Bacterial and plant community successional pathways in glacier forefields of the Western Himalaya

Glacier chronosequences offer a unique opportunity to observe primary successional patterns and assess the interaction between biological communities and abiotic conditions. Bacteria are one of the first organisms to colonize such ecosystems, yet factors determining their distribution and diversity are still in need of understanding. In this study, we investigated the associated abiotic and biotic factors related to bacterial communities across post-glacial moraines at two localities in the Ladakh region of the Western Himalaya which differed in elevation and climate. By measuring soil chemistry, plant, biological soil crust, and bacterial community composition while accounting for moraine age and topography, we reveal the successional paths of multiple trophic levels at the highest elevation glacier forefields known to be studied. Biological soil crust communities followed a trajectory of being dominated by the order Chroococcales before transitioning to filamentous Nostocales and Oscillatoriales and eventually decreasing in cover as plants colonize the area. Using variation partitioning, we found bacterial communities in the higher locality, Tso Moriri (5800 m), were more associated with soil conditions, while at the lower location, Nubra (5150–5400 m), bacterial communities were more coupled with plant community composition. Furthermore, using generalized linear models, bacterial family richness was found to be significantly correlated with plant species richness, however, topography was also significant, indicating geomorphological depressions or gullies at the bottom of moraines potentially harbor higher bacterial richness prior to the advanced colonization of plants. These results suggest the community structure and successional pathways of bacteria and plants in glacier forefields are influenced by differing biotic and abiotic factors at different geographical locations and provides a local framework for the future of deglaciated environments.