Subdirectories

I tried my hand at modding for the first time yesterday, and tried to come up with a modified tech tree. I was hoping that I'd create a new TechTree.xml file, place my handful of new techs in it, put it in the Data/Techs subdirectory, and have my new techs as part of the tech tree. Didn't work--absolutely no change what so ever. The rest of the mod worked fine--I took the example mod and kept it's interface, removed the custom races, and ended up with a default setup with new screens. Just no changes to the tech tree. After that, I moved my TechTree.xml file up to the Data directory, outside of the subdirectories, and now I have my techs, but only my techs. Am I missing something? For now I'm going to copy the original TechTree.xml and add my stuff to it, but if possible I'd like to keep those separate.

Any help is greatly appreciated Thanks!