The process described in the question is known as girdling or ring barking. It involves the removal of a ring of bark, which includes the phloem, the layer responsible for transporting nutrients produced during photosynthesis from the leaves to other parts of the tree.

Option 1 is incorrect because the tree`s water transport system, the xylem, is located inside the bark and is usually not affected by girdling.

Option 2 is correct . When girdling removes the phloem, the roots are cut off from the rest of the plant and starved of the sugars and other nutrients they need, causing the tree to die.

Option 3 is not necessarily true because the tree might already have defense mechanisms against soil microbes, and their infection is not directly caused by the removal of the bark.

Option 4 is also incorrect because roots typically get oxygen from the soil, and the removal of part of the bark at the tree`s base doesn`t affect this process. Hence, roots will still be able to respire.