Xeric Moisture Regime and Temperature Limits

Yes, you are correct. The Xeric moisture regime is not used with hyperthermic temperatures (>22C) or with soils in any ""iso"" temperature regime. If you read the definition for the ustic regime you'll see that it is constructed to include those soils which have a clear wet and dry season, but where temperature differences between the wet and dry seasons are not very important. In those cases there is little practical distinction between ustic and xeric, so we just use ustic for all of them. You may note that the criteria for Xerolls allows them to have an aridic moisture regime, so you concievably can have an ""iso... Xeroll"", but you can not have an ""iso... Xeralf"", or ""iso ... Xerept"", etc. I believe we have a few misclassified soils in our system today due to this somewhat overlooked part of the xeric definition.