人类工程活动影响下冻土生态系统的变化及其对铁路建设的启示

通过样带与样方结合的调查方法, 从冻土生态系统结构、群落种类、生物多样性以及生物生产力等生态要素和生物生境条件: 如土壤环境、冻土环境等方面研究了青藏公路沿线多年冻土区公路工程干扰迹地生态系统的变化特征. 结果表明, 经过近25年的自然恢复, 在生态系统恢复的生物学方面, 高寒草原生态系统明显优于高寒草甸生态系统, 表现在高寒草原的优势建群植物种类已出现并占据优势地位, 局部地带生物物种多样性与种群多度恢复到接近甚至高于自然未干扰草原系统水平; 在土壤环境方面, 高寒草原干扰迹地土壤有机质含量平均减少61.65%, 全氮含量减少52.51%, 但大部分地区其表层土壤养分现状与干旱区主要草原土壤相当, 有利于耐寒旱生物物种生长; 高寒草甸干扰迹地土壤(寒冻雏形土)平均养分含量高于天然寒冻干旱土壤, 保存草甸土壤结构的完整程度对于高寒草甸生态系统恢复至关重要. 受扰动高寒草原生态系统的恢复程度与冻土环境没有明显制约关系, 高寒草甸生态系统的分布和保育与冻土环境关系密切, 受工程活动破坏后恢复困难. 类比青藏公路沿线生态系统变化规律, 提出了青藏铁路建设过程中保护生态环境的几点启示.

Spatial pattern of soil carbon and nutrient storage at the Alpine tun-dra ecosystem of Changbai Mountain, China

In August 2003, we investigated spatial pattern in soil carbon and nutrients in the Alpine tundra of Changbai Moun-tain, Jilin Province, China. The analytical results showed that the soil C concentrations at different depths were significantly (p<0.05) higher in Meadow alpine tundra vegetation than that in other vegetation types; the soil C (including inorganic carbon) concentrations at layer below 10 cm are significantly (p<0.05) higher than at layer of 1020 cm among the different vegetation types; the spatial distribution of soil N concentration at top surface of 0-10 cm depth was similar to that at 1020 cm; the soil P concentrations at different depths were significantly (p<0.05) lower at Lithic alpine tundra vegetation than that at other vegetation types; soil K concentration was significantly (p<0.05) higher in Felsenmeer alpine tundra vegetation and Lithic alpine tundra vegetation than that in Typical alpine tundra, Meadow alpine tundra, and Swamp alpine tundra vegetations.. However, the soil K had not significant change at different soil depths of each vegetation type. Soil S concentration was dramatically higher in Meadow alpine tundra vegetation than that in other vegetation types. For each vegetation type, the ratios of C: N, C: P, C: K and C: S generally decreased with soil depth. The ratio of C: N was significantly higher at 010 cm than that at 1020 cm for all vegetation types except at the top layer of the Swamp alpine tundra vegetation. Our study showed that soil C and nutrients storage were significantly spatial heterogeneity.

Influence of Prospecting and Crude Oil Production on Geoecological Parameters of Permafrost

The large reserves ofoil are disposed in zones of permafrost in shelf and continental fields. In Europe the subarctic and arctic tundra are abundant only in Nenetsky autonomous area and in the north-east of the republic of Komi. Oil and gas production activity has threatened richest biological resources and health of the population of the region. A singularity of petroliferous fields of the north of Russia is the existence of the thick strata of permafrost. On top of them different heat-insulating overlying layers （snow, biogenic covers） reside. State and dynamics of permafrost cause progressing dangerous exogenic geoecological processes, which are exhibited completely. State of permafrost is instituted by exchange of heat in near-surface strata of a geological section. During the development of oil fields there is a disturbance of a temperature schedule of permafrost. For estimation of technical attack the analytical computational method of influence of the different factors on value of annual heat exchange and prediction of geocryological conditions is proposed. It is shown, that such dangerous phenomena as degradation of permafrost and thermokarst would develop in the first place, which would cause the destruction of natural ecosystems.

Changes in permafrost ecosystem under the influences of human engineering activities and its enlightenment to railway construction

Through the investigations of sample belt transects and sample quadrats, the variation characteristics of the disturbed ecosystem by highway engineering in the permafrost region along the Qinghai-Tibet highway line were studied from the ecological elements such as permafrost eco-system, community type,biodiversity and biological produc-tivity and biological habitat conditions including soil envi-ronmental conditions and permafrost environmental condi-tions. The results show that in the sense of biology the resto-ration of high-cold steppe ecosystem was much better than that of high-cold meadow ecosystem after nearly 5 a of natu-ral reconversion.This is mainly manifested in several resspects:The dominant plant species of the high-cold steppe have occurred or even held a predominant position; local zonal biodiversity and population abundance have reached or even exceeded the level of the undisturbed natural steppe system.Viewed from soil environment change, organic matter content in the disturbed high-cold steppe on an average de-creased by 61.5% and total N content decreased by 52.51%,but the nutrient regime of surface soil layer in most of the region corresponded to that of main grassland soil types in the arid region,which is favourable to the growth of cold-resistant species. The mean nutrient contents of the dis-turbed high-cold meadow soil(Gelic cambosols)were higher than those of natural cryic aridsols. The maintenance of the integrity of meadow soil structure is crucial to the restoration of high-cold meadow ecosystem.However,the distribution and maintenance of high-cold meadow ecosystem were closely related to the permafrost environment,the restoration degree of the disturbed high-cold steppe ecosystem did not show an obvious restrictive relation with permafrost environ-ment.Once the permafrost environment was destroyed by the engineering activities,the high-cold meadow ecosystem was very difficult to rehabilitate. From the comparison of the variation laws of the ecosystem along the Qinghai-Tibet highway line, the authors put forward two enlightenments for the eco-environmental protection in the construction processes of the Qinghai-Tibet railway.

Carbon turnover times shape topsoil carbon difference between Tibetan Plateau and Arctic tundra

The Tibetan Plateau(TP)and Arctic permafrost constitute two large reservoirs of organic carbon,but processes which control carbon accumulation within the surface soil layer of these areas would differ due to the interplay of climate,soil and vegetation type.Here,we synthesized currently available soil carbon data to show that mean organic carbon density in the topsoil(0-10 cm)in TP grassland(3.12±0.52 kg C m^(-2))is less than half of that in Arctic tundra(6.70±1.94 kg C m^(-2)).Such difference is primarily attributed to their difference in radiocarbon-inferred soil carbon turnover times(547 years for TP grassland versus 1609 years for Arctic tundra)rather than to their marginal difference in topsoil carbon inputs.Our findings highlight the importance of improving regional-specific soil carbon turnover and its controlling mechanisms across permafrost affected zones in ecosystem models to fully represent carbon-climate feedback.

Effect of a thermokarst lake on soil physical properties and infiltration processes in the permafrost region of the Qinghai-Tibet Plateau, China

Changes in the hydrological processes in alpine soil constitute one of the several key problems encountered with studying watershed hydrology and ecosystem stability against the background of global warming. A typically developing thermokarst lake was chosen as a subject for a study using model simulation based on observations of soil physical properties, infiltration processes, and soil moisture. The results showed that the selected thermokarst lake imposed certain changes on the soil infiltration processes and, with the degree of impact intensifying, the initial infiltration rate decreased. The greatest reduction was achieved in the area of moderate impact. However, the stable infiltration rate and cumulative infiltration gradually increased in the surface layer at a depth of 10 and 20 cm, both decreasing initially and then increasing, which is correlated significantly with soil textures. Moreover, the cumulative infiltration changed in line with steady infiltration rate. Based on a comparative analysis, the Horton model helps better understand the effect on the soil infiltration processes of the cold alpine meadow close to the chosen thermokarst lake. In conclusion, the formation of the thermokarst lake reduced the water holding capacity of the alpine meadow soil and caused the hydraulic conductivity to increase, resulting in the reduction of runoff capacity in the area of the thermokarst lake.