Ninth International Conference on Permafrost ... - IARC Research

Vegetation and Permafrost Long-Term Monitoring in the West Siberia SubarcticN.G. Moskalenko, O.E. Ponomareva, G.V. Matyshak, P.T. OrehovEarth Cryosphere Institute, Moscow, RussiaL.A, Kazantseva, E.V. UstinovaEarth Cryosphere Institute, Tyumen, RussiaLong-term ecosystem monitoring in cold regions wascarried out by few researchers (Timin et al. 1973, Bliss1975, Bocher 1949, Broll et al. 2003, Burgess et al. 1999 andothers). In this connection, results of long-term vegetationand permafrost monitoring since 1970 at the Nadym site inthe West Siberia North can be of interest for researchers ofArctic and Subarctic regions.The observation site is located 30 km south of the town ofNadym in the West Siberia northern taiga. This site is foundon a flat boggy surface of the fluvial-lacustrine plain (thirdterrace) with altitude ranging from 25 to 30 m. The plain iscomposed of sandy deposits interbedded with clays, with anoccasional covering of peat. Permafrost underlies the areasporadically. Patches of permafrost are closely associatedwith peatlands, tundras, mires, and frost mounds.The annual geobotanical descriptions are carried out onfixed plots and transects in natural and disturbed conditions.Observations over vegetation dynamics were accompaniedby soil descriptions, microclimatic observations, microreliefleveling, and measurements of permafrost temperature andseasonal thaw depths.Flat peatland with a Rubus chamaemorus-Ledum palustre-Sphagnum fuscum-Cladina stellaris community is dominanton the fluvial-lacustrine plain (Fig. 1A). For this community,the complex horizontal structure caused by the presence ofhummocks, interhummocks, pools, and in this connection,significant spatial variability of seasonal thaw depths (from0.5 m in inter-hummocks up to 1 m and more in pools) ischaracteristic.At the peatland in the first years after vegetation removal,cotton grass-cloudberry groupings formed over only 20%of the surface. Within 15 years on the disturbed peatland,continuous cloudberry-cotton grass-Polytrichum-Sphagnumcover had formed. This cover within 30 years, as a result ofsurface settlement, downturn of permafrost table up to 2–3m, development of thermokarst, and bogging, was replacedby cotton grass-peat moss cover. The generated fragmentof cotton grass-peat moss bog is present 35 years afterdisturbance (Fig. 1B)The carried-out definitions of plant biomass have shownthat, as compared with boggy communities in tundracommunities, the biomass on the disturbed sites increased2.5 times.In this tundra, a Ledum palustre-Betula nana-lichen-Polytrichum plant community developed, replaced within30 years after disturbance by a Betula nana-Ledum palustre-Sphagnum-lichen plant community, which developed here.On disturbed hummocky tundra, downturn of the permafrosttable, rise in ground temperature, appearance of surfacesettlements, and formation in them of pools are observed;during the winter period, snow capacity has increased. It hasbeen accompanied by a sharp increase in vegetation structureof Betula nana participation, having an average height of 1m, and also Polytrichum mosses. The participation of thesespecies has led to a substantial increase in plant biomass thatwas reflected in biodiversity, and abundance and biomass ofsmall mammals in the disturbed tundra.Evolution of soils on the disturbed flat peatland goes on inbog type, and bog oligotrophic soils are formed here. On thepeatland, there are changes of hydrothermal regime and, asa consequence, changes of intensity and orientation of suchmajor soil processes as respiration and transformation oforganic material.Background gas emission from the soil surface wasmeasured. After that active layer left and measurements ofgas emission from a permafrost surface directly after itsopening and in 24 hours were carried out. On all investigatedplots, sharp emission of the investigated gases (CO 2, CH 4), onsome orders exceeding background emission, was observed(Table 1).Measurements of ground temperatures in boreholes onthe natural and disturbed peatland have shown (Fig. 1C)that distinctions in temperatures in natural and disturbedconditions have appreciably increased at a depth of 1 m (on0.5°C). Temperature rise at a depth of 5 m was small, andat a depth of 10 m, it is not traced yet. Also we can see thatthe depth increase in ground temperature (on 0.8°C) for theperiod from 1972 to 2007, caused with rise in air temperature,is well defined. According to the Nadym weather station for1970–2006, the trend in rise of air temperature has reached0.04°С in a year.The leveling of a peatland surface was carried out alonga fixed transect once a year—at the end of August–thebeginning of September—when seasonal thaw depthreaches maximum and surface position reflects the long-termprocess of frost heave. Marks of a surface were determinedconcerning a deep reference point.It is established that the surface of flat peatland testedspasmodic rise in severe winters 1985, 1999, and for 32 yearsbecame 67 cm higher than in the beginning of observations.A feature of flat peatland frost heave is the rise of uniformityin the area. After 1999, the surface rise slowed down. TheTable 1. Gas emission (CH 4) from permafrost surface underdisturbances (mg/m 2 per hour).Landscape Background In 24 hoursFlat peatland 0.0624807 0.4265244Palsa peatland 0.0003942 0.1820547217