show crop gains on 25-year 

 rotations that are estimated 

 to be as high as 12 percent 

 in cubic volume and 32 

 percent in harvest values 

 (Zobel and Talbert 1984). 

 Rates of return on invest- 

 ments in these seed or- 

 chards appear to be as 

 high as 17 to 19 percent 

 after taxes. Yields from 

 first-generation orchards 

 are not great enough to 

 allow most members to 

 meet regeneration needs 

 with improved stock. 



As a result of work by these 

 and other scientists, tree 

 improvement is a reality 

 today, and a major phase 

 of forestry in the South is 

 the production and use of 

 seed from pine trees that 

 show superior growth, form, 

 and resistance to disease 

 (e.g., Powers and others 

 1979). It is estimated that 

 by the early 1 980's some 

 10,600 acres of seed or- 

 chards had been estab- 

 lished over the South. These 

 include orchards for produc- 

 tion of genotypes resistant 

 to fusiform rust, although 

 only limited quantities of 

 seed from such sources 

 are as yet available (Powers 

 and others 1979). 



Seed orchard management 

 also has been the focus of 

 related studies that show 

 that proper spacing and 

 fertilization can significantly 

 increase yields of seed. 

 Research in crossbreeding 

 pines has produced a 

 variety of hybrids, including 

 crosses of shortleaf and 

 slash pines, for example, 

 that outperform the parents 

 (Wells and others 1978). 

 Research relating to hard- 

 woods has included devel- 

 opment of clones of 

 cottonwoods and hybrid 

 poplars that grow considera- 

 bly faster than average 

 trees (e.g., Randall 1973). 



Much of the information 

 developed on the genetics 

 and breeding of southern 

 pines has been summarized 

 in Agriculture Handbook 

 471 (Dorman 1976). This 

 major compilation includes 

 material from more than a 

 thousand references on 

 factors affecting flowering 

 and seed production; geo- 

 graphic, racial, stand, and 

 tree variation in genetic 

 characteristics; techniques 

 for enhancing production of 

 superior seed; methods of 

 vegetative propagation; 

 and techniques for breeding 

 new strains of southern 



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