Tennyson evidently enjoyed keeping each line strictly to three syllables and to the pattern  / * /, the amphimacer, in "The Oak." We do have to reduce "soberer" to two syllables through syncope to make it fit, but that's not too hard to imagine: "sobr'er." With a little ingenuity one could also call it catalectic   trochaic dimeter, omitting the final syllable in every line. But amphimacic monometer is rare enough to be worth valuing, when we can catch one.

 
                           /     *     /
                         Live thy Life,
                                 Young and old,
                            Like yon oak,
                            Bright in spring,
                                 Living gold;

                            Summer-rich
                                 Then; and then
                            Autumn-changed
                            Soberer-hued
                                 Gold again.

                            All his leaves
                                Fall'n at length,
                            Look, he stands,
                            Trunk and bough
                                 Naked strength.

Most of William Blake's poem "Spring" is in the same meter:

                                  Little boy,
                                  Full of joy;
                                  Little girl,
                                  Sweet and small;
                                  Cock does crow,
                                  So do you;
                                  Merry voice,
                                  Infant noise