The ground temperature and active layer are greatly influenced by vegetation in the Greater Hinggan Mountains in Northeastern China.However,vegetation,as a complex system,is difficult to separate the influence of its different components on the ground thermal regime.In this paper,four vegetation types,including a Larix dahurica–Ledum palustre var.dilatatum–Bryum forest(P1),a L.dahurica–Betula fruticosa forest(P2),a L.dahurica–Carex tato forest(P3) in the China Forest Ecological Research Network Station in Genhe,and a Carex tato swamp(P4) at the permafrost observation site in Yitulihe,have been selected to study and compare their seasonal and annual influence on the ground thermal regime.Results show that the vegetation insulates the ground resulting in a relatively high ground temperature variability in the Carex tato swamp where there are no tree stands and shrubs when compared with three forested vegetation types present in the area.Vegetation thickness,structure,and coverage are the most important factors that determine the insulating properties of the vegetation.In particular,the growth of ground cover,its water-holding capacity and ability to intercept snow exert a significant effect on the degree of insulation of the soil under the same vegetation.
This article, based on the field work took place on the zone of Tuomuer (托木尔) Peak, western Tian Shan (天山) during the period May 2008 to September 2009, obtained the spatial distribution of debris layer on the reference glaciers (Glacier No. 72, Glacier No. 74, Tuomuer Glacier) by detailed measurements of debris thickness and ablation rates on glacier and further by Spot-5 (5 m, 2005) high-resolution satellitic image applying remote sensing and geographic information systems approach to research the spatial distribution of debris layer on the zone of Tuomuer Peak. Specifically, the results indicate a sharp in ablation with debris cover thickness increasing from 0-4 cm followed by a decrease in ablation with debris thickness increasing beyond 4 cm for the glaciers No. 72 and No. 74. Spatial distributions of debris layer on the three reference glaciers have the same characteristics, the overall distribution from the vertical, the maximum thickness of debris in the glacier terminal, and the thickness of debris is constantly thinning since the end of the glacier increases with altitude. For the overall distribution from the horizontal, the regular pattern of debris thickness from both sides to the middle is diminishing. The debris on the zone of Tuomuer Peak mostly covered the glacier tongue and is mainly distributed below the altitude of 4 000 m; the area of debris covered approximate accounted for 14.9% on the entire glacier area in this region. Spatial distribution of debris layer on the zone of Tuomuer Peak is mainly affected by the elevation of the glacier terminal, followed by the slopes orientation, the sizes, and so on.
During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21.7% of the 1956 value, with a mean reduction for the individual glacier of 0.10 km2. The relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than large ones. Over the past ～50 years, glacier area decreased by 29.6% in the Heihe (黑河) River basin and 18.7% in the Beidahe (北大河) River basin, which were the two regions investigated in the Middle Qilian (祁连) Mountain region. Compared with other areas of the Qilian Mountain region, the most dramatic glacier shrinkage had occurred in the Middle Qilian Mountain region, mainly re-sulting from rapid rising temperatures. Regional differences in glacier area changes are related to local climate conditions, the relative proportion of glaciers in different size classes, and other factors.
