There are two different plants at the bottom, but their names elude me.  They're the plants sold at nurseries to plant between stepping stones.  I'll have to see if I still have the tags somewhere.  The "cork bark" is actually a piece of branch I found in the woods while looking for caudates.  There is a myriad of things growing on it (bracket fungi, lichens, ect.).  The bare area in the center is actually holes made by a woodpecker or flicker.  I've seen quite a few animals (tiny slugs,land snails, insects) appear over the week that probably came from it.