Vertical arrays of carbon nanotubes, called 'forests', are a common type of three-dimentional (3D) nanotube assembly that researchers work with in their labs. These forests can be produced by chemical vapor deposition technique and used for diverse applications such as in photo- or thermoacoustics, highly elastic conductive composites, for mechanical nanomanipulation, in catalysis, or as sensors in nanomedicine, just to name a few examples. These and other applications relay on connectivity of carbon nanotubes in the forest structure. New measurements show that room temperature electrical properties of this nanotube network reveal quite substantial nonlinerarities that became more pronounced at sample cooling.