I suspect if the trees were on his property he has the right to remove them, and if they were on your property you may have statutory remedies assuming your state has a timber trespass statute. But since you are the one claiming he did something wwrong, it would seem to behoove you to establish that neighbor is doing these things on your land. So engage a surveyor to establish the property line, if it's not clearly marked.
Not legal advice, just my two cents. I don't practice law in Washington or hold Washington licensure. Consult Washington counsel if you need legal advice. I practice in Vermont ONLY.
If it is clear that the trees were on your property, you can sue the neighbor for trespass and seek damages for the value of the trees. You should get an estimate of the cost of replacing them and have a lawyer write a demand letter to the neighbor. You could also file a claim in Small Claims Court for the damage (be sure you can establish property line) up to $5000 without using an attorney.
I agree with both previous answers and the first step is to find the property line. If the survey and yes you may need a survey show the trees were your or on the line. Call a lawyer ASAP if the trees were on the neighbors property get the fence up to protect your dogs, you may have a claim if the holes were on your side. Timber trespass law is well estabilished here in Washington and a real estate lawyer will need all the facts to help you.
Only If and until you and I sign an Agreement for Legal Services, I am not your attorney. These answers are provided for informational and/or novelty purposes
I agree with my colleagues. RCW 64.12.030 makes it unlawful to go onto another person's property and remove trees. RCW 64.12.030 also provides that where the trespass is willful the trespasser will be liable for treble damages. The first and most important step is to commission a survey. To save cost you can ask first that the boundary line be staked but not mapped to have a visual idea of where the true boundary line lies. The second step is to have an Arborist estimate your damages. Then, I recommend hiring an attorney to help you recover your damages.