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Abstract
<br />t OCJ =.E.. R. EVERSON L_NI1 f O AN K. WALL'
<br />The quantity and quality of seeds present in prairie soils prior to
<br />surface mining were determined in this study. Samples were col-
<br />lected near Beulah in western North Dakota from 4 sites (1 each
<br />from grazed and ungrazed areas, 1-year old stockpiled topsoil, and
<br />a fresh stockpile). Samples were taken from 3 depths and allowed
<br />to germinate in a growth chamber for 16 months. The grazed site
<br />had a seed density of over 7,700 seeds m (43% were from weed
<br />species), and the ungrazed site had 3,900 seeds m_ (7% were
<br />weeds); the stockpiled topsoils had very low seed densities. Seed
<br />density and diversity decreased with depth on both the grazed and
<br />ungrazed sites; this was especially true for the grazed site where
<br />94% of the seeds were found in the top 7.5 cm. Comparisons were
<br />made between the seed banks and the aboveground vegetation of
<br />the unmined site and 4 mined sites (ages 1 -4 years after reclama-
<br />tion). Analysis indicated that seeds of the most prevalent coloniz-
<br />ers after reclamation [e.g. summer cypress (Kochia scoparia),
<br />green pigeongrass (Setaria viridis), and Russian thistle (Salsola
<br />collina)] were not present in the topsoil; rather, they immigrated
<br />from the surrounding areas. Several species which were present in
<br />the seed bank [e.g. rough penny royal (Hedeoma hispida), buck -
<br />horn (Plantago patagonica), white sage (Artemisia ludoviciana),
<br />fringed sage (A. frigida), and wormwood (A. absinthium)] were
<br />found in the aboveground vegetation of 3- and 4- year -old mined
<br />sites, and at the unmined site. Evidence fr am seed banks and extant
<br />aboveground vegetation suggests that both seed dispersal m time
<br />(dormancy) and dispersal in space (immigration) are important in
<br />determining the type of vegetation on mined areas after topsoil has
<br />been replaced.
<br />The vegetation that emerges following currently mandated
<br />mined land reclamation practices (viz., contouring, replacing top-
<br />soil, fertilizing, and seeding), is determined not only by the planted
<br />seed mix, but also by the seed stock (seed bank) present in the
<br />topsoil and the immigration of seeds and disseminules from neigh-
<br />boring ecosystems. It is, therefore, important to determine the
<br />kinds of species and quantity of viable seeds in the topsoil prior to
<br />mining. Such information would be of value in evaluating the
<br />potential of topsoil to determine the initial course of succession on
<br />these sites.
<br />Several factors determine the quantity and quality of seed banks:
<br />(1) reproductive potential of plants; (2) dispersal mechanisms; (3)
<br />dormancy patterns: (4) characteristics of the soil; (5) biotic influen-
<br />ces, i.e. predation and decomposition; (6) weather fluctuations;
<br />and (7) disturbances to the soil surface (Thurston 1960, Barton
<br />1962). it has been noted that disrupting the soil surface often
<br />breaks seed dormancy by exposing seeds to unfiltered light, fluc-
<br />tuating temperatures, and reduced CO2 concentrations (Bazzaz
<br />The authors are postdoctoral research associate, Project Reclamation, and director,
<br />Project Reclamation and professor of biology, respectively, at the University of North
<br />Dakota, Grand Forks 58202.
<br />This research was supported by National Science Foundation Energy Traineeship
<br />to L.R.E., and by Grant No. G0264001 and Contract No. J0295015 from the U.S.
<br />Department of the interior- Bureau of Mines to M.K.W. The authors are indebted to
<br />:,r. Stuart Nicholson and Mr. Richard H. Bares for useful comments on the manu-
<br />script. and Ms. Laura Brophy and Ms. Diana Schimrneipfennig for technics
<br />assistz
<br />Manuscript received Dece.m er 20, i981.
<br />Surface M Mining
<br />1970, 1979). Therefore, variations in methods and duration of
<br />removing, stockpiling, and respreading of topsoil during surface
<br />mining assume significance.
<br />Several seed bank studies have been conducted to ascertain ;
<br />means of removing weedy seeds from arable agricultural soils.
<br />Major studies are from the British Isles (Brenchley and Warington
<br />1930, 1933, 1936, 1945; Brenchley 1944; Roberts 1963, 1968;
<br />Roberts and Neilson 1981), Denmark (Jensen 1969), Saskatche-
<br />wan (Chepil 1946, Budd et al. 1954), and from Minnesota (Robin-
<br />son 1949). Pasture soils have been examined for weeds in Wales
<br />(Chippindale and Milton 1934, Milton 1948), and in New Hamp-
<br />shire
<br />(Prince and Hodgdon 1946). But seed bank studies in grass-
<br />lands of the North American Great Plains are limited. In Kansas,
<br />Lippert and Hopkins (1950) studied native mixed grass and short
<br />grass prairies, an abandoned field, and a denuded pasture. Rabino-
<br />witz (1981) studied the seed bank and seed rain on a tall grass
<br />prairie in Missouri. Johnston et al. (1968) studied rangelands in
<br />Alberta for seed populations of mixed grass prairie and fescue
<br />grasslands including sites that ranged from ungrazed to heavily
<br />grazed. Dwyer and Aguirre (1978) determined germinable seed
<br />populations for 2 range condition classes on the Desert Grassland
<br />in New Mexico. Only a few seed bank studies in relation to surface'
<br />mined land reclamation are available. Beauchamp et al. (1975)
<br />studied Wyoming sagebrush -grass topsoils as a potential seed
<br />source for re- seeding mined spoils, and Brophy (1980) studied
<br />viable seed populations in soils of revegetated North Dakota coal
<br />mines. Results of some of the above - mentioned studies have been
<br />tabulated (Table 1).
<br />In the present study, we (1) estimate the viable seed populations
<br />in the native topsoil prior to mining in western North Dakota, and ._,1
<br />(2) compare the relative contributions of seed bank populations to
<br />seed populations migrating from surrounding areas as they deter-
<br />mine the initial vegetation of mined areas.
<br />Procedures
<br />Two sites. one ungrazed, the other moderately to heavily grazed,
<br />on native mixed grass prairie (Whitman and Wali 1975) adjacent to
<br />active mining sites, were sampled in April, 1979 for estimation of
<br />buried seed populations. These sites, located 4.5 km south of
<br />Beulah, North Dakota, were typical pre -mined areas in western
<br />North Dakota which, during the mining process, have the topsoil
<br />and subsoil removed separately (up to a total of 1.5 m depth). The
<br />topsoil is then stockpiled while the overburden and coal are
<br />removed; after removal of coal, the areas are backfilled, recon-
<br />toured, and the topsoil replaced. A total of 50 randomly placed,
<br />5-cm diameter cores were taken from each site to provide 10-20
<br />replicate samples representing the surface 2.5 cm, top 7.5 cm, and
<br />7.5 -15 cm depths. Eighteen replicate samples were also taken from
<br />each of the 2 nearby topsoil stockpiles: one stockpiled a year
<br />previously, the other only a week prior to sampling.
<br />Samples were collected in airtight bags, transported to the labor-
<br />atory, and stored at 4° C for 1 month. Storage at this temperature
<br />prevented seed germination but may have aided in the vernaliza-
<br />tion of seeds.
<br />=L� JCURNAf_ CF RANGE MANAGEMENT- 35(5). September 1982
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