In light of the grammar given by Ji for the \((\alpha ,\beta )\) -Eulerian polynomials introduced by Carlitz and Scoville, we provide a labeling scheme for increasing binary trees. In this setting, we obtain a combinatorial interpretation of the \(\gamma \) -coefficients of the \(\alpha \) -Eulerian polynomials in terms of forests of planted 0-1-2-plane trees, which specializes to a combinatorial interpretation of the \(\gamma \) -coefficients of the derangement polynomials in the same spirit. By means of a decomposition of an increasing binary tree into a forest, we find combinatorial interpretations of the sums involving two identities of Ji, one of which can be viewed as \((\alpha ,\beta )\) -extensions of the formulas of Petersen and Stembridge.