Deployed log4j.properties does not affect non log4j logging systems

If I create the file

my.ear/META-INF/log4j.properties

with

log4j.rootLogger=DEBUG, FA
log4j.appender.FA=org.apache.log4j.FileAppender
log4j.appender.FA.File=/tmp/my.log
log4j.appender.FA.layout=org.apache.log4j.PatternLayout
log4j.appender.FA.layout.ConversionPattern= %-4r [%t] %-5p %c %x - %m%n

this results in nothing in the server.log and an empty /tmp/my.log

but if I create a

my.ear/META-INF/logging.properties

this results in everything beeing logged to /tmp/my.log

We're using SLF4J in our application and also using a library that uses COMMONS-LOGGING

I also did a test with doing an additional log statement using the log4j api directly and this one (and only this one) did get logged to /tmp/my.log