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Species
<br />Table 4- Seeding rates and 1978 ratings of percent stand by species for topsoil thickness treatments in the field study,
<br />Energy Fuels Mine No. 1, Steamboat Springs, Colo.
<br />Agropyron desertorum, crested wheatgrass
<br />Agropyron elongatum, tall wheatgrass
<br />Agropyron intermedium, intermediate wheatgrass
<br />Agropyron riparium, streambank wheatgrass
<br />Agropyron smithii, western wheatgrass
<br />Agropyron trachycaulum, slender wheatgrass
<br />Agropyron trichophorum, pubescent wheatgrass
<br />Bromus biebersteinii, meadow brome
<br />Bromus inermis, smooth brome
<br />Dactylis glomerata, orchardgrass
<br />Elymus junceus, Russian wildrye
<br />Festuca ovine duriuscula, hard fescue
<br />Phleum pratense, timothy
<br />Poa ampla, big bluegrass
<br />Poa pratensis, Kentucky bluegrass
<br />Stipa viridula, green needlegrass
<br />Astragalus cicer, cicer milkvetch
<br />Aster sp., aster
<br />Balsamorhiza sagittata, arrowleaf balsamroot
<br />Coronilla varia, crownvetch
<br />Hedysarum boreale utahensis, Utah sweetvetch
<br />Helianthus annuus, sunflower
<br />Lupinus sp., lupine
<br />Medicago sativa, alfalfa
<br />Amelanchier alnifolia, Saskatoon serviceberry
<br />Artemisia tridentate, big sagebrush
<br />A triplex canescens, four -wing saltbush
<br />Ceratoides Janata, winterfat
<br />Chrysothamnus nauseosus, rubber rabbitbrush
<br />Chrysothamnus viscidiflorus, green rabbitbrush
<br />Cowania mexicana, cliffrose
<br />Ephedra uiridis, Mormon tea
<br />Total
<br />t % stand rating based on a scale 0 to 100 where 0 indicates no plants and 100 indicates the maximum possible stand existed.
<br />roots were not as fine - textured as those growing in top-
<br />soil.
<br />Biomass (total herbage and root weights) for both
<br />intermediate wheatgrass and wheat increased linearly
<br />with topsoil thickness (r = 0.95 and 0.97, respectively).
<br />Average herbage production per can was greater for
<br />wheat than for intermediate wheatgrass, but root pro-
<br />duction of intermediate wheatgrass was greater in both
<br />topsoil and spoil (Table 2); therefore, biomass produc-
<br />tion per can for intermediate wheatgrass was greater
<br />than for wheat. Nitrogen fertilizer increased biomass
<br />weights for intermediate wheatgrass an average of 73
<br />over similar nonfertilized treatments.
<br />A "topsoil treatment" of 30 cm (12 inches) using a
<br />mixture of 50% topsoil and 50'o spoil was presumed to
<br />be equivalent to use of 15 cm of topsoil alone. No 15 -cm
<br />topsoil treatment was tested, so averages of the 10 -cm
<br />and the 20 -cm treatments (these averages appear in
<br />Table 3 as "15 -cm" values) were calculated and
<br />compared with production obtained for the top -spoil
<br />mixture. Herbage and root production for the calcu-
<br />lated "15 -cm" values was similar to production for the
<br />topsoil -spoil mixture treatment (Table 3). The use of
<br />topsoil and spoil mixtures for a plant growth medium
<br />has also been evaluated by Shuman and Taylor (1978).
<br />684 J. Environ. Qual., Vol. 9, no. 4, 1980
<br />Topsoil thickness treatments icm)
<br />Seeding rate 46 30 20 10 0
<br />Average
<br />kg/ha % stand
<br />Grasses
<br />3.25t 6.9 6.2 1.7 2.0 2.5 3.9
<br />1.12 0.0 0.0 0.0 0.0 0.0 0.0
<br />3.25 2.2 0.8 2.3 3.5 1.9 2.1
<br />1.34 4.5 3.5 3.4 2.3 0.6 2.9
<br />1.57 3.2 0.9 1.8 0.8 0.0 1.3
<br />1.12 0.0 0.0 0.0 0.0 0.0 0.0
<br />1.23 0.5 0.4 0.3 0.9 0.3 0.6
<br />1.23 8.6 4.8 6.9 6.5 1.6 6.7
<br />1.90 7.3 3.9 7.8 3.3 0.7 4.6
<br />0.56 1.9 3.3 2.0 1.4 0.8 1.9
<br />1.23 0.0 0.0 0.0 0.0 0.0 0.0
<br />1.23 0.0 0.4 0.3 0.3 0.0 0.2
<br />0.56 2.3 0.9 2.3 0.5 1.1 1.4
<br />0.90 0.5 0.0 0.0 0.0 0.0 0.1
<br />1.12 0.0 2.2 0.0 0.0 0.0 0.4
<br />1.12 0.0 0.0 0.9 0.6 0.0 0.3
<br />Forbs
<br />0.56 0.4 1.1 0.0 0.0 0.2 0.3
<br />0.28 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.28 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.56 0.0 0.0 0.0 0.0 0 0 0.0
<br />0.28 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.28 0.0 0.0 0.0 0.0 0.0 0 0
<br />0.28 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.56 10.8 6.7 4.1 5.1 6.7 6.7
<br />Shrubs
<br />0.56 0.0 0.6 0.0 0.0 0.0 0.1
<br />0.17 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.56 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.56 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.17 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.17 0.0 0.0 0.0 0.0 0.0 0.0
<br />0.22 0.0 0 0 0.0 0.0 0.0 0.0
<br />0.17 0.0 0.0 0.0 0.0 0.0 0.0
<br />28.39 49.1 35.7 33.8 27.2 16.4 32.4
<br />Field Study
<br />At the time of seeding in the fall of 1976, the redis-
<br />tributed topsoil was dry and loose; therefore, the seed-
<br />bed was not firm enough to ensure accurate seed place-
<br />ment and good germination. Later, during the winter
<br />and spring months, only 56% of the average seasonal
<br />amount of snow fell at the study site. What little snow
<br />accumulated did not persist, melted rapidly in the
<br />spring, and initiated considerable erosion and seed loss
<br />from these areas and, in turn, resulted in diminished
<br />plant establishment.
<br />In the first growing season, 1977, seedling establish-
<br />ment was greater on topsoiled plots than on similar non -
<br />topsoiled plots. However, results were inconclusive with
<br />respect to any effects of thickness depth of topsoil
<br />placed over spoil. Root systems might not have been
<br />well developed at this time, and the limited soil moisture
<br />in 1977 may have been detrimental to initial seedling
<br />establishment. Schafer et al. (1977) found that in recent
<br />minespoils, plants had over 90 of their roots in the
<br />upper 25 cm of soil and suggested that shallow roots de-
<br />velop first in reclaimed plant communities.
<br />In contrast to the low level of precipitation received
<br />on the field plots in the winter of 1976 -1977, 34% more
<br />
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