The Relationship Between Gap Size and Performance of Several Colonizing Annuals

Abstract

Several colonizing annual species comprising a range of seed masses were grown in artificially created disturbances in an old field. Gaps of 5, 10, 20, and 40 cm in diameter were established in a Poa pratensis L. background. Undisturbed vegetation was used as a control. Although survivorship was greater in larger gaps only for small—seeded species, the probability of reaching reproductive maturity increased with gap size for six of the species tested. Other measures of species performance, such as plant mass and number and mass of seeds produced, followed similar trends. Ipomoea hederacea, a climbing plant, was unique in its lack of response to gap size. Many differences in responses among species suggest that the size of a disturbance might direct the events of colonization.