The Effects of Black Locust on Associated Species with Special Reference to Forest Trees

For a number of centuries, it has been known among agriculturists that such crop plants as beans, peas, and clover lead to increased yields of certain other crop plants following in the rotation; but it remained for modern investigators to demonstrate that nodule formation on roots of leguminous species is due to infection by nitrogen-fixing bacteria and that through the activity of these bacteria the nitrogen content of the soil is increased. In 1888 Beijerinck isolated and cultured the organism and named it Bacillus radicicola; Prazmowski, in 1889, changed the name to Bacterium radicicola; and later the Society of American Bacteriologists placed the Bacterium radicicola in the genus, Rhizobium, that commonly in use at present. In 1932, Fred, Baldwin,(and McCoy listed all leguminous species, whose nodule bacteria have been studied, in sixteen groups on the basis of interinoculation; thus, each species within a group may successfully be inoculated with bacteria from the nodules of any other species within the category. The bacteria, inoculating roots of species in any one group, are deemed distinct enough from those inoculating other groups to be considered as a separate species. Black locust (Robina pieudoacacia L.) alone comprises "Group XII. Although foresters have reported, during the last decade, their recognition of the importance of this tree legume as a benefactor to associated tree species, their data represent studies on camparatively few plantations with associated species, primarily catalpa. In 1922, Ferguson, from studies of adjacent black locust and catalpa plantings at College Farm, State College, Pennsylvania, showed small but consistent decreases in total nitrogen content of the soil at increasing distances from the locust planting. Also average heights and diameters of the catalpa trees were shown to decrease as distance from the locust increased. McIntyre and Jeffries, in 1932, reported recent studies of soil nitrogen in relation to height and diameter growth on two catalpa plantings adjacent to black locust at the Pennsylvania State College, State College, Pennsylvania. Their results in general were similar to those of Ferguson. Black locust may become established under widely varying combinations of site factors. Cuno, 1930, suggests that the range of black locust may have been originally restricted to the Appalachian Mountains from Pennsylvania to Georgia, and to parts of western central Arkansas and eastern central Oklahoma. He further states that the best development of the species occurs on the western slopes of the Appalachians in West Virginia. This tree has been introduced into practically every state for one or another of its many uses. In the western states, eminent success with plantations has been attained in the valleys of the northern Roeky Mountain region, particularly, in Idaho, eastern Oregon and Washington. Black locust was introduced into Europe in 1601 and has been considered the most successful of the tree species