Depends on what you mean by "effective." It might delay them for a few hours or a day. There's a long history of this kind of thing, although it's usually more effective to do a treesit rather than a lockdown for trees. You could do a lockdown on equipment like bulldozers/feller bunchers though. The Earth First! Direct Action Manual has a lot of info.

Be prepared to be literally tortured in various ways, including pepperspray placed directly in your eyes, pain compliance holds, or they just cut the chains/lockbox you're in and if you get cut with it too bad.

Personally I'm not a big fan of get-arrested-on-purpose types of direct action, but it has its uses. I strongly recommend that if you're going to do something like this you connect with a group that knows how to do it and you have a support crew, including jail/legal support.