Chart (IMAGE) American Society of Agronomy Caption Scientists compared the roles of various types of soil microbes (abundance indicated by the size of the ball) with different variables, including temperature, soil pH and the availability of ammonium. These environmental factors influence the abundance of the microbes. Credit Soil Science Society of America Journal doi:10.1002/saj2.20029 Usage Restrictions For use with story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.