The bottom component of a Bee Tree Hive is the combination Eco-Floor and Stand.
A honey bee colony is not designed to live as a solitary organism in a sterile environment. In the wild, they live in symbiotic relationship with thousands of other organisms - from yeasts, molds, and fungi, to many other insects... including several varieties of mites!
The Eco-Floor is open on the top and screened on the bottom. This allows you to fill it with detritus from the ground in the region where the hive will be located. This adds indigenous organisms to the hive environment, which brings health to the colony in ways that we have yet to begin to understand.
Because the Eco-Floor is screened on the bottom, it allows a slow movement of air, up through the detritus, that provides year-round ventilation. Because the air moves slowly through the detritus, where countless biological processes are occurring, the detritus also provides insulation. There are no drafts of cold air blowing in a bottom entrance or up through a screened bottom board. The temperature, humidity, and pH levels inside the hive stay much more consistent.
The detritus is also hygroscopic. It absorbs, and then slowly releases, any excess moisture that may drip down from inside the hive. This also helps to keep both the temperature and the relative humidity more consistent inside the hive. The bees will therefore consume fewer resources to regulate the hive's micro-climate.
And, in conjunction with the top entrances in each hive body, the Eco-Floor makes a bottom board completely unnecessary.
The Eco-Floor/Stand, with its cedar legs, gets the bottom of the brood nest 16" off the ground. That is twice as high as a concrete block with a conventional bottom board. Plus, the cedar legs act as an insulator from the cold ground. (Concrete actually conducts cold.)