Thanks. Just came across this pic. In Sonoma Co, CA, so not familiar enough to ID the trees, tho the straight one might be a coastal redwood, and the other perhaps a madrone?

Ben, it looks like they're in a warm embrace or perhaps dancing.

I no longer have the picture, but for several years while working I'd pass a large deciduous tree (Silver Maple) in Superior, WI, which had a White Spruce growing in it, similar to what floral has shown. I haven't seen it in many years, but I'd make a point to drive by this/these trees to see how it/they were doing whenever I was working in the Twin Ports. The spruce was about 3' tall when I last saw it and quite healthy.

Commensalism or parasitism?

maackia, it wouldn't be true parasitism unless the roots of the white spruce had penetrated into the cambium of the silver maple and sucking the nutrients out of it, instead of just living off the organic debris collected in the fork. So I'd think your and floral's example is commensalism. The tropical strangling fig examples are kinda parasitic as tho not sucking nutrients directly out of the host, they are using it for support to grow and eventually kill it by smothering.