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Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations
Published on: September 11, 2016
Altitude-dependent variations in environmental conditions and human activities regulate microbial community assembly
Zaizhi Yang1, Zuobing Liang2, Lixiang Cao3
1College of Water Resources and Coastal Engineering, Beibu Gulf Marine Environmental Structural Materials Durability Field Observation Station of Guangxi Transportation Industry, Beibu Gulf University, Qinzhou, 535011, China; Pinglu Canal and Beibu Gulf Coastal Ecosystem Observation and Research Station of Guangxi, Guangxi Key Laboratory of Marine Environmental Disaster Processes and Ecological Protection Technology, College of Marine Sciences, Beibu Gulf University, Qinzhou, 535011, China.
Abstract:
Microorganisms are core drivers of biogeochemical processes in headwater stream ecosystems, yet the response mechanisms of their community composition and carbon metabolic traits to altitudinal gradients and local environmental conditions remain poorly resolved. Elucidating these altitude-dependent patterns is critical for understanding microbiome-mediated ecosystem functioning in vulnerable headwater freshwater habitats. Here, we investigated microbial community structure and carbon substrate utilization in three headwater streams with >1000 m altitudinal span, combining 16S rRNA gene amplicon sequencing, Biolog EcoPlate metabolic phenotyping, and multivariate statistics to characterize microbial taxonomic and functional diversity and their key environmental drivers. Proteobacteria (45.7% average relative abundance) and Bacteroidota (13.6%) dominated all samples, collectively accounting for >60% of the total community. A 1000 m altitude was identified as the ecological threshold, with significant divergences in microbial diversity, community assembly, and carbon utilization patterns across this boundary. Stochastic processes dominated community assembly in steep-gradient streams (68% relative contribution), while deterministic homogeneous selection prevailed in topographically gentle streams (67% contribution); increasing human activity shifted the dominant assembly process from homogeneous selection (67%) to heterogeneous dispersal (52%). Microbial carbon utilization efficiency showed three distinct altitudinal patterns (decreasing, hump-shaped, U-shaped). Variation partitioning analysis revealed that altitude, hydrochemistry, and water physical parameters independently explained 21%, 17%, and 9% of community variation, respectively. Proteobacteria acts as the key phylum governing carbon utilization. This study confirms that altitude is a pivotal driver of headwater microbial diversity and metabolic function, and microbes can adapt to environmental changes by adjusting carbon substrate utilization strategies. Our findings provide new insights into the links between microbial functional traits, ecosystem stability, and nutrient cycling in headwater streams.
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