Distinct geographic patterns and drivers of plant, bacterial, and fungal β-diversity in semi-arid grasslands: Insights from a 1,700 km transect in northern China

The β-diversity, as the variation in community composition across habitats, is crucial for understanding regional community assembly and biodiversity conservation. While biogeographic patterns of both macro- and microorganisms have been well-documented, little is known about studies that simultaneously examine these patterns and their driving mechanisms across continuous spatial scales in both above- and belowground communities. Here, we conducted a field survey along a 1,700-kilometer transect across diverse landscapes, including meadow steppe, typical steppe, desert steppe, and inland dunes in the semi-arid region (aridity ranging from 0.66 to 0.83) of northern China to investigate the patterns and drivers of β-diversity in plant, bacterial, and fungal communities at continuous spatial scales. We found that organisms with various dispersal traits exhibited significantly different distance-decay relationships, with plants showing the steepest slope (–0.190), followed by fungi (–0.095) and bacteria (–0.061). Species turnover was the primary component of β-diversity across plant, bacterial, and fungal communities at various spatial scales. Furthermore, β-diversity, its turnover components, and β-deviation of plant, bacterial and fungal communities all showed significant and positive relationships with spatial scale. Moreover, environmental distance had a greater impact on β-diversity patterns than geographic distance. Among environmental factors, aridity emerged as the dominant driver significantly influencing the β-diversity of plant and microbial communities, with the strongest effect on the bacterial community. These findings provide essential insights into the mechanisms influencing β-diversity in both plant and soil microbial communities, highlighting the importance of spatial scale and environmental filtering in community assembly.