Alpine Soils Research Articles

Exploring the physical properties of Australian alpine soils to inform ecosystem restoration

Alpine soils are globally threatened and are particularly vulnerable to the impacts of climate change. In Australia, development and grazing put further pressure on alpine ecosystems. Consequently, land managers and restoration practitioners are increasingly interested in understanding how to tailor revegetation approaches to enhance their success in mountain environments. Because of the intrinsic role of soils in plant-water relationships, the aim of this study was to quantify and compare the physical and hydraulic properties of soils in the Australian Alps. We investigated four common soils that occur across the Australian Alps bioregion: peat soils (organosols), alpine humus soils, skeletal mountaintop soils, and disturbed soils (anthroposols). We quantified and compared soil bulk density, particle density, porosity, water content, infiltration, hydraulic conductivity, and wilting point between soils. We found significant differences in soil properties both within and among each soil, highlighting the importance of understanding local edaphic conditions to improve revegetation outcomes. We recommend that direct measurements of plant establishment, growth, and survival are linked with soil physical, chemical, and hydraulic properties in future research, to build upon these findings.

Relationship between soil structure and hydrological properties of the active layer in the permafrost region of the Qinghai–Tibet Plateau based on fractal theory

Soil structure and hydrological properties influence ecosystem stability and hydrological cycles. Fractal theory has been widely used in the quantitative analysis of soil particle-size distribution (PSD), aggregate and pore distribution, and evaluation of soil degradation, desertification, and wind erosion. However, the complex relationships between soil physiochemical properties and soil hydrological processes based on fractal theory have not been thoroughly investigated. This study focused on the correlation among soil structure, physicochemical properties, and hydrological properties in the active layers of various soil types and vegetation coverages in the permafrost region of the Qinghai–Tibet Plateau (QTP) using the principles of fractal theory. The results showed that the fractal dimension of soil PSD (DPSD) in the active layer of the QTP was predominantly within the range of 2.13–2.70, which is notably smaller than the fractal dimension of the soil water retention curve (DWRC: 2.72–2.93). With decreased vegetation coverage, the alpine soil particles exhibit gradual fineness, increasing the DPSD. Soil physicochemical properties were affected by the interactions among internal factors and the external environment, such as geographical locations, slope orientations, vegetation coverages, and soil freeze–thaw cycles. The results of correlation analysis indicated that the fractal dimension of PSD and the soil water retention curve (WRC) were significantly correlated with soil textural, physicochemical, and hydraulic properties, particularly in clay, silt, and very fine sand content. Finally, a fractal model of WRC in the permafrost region was established based on DPSD and WRC parameters of the Gardner and van Genuchten models. The study provides an improved perspective for revealing the transport process and influencing mechanism of soil water and salt in the active layer of the QTP and a more accurate prediction of soil physiochemical and hydrological properties for climate warming and wetting.

The Multifaceted Soils of Himachal Pradesh, India: Types and Characteristics

The soils of Himachal Pradesh face a multitude of pressing issues that threaten their health and agricultural productivity. The diverse geographical features, temperature regimes and biological zones of Himachal Pradesh have resulted into a vast range of soil types in the state. Alpine, forest, alluvial and sub-mountain soils are the four major soil categories into which the state's soils can be generally divided. Only a particular species and adapted plants can thrive in the extreme weather circumstances of alpine soils, which are located at higher elevations and possess soils having thin, stony and acidic in reaction. The mid-hill areas are dominated by forest soils which are distinguished by their high levels of organic matter and nutrients. These soils support luxuriant vegetation and make effective agricultural methods possible. Alluvial soils, which are mostly found in river valleys and are deposited by ravine systems are extremely rich and perfect in fertility and suitable for growing a range of crops including vegetables, rice and maize. Located in the foothills, sub-mountain soil exhibits a blend of traits from alluvial and forest soils, thus providing a range of uses for horticulture and agriculture. In addition to supporting a diverse array of plant and animal life, Himachal Pradesh's varied soil types are vital to the region's agricultural economy. One of the biggest problems is soil erosion, which is made worse by the steep terrain and abundant rainfall in the area. This results in the loss of topsoil and decreased fertility. Deforestation, overgrazing, and unsustainable farming methods all contribute to land degradation, which further reduces biodiversity and soil quality. Furthermore, crop development is impacted by soil acidity in high-altitude regions, which restricts nutrient availability. However, these issues need efficient conservation measures and soil management techniques. In order to maintain Himachal Pradesh's rich biodiversity and agricultural potential for future generations, sustainable agricultural development and environmental protection in this ecologically sensitive area depend on an understanding of the complex soil dynamics. Addressing these interconnected issues requires a comprehensive approach, emphasizing sustainable land management practices, community engagement, and restoration efforts to preserve the vital soil resources of this ecologically sensitive region.

Elevational Patterns, Source Identification and Ecological Risks of Heavy Metals in Tropical Alpine Soils

Elevational Patterns, Source Identification and Ecological Risks of Heavy Metals in Tropical Alpine Soils

Asymmetric winter warming reduces microbial carbon use efficiency and growth more than symmetric year-round warming in alpine soils

Asymmetric seasonal warming trends are evident across terrestrial ecosystems, with winter temperatures rising more than summer ones. Yet, the impact of such asymmetric seasonal warming on soil microbial carbon metabolism and growth remains poorly understood. Using 18O isotope labeling, we examined the effects of a decade-long experimental seasonal warming on microbial carbon use efficiency (CUE) and growth in alpine grassland ecosystems. Moreover, the quantitative stable isotope probing with 18O-H2O was employed to evaluate taxon-specific bacterial growth in these ecosystems. Results show that symmetric year-round warming decreased microbial growth rate by 31% and CUE by 22%. Asymmetric winter warming resulted in a further decrease in microbial growth rate of 27% and microbial CUE of 59% compared to symmetric year-round warming. Long-term warming increased microbial carbon limitations, especially under asymmetric winter warming. Long-term warming suppressed the growth rates of most bacterial genera, with asymmetric winter warming having a stronger inhibition on the growth rates of specific genera (e.g., Gp10, Actinomarinicola, Bosea, Acidibacter, and Gemmata) compared to symmetric year-round warming. Bacterial growth was phylogenetically conserved, but this conservation diminished under warming conditions, primarily due to shifts in bacterial physiological states rather than the number of bacterial species and community composition. Overall, long-term warming escalated microbial carbon limitations, decreased microbial growth and CUE, with asymmetric winter warming having a more pronounced effect. Understanding these impacts is crucial for predicting soil carbon cycling as global warming progresses.

Temperature sensitivity of soil respiration declines with climate warming in subalpine and alpine grassland soils

Warming as a climate change phenomenon affects soil organic matter dynamics, especially in high elevation ecosystems. However, our understanding of the controls of soil organic matter mineralization and dynamics remains limited, particularly in alpine (above treeline) and subalpine (below treeline) grassland ecosystems. Here, we investigated how downslope (warming) and upslope (cooling) translocations, in a 5-years reciprocal transplanting experiment, affects soil respiration and its temperature sensitivity (Q10), soil aggregation, and soil organic matter carbon (C) and nitrogen (N) composition (C/N ratio). Downslope translocation of the alpine (2440 m a.s.l.) and subalpine (1850 m a.s.l.) to the lowland site (350 m a.s.l.) resulted in a temperature change during the growing seasons of + 4.4K and + 3.3K, respectively. Warming of alpine soils (+ 4.4K) reduced soil organic carbon (SOC) content by 32%, which was accompanied by a significant decrease of soil macroaggregates. Macroaggregate breakdown induced an increased respiration quotient (qCO2) by 27% following warming of alpine soils. The increase in qCO2 respiration was associated with a significant decrease (from 2.84 ± 0.05 to 2.46 ± 0.05) in Q10, and a change in soil organic matter composition (lower C/N ratios). Cooling did not show the opposite patterns to warming, implying that other mechanisms, such as plant and microbial community shifts and adaptation, were involved. This study highlights the important role of SOC degradability in regulating the temperature response of soil organic matter mineralization. To predict the adverse effect of warming on soil CO2 release and, consequently, its negative feedback on climate change, a comprehensive understanding of the mechanisms of C storage and turnover is needed, especially at high elevations in the Alps that are particularly affected by rising temperatures.

Bacterial Community Structure Modulates Soil Phosphorus Turnover at Early Stages of Primary Succession

AbstractMicrobes are the drivers of soil phosphorus (P) cycling in terrestrial ecosystems; however, the role of soil microbes in mediating P cycling in P‐rich soils during primary succession remains uncertain. This study examined the impacts of bacterial community structure (diversity and composition) and its functional potential (absolute abundances of P‐cycling functional genes) on soil P cycling along a 130‐year glacial chronosequence on the eastern Tibetan Plateau. Bacterial community structure was a better predictor of soil P fractions than P‐cycling genes along the chronosequence. After glacier retreat, the solubilization of inorganic P and the mineralization of organic P were significantly enhanced by increased bacterial diversity, changed interspecific interactions, and abundant species involved in soil P mineralization, thereby increasing P availability. Although 84% of P‐cycling genes were associated with organic P mineralization, these genes were more closely associated with soil organic carbon than with organic P. Bacterial carbon demand probably determined soil P turnover, indicating the dominant role of organic matter decomposition processes in P‐rich alpine soils. Moreover, the significant decrease in the complexity of the bacterial co‐occurrence network and the taxa‐gene‐P network at the later stage indicates a declining dominance of the bacterial community in driving soil P cycling with succession. Our results reveal that bacteria with a complex community structure have a prominent potential for biogeochemical P cycling in P‐rich soils during the early stages of primary succession.

Anthropogenic origin pollutants shape microbial metabolites in an alpine soil, Romania

Anthropogenic origin pollutants shape microbial metabolites in an alpine soil, Romania

Aridity threshold for alpine soil nitrogen isotope signature and ecosystem nitrogen cycling.

Determination of tipping points in nitrogen (N) isotope (δ15N) natural abundance, especially soil δ15N, with increasing aridity, is critical for estimating N-cycling dynamics and N limitation in terrestrial ecosystems. However, whether there are linear or nonlinear responses of soil δ15N to increases in aridity and if these responses correspond well with soil N cycling remains largely unknown. In this study, we investigated soil δ15N and soil N-cycling characteristics in both topsoil and subsoil layers along a drought gradient across a 3000-km transect of drylands on the Qinghai-Tibetan Plateau. We found that the effect of increasing aridity on soil δ15N values shifted from negative to positive with thresholds at aridity index (AI) = 0.27 and 0.29 for the topsoil and subsoil, respectively, although soil N pools and N transformation rates linearly decreased with increasing aridity in both soil layers. Furthermore, we identified markedly different correlations between soil δ15N and soil N-cycling traits above and below the AI thresholds (0.27 and 0.29 for topsoil and subsoil, respectively). Specifically, in wetter regions, soil δ15N positively correlated with most soil N-cycling traits, suggesting that high soil δ15N may result from the "openness" of soil N cycling. Conversely, in drier regions, soil δ15N showed insignificant relationships with soil N-cycling traits and correlated well with factors, such as soil-available phosphorus and foliage δ15N, demonstrating that pathways other than typical soil N cycling may dominate soil δ15N under drier conditions. Overall, these results highlight that different ecosystem N-cycling processes may drive soil δ15N along the aridity gradient, broadening our understanding of N cycling as indicated by soil δ15N under changing drought regimes. The aridity threshold of soil δ15N should be considered in terrestrial N-cycling models when incorporating 15N isotope signals to predict N cycling and availability under climatic dryness.

Role of Cryoconite Translocation on the Biogeochemical Features of Alpine Soils at the Central Caucasus Region, Mount Elbrus

Role of Cryoconite Translocation on the Biogeochemical Features of Alpine Soils at the Central Caucasus Region, Mount Elbrus

Warming-induced shifts in alpine soil microbiome: An ecosystem-scale study with environmental context-dependent insights

Climate warming is a pressing global issue with substantial impacts on soil health and function. However, the influence of environmental context on the responses of soil microorganisms to warming remains largely elusive, particularly in alpine ecosystems. This study examined the responses of the soil microbiome to in situ experimental warming across three elevations (3850 m, 4100 m, and 4250 m) in the meadow of Gongga Mountain, eastern Tibetan Plateau. Our findings demonstrate that soil microbial diversity is highly resilient to warming, with significant impacts observed only at specific elevations. Furthermore, the influence of warming on the composition of the soil microbial community is also elevation-dependent, underscoring the importance of local environmental context in shaping microbial evolution in alpine soils under climate warming. Notably, we identified soil moisture at 3850 m and carbon-to-nitrogen ratio at 4250 m as indirect predictors regulating the responses of microbial diversity to warming at specific elevations. These findings underscore the paramount importance of considering pre-existing environmental conditions in predicting the response of alpine soil microbiomes to climate warming. Our study provides novel insights into the intricate interactions between climate warming, soil microbiome, and environmental context in alpine ecosystems, illuminating the complex mechanisms governing soil microbial ecology in these fragile and sensitive environments.

Near-surface chemical properties of soils in the Australian Alps

Alpine soils are globally threatened and are highly vulnerable to the impacts of disturbance. In Australia, alpine soils are critically understudied and remain poorly understood. Here, the soil chemical properties of four common soil types across the Australian Alps were investigated. Soil carbon (C) and nitrogen (N) concentrations, carbon and nitrogen densities (mg cm3), carbon-to-nitrogen ratios (C:N), electrical conductivity (EC), and pH were quantified among four soils: peat soils (organosols), alpine humus soils, skeletal mountaintop soils, and disturbed soils (anthroposols). All measured soil chemical properties varied significantly among different soils, highlighting the value of understanding site-specific edaphic factors to enhance the success of restoration interventions in the Australian Alps. Large C concentrations (17.5 ± 16.6%) and C:N (30.2 ± 25.5), together with low pH (4.2 ± 0.8), EC (66.8 ± 59.6 ɥs cm−1), and N concentrations (0.55 ± 0.3%), indicate nutrient-poor soils with relatively recalcitrant C stocks across the Australian Alps, particularly in peat soils. Carbon and nitrogen densities, conversely, were greater in the alpine humus and disturbed soils, due to greater bulk densities in these soils. These results suggest that the 12,300 km2 Australian alpine bioregion appears to represent a significant terrestrial C reservoir, which may be negatively impacted by climate change. Furthermore, the findings presented suggest that active restoration of the soil physico-chemical environment alongside revegetation activities could enhance the protection of alpine soil carbon into the future.

Warming drives dissolved organic carbon export from pristine alpine soils

Despite decades of research, the influence of climate on the export of dissolved organic carbon (DOC) from soil remains poorly constrained, adding uncertainty to global carbon models. The limited temporal range of contemporary monitoring data, ongoing climate reorganisation and confounding anthropogenic activities muddy the waters further. Here, we reconstruct DOC leaching over the last ~14,000 years using alpine environmental archives (two speleothems and one lake sediment core) across 4° of latitude from Te Waipounamu/South Island of Aotearoa New Zealand. We selected broadly comparable palaeoenvironmental archives in mountainous catchments, free of anthropogenically-induced landscape changes prior to ~1200 C.E. We show that warmer temperatures resulted in increased allochthonous DOC export through the Holocene, most notably during the Holocene Climatic Optimum (HCO), which was some 1.5–2.5 °C warmer than the late pre-industrial period—then decreased during the cooler mid-Holocene. We propose that temperature exerted the key control on the observed doubling to tripling of soil DOC export during the HCO, presumably via temperature-mediated changes in vegetative soil C inputs and microbial degradation rates. Future warming may accelerate DOC export from mountainous catchments, with implications for the global carbon cycle and water quality.

Warming and altered precipitation independently and interactively suppress alpine soil microbial growth in a decadal-long experiment

Warming and precipitation anomalies affect terrestrial carbon balance partly through altering microbial eco-physiological processes (e.g., growth and death) in soil. However, little is known about how such processes responds to simultaneous regime shifts in temperature and precipitation. We used the 18O-water quantitative stable isotope probing approach to estimate bacterial growth in alpine meadow soils of the Tibetan Plateau after a decade of warming and altered precipitation manipulation. Our results showed that the growth of major taxa was suppressed by the single and combined effects of temperature and precipitation, eliciting 40–90% of growth reduction of whole community. The antagonistic interactions of warming and altered precipitation on population growth were common (~70% taxa), represented by the weak antagonistic interactions of warming and drought, and the neutralizing effects of warming and wet. The members in Solirubrobacter and Pseudonocardia genera had high growth rates under changed climate regimes. These results are important to understand and predict the soil microbial dynamics in alpine meadow ecosystems suffering from multiple climate change factors.

Warming and altered precipitation independently and interactively suppress alpine soil microbial growth in a decadal-long experiment

Warming and precipitation anomalies affect terrestrial carbon balance partly through altering microbial eco-physiological processes (e.g., growth and death) in soil. However, little is known about how such processes responds to simultaneous regime shifts in temperature and precipitation. We used the 18O-water quantitative stable isotope probing approach to estimate bacterial growth in alpine meadow soils of the Tibetan Plateau after a decade of warming and altered precipitation manipulation. Our results showed that the growth of major taxa was suppressed by the single and combined effects of temperature and precipitation, eliciting 40–90% of growth reduction of whole community. The antagonistic interactions of warming and altered precipitation on population growth were common (~70% taxa), represented by the weak antagonistic interactions of warming and drought, and the neutralizing effects of warming and wet. The members in Solirubrobacter and Pseudonocardia genera had high growth rates under changed climate regimes. These results are important to understand and predict the soil microbial dynamics in alpine meadow ecosystems suffering from multiple climate change factors.

Searching for new plastic-degrading enzymes from the plastisphere of alpine soils using a metagenomic mining approach.

Plastic materials, including microplastics, accumulate in all types of ecosystems, even in remote and cold environments such as the European Alps. This pollution poses a risk for the environment and humans and needs to be addressed. Using shotgun DNA metagenomics of soils collected in the eastern Swiss Alps at about 3,000 m a.s.l., we identified genes and their proteins that potentially can degrade plastics. We screened the metagenomes of the plastisphere and the bulk soil with a differential abundance analysis, conducted similarity-based screening with specific databases dedicated to putative plastic-degrading genes, and selected those genes with a high probability of signal peptides for extracellular export and a high confidence for functional domains. This procedure resulted in a final list of nine candidate genes. The lengths of the predicted proteins were between 425 and 845 amino acids, and the predicted genera producing these proteins belonged mainly to Caballeronia and Bradyrhizobium. We applied functional validation, using heterologous expression followed by enzymatic assays of the supernatant. Five of the nine proteins tested showed significantly increased activities when we used an esterase assay, and one of these five proteins from candidate genes, a hydrolase-type esterase, clearly had the highest activity, by more than double. We performed the fluorescence assays for plastic degradation of the plastic types BI-OPL and ecovio® only with proteins from the five candidate genes that were positively active in the esterase assay, but like the negative controls, these did not show any significantly increased activity. In contrast, the activity of the positive control, which contained a PLA-degrading gene insert known from the literature, was more than 20 times higher than that of the negative controls. These findings suggest that in silico screening followed by functional validation is suitable for finding new plastic-degrading enzymes. Although we only found one new esterase enzyme, our approach has the potential to be applied to any type of soil and to plastics in various ecosystems to search rapidly and efficiently for new plastic-degrading enzymes.

Microbial phosphorus-cycling genes in soil under global change.

The ongoing climate change on the Tibetan Plateau, leading to warming and precipitation anomalies, modifies phosphorus (P) cycling in alpine meadow soils. However, the interactions and cascading effects of warming and precipitation changes on the key "extracellular" and "intracellular" P cycling genes (PCGs) of bacteria are largely unknown for these P-limited ecosystems. We used metagenomics to analyze the individual and combined effects of warming and altered precipitation on soil PCGs and P transformation in a manipulation experiment. Warming and increased precipitation raised Olsen-P (bioavailable P, AP) by 13% and 20%, respectively, mainly caused by augmented hydrolysis of organic P compounds (NaOH-Po). The decreased precipitation reduced soil AP by 5.3%. The richness and abundance of the PCGs' community in soils on the cold Tibetan plateau were more sensitive to warming than altered precipitation. The abundance of PCGs and P cycling processes decreased under the influence of individual climate change factors (i.e., warming and altered precipitation alone), except for the warming combined with increased precipitation. Pyruvate metabolism, phosphotransferase system, oxidative phosphorylation, and purine metabolism (all "intracellular" PCG) were closely correlated with P pools under climate change conditions. Specifically, warming recruited bacteria with the phoD and phoX genes, which encode enzymes responsible for phosphoester hydrolysis (extracellular P cycling), strongly accelerated organic P mineralization and so, directly impacted P bioavailability in alpine soil. The interactions between warming and altered precipitation profoundly influenced the PCGs' community and facilitated microbial adaptation to these environmental changes. Warming combined with increased precipitation compensated for the detrimental impacts of the individual climate change factors on PCGs. In conclusion, warming combined with rising precipitation has boosting effect on most P-related functions, leading to the acceleration of P cycling within microbial cells and extracellularly, including mineralization and more available P release for microorganisms and plants in alpine soils.

Fire simulation effects on the transformation of iron minerals in alpine soils

Heat-induced changes in topsoil iron (Fe) species triggered by the relatively low temperatures (Ts) produced by wildfires (200–300 °C) have not been fully elucidated. Changes in the chemistry of Fe minerals can produce cascading impacts on the environment, and the resulting aftermath may be exacerbated in erosion-prone alpine soils. The aim of this study was to determine - at environmentally realistic conditions - changes in the composition and crystallinity of Fe species, and the dispersible organic matter (OM) pool (evaluated by the pyrophosphate extraction), as a function of rising Ts, native Fe phases and OM in alpine soils. Multiple techniques were employed, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), magnetic measurements and Fe K-edge X-ray absorption spectroscopy (XAS). The results demonstrated the dominance of poorly crystalline Fe phases at 300 °C. At the same T, we observed the partial conversion of maghemite to hematite (supporting the involvement of oxidative processes) and, in the presence of high organic carbon (OC) contents, an enrichment in magnetic minerals (suggesting the onset of reducing conditions). The heat-induced modifications in Fe species and organic compounds did not promote the stabilization of the remaining OM, highlighting the weak nature of soil organo-mineral associations in an after-fire scenario. These phenomena can be further aggravated in case of the steep terrain that characterize alpine soils.

Altitudinal patterns of alpine soil ammonia-oxidizing community structure and potential nitrification rate.

Nitrogen availability limits the net primary productivity in alpine meadows on the Qinghai-Tibetan Plateau, which is regulated by ammonia-oxidizing microorganisms. However, little is known about the elevational patterns of soil ammonia oxidizers in alpine meadows. Here, we investigated the potential nitrification rate (PNR), abundance, and community diversity of soil ammonia-oxidizing microorganisms along the altitudinal gradient between 3,200 and 4,200 m in Qinghai-Tibetan alpine meadows. We found that both PNR and amoA gene abundance declined from 3,400 to 4,200 m but lowered at 3,200 m, possibly due to intense substrate competition and biological nitrification inhibition from grasses. The primary contributors to soil nitrification were ammonia-oxidizing archaea (AOA), and their proportionate share of soil nitrification increased with altitude in comparison to ammonia-oxidizing bacteria (AOB). The alpha diversity of AOA increased by higher temperature and plant richness at low elevations, while decreased by higher moisture and low legume biomass at middle elevations. In contrast, the alpha diversity of AOB increased along elevation. The elevational patterns of AOA and AOB communities were primarily driven by temperature, soil moisture, and vegetation. These findings suggest that elevation-induced climate changes, such as shifts in temperature and water conditions, could potentially alter the soil nitrification process in alpine meadows through changes in vegetation and soil properties, which provide new insights into how soil ammonia oxidizers respond to climate change in alpine meadows.IMPORTANCEThe importance of this study is revealing that elevational patterns and nitrification contributions of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities were primarily driven by temperature, soil moisture, and vegetation. Compared to AOB, the relative contribution of AOA to soil nitrification increased at higher elevations. The research highlights the potential impact of elevation-induced climate change on nitrification processes in alpine meadows, mediated by alterations in vegetation and soil properties. By providing new insights into how ammonia oxidizers respond to climate change, this study contributes valuable knowledge to the field of microbial ecology and helps predict ecological responses to environmental changes in alpine meadows.

Simplified microbial network reduced microbial structure stability and soil functionality in alpine grassland along a natural aridity gradient

Increasing aridity is known to influence the diversity and function of soil microbiome. However, how it affects the microbial co-occurrence network are poorly understood, particularly in alpine ecosystem, which is one of the most vulnerable ecosystems. Here, we investigated the co-occurrence networks of soil microbiomes based on 60 sites along a natural aridity gradient across the Tibetan Plateau and evaluated their relationship with soil functionality. We hypothesized that increasing aridity could lead to a reduction in the complexity of microbial networks (e.g., the decreased number of nodes and edges, lower connectance, average degree, clustering coefficient and centralization degree), and this changed network complexity is strongly relate to microbial structure stability (network robustness and vulnerability) and soil functionality. Our results supported the hypothesis that the network complexities of bacteria, fungi and protists decreased along the aridity gradient. Microbial network complexity was significantly correlated with network robustness and vulnerability, suggesting that soil network complexity supports structure stability. Bacterial and fungal network complexities were strongly related to community functional traits (e.g., enzymes activities, carbohydrate and amino acid metabolism, C degradation genes), soil processes (e.g., CO2 and CH4 emission, N mineralization) and multifunctionality. This suggests a key relationship of microbial networks to alpine soil functionality, with a more significant impact observed in semi-arid and arid habitats than that in humid and semi-humid habitats. Plants played key roles in driving microbial network through altering soil organic C, with plant diversity having a greater impact in humid habitats, while plant biomass was more influential in semi-arid and arid habitats. Our results indicate that aridity-induced simplification of microbial communities can potentially weaken community stability and alpine soil functionality. Therefore, preserving the complexity of belowground communities is critical for ecosystem management and for predicting the ecological consequences of future aridification.