There is no such thing as a 'firebreak trench'. A actual firebreak in the Pinelands is more like 50ft wide. What you are mapping here are probably plow lines, narrow cuts through the woods created by the Forest Fire Service for their exclusive use, usually one time, to access a wildfire or prescribed burn area. They are supposed to revert to nature and disappear over time afterwards. Which they will NOT do if people map them, walk them, and ride bikes on them.

It would really be better if you only mapped paths based on aerial imagery (NOT elevation changes), or on-site surveys with GPS.