Sheviis 4:5

If a person chops wood from an olive tree in the sabbatical year, he may not cover the stumps with dirt (which is beneficial to them) but he may cover them with rocks or straw. Similarly, if a person chops beams from a sycamore tree in the sabbatical year, he may not cover it with dirt but he may cover it with rocks or straw. One may not cut a sycamore tree for the first time in the sabbatical year because it is a form of working the tree. Rabbi Yehuda says one may not do so in the normal fashion but he may if he cuts it ten handbreadths high or all the way down at the roots.

Sheviis 4:6

If one trims vines or reeds, Rabbi Yosi HaGlili says he may not do so within a handbreadth of the ground. Rabbi Akiva says he may cut in the normal way, using an axe, a sickle, a saw, or any other tool he likes. If a tree split, it may be tied together in the sabbatical year – not to heal it but to keep the split from worsening.