Unless it is otherwise provided by the will creating a testamentary trust, the instrument creating an express trust, or by an order or decree duly entered by a court of competent jurisdiction, a trustee shall have all the powers granted a trustee under sections 633A.4401 and 633A.4402. Documents incorporating by reference powers granted a trustee under the probate code or under this section shall be interpreted accordingly, even if the execution or adoption of the instrument creating the trust occurred prior to July 1, 2005.