in contrast to Breeze and Silvertail themes the Sapphire theme has a different padding defined for its tree cells so that the whole tree height is affected
in this example you can see that the tree gets quite loose in Sapphire theme, the nodes have almost no visual connection
http://localhost:8080/zkdemo/tree/dynamic_styling (switch theme on upper right)

z-treecell-cnt

Sapphire
padding: 8px 5px 7px;

Breeze and Silvertail
padding: 0;