What causes imported Maven project in Eclipse to use Java 1.5 instead of Java 1.6 by default and how can I ensure it doesn't?

Question

I imported a Maven project and it used Java 1.5 even though I have 1.6 configured as my Eclipse default Preferences->Java->Installed JREs.

When I

Answer 1

    

    
        
            
                org.apache.maven.plugins
                maven-compiler-plugin
                3.2
                
                    1.8
                    1.8