Alpine SOC and Microbial Community Assembly Were Buffered Through Soil Pore Structure Along an Altitudinal Gradient

Elevation changes influence various environmental factors including cloudiness, atmospheric density, and temperature. Previous studies on the effects of elevation on microbial communities and soil organic carbon (SOC) yielded inconsistent results. This study tried to reveal the distribution patterns of microbial communities and SOC concentrations, as well as their interactions with soil structure along an elevational gradient in the alpine region. We investigated six typical ecosystems along an elevational gradient on the north-eastern Qinghai-Tibet Plateau. Phospholipid fatty acid (PLFA) analysis and X-ray computed tomography (CT) methods were used to quantify microbial abundance and pore structure of soils, respectively. The results demonstrated that SOC content and total PLFAs peaked in the meadow ecosystem. In the subsoil, total PLFAs, fungal, and bacterial PLFAs followed the U-shape pattern with increasing elevation. In both topsoils and subsoils, the surface area density of pores increased with elevation, and it was found to be positively correlated with SOC and microbial abundance. Soil structure mainly affects the input and adsorption of root nutrients by altering the pore surface area, thereby regulating the enrichment of microorganisms. The impact of pore structure on microbes were more obvious in the topsoil than in the subsoil. Interactions among pore structure, soil properties, and environmental factors jointly affects the microbial communities, demonstrating that elevation indirectly affects microbial communities through soil resource regulation.