From below, this looks like a shrubby deciduous tree. It is really just a Douglas fir, like those around it. All the defoliated thicket growth is overgrown poison oak. It has likely been climbing the fir tree since it was quite young. Poison oak is not very proficient at climbing bare trunks. It typically climbs into lower limbs, and then into higher limbs before the lower limbs are shed.
No one has bothered to cut this poison oak out of the fir tree because it is not within a landscapes area. That dark margin at the top of the picture is the underside of a bridge, from which, not much of the thicket growth below is visible. The area from which this picture was taken is used for piling greenwaste and parking, where no one is concerned about wild vegetation beyond.
However, now that I sometimes park in that particular parking area, I am finding this mess of poison oak difficult to ignore. There was a similar but even bigger thicket of poison oak up in a redwood tree at the farm, from where it tossed seed into horticultural commodities below. The resulting seedlings added a whole new dimension to weeding the stock. The thicket had to go.
The problem with the thicket in the picture above, although not as serious, is that it too tosses seed into area where people work. Seedlings are likely to grow where greenwaste is processed, and where I sometimes park. Poison oak that grows on the far side of this fir grove will be uncomfortably close to the right field foul line of a ball field that will eventually be restored there.
I have no intention of cutting the poison out of the fir tree. I will merely sever the main trunk at the base, as seen in the picture below. As it deteriorates over several years, no one will mind if it is somewhat unsightly on the industrial yard side. The adjacent fir trees sufficiently obscure it from view from the ball field side. The priority will be preventing seed from proliferating.