Section 2 Bacteria in Nature

**Chapter 3**

**Abstract**

First Insights into the Resilience of

the Soil Microbiome of a Tropical

This study evaluated the effect that tree species traits and wet/dry periods display on soil microbial communities in a tropical dry forest in Puerto Rico. Understanding the ecological role of soil microorganisms in tropical dry forests and how they relate to different tree species is necessary to protect these fragile forest ecosystems. Thus, by using 454 pyrosequencing, we explored how microbial diversity was affected by dominant tree species during the wettest and driest periods at the Guánica Dry Forest. We found that 9 out of 17 phyla were more abundant during the dry period demonstrating that soil communities have adapted to historically low rainfall patterns. The most abundant phyla during both periods were Proteobacteria, Actinobacteria, and Bacteroidetes. During the dry period, Actinobacteria increased significantly (p < 0.0001), whereas Proteobacteria and Bacteroidetes decreased significantly (p < 0.0001; p < 0.001). Canonical correspondence analysis (CCA) also demonstrated that soil microbes are shaped by wet and dry periods, thus axis 1 of CCA explained 80% of the variation. This study offers baseline information in order to help elucidate how microbial diversity is affected by climate change in tropical areas and extrapolate this information to

Dry Forest in Puerto Rico

*Michelle Jovanne Rivera-Rivera and Elvira Cuevas*

agricultural areas in order to develop better management practices.

bacterial diversity, DNA sequencing

**1. Introduction**

**45**

**Keywords:** historical rainfall patterns, bacterial resilience, soil microbiome, soil microbial ecology, soil enzyme activity, Guánica Dry Forest, Puerto Rico,

Arid and semiarid ecosystems comprise almost 1/3 of the Earth's surface, and it

is expected that these ecosystems will increase their total coverage area due to anthropogenic activities and climate change [1]. In tropical dry forests, seasonality and rainfall distribution fluctuate more often than in other ecosystems. Dry periods can extend for many months, and in some cases, they are accompanied by pulsed rainfall that can last from hours to days. These fluctuations control temporal growth patterns, productivity, turnover of organic matter, and other forest soil functional traits [2]. After a dry period, the first pulse of rainfall causes abrupt changes in soil moisture and water potential leading to microbial physiological stress and the reawakening of soil microbial communities. Seasonally tropical dry forests are already towards the extreme of water availability. Climate model predictions for
