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28Tomoki Morozumi1 VEGETATION ON THE PINGO IN THE CENTRAL YAKUTIA
Pingo and Alas are unique landscape structure in permafrost zone, and there is large variation of vegetation from Steppes to aquatic swamp in the Central Yakutia. This vegetation is growing on dry-wet environmental gradient, and it may be affected by recent anthropogenic effect and climate change. In this paper field observation of 3 Pingo transect and literature studying about Central Yakutian vegetation were coupled to understand the nature of permafrost zone which may vulnerable for further climate change. Steppe vegetation, which appeared on the top of Pingo, has its longer history as dynamics of Alas formation since Late Pleistocene from literature. Surface disturbance and thermokarst depression alter the type of vegetation on the top of Pingo. In contrast, more diversified swamp vegetation covered foot of the hill slope. 3 viewpoint of variation in the observed 3 Pingos vegetation were noticed as size-effect, stability of soil and anthropogenic effect. These sights will help to understand condition of Pingo from outside, and it may provide possibility to assess permafrost stability for future.
Keywords: landscape, permafrost zone, vegetation, climate change, Alas, communities, field observation.
Introduction
The Central Yakutia is a cold climate region where the world largest and thickest permafrost exists. Extreme cold weather of the last glacier maximum made exposed ground freeze down to 1000m below. After early Holocene warm period, this permafrost still survived and several meter surface were somehow degraded by thermokarst process. During this summer school, we had seen beautiful landscapes of large thaw basin "Alas" and sometimes with an ice-cored frost mound "Pingo" or "Bulgunnyakh" on the Lena river terrace. As many landscape, as many vegetation. Vegetation play a role of frontier between underground and aboveground, and provide materials for thermal offset effect on permafrost. It is also key for understanding the biogeochemical transportation process such as C02 and methane. Additionally, vegetation is visible from outside. That means it is possible to estimate its extent using optical remote sensing techniques. In this report I will focus on vegetation on the unique landscape, Pingo in the Central Yakutia. Thus there are only a few English paper available, and hard to read Russian literatures, I also add some data from my field note in summer school for better understanding.
1 Tomoki Morozumi - PhD student in Graduate school of Environmental Science, Hokkaido University, Japan. Main research is Siberian Taiga -Tundra boundary vegetation and biogeochemical cycles in Indigirka Lowland. E-mail: both-horns@ees.hokudai.ac.jp.
1. Method 1.1. Literature
There has been extensive study for vegetation in Yakutia. They collected the species compositions of releves and classified based on Braun-Blanquet approach that could distinguish common vegetation unit applicable for all region. Here, I picked up an English paper (Mirkin, Gogoleva and Kononov (1985)) on Folia Geobotanica and English literature (Troeva etal., 2010) on Springer to understand the nature of permafrost zone.
1.2. Field excursion data
Field excursion was held during UArctic program from 5th August till 18August, 2016 in Central Yakutia, Sakha Republic. Vegetation data was obtained in Muguday, Churapcha region in 7th, in Namsky region in 12th, and Yakutsk city in 16th August. Species composition were visually observed in the field and described along the top to bottom gradient of Pingo. Some of the plant species were collected for detail identification in Institute of Biological Problems Cryolithozone.
2. Result 2.1. Literatures
Mirkin, Gogoleva and Kononov (1985) reported vegetation community composition on unique landscape of Alas in Central Yacutia (Yakutia). The authors investigated alases between Lena and Amga river in 1978-1981. They categorized the vegetation into 3 groups; wet glycophyllous meadow and hygrophytic communities, salt meadow, steppe and steppe-meadow communities. The alas bottom were distinguished into 3 zones. The first wet zone is covered with such as Phragmitetea, and the second middle-moist zone with Tharict-Hordeetum, and the third dry zone with Artemisio commutatae-Hordeetum communities. These 3 zones correspond to vegetation categories; hydrophytic swamp, meadow and steppe communities. At the end of the alas formation cycles, Pingo (bulgunnjachs) will be formed. They described vegetation of bulgunnjachs into 3 principal stages of dynamics (Fig.1 (a)). Excerpt below:
1. A small bulgunnjachs (1-2 m high and the diameter 30-50 m) with gentle swarding slopes. On the south, east and west exposure - Carici duriusculae-Festucetum lenensis, on the north - Pulsatilletum flavescentis.
2. A medium bulgunnjach (2-5 m high, diameter 50-80 m) with erosion-activity on the south slope, where serial communities such as Artemisietum jacuticae, Psathyrastachetum junceae, Stipetum krylovii are formed.
3. A large bulgunnjach (5-12 m high, diameter 120 m). Such bulgunnjachs begin to disintegrate and on their tops a depression like a volcanic crater occurs. The different
slopes of the crater are occupied by different communities according to the different slopes of bulgunnjachs. Larixgmelinii as "climax precursor" appears, usually, on the north slope of such "crater". This is the finale of a bulgunnjach evolution. (Mirkin et al. 1985)
In the literature of The Far North: Plant Biodiversity and Ecology of Yakutia (Troeva et al. 2010), Zakharova et al. (2010) described the azonal steppes vegetation. The forest-steppe landscapes of Yakutia are the relics of the Late Pleistocene (Lavrenko 1981). The Festuca-Stipa community on the terrace of the middle Lena river close to Yakutsk were predominant in 20th century, while there is only fragment of these community presently. The Stipa steppe communities are characteristics for stabilized landscapes, and these cover a part of south-facing slope of large river. On the other hand, the bunchgrass steppe communities are characteristics for eroded and loosing soil landscape. Xerophilous species (Festuca lenensis and Poa botryoides) in a Betulapendulaforests, distinct relic forest steppe, are common in the Lena-Amga Interfluve.
2.2. Field notes
Pingo that located in the middle of alas thermokarst thaw lake basin, is basically covered by vegetation. However, a top of Pingo was very dry condition and less vegetated, and species composition shows sharp contrast.
Muguday Pingo was located at 62o1'38" N, 132o51'38" E and it is surrounded by large alas basin and lakes (Fig.1 b-iii). Species composition were shown in Table. 1. Grassland were covered by high perennial herbs and grasses such as Calamagrostis sp., Agrostis sp., Artemisia sp., Potentilla, Pullsatilla, etc. The top of the Pingo was covered by Stipadecipience (syn. S. krylovii (Malyschev and Peschkova 2001)J (Fig. 2), Artemisia commutata, Elyrigia sp.. Interestingly, north slope top with crater was covered by Larix high tree.
Namsky "Baby-Pingo" was located at 62o22'43" N, 129o47'10" E and it is surrounded by relatively small alas wetland and Birch-Larch mixed forest around them (Fig.1 b-i). Species composition were shown in Table. 2.
Yakutsk Pingo was located at 62o0'36.94"N, 129o40'3.06"E and it is close to the residential area of Yakutsk city. A northern part of Pingo was covered by fence and eroded, however south side was covered by vegetation such as herbs, small lakes and high grassland (Fig.1 b-ii). Species composition were shown in Table. 3. In this field note, Graminoid species has difficulties of its identification without specimen, therefore tentative-Elytrigia sp. might be different genus of other thin flower graminoid. Eroded side were not take account of this report, however there were different species such as Chamerion angustifolium which is typical on unstable soil condition.
3. Discussion
Vegetation on a Pingo and alas has been evolved for a long time since cryogenic process began. On the top of the pingo, the Late Pleistocene relic steppe vegetation remains. The
dynamics of Alas formation allowed steppe communities to grow on the slope of the alas or pingo, while pingo were younger than steppe communities. In this field trip, we found the Stipa steppe communities on the top of Muguday Pingo and Yakutsk Pingo. The Stipa steppe communities are characteristic for stabilized landscapes with decreasing erosion processes (Ivanova and Perfilyeva 1972; The Far North 2010), therefore it suggests that these 2 Pingo top may be stable condition.
Variations of 3 pingo were also shown as its size-vegetation relations. According to the dinamical row in Mirkin et al. (1985), Muguday Pingo and Yakutsk Pingo are categorized in a large bulgunnjach and we could see Stipa on the top. Especially Muguday Pingo has a crater on the top and covered by Larix gmelinii as Mirkin et al. described. Namsky Baby Pingo were relatively small to medium size, and with no erosional communities. Actual vegetation seems to correspond to Carici duriusculae-Festucetum lenensis (Fl in Fig. 1 (a)) with Saussureaamara, although diagnostic species were not described enough in Table.2.
Parasite plant Odontites vulgaris is Mediterranean species wide spread in Eurasia. Taraxacum sp. are also cosmopolitan species growing urban zone. These species were rare in the list of Mirkin et al. (1985), and it means that Yakutsk Pingo vegetation was partially introduced by recent anthropogenic effect.
4. Conclusion
The vegetation of Pingo and Alas showed large variation from Steppes to aquatic swamp in the literature and the field note. Steppe vegetation has its longer history as dynamics of Alas formation since Late Pleistocene. I noticed 3 viewpoint of variation in the observed 3 Pingos vegetation; size-effect, stability of soil and anthropogenic effect. These sights will help to understand condition of Pingo from outside, and it may provide possibility to assess permafrost stability for future.
5. Figure and table
Table 1
Species composition of Muguday "Largest-Pingo"
Plot No. 1(Pingo top) 2(Grassland) 3(Grassland)
Species Stipa decipience Calamagrostis sp. Pulsatilla flavescens
Artemisia commutata Agrostis sp. Potentilla bifurea
Elytrigia sp. Artemisia mongolica Gentiana macrophylla
Saussurea amara Antennaria dioica Geranium pretense
Potentilla bifurca
Table 2
Species composition of Namsky "Baby-Pingo"
Plot No. 1(Pingo top) 2(Grassland) 3(Wetland) 4 (Forest)
Species Artemisia commutata Aster Salix Larix
Elytrigia sp. Agrostis Carex Betula
(Betula platyphilla) Gentiana Rumex
Saussurea amara Senecio congestus
Table 3
Yakutsk Pingo
Plot No. 1(Pingo top) 2 3 4(Grassland) 5(Wetland)
Species Stipa decipience Potentilla bifurca Elytrigia sp. Agrostis sp. Phragmites sp.
Artemisia commutata Poa sp. Allium strictum Sonchus sp. Phleum or Alopeculus
Elytrigia sp. Pulsatilla flavescens Saussurea amara Artemisia macrantha
Galium verum Artemisia commutata Taraxacum sp.
Dianthus sp. Odontites vulgaris
Fig. 1. (a) Thematic vegetation units of Pingo(bulgunnyakh) in Mirkin et al. (1985) modified. Dynamical row of bulgunnyakh evolution (a-I: little, a-II: medium, a-III: large bulgunnyachs)
The following abbreviation were used for vegetation unit: (Ar: Artemisietum-acuticae, Ps: Psatyrostachetum junceae, St: Stipetura krylovii, FI: Carici duriusculae-Festuceturn lenensis, P1: Pulsatilletum flavescentis, Pt: Puccinellietum-tenuiflorae). (b) Alternate 3 different bulgunnyakh observed in UArctic summer course: Namsky (b-i), Yakutsk city (b-ii) and Muguday (b-iii).
Fig. 2. Stipa decipience (syn. S. krylovii) (a) flower, (b)whole shape
6. Acknowledgements
I wish to thank organizer Prof. Yoshikawa and lecturers during this UArctic short course for providing chance and basic knowledge to observe permafrost. Plant species identification was supported by Dr. Zakharova in IBPC. Also, I would like to thank to my supervisor Prof. Sugimoto and collaborator Prof. Maximov for support and guidance.
References
1. Mirkin, B.M., Gogoleva, P.A. & Kononov, K.E., The vegetation of central yacutian alases, Folia geobot. phytotax. (1985) 20: 345. doi:10.1007/BF02853283
2. Troeva E.I., Isaev A.P., Cherosov M.M., Karpov N.S., The Far North: Plant Biodiversity and Ecology of Yakutia., Springer. (2010) doi:10.1007/978-90-481-3774-9
3. М.Ф. Бысыин. Конспект флоры термокарстовых аласов (Центральная Якутия), Биологические науки,(2006)
4. Malyschev L. I. and Peschkova G. A., Flora of Siberia volume 2 Poaceae (Gramineae) Science Publishers, Inc. (2001), ISBN 1-57808-101-7
5. Ivanova V.P. and Perfilyeva V.I., Sokhranit kovylnye stepi Yakutii. In: Priroda Yakutii I eyo okhrana. Knizhnoye izd-vo, Yakutsk (1972) [Russian paper referenced in Troeva et al. 2010]
6. Lavrenko E.M. (1981) О rastitelnosti pleistotsenovykh periglyatsialnykh stepey SSSR. Botanichesky zhurnal 66(3): 313-327 [Russian paper referenced in Troeva et al. 2010]
