Buried, Viable Seeds and Their Relation to Revegetation after Surface Mining

Abstract

The quantity and quality of seeds present in prairie soils prior to surface mining were determined in this study. Samples were collected near Beulah in western North Dakota from 4 sites (1 each from grazed and ungrazed areas, 1-year old stockpiled topsoil, and a fresh stockpile). Samples were taken from 3 depths and allowed to germinate in a growth chamber for 16 months. The grazed site had a seed density of over 7,700 seeds m2 (43% were from weed species), and the ungrazed site had 3,900 seeds m-2 (7% were weeds); the stockpiled topsoils had very low seed densities. Seed density and diversity decreased with depth on both the grazed and ungrazed sites; this was especially true for the grazed site where 94% of the seeds were found in the top 7.5 cm. Comparisons were made between the seed banks and the aboveground vegetation of the unmined site and 4 mined sites (ages 1-4 years after reclamation). Analysis indicated that seeds of the most prevalent colonizers after reclamation [e.g. summer cypress (Kochia scoparia), green pigeongrass (Setaria viridis), and Russian thistle (Salsola collina)] were not present in the topsoil; rather, they immigrated from the surrounding areas. Several species which were present in the seed bank [e.g. rough penny royal (Hedeoma hispida), buck-horn (Plantago patagonica), white sage (Artemisia ludoviciana), fringed sage (A. frigida), and wormwood (A. absinthium)] were found in the aboveground vegetation of 3- and 4-year-old mined sites, and at the unmined site. Evidence from seed banks and extant aboveground vegetation suggests that both seed dispersal in time (dormancy) and dispersal in space (immigration) are important in determining the type of vegetation on mined areas after topsoil has been replaced.