Volume 1 Issue 1 (2025)

With the intensification of human activities, nitrogen (N) deposition has become a major global change factor affecting terrestrial ecosystem structure and function. Arid zone ecosystems are inherently N-limited, making them highly sensitive to exogenous N input. Soil microorganisms are the core drivers of soil N cycling processes, but the mechanisms by which N deposition regulates microbial community structure and further affects N transformation in arid zones remain unclear. This study conducted a 3-year in-situ N deposition simulation experiment in the southern Gobi Desert (a typical arid zone in Northwest China) to explore the effects of different N deposition levels (control, low N, medium N, and high N) on soil bacterial and fungal communities, as well as key N cycling functional processes. High-throughput sequencing, functional gene quantification, and soil N fraction determination showed that N deposition significantly altered microbial community composition, diversity, and co-occurrence network structure. Compared with the control, medium and high N deposition significantly reduced bacterial alpha diversity (Shannon index decreased by 15.7% and 23.2%, respectively) but increased fungal alpha diversity (Shannon index increased by 11.3% and 18.5%, respectively). The microbial co-occurrence network under high N deposition showed lower complexity (node number decreased by 42.1%) and stability (modularity decreased by 28.6%) than the control. Taxonomically, N deposition promoted the enrichment of copiotrophic taxa (e.g., Proteobacteria, Ascomycota) and inhibited oligotrophic taxa (e.g., Actinobacteria, Basidiomycota). Functionally, low and medium N deposition enhanced the abundance of functional genes related to nitrification (amoA) and denitrification (nirK, nirS), while high N deposition significantly inhibited these genes and increased the abundance of N fixation genes (nifH). Redundancy analysis revealed that soil pH, available N (AN), and electrical conductivity (EC) were the key drivers of microbial community changes. Structural equation modeling indicated that N deposition regulated arid zone soil N cycling mainly by altering microbial community composition and functional gene abundance. This study clarifies the response patterns and functional consequences of soil microbial communities to N deposition in arid zones, providing a theoretical basis for predicting the dynamics of arid zone ecosystems under future global change scenarios.

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Hydrological fluctuations (HFs) are a core characteristic of wetland ecosystems and are intensifying under global climate change, profoundly affecting soil microbial community structure and the associated carbon (C) cycling processes. However, the mechanisms underlying microbial community responses to HFs and their regulatory effects on wetland soil C sequestration and emission remain unclear. This study conducted a 4-year in-situ manipulation experiment in the Baiyangdian Wetland (a typical freshwater wetland in North China) to explore the effects of different hydrological fluctuation patterns (static flooding, moderate fluctuation, and extreme fluctuation) on soil bacterial and fungal communities, as well as their C cycling functions. High-throughput sequencing, microbial functional prediction, and soil C fraction determination showed that HFs significantly altered microbial community composition, diversity, and co-occurrence network structure. Compared with static flooding, moderate and extreme HFs reduced bacterial alpha diversity (Shannon index decreased by 12.3% and 21.5%, respectively) but increased fungal alpha diversity (Shannon index increased by 8.7% and 15.2%, respectively). The microbial co-occurrence network under extreme HFs showed lower complexity (node number decreased by 38.6%) and stability (modularity decreased by 25.3%) than static flooding. Taxonomically, HFs promoted the enrichment of anaerobic taxa (e.g., Deltaproteobacteria, Methanomicrobia) and inhibited aerobic taxa (e.g., Actinobacteria, Alphaproteobacteria). Functionally, moderate HFs enhanced the abundance of functional genes related to recalcitrant C decomposition (e.g., laccase, cellulase), while extreme HFs significantly increased methanogenesis-related genes (e.g., mcrA) and reduced C fixation genes (e.g., cbbL). Redundancy analysis revealed that soil redox potential (Eh), water-filled pore space (WFPS), and dissolved organic carbon (DOC) content were the key drivers of microbial community changes. Structural equation modeling indicated that HFs regulated wetland soil C sequestration capacity mainly by altering microbial community composition and functional gene abundance. This study clarifies the response patterns and functional consequences of soil microbial communities to HFs in wetlands, providing a theoretical basis for predicting wetland C cycle dynamics under future climate change scenarios.

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Extreme precipitation events (EPEs) are increasing in frequency and intensity in arid zones due to global climate change, profoundly altering soil hydrological conditions and nutrient availability, which in turn affect soil microbial community structure and ecological functions. However, the responses of soil microbial co-occurrence networks (an important indicator of community stability and interspecific interactions) to EPEs remain poorly understood. This study conducted a 3-year field manipulation experiment in the Gurbantunggut Desert, a typical arid zone in Central Asia, to explore the effects of different EPE magnitudes (light: 20 mm, moderate: 40 mm, heavy: 60 mm) on bacterial and fungal co-occurrence networks. High-throughput sequencing combined with network analysis showed that EPEs significantly restructured soil microbial networks: compared with the control (natural precipitation), moderate and heavy EPEs increased network complexity (node number, edge number, average degree) and modularity, while light EPEs had no significant effect. Bacterial networks were more sensitive to EPEs than fungal networks, with heavy EPEs increasing bacterial network connectivity by 42.3% but fungal network connectivity by only 18.7%. Soil moisture, available nitrogen, and organic carbon were the key drivers of network changes, explaining 35.6%, 22.1%, and 18.9% of the variation in microbial network structure, respectively. Keystone taxa in microbial networks shifted from oligotrophic groups (e.g., Actinobacteria) under natural precipitation to copiotrophic groups (e.g., Proteobacteria) under heavy EPEs. Additionally, microbial network complexity was significantly positively correlated with soil nutrient cycling potential (indicated by functional gene abundance). This study reveals the response patterns and driving mechanisms of soil microbial networks to EPEs in arid zones, providing a theoretical basis for predicting the stability of arid ecosystem functions under future climate change scenarios.

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Agricultural intensification (AI) has significantly altered soil ecosystems, affecting microbial community structure and function, which are crucial for soil fertility and ecosystem stability. This study investigated the responses of soil microbial communities (bacteria, fungi, archaea) to different AI levels (conventional farming, intensive farming, and organic farming) in three agricultural regions across the Northern Hemisphere. High-throughput sequencing and functional prediction revealed that AI significantly reduced microbial alpha diversity, shifted community composition, and altered functional gene abundances related to nutrient cycling and organic matter decomposition. Specifically, intensive farming increased the relative abundance of copiotrophic bacteria while decreasing that of oligotrophic bacteria and ectomycorrhizal fungi. Additionally, soil physicochemical properties (pH, organic carbon, total nitrogen) were key drivers of microbial community changes. Organic amendments and crop rotation were effective in mitigating the negative impacts of AI on microbial communities. This study provides insights into the mechanisms underlying microbial responses to AI and offers practical strategies for sustainable agricultural management.

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