Final answer:
In the context given, the ecological relationship between the salamander and the tree is commensalism, which is facultative for the tree, as the tree does not derive benefits nor harm from the salamander's presence.
Step-by-step explanation:
The ecological relationship described where the salamander benefits and the small tree is not harmed is called commensalism. Since the tree is unaffected whether or not the salamander is present, for the tree, this relationship is neither obligatory for survival, nor does it provide any specific advantage, so it would be considered facultative. Therefore, the correct answer is 1) commensalism; facultative.
The relationship described between the salamander and the small tree is an example of commensalism. In commensalism, one species benefits while the other is neither harmed nor benefited. In this case, the salamander benefits from the tree by finding shelter, while the tree is not affected.
For the tree, this relationship can be considered facultative, meaning it is not required for the tree's survival. The tree can survive even without the salamander's presence.