Is it possible to create a patch config file for log level?

I've created this patch file for a Sitecore 9 instance, but looking at showconfig.aspx it has had no effect. The config file name begins with a 'z' to try to ensure it's processed last.

<?xml version="1.0" encoding="utf-8" ?><configuration xmlns:patch="http://www.sitecore.net/xmlconfig/"><sitecore><log4net><root><priority value="ERROR" /></root><logger name="Sitecore.Diagnostics.WebDAV" additivity="false"><level value="ERROR"/></logger><logger name="Sitecore.Diagnostics.Publishing" additivity="false"><level value="ERROR"/></logger></log4net></sitecore></configuration>

Is it possible to patch in log4net config settings? If so, is my config file formatted incorrectly?