Crucial role of rare taxa in preserving bacterial community stability

Stable bacterial communities are essential for maintaining soil functions. However, the role of abundant and rare bacterial taxa in maintaining bacterial community stability remains controversial. To explore the relationship between abundant and rare taxa and bacterial community stability, we used high-throughput sequencing technology and molecular ecological networks to characterize the distribution of abundant and rare bacterial taxa under different nitrogen (N) fertilization rates (0, 150, 200, and 250 kg N hm⁻²). Our findings revealed that rare taxa had much higher Simpson's diversity index values than abundant taxa. Moreover, rare taxa Simpson's diversity decreased with increasing N application, while bacterial community differences (Bray–Curtis distance dissimilarity) increased (i.e., bacterial community stability decreased with increasing N application). The network topology showed that rare sub-communities had higher modularity and a greater proportion of positive links than abundant taxa. The rare bacterial Simpson's diversity was significantly and negatively correlated with bacterial community differences, no correlation occurred between abundant bacterial Simpson's diversity and bacterial community differences. This study underscores the importance of rare species in maintaining bacterial community stability. Consequently, when optimizing agricultural management practices to ensure the stability of bacterial communities and soil functions, it is crucial not only to concentrate consider the roles of abundant species involved in nutrient cycling but also to give greater consideration to the role of rare taxa.