On the Origin of the Field Plants of the Northeastern United States

Abstract

Old fields have dominated studies of terrestrial plant succession in the eastern United States. In spite of the tremendous amount of work on old field succession, fundamental questions remain. One such question is the subject of the present paper: In the primeval landscape, where were the plants that are abundant today in old fields? The question holds interest not only for interpretation of the northeastern landscape but also for understanding of the habitats in which field plants evolved. The plants of fallow agricultural fields are widely assumed to be early successional species, i.e., plants adapted to move from one temporary opening to another, but did they really evolve as successional plants? Many of the plants that grow in abandoned fields today are not native to North America and were thus not part of the landscape prior to European settlement. Bard (1952) reported that between one fifth and one third of the plant species in old fields in New Jersey were alien to North America. It is of the remaining two thirds (roughly 100 species) that we can ask, Where was a sun-loving field flora growing in a landscape that was heavily forested? According to Braun (1950, p. 7), "When the first settlers colonized the Atlantic seaboard ... they found an endless expanse of forest broken only by swamps and bogs, by cliffs or river bluffs too steep for forest, by windfalls and burns, by small grassy openings such as the serpentine barrens of the northern Piedmont, and by the prairie patches and 'barrens' of the interior.' Four hypotheses can be suggested to account for the location of native field plants in the presettlement landscape. (1) They evolved on agricultural land abandoned by Indians far back in time. (2) Native field plants migrated eastward from prairies and savannas at the western margin of the deciduous forest with the onset of extensive clearing for settlement and agriculture and with the development of continuous east-west corridors of open field habitat along railroads and canals. (3) Native field plants were true pioneer or early successional species that colonized temporary forest openings caused by wind, fire, and other kinds of