Unless they are put there by some timber company. They are survey markings. "Survey" as in a study, like a growth survey, or amount of carbon in an area etc. They are reference points put there for use while the study is happening. The forestry uses what ever color paint happens to be in the truck/garage when they leave. We use pink, orange, blue. There is a HUGE amount of research going on in the Chippewa National Forest.