This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene...This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene glaciers and the climate. It isconsidered that lichenometry is one applicable method for dating the mid- and late-Holocene deposits in the cold and mountainous regions. Rhizocarpon geographicum (L.)DCand Xanthoria elegans (Link.) Th. Fr. could be used for dating the deposits of about 4500and 500 a B.P. respectively. There existed at least four periods of glacial advances whichoccurred before about 5700, 4100, 2800 and 403- 74 a B. P. respectively with the firstperiod the longest. Little Ice Age includes three stages of glacial advances which endedbefore about 403, 208 and 74 a B. P. respectively with the second stage the maximum.During the general Holocene warming processes, there existed at least four cold peri-ods which ended before about 5700, 4100, 2800 and 420- 91 a B.P. respectively, the averageair temperatures of which were about 1.5, 1.25, 0.9 and 0.65℃ higher than the presentone respectively with the warm periods in between. The amplitude of air temperaturechanges is about 2.5℃.展开更多
Previous lichenometric dating of young geomorphological forms in the Tatra Mountains has been hindered by differences in the determination of initial colonisation of fresh rock surfaces by the Rhizocarpon geographicum...Previous lichenometric dating of young geomorphological forms in the Tatra Mountains has been hindered by differences in the determination of initial colonisation of fresh rock surfaces by the Rhizocarpon geographicum lichen.In order to determine precisely the time needed for the first thalli to appear on newly exposed rock surfaces,two experimental sites were created in 2013.The results from these sites were compared with the measurements taken on boulders in debris formed by a 2013 debris flow.In 2018,the largest thalli measured within the experimental sites and the debris flow area reached a size of approximately 2 mm.Based on this,the time of initial colonisation of rock surfaces was determined to be 5±1 years,which is about half the period previously described in the literature.展开更多
In 1950, R. E. Beschel proposed the lichenometric dating technique. For age determination, the diameter growth rate of lichens is usually taken as a constant. Alternatively, the growth curve of lichens is derived by d...In 1950, R. E. Beschel proposed the lichenometric dating technique. For age determination, the diameter growth rate of lichens is usually taken as a constant. Alternatively, the growth curve of lichens is derived by dating objects of known age in some area, and it can then be used for age determination in the same area or areas of similar environment. Unfortunately it is very difficult to obtain such growth curves in many places. The growth curves differ in different environments. In order to use this technique under all conditions, the relationship between the lichen growth and the environment has to be investigated.展开更多
文摘This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene glaciers and the climate. It isconsidered that lichenometry is one applicable method for dating the mid- and late-Holocene deposits in the cold and mountainous regions. Rhizocarpon geographicum (L.)DCand Xanthoria elegans (Link.) Th. Fr. could be used for dating the deposits of about 4500and 500 a B.P. respectively. There existed at least four periods of glacial advances whichoccurred before about 5700, 4100, 2800 and 403- 74 a B. P. respectively with the firstperiod the longest. Little Ice Age includes three stages of glacial advances which endedbefore about 403, 208 and 74 a B. P. respectively with the second stage the maximum.During the general Holocene warming processes, there existed at least four cold peri-ods which ended before about 5700, 4100, 2800 and 420- 91 a B.P. respectively, the averageair temperatures of which were about 1.5, 1.25, 0.9 and 0.65℃ higher than the presentone respectively with the warm periods in between. The amplitude of air temperaturechanges is about 2.5℃.
文摘Previous lichenometric dating of young geomorphological forms in the Tatra Mountains has been hindered by differences in the determination of initial colonisation of fresh rock surfaces by the Rhizocarpon geographicum lichen.In order to determine precisely the time needed for the first thalli to appear on newly exposed rock surfaces,two experimental sites were created in 2013.The results from these sites were compared with the measurements taken on boulders in debris formed by a 2013 debris flow.In 2018,the largest thalli measured within the experimental sites and the debris flow area reached a size of approximately 2 mm.Based on this,the time of initial colonisation of rock surfaces was determined to be 5±1 years,which is about half the period previously described in the literature.
文摘In 1950, R. E. Beschel proposed the lichenometric dating technique. For age determination, the diameter growth rate of lichens is usually taken as a constant. Alternatively, the growth curve of lichens is derived by dating objects of known age in some area, and it can then be used for age determination in the same area or areas of similar environment. Unfortunately it is very difficult to obtain such growth curves in many places. The growth curves differ in different environments. In order to use this technique under all conditions, the relationship between the lichen growth and the environment has to be investigated.
