Evidence for Longevity of Seeds and Microorganisms in Permafrost

230 SHORTPAPERS AND NOTES Evidence for Longevity of Seeds and Microorganisms in Permafrost The problem of whether seeds and microorganisms are able to remain viable in permanently frozen ground during a very long span of years was recently considered by Porsild et al.1 who germinated Lupinus arcticus seeds from fossil rodent burrowsin permanently frozen silt deposited in a placer mining area in the Yukon Territory. Based on the geology of the locality, Porsild et al. estimated the age of the seeds to be at least 10,000 years. Moreover, in that and in pre- vious papersz73 Porsild suggests that seeds of Rorippabarbareaefolia, Descurainia sophioides, and Senecio congestus may be able to survive in permanently frozen silt as these FIG. 2. Numerousplants of Descurainia sophi- species apparently are restricted to freshly oides growingon thawed silt 20 m. north of disturbed soil within the placer mining dis- Fig. 1. tricts. Discussing in general the problems of recently been exposed (Fig. 1). The silt is dating viable seeds in old deposits Godwin4 rich in organic material, and thick deposits questions the dating of the Lupinus arcticus of this type of sediment are present at several seeds because of the indirect method applied. localities around Fairbanks. Detailed descrip- In view of these studies and the investigations of geology and faunal remains of these tions made by @dum5 on the presence and silt deposits in the region have been published age of viable seeds inDanish soils, Ester by Péwée, by Repenning et a1.7, and by Creek placer minewest of Fairbanks, Alaska, Guthrie8.9. The exposed section through the was visited 16 to 19 July 1968. Some obser- Ester Creek deposit showed a great amount vations on the vegetation on the exposed silt of buried wood and roots of small diameter and disturbed soil were made and soil sam- mainly concentrated at more or less horizon- ples were taken for further examination. tal strata. In the upper part there were a few At the time of the visit an 8 m. to 10 m. large masses of almost pure ice. The original section of the permanentlyfrozen silt had unfrozen top soil had earlier been partly removed. Exposed silt (20 m. to the right of the sec- tionshown in Fig. 1) had been left undis- turbed since the fall of 1966. Some of the silt had slid down forming a southeast-facing, rathersteep slope. The vegetation of this slope was dominated by Descurainia sophioides (Fig. 2). Within 10 different m.2, all plantswere counted and the result of this vegetation analysis gave a total of: 18 Agro- stis sp., 117 Betula sp., 467 Descurainia sophioides, 24 Epilobiumadenocaulon, 25 Equisetum arvense, 1 E. silvaticum, 5 Poly- gonum alaskanum, 1 P. buxiforme, 2 Rorip- pa barbareaefolia, 2 Salix sp., 3 Senecio congestus, 1 Taraxacum sp., 2 undetermined grasses. On the disturbed gravel and sand beneath theslope the very open vegetation con- sisted mainly of common widespread anthro- pochorous species; of scattered Rorippa bar- FIG. -1. Sectionthrough the recentlyexposed bareaefolia and Seneciocongestus; of species silt deposit. The numbers indicate where the soil with airborne seeds present in the surround- samples have been taken, sample no. 2 was collected a few meters to theright, at the samelevel ing landscape; and Of herbs trans- as no. 1. portedfragmentswith in offew Aturf. SHORT PAPERS AND NOTES 23 1 plants of Deqcurainiasophioides were also From 1 August to 1 October the big soil found, most of them growing on displaced sampleswere placed in a greenhouse. NO pieces of silt. plants germinated from thesoil. Soil analyses List of flora: Achilleasibirica, Agrostis ofsamples 1 and 7 were carriedout, and sp., Alnus sp., Alopecurusalpinus, Betuta theresults are given inTable 1. Wood- sp., Blitumcapitatum, Calamagrostis sp., remains from samples 2 and 4 have been Charnaenerium angustifolium, Chenopodium C14-dated to > 35,000 years. Eighty pieces album,Descurainia sophioides, Epilobium of wood were all from angiosperm species. adenmaulon,Equisetum arvense, Hordeum U. Mohl at the Zoological Museum, Uni- jubatum, Matricaria suavedens, Plantago versityof Copenhagen, identified the bones major, Polygonum Alaskanum, P. buxiforme, as femur of Mammuth primigenius and pa- Potentillachamissonis, Rorippa barbareae- rietale, scapula, and humerus of Bison sp., folia, R. palustris, Salix spp., Seneciocon- and he drew attention to the fact that the gestus, Silene williamsii. boneswere frayed and had obviouslybeen Above the slope the vegetation was com- transported. posed partly of a densecover of perennial The contents of microorganisms in the soil herbs, mainly grasses, a few trees (Betula and samples were examined by using the dilution Populus), andon disturbedsoil an open plate technique: 10 g. of each sample were vegetationincluding most of theannual mixed with 90 ml. of sterile water and placed species found below the slope. on a shakingtable for 20 minutes. Serial Herbarium specimensof most of the dilutions were made, and 0.1 ml. of each of speciespresent were collected. Soil samples 10-1,10-2, 10-3, and 10-4 suspensions were of 3kg. to 5 kg. fresh weight weretaken plated on Bengal Rose-, Sabouraud-, Cook-, from the exposed silt at the places shown in and V-8-agar. Besides 1 ml. of each suspen- Fig. 1. The outer surface soil was removed sion was added to test tubes with NIH. andthe recently-thawed silt wasput into After one weekof incubation at4”C., plastic bags to be examined for viable seeds. 24”C., and 37°C. the colonies were counted Samples nos. 1 to 6 were collected here, and andthe different strainsisolated on slants sampleno. 7 wascollected from unfrozen with V-&agar. subsoil just outside the placer mine area. At The sample from the top soil showed c. the sites of samples 1, 2, 4, 5 and 6, pieces 103 fungi per gr. soil at 24”C., representing of woodwere collected for 04-dating and thefollowing genera, known from similar for microscopic examination. localities: Cladosporiumherbarum, Mortie- At the same 7 sites soil was scraped direct- rella sp., Mucorcircinelloides, Penicillium ly intosterile Petri dishes to beexamined spp,., Trichodermaviride, and unidentified, for. possible microorganisms. Four mammal sterile imperfects and phycomycetes. bones collected at the level of samples 1 and The permafrost samples nos. 1, 3, 5, and 6 2 by E. Clark, a miner at the place,were showed no growth at all. added to the collections. No. 2 showed on Sabouraud-agar at 24°C. growth of red-orangeand yellow,shiny colonies, IO4 per g. soil. TABLE 1. soil analyses of samples 1 and 7. Methodsas describedby Kjeld Hansenl2 No. 4 showed on Sabouraud-agar at 37°C. whose laboratory made theanalyses. growth of yellow shiny colonies, 2 x 103 per g. soil, and at 24°C.growth on all substrates, Sample Sample averaging 2.6x 104 per g. soil. Besides the No. 1 No. 7 same organism grew in NIH at 37°C. ~ The two isolates from no. 2, andthat Loss of weight by drying, % 27.5 2.6 from no. 4showed thesame morphology, pH 6.8 6.3 and were identified as an actinomycete, No- Conductivity, p mho 96 170 cardia sp. Unfortunately the red-orange P. PPm 331 361 strain later died; the two yellow strains were Na exchangeable cont., meg/lOO g. 0.10 0.42 kept on slantswith V-8 agarcovered with K ” 0.16 0.17 paraffin-oil at 4°C. Mg ” 3.1 5.0 The twoorganisms have beentested Ca ” 9.2 6.2 against20 bacteria and fungi inorder to Mn ” 0.032 0.021 determine their antibiotic activity, but with Kation exchange capacity ” 335 253 negative result. Furthermorethe investiga- 6220 703 Fe. ppm tions have shown that they produce an en- cu, ” 25.8 16.8 zyme,fucidinase, destroying the antibiotic, Zn, ” 11.4 7.2 fucidin. L ” 2.0 1.5 Nocardia sp. was only found in 2 samples 232 SHORT PAPERSAND NOTES of permanently frozen silt. No actinomycetes ACKNOWLEDGEMENTS were present in the topsoil sample. Further- Field observations and collecting of sam- more the collection of the samples and the ples werecarried out in 1968 by S. @dum analyses were carried out with extreme care on a botanical collecting tour made possible without contamination of the plates. There- by afellowship fromthe CharlesBullard fore it seems probable that livingmicro- Fund for Forest Research, Harvard Univer- organisms are present in soils that have been sity, and a NATO-travel grant. The isolation frozen for manyyears. and determination of the viable microorga- Only a few investigations have been carried nism was carried out by A. Kjgiller, while the out to find living microorganisms in perma- dating analyses were made by H. Tauber at nently frozen soil, and generally onlythe the C-14 laboratory of the Danish National upper layershave been studied, because of Museum. the difficulties of sampling throughperma- Annelise KjZller frost. HoweverBecker and Volkmannlo re- University of Copenhagen covered 8 bacteria at 20 to 60 feet below the Botanical Institute surface in permanently frozen soil near Fair- Denmark bazks. Boyd and Boydl1 also studied permafrost soils from Barrow, Alaska, near Elson S@ren@dum Lagoon, and found living bacteria at 8 to The Royal Veterinary and Agricultural University 15 feet. Botanical Institute The distribution of Descurainia sophioides Denmark within the placer mine area and its extremely high frequency on the exposed muck does strongly support Porsild's theory.However, REFERENCES the fact that theseeds of the species are lack- IPorsild, A. E., C. R. Harington and G. A. ing in the investigated samples may lead to Mulligan. 1967. Lupinusarcticus Wats. the alternative possibility that the ecology of grown from seeds of Pleistocene age. the species is rather specific.

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