NATIVE WOODY PLANTS OF THE UNITED STATES 5 



cover plants should be unobjectionable from the agricultural stand- 

 point. The striking similarity of Leopold's criteria for game-cover 

 plants and the characters valuable in erosion control is at once 

 apparent. 



It has been pointed out that the restoration of cover, important alike 

 for soils and for wildlife, is the objective sought in soil conservation 

 as well as in wildlife conservation. The correlation of erosion control 

 with wildlife planting, therefore, is obviously an easy one to make. 

 Furthermore, the utilization for wildlife production of submarginal 

 lands upon which man-made erosion is unusually severe is a sound 

 economic practice. 



PLANTING FOR SOIL AND WILDLIFE CONSERVATION 



It is obvious to those who have had experience in landscaping or 

 forestry that the old maxim about putting all of the eggs in one 

 basket applies very well to the planting of woody species. The most 

 important rule to follow, whether planting for timber, pulpwood, ero- 

 sion control, wildlife, or any combination of these, is that the species 

 used must be varied that the planting must be a mixture, not a pure 

 stand. This is true for several reasons (^8^), namely: 



1. Solid stands of plants favor the rapid spread of disease and 

 insect pests. Fungi, as well as insects, find it easy to travel from 

 one plant to another of the same kind. In mixed plantings spread is 

 slower and control is consequently easier. Isolation of individuals 

 and groups from others of their own kind is the natural safeguard 

 against infection. 



2. Solid plantations of one species have for some time been known 

 to result in depletion of the soil. Further, pure stands do not repre- 

 sent the maximum productive capacity of the soil. 



3. Maximum interspersion of species ensures that all ecological 

 niches will be filled. This results in a greater utilization of space 

 and better erosion control. Competition between individuals, and 

 therefore waste of energy, is at its highest in pure stands. 



4. In planting for wildlife, variety is essential. What one species 

 of plant may lack, another may possess. The effort should be made 

 to attain a well-balanced habitat, approaching as nearly as possible 

 the "orderly confusion of nature." Insectivorous birds are generally 

 discouraged by pure stands, but encouraged by mixtures. The en- 

 couragement of such birds leads to greater control of injurious insects. 

 In several European countries it has been found an economically 

 justifiable practice to put up bird houses in forest plantations to 

 attract insectivorous birds and thereby to ensure some control of 

 insects. The idea is extending even to this country, but proper mix- 

 ing of species in planting should make such a practice unnecessary. 



It is very essential that careful planning precede actual field opera- 

 tions. Press of work and the need that considerable planting be 

 done in a short time are often advanced as excuses for improper 

 spacing, poor selection of site and species, and faulty organization 

 of the work. Actually such excuses are never valid, for the planting 

 seasons are preceded by periods sufficiently long to permit of careful 

 planning. Because of the impossibility of obtaining sufficient plant- 

 ing stock of the kind desired, it may often be necessary to substitute 



