Any place for landscape fabric inside a greenhouse (I originally bought it to help warm the soil)

Hi, I finally built a 12x20 greenhouse off craigslist.  It's a hoop style with raised side walls.  Last year I purchases landscape fabric thinking I was going to use it on raised beds to help warm my soil.  I live up at 7,800' and the soil isn't warm until July -- or at least that when my plants finally start to grow.  But then I found a good deal on this greenhouse.  I thought maybe I could do the same with the soil inside my greenhouse, but as I just laid out my soil on top of the thick layer of woodchips where I placed my greenhouse, I'm noticing the soil itself is pretty dark.  

Would adding this landscape fabric help warm up my soil faster?  Or is dark soil good enough?   Less plastic is better, but I already bought the stuff.  Is there another good reason to have landscape fabric inside a greenhouse?  Keep the dog from digging?  

I assume landscape fabric is mostly for weed control.  I thought inside a greenhouse that would be less of an issue.  The soil I used came in bags so hopefully it wasn't full of seeds.  

Seth