Ninth International Conference on Permafrost ... - IARC Research

Reaction of Northern Taiga Ecosystems on Human-Induced Degradation ofPermafrost in West SiberiaP.T. OrekhovEarth Cryosphere Institute, Moscow, Russia, 744001The development of the oil and gas industry has aconsiderable effect on permafrost ecosystems. Major andhighly dynamic human-induced changes of the WesternSiberia ecosystems have been caused due to the establishmentand maintenance of the transport infrastructure of the oil andgas industrial system. Even a single facility, such as a maingas pipeline due to its length, is likely to have a drastic effecton ecosystems of different natural environment zones. Thestudy of human impact on permafrost ecosystems appearsto be especially urgent, taking into consideration an indirecteffect of the disturbed vegetation, soil, and micro-topographyon permafrost conditions.This investigation has been conducted within the area ofthe Nadymsky Station of the SB RAS (Siberian Branch,Russian Academy of Science) Earth Cryosphere Institute,located in the northern taiga subzone of Western Siberia. Thesite occupies the area of sporadically distributed permafrost,and it is characterized by varied permafrost conditions. Thepermafrost patches are found in peat bogs, hilly lands, andfrost heave areas. Mean annual temperatures of rocks varywithin a range of +1.0 to -2.0°С.Tundra ecosystems are widespread in peat bogs of thenorthern taiga. Perennially frozen grounds under the tundraecosystems are referred to as the continuous permafrostzone. The temperature of perennially frozen ground variesfrom -0.5 to 1°С. A thickness of a seasonally thawed layeris within the range of 0.8 to 1.2 m in peat and mineral frostheave mounds and 0.5 to 0.7 m in peat mounds.Associations of tundra plants such as grass, dwarf shrubs,moss, and lichen make up the specific vegetation coverof peat bogs. Dominant plants among those are Ledumpalustre, Vaccinium vitis-idaea, Rubus chamaemorus, Carexglobularis, Cladina stellaris, C. rangiferina, Sphagnumfuscum, and Polytrichum commune (Moskalenko 1999). Inthe almost complete ground cover of the undisturbed tundraecosystems, lichens appear to be prevailing, that is, Cladinastellaris and C. Rangiferina. Apart from those, Cetrariaislandica is commonly found among the ground cover plantstogether with C. cucullata and peat mosses. Foliage cover ofthe ground vegetation makes up 70%. The prevalent dwarfshrubs are presented by Ledum palustre, Betula nana, andVaccinium vitis-idaea. Commonly found are Vacciniumuliginosum, Carex globularis, and Rubus chamaemorus.Foliage cover of the grass-and-dwarf shrub layer is 40–45%. The frost peat mounds vegetation cover is comprisedof Polytrichum strictum, Cladonia coccifera, and Cladinastellaris; Rubus chamaemorus is abundant in the grass-anddwarfshrub layer. In the natural tundra ecosystems, a totalabundance of small mammal populations on average makesup 16.9 ± 1.1 species/10 pitfall trapnights. Biomass of smallmammals is 259.4 ± 25.6 g/10 pitfall trapnights (Fig. 1).6543210Clethrionomys5,35 5,34rutilusMicrotusagrestisabundance of species3,11Sorex1,921,18Figure 1. Abundance of small mammal species in the natural tundraecosystems.In 1971 in this area, the route was cleaned up to lay thegas pipeline Nadym-Punga. As the route was cleaned up, thevegetation cover was removed, the micro-topography wasdisturbed, and the upper peaty layer was withdrawn. Thepipeline was laid in-ground with the earth fill made later. Thepipeline laying lead to disturbance of the tundra ecosystemsthat resulted in an increase of water due to deteriorateddrainage conditions, an increased number and enlargedarea of hollows, bog formation, thermokarst activation, andfinally, in peat surface subsidence with the top layer of thepermafrost ground being dipped down to 6 m and, in areaswith a thinner permafrost layer, being completely degraded.Secondary ecosystems formed by 32 years after theoccurrence of the primary disturbance. Ground cover ofthe secondary ecosystems has mosses prevailing, that is,Polytrichum commune and Cladina stellaris. C. rangiferinais not commonly found. Foliage cover makes up about 75%.Apart from those, species found in the ground cover areCetraria islandica and C. cucullata. Among dwarf shrubscovering 40–45% of the ground surface, Betula nana,Vaccinium uliginosum, and Empetrum nigrum are growingabundantly. Species commonly found include CalamagrostisLangsdorfii, Carex canescens, C. Globularis, Eriophorumrusseolum, and E. vaginatum. It should be noted that thereare species which started growing abundantly along thepipeline, particularly, Betula tortuosa (height 5–7 m), Salixviminalis (height 3–5 m), and Alnus fruticosa, and these arespecies not specific for the tundra ecosystems (Sorokina2003). Temperatures of top soil layers in September go upto 9.1°C.tundrensisSorexcaecutiensabundanceother species239