 What you're seeing in many cases are soil deficiencies, meaning that those are areas where the lawn has a very limited root system. That may be related to a pipe under the ground. It may be related to a hard pan under the ground. It could be related to a concrete vault under the ground. There could be a whole bunch of stuff under the ground. So basically, this shows you that there is a very shallow root system in that turf grass at that point in time.