The suillus lakei mushroom is commonly found
growingaround the bas of conifers, especially the douglas fir.
offer apossible explanation of this association of a fungus and
plant.

Suillus lakei mushroom refers to a mycorrhizal fungus, which grows in company with Douglas fir, and can be witnessed in the locations where this tree is found.  

This association illustrates a symbiotic relationship, known as mycorrhizae, which is produced between the plant and the fungi. The fungi colonize the root system of the host plant, in this case, Douglas fir, and provide enhanced nutrient and water absorption tendencies, while the plant offers the fungus with carbohydrates produced from the process of photosynthesis.