After notice to the qualified beneficiaries, a trustee may combine two or more trusts into a single trust or divide a trust into two or more separate trusts, if the result does not impair rights of any beneficiary or adversely affect achievement of the purposes of the trust. The terms of each new trust created by a division under this section do not have to be identical if the interest of each beneficiary is substantially the same under the terms of the trust prior to its division and the combined terms of all trusts after the division. Two or more trusts may be combined into a single trust if the interests of each beneficiary in the trust resulting from the combination are substantially the same as the combined interests of the beneficiary in the trusts prior to the combination. The trustee shall determine the terms controlling any trust after its combination as authorized by this section.