation at different soil depths in temperate grasslands. The addition of water and nitrogen over nine years has been observed to exhibit a decreasing trend in the MNC at different soil depths. Notably, MNC in the topsoil layer (0-10 cm) decreased significantly by 18.56 % under low nitrogen addition treatment, while MNC in the subsoil layer (40-60 cm) declined significantly by 27.19 % under high nitrogen addition treatment. Fungal microbial necromass carbon (FNC) contributed 3.25 times more to SOC than bacterial microbial necromass carbon (BNC). In the 0-10 cm soil layer, MNC is primarily governed by both microbial attributes and the physicochemical properties of the soil, in the 20-40 cm soil layer, the physicochemical properties of the soil predominantly control MNC, in the 40-60 cm layer, microbial characteristics exert a more significant influence on MNC. Collectively, our observations suggest that soil MNC decreased with the addition of water and nitrogen in the 0-60 cm soil slope, which could enable the accurate prediction of global change impacts on the accumulation of soil carbon, thus facilitating the implementation of strategies to augment soil carbon sequestration.

The Fungal Community Structure Regulates Elevational Variations in Soil Organic Carbon Fractions in a Wugong Mountain Meadow

Soil organic carbon (SOC) fractions are vital intrinsic indicators of SOC stability, and soil fungi are the key drivers of soil carbon cycling. However, variations in SOC fractions along an elevational gradient in mountain meadows and the role of the fungal community in regulating these variations are largely unknown, especially in subtropical areas. In this study, an elevation gradient experiment (with experimental sites at 1500, 1700, and 1900 m) was set up in a Miscanthus sinensis community in a meadow on Wugong Mountain, Southeast China, to clarify the effects of elevation on soil fungal community composition, microbial residue carbon, and SOC fractions. The results showed that the contribution of soil microbial residue carbon to SOC was only 16.1%, and the contribution of soil fungal residue carbon to SOC (15.3%) was far greater than that of bacterial residue carbon (0.3%). An increase in elevation changed the fungal community structure and diversity, especially in the topsoil (0-20 cm depth) compared with that in the subsoil (20-40 cm depth), but did not affect fungal residue carbon in the two soil layers. When separating SOC into the fractions mineral-associated organic carbon (MAOC) and particulate organic carbon (POC), we found that the contribution of MAOC (66.6%) to SOC was significantly higher than that of POC (20.6%). Although an increased elevation did not affect the SOC concentration, it significantly changed the SOC fractions in the topsoil and subsoil. The soil POC concentration and its contribution to SOC increased with an increasing elevation, whereas soil MAOC showed the opposite response. The elevational variations in SOC fractions and the POC/MAOC ratio were co-regulated by the fungal community structure and total nitrogen. Our results suggested that SOC stabilization in mountain meadows decreases with an increasing elevation and is driven by the fungal community structure, providing scientific guidance for SOC sequestration and stability in mountain meadows in subtropical areas.

Greenhouse gas emissions from the growing season are regulated by precipitation events in conservation tillage farmland ecosystems of Northeast China

Reducing greenhouse gas (GHG) emissions from agricultural ecosystems is vital to mitigate global warming. Conservation tillage is widely used in farmland management to improve soil quality; however, its effects on soil GHG emissions remain poorly understood, particularly in high-yield areas. Therefore, our study aimed to evaluate the effects of no-tillage (NT) combined with four straw-mulching levels (0 %, 33 %, 67 %, and 100 %) on GHG emission risk and the main influencing factors. We conducted in-situ observations of GHG emissions from soils under different management practices during the maize-growing season in Northeastern China. The results showed that NT0 (705.94 g m-2) reduced CO2 emissions by 18 % compared to ridge tillage (RT, 837.04 g m-2). Different straw mulching levels stimulated N2O emissions after rainfall, particularly under NT combined with 100 % straw mulching (2.89 kg ha-1), which was 45 % higher than that in any other treatments. The CH4 emissions flux among different treatments was nearly zero. Overall, straw mulching levels had no significant effect on the GHG emissions. During the growing season, soil NH4+-N (< 20 mg kg-1) remained low and decreased with the extension of growth stage, whereas soil NO3--N initially increased and then decreased. More importantly, the results of structural equation modeling indicate that: a) organic material input and soil moisture are key factors affecting CO2 emissions, b) nitrogen fertilizer and soil moisture promote N2O emissions, and c) climatic factors exert an inexorable influence on the GHG emissions process. Our conclusions emphasize the necessity of incorporating precipitation-response measures into farmland management to reduce the risk of GHG emissions.

Dynamics of the soil microbial community associated with Morchella cultivation: diversity, assembly mechanism and yield prediction

Introduction

The artificial cultivation of morels has been a global research focus owing to production variability. Understanding the microbial ecology in cultivated soil is essential to increase morel yield and alleviate pathogen harm.

Methods

A total of nine Morchella cultivation experiments in four soil field types, forest, paddy, greenhouse, and orchard in Shanghai city were performed to determine the potential ecological relationship between Morchella growth and soil microbial ecology.

Results

Generally, significant variation was observed in the soil microbial diversity and composition between the different experimental field types. The niche width analysis indicated that the bacterial habitat niche breadth was significantly greater than the fungal community width, which was further confirmed by a null model that revealed that homogeneous selection could explain 46.26 and 53.64% of the variance in the bacterial and fungal assemblies, respectively. Moreover, the neutral community model revealed that stochastic processes dominate the bacterial community in forests and paddies and both the bacterial and fungal communities in orchard crops, whereas deterministic processes mostly govern the fungal community in forests and paddies and both the bacterial and the fungal communities in greenhouses. Furthermore, co-occurrence patterns were constructed, and the results demonstrated that the dynamics of the soil microbial community are related to fluctuations in soil physicochemical characteristics, especially soil potassium. Importantly, structural equation modeling further demonstrated that the experimental soil type significantly affects the potassium content of the soil, which can directly or indirectly promote Morchella yield by inhibiting soil fungal richness.

Discussion

This was the first study to predict morel yield through soil potassium fertilizer and soil fungal community richness, which provides new insights into deciphering the importance of microbial ecology in morel agroecosystems.

Biochar Enhances the Resistance of Legumes and Soil Microbes to Extreme Short-Term Drought

Short-term drought events occur more frequently and more intensively under global climate change. Biochar amendment has been documented to ameliorate the negative effects of water deficits on plant performance. Moreover, biochar can alter the soil microbial community, soil properties and soil metabolome, resulting in changes in soil functioning. We aim to reveal the extent of biochar addition on soil nutrients and the soil microbial community structure and how this improves the tolerance of legume crops (peanuts) to short-term extreme drought. We measured plant performances under different contents of biochar, set as a gradient of 2%, 3% and 4%, after an extreme experimental drought. In addition, we investigated how soil bacteria and fungi respond to biochar additions and how the soil metabolome changes in response to biochar amendments, with combined growth experiments, high-throughput sequencing and soil omics. The results indicated that biochar increased nitrites and available phosphorus. Biochar was found to influence the soil bacterial community structure more intensively than the soil fungal community. Additionally, the fungal community showed a higher randomness under biochar addition when experiencing short-term extreme drought compared to the bacterial community. Soil bacteria may be more strongly related to soil nutrient cycling in peanut agricultural systems. Although the soil metabolome has been documented to be influenced by biochar addition independent of soil moisture, we found more differential metabolites with a higher biochar content. We suggest that biochar enhances the resistance of plants and soil microbes to short-term extreme drought by indirectly modifying soil functioning probably due to direct changes in soil moisture and soil pH.