Spatial heterogeneity of resource availability drives soil bacterial community assembly along the sandy coast of Southern China

Resources scarcity is prevalent in natural microbial communities, affecting both biodiversity and coexistence. However, its intricate impacts on community assembly remain incompletely understood. In this study, we examined the bacterial community assembly processes in low-resource soil patches along the sandy coast of Southern China, focused on the relative importance of abiotic and biotic factors. Our study revealed a slightly decreasing trend in bacterial community similarity with increasing geographic distance, whereas the spatial heterogeneity of soil resource availabilities, including total nitrogen (TN), ammonium (NH 4 + -N), and total phosphorus (TP), explained 75 % of the total variation in the soil bacterial community. Nitrogen was identified as the primary limiting resource, playing a key role in shaping the composition of bacterial communities. Notably, elevated N availability did not alleviate N limitations or promote biodiversity. Instead, it led to deterministic community assembly processes by increasing the overall demand for N and intensifying negative biological interactions among taxa. These processes favored the selection of specific communities dominated by highly competitive species with overlapping niches. Our findings offer novel insights into the biogeographic patterns of soil bacterial communities, highlighting how resource availability shapes their compositions and has potential ecological implications, including effects on seedling establishment and the resilience of belowground communities to disturbances. • The bacterial communities were shaped mainly by spatial heterogeneity in soil resource availability. • Soil nitrogen was a primary limiting resource and played a key role in driving community variations. • The similarity of soil bacterial community increased with resource availabilities. • The transition from stochastic to deterministic community assembly was observed with increasing resource availability. • Increased nitrogen availability stimulated N demand and niche overlap in bacterial communities.