Trees in Otherworld have thoughts and emotions like many creatures in the same world. Most of them can't express their thoughts and emotions with anything other than body language. Their thoughts are especially hard to understand and only a few creatures can hear them without aid from some technology, but their emotions are easier to recognize. A happier tree's branches are fairly relaxed and look how a tree normally looks. A sad tree's branches will be lowered depending on how sad the tree is, almost like the tree is wilting. An angry tree's branches stick almost straight outward and look stiff. The area surrounding a tree may also be affected by their emotions if they are strong enough. For example, a very sad tree might be surrounded by wilting or dead plants while a very angry tree's roots might be almost ripping themselves out of the ground as if the tree is trying to revolt against whatever offended it. Some trees have different ways to express their emotions. Powder trees produce certain powders based on their emotions such as a poisonous powder when angry.
Tree sap is different depending on the tree's mood. Sometimes potions call for sap from a tree that is in a certain mood. Potion makers sometimes manipulate the tree's mood so it produces the desired sap. This is seen as cruel by environmentalists and some are very loud about denouncing the practice. That doesn't stop all potion makers from continuing, though.
A tree's emotions are largely affected by the environment or how they are being treated. Breaking off a tree's limbs or destroying the surrounding environment are some ways to anger or depress it.
Of course, anger, sadness, and happiness are not the only emotions trees can have, the examples here are simply some ways they express emotions. They are a bit complex in their emotions similar to other creatures. Each individual tree is thought to have its own personality which may determine how it behaves in certain situations.
Some activists assert that lumberjacking is evil. Lumber-jacking itself isn't really evil. Cutting down trees for shelter is necessary for survival just like killing animals for food. It is only wrong when the lumber-jacker cuts too many trees down which can deplete the population of trees. Lumber-jacks have some tools they use when cutting down trees to avoid upsetting them. One of these tools is a syringe filled with a fluid that will numb the tree so it doesn't feel anything. The surrounding trees won't get upset about trees being cut down unless the lumber-jacker is cutting too much to be greedy or destructive. Some lumber-jackers will replace the cut down tree with a seed to eventually grow a new tree.