By timber trespass do you mean
firewood cutters or logging operation because if it is the latter you can sue them which tends to get not only thier attention but other companies in the area. For firewood cutters I have found hearing the saw and showing up with my 12 guage in one had and sherrif on the way helps same as it does with ATVs or other trespassers (I got a
pond that used to draw em in till word of the crazy guy with the gun spread). A less agressine approach is one that has been mentioned and that is natural barriers like thich thorny hedges, close spaced
trees, etc. I also have been known to string 3 strands of barbwire as a
fence making sure to flag it with white or orange strips as well as no trespassing signs. Of course it is easy to cut but it is a deterent as would be any fencing. Also if they are not paying close attention and hit it in an ATV I can prove I did everything I could to prevent it. Game cameras placed along the popular illegal ATV trails would also be a good idea and nothing says if you can't ID the rider a couple printed posters or an ad in the
newspaper shaming the rider(s) would not at the very least have the folks who know them by say the ATV giving them hell. These things will help for the outlying property. As far as the outbuildings and such go I recomend whatever large dog(s) that is not a lab or hunting dog. You get them as pups and raise them to be basically friendly so no one gets hurt by a mean dog though. Just the simple fact you have a big "mean", "unfriendly", etc dog tends to keep people honest. Good luck and I wish you the best because security can be a pain because of idiots out there.