In addition to his studies of the habits and reproduction of the different trees for working plans or timber sales, or simply to increase his knowledge of the forest, the Forest Examiner is often called upon to lay out sample plots for ascertaining the exact relation of each species to light, heat, and moisture, or for studying its rate of growth. He may find it necessary to determine the effect of the grazing of cattle or sheep on young growth of various species and of various ages, or to ascertain their relative resistance to fire. In general, what time he can spare from more pressing duties is very fully occupied with adding to his silvical knowledge by observation, with studies of injurious insects or fungi, of the reasons for the increase or decrease of valuable or worthless species of trees in the forest, the innumerable secondary effects of forest fires, the causes of the local distribution of trees, or with some other of the thousand questions which give a never-failing interest to work in the woods.
The protection of a valuable kind of tree often depends upon the ability to find a use for, and therefore to remove, a less-valuable species which is crowding it out, for as yet the American Forester can do very little cutting or thinning that does not pay. Just so, the protection of a given tract against fire may depend upon the ability to use, and therefore to remove, a part or the whole of the dead and down timber which now makes it a fire trap. For such reasons as these, the uses of wood and the markets for its disposal form exceedingly important branches of study for the Forest Examiner, who will usually find that his duties require him to be thoroughly familiar with them.
It is more and more common to find each Forest Officer--Ranger, Forest Examiner, or Supervisor--combining in himself the qualities and the knowledge required to fill any or all of the other positions. The professionally trained man who develops marked executive ability is likely to become a Supervisor, just as a Ranger, with the necessary training and experience, who may wish to devote himself to silvical investigations may be transferred to that work. The point is that each man has individual opportunity to establish and occupy the place for which he is best fitted.