I doing a science fair and I need to find logical reasons my results came out like this. And even though I researched through webs and surfed through educational websites, I still don't know if dry leaves are good insulator, why or why not?

When dry material is piled up it traps air in the hollow spaces in between the individual pieces of material (leaves, pine needles, etc.). This is called dead air space. The dead air space becomes a barrier that holds the warm air in and repels the cold air.

George W. Jasper (https://www.facebook.com/note.php?note_id=294106277302926), Ex Ranger