UC Riverside

Biological soil crusts (biocrusts) are major components in the dryland environment. They contain diverse microbial communities with crucial functions to dryland ecosystems. However, very little is known about these microorganisms because the biocrusts are defined by their external morphology which oftentimes neglect these unseen world. To better understand biocrusts microbial communities, extensive and integrated microbial research (external morphology and microorganisms) on biocrust is needed. Therefore, in my dissertation work I aimed to 1) summarize previous and current research, and identify knowledge gaps about biocrust microbes to provide baseline understanding about biocrust microorganisms, 2) identify key factors that influenced the biocrust microbes from three domains of life (archaea, bacteria, and fungi), and 3) to further expand our understanding about temporal/seasonal effect on these microorganisms. We employed amplicon-based metabarcoding sequencing to investigate biocrusts microbial communities. In chapter 2, our results showed that biocrusts microorganism are diverse and we are only at the beginning of biocrust microbes investigation because many microorganisms cannot be identified which could be new to science. We have modified sequencing protocols that work well with JTNP biocrusts and a baseline knowledge about biocrust microbes was established. Then, in chapter 3, we expanded our study to cover the Mojave Desert. To test our hypotheses that geography, soil depth, and crust types influenced biocrust microbial communities, 5 common biocrust types samples were collected from 4 sites across the Mojave desert. The results showed that 1) Biocrust in central Mojave were distinct from southern Mojave site, 2) biocrust surface harbored different microorganisms from subsurface soil, and 3) crust types displayed different community signatures. Moreover, microbials hubs species that connect biocrust microbes together were also identified. Lastly, chapter 4 concluded this dissertation by improving our baseline knowledge documenting how these microbial communities changes over the year and investigate how weather patterns that influenced these changes in microbial communities. We hypothesized, biocrust microbial communities were dynamic and weather including temperature, precipitation, wind speed, atmospheric pressure, humidity, and dew point influenced biocrust microbial composition. These findings not only improve our baseline understandings about biocrust microorganisms but also provide essential information for future biocrust management and conservation.