Logs that artist use to make log art are not kiln dried like regular wood used for indoor furniture. Kiln-dried wood is wood that has been dried in an oven. (Kiln) With a kiln, you can control the environment, temperature, humidity, and steam levels for a set period of time. Usually 150 degrees for 28 days. Allowing you to dry the wood to a desired moisture content faster than air-drying.
Log art is not kiln dried and still has a lot of moisture in the wood.
A bit of checking (cracking) is the nature of log art. In most cases it adds to the patina of the piece.
To keep checks to a minimum place your carving away from direct sun or excess heat. Avoid extreme temperature changes.
If Indoors be mindful of how closely your carving is to heater vents, fireplaces and other heat sources. The dry hot air rapidly pulls the moisture from your carving and causes cracking.