  We prove that the decreasing rearrangement of a dyadic A1 weight w with
dyadic A1 constant [w]_{1,T}=c with respect to a tree T of homogeneity k,on a
non-atomic probability space, is a usual A1 weight on (0,1] with A1 constant
not more than kc-k+1.We prove also that the result is sharp, when one considers
all such weights w.
