Tractor
"Markagrensa" is the legal boundary for areas protected according to "lov om naturområder i Oslo og nærliggende kommuner (markaloven)", <https://lovdata.no/dokument/NL/lov/2009-06-05-35>.

Nordmarka <https://www.openstreetmap.org/relation/1904403>, on the other hand, is a geographical area. By the way, this place is in Lillomarka <https://www.openstreetmap.org/relation/5806405>, not in Nordmarka.