322 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 53 



Twenty-three research areas, mainly sprayed rights-of-way, have 

 noAv been established in 11 States, in cooperation with research, edu- 

 cational, and nonprofit organizations. Over 75 species of trees are 

 on the plots, none of which show significant evidence of invading 

 shrub communities. Pines, birches, elms, tulip-trees, maples, and 

 ashes can invade the grasslands however, sometimes so readily and in 

 such numbers as to require respraying at 5-year intervals. Over 90 

 kinds of shrubs can be sufficientl,v abundant to characterize the vegeta- 

 tion, and the majority of these have high values as ornamentals and 

 as a source of food for wildlife. Only four ferns and six forbs (all 

 goldenrods) form relatively pure plant comnumities, and all are re- 

 sistant to tree reinvasion. The number of upland grasses and grass- 

 like plants that predominate in pure stands has been far few^er than 

 originally anticipated. The commonest in the Northeast and Central 

 East belong to but seven genera. All except two panics show them- 

 selves open to invasion by tree seedlings, but not hj shrub seedlings. 

 Creation of these grasslands is therefore usually detrimental to the 

 interests of both the managers of the lands and the public through 

 the permanent loss of attractive landscape and wildlife habitats. 



In conclusion, present botanical knowledge indicates that most of 

 the upland grasslands are easily invaded by a few species of trees, 

 whereas the shrublands are relatively sealed against tree reinvasion. 



A list of literature references concerning the American Museum 

 System of Rightofways Vegetation Management may be had on 

 request from the Department of Conservation and General Ecology, 

 American Museum of Natural History, New York 24. Arrangements 

 for the loan of a colored talking film on the subject may be made b}^ 

 addressing the Film Library of the Museum. 



