2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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■ MOO 4500 4200 3900 - 27 P 2100 r' ;- or - - . Ism 1500 1200 SOO ■ • , , tam (U%) I1 _.7In 2200 - MIMIL7 (80111A: - 22ZEI Te‘ta A■StarAve. 1970(111) ?- 1800 8$,p-Des. 1979 (20%) 4 !: • = C■Jen-Apr. 1910 115%) , • 4,4 • - 04, ---1 Total seedlings emerging m grazedsoie over 4 time periods. t „ = vated and grazed' areas tend to have the Iar most of which belong to weed gl• Basedoith 134- _fringed sage, and wormwood were present both in at least one of numbers of buried viable seeds It North Alifeilairtiridistu the seed banks (Fig. 1, 2) and in the 4-year post-mining vegetation grasslands apparently decrease from the tall to the gesat (Iverson and Wal 1982). It may be that some seeds from such grass prairies.,:,, - :41 species were lying dormant in the seed bank until establishment Role in Revegetation _ was possible (see Thompson and Griiiie 1979). The seed bank also Comparison of the species composition of the bank to that .g.t, contained seeds from 9 species found only on unmined sites in the of the above-ground vegetation of newlkreclaiined:Urfa6emin ed;„,vegetation 'survey. (Fig. 1, 2; Iverson and Wali 1982). It is not areas (see Iverson 1981, Iverson and,Walii982)reVeili species "- known whether these seeds remain viable in the soil for more than 4 dispersal in time (through dormancy) as well as dispeiial in space , years; if they do germinate at a later date, the diversity of the (through immigration) are important in revegetation. Pioneering ' aboveground vegetation would be enhanced, a desired goal in species common to both aboveground vegetation the seed reclamation. Evidence from Dr. W.J. Beal's experime nt s ( Darling- bank included horseweed, witchgrass (Panicum papillae), prickly ton 1931, 1941), and others, indicates that seeds frequently remain lettuce (Lactuca serriola), peppergrass (Lepidinni deissOoruir), viable for more than 4 years. Along with aiding in amelioration of bluegrass (Poa sp.), and ragweed (Ambrosia sp.). However, in the first 2 years of succession, dispersal in space seems to predominate, for none of the following dominant aboveground specs were found in the seed bank: summer cypress, green pigeongrass, and Russian thistle (Iverson and Wali 1982). Chepil (1946) investigated dormancy lengths for a number of weedy species in Saskatchewan and found summer cypress sends to have a short dormancy period (2-3 months) and Russian thistle and green pigeongrass to have dormancies of less than one year. The absence of some colonizers in the seed bank that are dominant in the aboveground vegetation indicates that their seeds arrive after the respreading of topsoil; wind and water dispersal seem to be the most important, especially for the "tumbleweed" chenopods. However, there is evidence that spreading topsoil is beneficial .0,11.112 • "f• • • 4e+ GRAZED SITE - 2800 — 2800 _ 2400 — 2000 — 1400 ' 1200 ro 1000 — i . 4 4 *** • • • 0 0 • . • 0 • • 0:0 t:$ t • • 0.: UNGRAZED SITE 200 Depth of Semple 0-2.5crn (58%) EMS:I 2.5-7.5cm 116%) 7.5-15em (26%) fa221 Total Time of Emergence A■May-Aug. 1979 (71%) 13.•Sep-Dec. 1979 (7 C.Jen•Apr. 1980 (12%) 1:MMay•Sep. 1980 (10%) —I C D Ti Total seedlings emerging m from ungrazed site samples at 3 depths over 4 time periods. ; 0 ntra. for reintroducing some species which otherwise do not colonize t , readily. Species such as rough penny royal, buckhorn, white sage, water-holding capacity and nutrient concentrations, topsoil spreading during the reclamation process may increase seed and consequently plant diversity. As the surface 7.5 cm contains the greatest proportion of seeds, (Table 2) it would be ideal if this layer from the premined areas could be placed on top of the post-mined areas. Recent studies on succession (Connell and Slatyer 1977, Noble and Slatyer 1980) point to the key role of seed and propagule dissemination in community dynamics. From this study, it appears that the seed bank of the pre-mined prairie sites influences the post-mined vegetation in later stages via persistent seeds (dispersal in time), whereas seeds of most of the initial colonizers after reclamation immigrate from the surrounding environs (dispersal in space) after the topsoil is respread.