Ninth International Conference on Permafrost ... - IARC Research

1970 2005Repeated Mapping of the Northern Taiga Ecosystems in West Siberia, Disturbed byPipeline ConstructionE.V. UstinovaEarth Cryosphere Institute, Tyumen, RussiaEngineering construction in the north of West Siberialeads to disturbances of vegetation cover and changingpermafrost conditions. The scale of changes is in directrelation to the degree of human-induced disturbanceand landscape properties. Many natural features can be lostunder increasing anthropogenic pressure; therefore, solvingthe problem of rational land usage and wildlife managementbecomes extremely difficult. The information presented hereresults from ecosystem monitoring.Monitoring of disturbed ecosystems has been carriedout for 35 years along a gas pipeline located in the subzoneof northern taiga at the Nadym field station. Terrainchanges are studied every 3–5 years by large-scale repeatedmapping of the territory, using contemporary air photos andfieldwork. The last analyses were made in 2006. The greatestenvironmental disturbances occurred during pipelineconstruction in 1971–1972 and pipeline replacement in2004. Smaller changes took place in 1974 in relation toelectrical line construction, and in 1983, in adding new fillto the embankment. The service road along the pipeline isreconstructed every year.Disturbance of natural conditions triggered activation ofthermokarst and frost heave. Bog formation in areas pondedby embankments and wind erosion of sand on dry sites alsotake place. Observations show that in disturbed areas theoccurrence of lakes has increased 22%.The landscape hierarchy was described accordingto Melnikov (1983) using information on permafrostdistribution, topography, and vegetation. A series of digitalmaps shows natural terrain units (ecosytems) as well asterrain units affected by construction over the time periodfrom 1970 to 2006. These maps are based on air photographyof different years and on field surveys. The location ofmonitoring sites, temperature boreholes, and features relatedto сryogenic processes are shown as well. The database ofboreholes is linked to the maps.The analysis of the maps compiled for differentyears revealed changes in the area of human-induceddisturbances and trends in ecosystem development underthe impact of climatic changes and disturbances (Fig.1). After construction, the width of the disturbance zoneincreased differently in the various terrains. The increase inboggy areas due to swamping of the forest ecosystems wasdetermined by comparing the maps of 1970 with those of1988 (Fig. 1).During 2004 pipeline reconstruction, pipes were replaced.The histogram (Fig. 2) is based on comparison of the terrainmap of 1970, which was prepared prior to construction ofa gas pipeline, and the map of 2005. Figure 2 shows thathuman-induced disturbance has caused an increase of 2.9%25201510504 16 19 20 23 45 46 48 49 50 60 61 72 100 .1970 1988Figure1: Frequency of ecosystems at the Nadym site in 1970 and1988 years.4 - dry gentle slopes with birch-pine-cowberry-lichen sparseforests; 16 - flat slightly drained sites with birch-pine-wildrosemary-lichen–moss sparse forests; 19 - flat boggy sites withlarch-wild rosemary-moss open forests; 20 - flat boggy sites withhummocky larch-wild rosemary-lichen-moss open forests; 23- peat-mineral frost mounds with sedge-shrub lichen-moss openlarch-pine woodland; 45 - hollows with sedge-moss mires; 46 -hollows and flat sites with tussocky sedge-moss mires; 48 - flatsites with hummocky sedge-peat moss bogs; 49 - flat sites withdwarf shrub-sedge-peat moss bogs; 50 - hollows occupied bogswith dwarf shrub-sedge-peat moss ridges and sedge-moss pools;60 - flat sites with cloudberry-wild rosemary-moss- peatlands, 61- flat sites with cloudberry-wild rosemary-moss-lichen peatlands;72 - palsa peatland with sedge-shrub-moss-lichen cover on palsaand sedge-peat moss on pools between palsa; 100 - flat siteswith hummocky tundras with sedge-shrub-moss-lichen cover onhummocks and sedge-peat moss on pools and rare frost boils; 03- lakes.in the area of hummocky sites (ecosystem 100), 1.8% in theareas of bogs (ecosystems 45, 46, 48), and 1.5% in the area ofpalsa peatland (ecosystem 72). Some flat areas (ecosystems60 and 61) have partly recovered, however, and disturbancedecreased by 2.8%.Most disturbance relates to the removal of vegetation,modification of a microrelief, removal of 10 to 20 cm of peatduring clearing of the right-of-way, and partial destructionof vegetation as a result of road transportation. The smallerareas occupy the sites disturbed as a result of caterpillartransport travel, where vegetation, soil cover, and microreliefhave been broken only in part. The areas occupied by sites325