What is the main function of the mission and what specific trees were found on most missions?

The main purpose of all of the missions from the viewpoint of the Spanish Crown was to confirm the claim of Spain to this wilderness by settling it and creating communities (and ultimately four presidios or forts) that would defend the land. The purpose of the missions from the perspective of the padres was to convert the Native Americans, who were recruited into the missions and converted to Catholicism.

There were two types of trees - the trees that were there at the time of the arrival of the Europeans (the most dramatic of which were the Redwoods, the most important of which were Oak trees whose acorns were an important source of food to the Indians) and trees that were imported - particularly fruit trees, olive trees etc.