NATIVE WOODY PLANTS OF THE UNITED STATES 13 
sidering the length of time required for the appearance of the climax 
stages; if they are planted, we can rely upon their being replaced, 
sooner or later, by other species. But the initiation of a secondary 
succession will ensure the control of erosion on a given area and the 
production of habitats useful for wildlife. 
A list of pioneer species for various areas throughout the United 
States could easily be drawn up here. A much more certain manner 
of determining them, however, is to examine eroded areas where pio- 
neers have already begun to grow. The identification of the species 
informs the technician what to plant. And, it may be emphasized that 
the pioneers observed on such places are the results of long ages of 
natural selection of a sort that permits the survival of only those 
best adapted to initiate successions. With proper interpretation of the 
results of such long-time, natural “experimental plantings” the recla- 
mation of eroded land can be carried out with confidence. 
With these ideas in mind a principle may be stated that any techni- 
cian who wishes to plant woody species to control erosion would do 
well to remember; namely, that careful observation of local vegeta- 
tional successions, coupled with accurate determination of the species 
involved, will often indicate the best means to employ. As Shantz 
(504, p. 855) has said: “Wherever one looks, nature has pointed the 
way to recovery.” 
We have in this country one vast testing ground, comprising many 
kinds of climate, soil, and site, wherein species have failed or suc- 
ceeded for significantly long periods. As long as a species is planted 
within its known range of occurrence, in its proper site as determined 
by observation of its so-called preferences, and is intermingled 
with other species in a ratio and position approaching natural condi- 
tions, we may be satisfied that except for failures attributable to seri- 
ous local variations in environment our plants will grow and thrive. 
Aldous and Shantz (9) point out that the natural or normal plant 
cover is a result of all the growing conditions of the area wherein it is 
produced. It is, therefore, an index or measure of the factors influenc- 
ing its growth, and it serves as an indicator of the possibilities of 
producing other plants on the same land. 
NATIVE VERSUS INTRODUCED SPECIES 
A clear distinction should be made between crop plants that must 
be planted and cultivated each year, or every several years, and woody 
plants, which are untended and uncultivated (if planted in the wild) 
and which must depend for their existence upon any ability they may 
have to compete successfully with the native species that will eventu- 
ally grow around them or that are already there. In planting species 
on sites where they must be able to survive competition, it is hazard- 
ous to select plants other than those that have already shown them- 
selves capable of succeeding in similar sites. If all competition is to 
be removed through cultivation, then such an argument would neces- 
sarily be invalid. Erosion cannot be controlled by cultivation alone, 
however, and most sites needing revegetation with woody plants are 
those that are being retired from cultivation, not those on which culti- 
vation is still to be practiced. 
Many technicians engaged in planting apparently do not under- 
stand that our first choice of species for planting on a given site 
