Based on the revised First and Second Chinese Glacier Inventories and Landsat OLI imagery in 2016 - 2017， we analyzed the spatial-temporal variation characteristics of glaciers in the Hexi interior from 1956 to 2017 and researched the cause and mechanisms of glacier changes using temperature and precipitation data. The results showed that： ① In total， there were 1 769 glaciers covering an area of 976.59 km2 and having ice volume of 49.82 km3 in the Hexi interior in 2016/2017. The glaciers in 0.1~10 km2 interval contained the largest area and that <0.5 km2 interval had the maximum number. The glaciers in the study area were mainly distributed in the Qilian Mountains， where the glacier number， area and ice volume accounted for 98.47%， 97.52% and 97.53%， respectively. ② The Shule River contained the most of the glaciers number， area and ice volume， with average glacier area of 0.81 km2. However， in the Shiyang River it was the minimum. In the fourth class watersheds， the most developmental glacier in the Ningzhang basin included most of the glaciers number， area and ice volume， and the maximum average glacier area was in the Zalmoho basin. To the contrary， Jiadaogou-Panjia River had the minimum average glacier area （0.05 km2）. ③ In the past 60 years， the area， number and volume of glaciers had decreased by 417.85 km2， 556 and 20.16 km3， respectively. The majority of glacier area loss in the Hexi interior had been mainly concentrated in between 4 400~5 400 m a.s.l. and the area and number of glaciers in the 0.1~0.5 km2 interval constituted the main body of the loss （457 glaciers and -117.49 km2）. Within the study region， glaciers with the north orientation suffered the largest area loss， while those with the northwest orientation had the fast change in glacier area. ④ During the period from 1956 to 2017， the glacier area of different drainage basins had a tendency of retreat in the Hexi interior and the glacier change was gradually accelerated from west to east. However， there were three glaciers had clearly advanced during 1986 - 2017. The main reason for glacier retreat in this region was temperature rising.
Based on the improved CASA model， in this paper， the net primary productivity （NPP） quality of vegetation in the Qilian Mountains is estimated， and the vegetation and soil carbon sequestration and value are further estimated in the study area in 2005， 2010 and 2015 based on photosynthesis equation and carbon cycle process model. The quantitative analysis of the spatial and temporal evolution of vegetation and soil carbon sequestration values of various vegetation ecosystems in this region provide a scientific basis for the development of more scientific and rational carbon management measures. The research shows that the value of vegetation and soil carbon sequestration in the Qilian Mountains had increased from 2005 to 2015. The value of vegetation was 515.95×108 yuan， 491.05×108 yuan and 581.55×108 yuan in 2005， 2010 and 2015； the value of soil carbon sequestration was 356.56×108 yuan， 404.36×108 yuan and 465.65×108 yuan in 2005， 2010 and 2015. The change of land type has increased the soil and soil carbon sequestration by 12.72% and 30.39%， respectively. From the perspective of spatial distribution， the carbon sequestration in the eastern vegetation and soil is significantly higher than that in the west. The carbon sequestration capacity of the forest is the highest， and the carbon sequestration per unit area is 10.19 t·hm-2. Grassland is the most widely distributed vegetation in the study area， of which the contribution ratio to vegetation and soil carbon sequestration in this area is 51.13% and 49.34% respectively.
Base-flow is main supply source of runoff during the dry season. The reliable method of base-flow separation plays an important role in base-flow research and the management and utilization of water resources. Based on the daily runoff data from Changmabao Hydrological Station in the upper reaches of the Shule River from 2007 through 2016， in this study， using single parameter digital filtering method， minimum smoothing method， recursive digital filter technique， fixed interval method， sliding interval method and local minimum method， the base-flow is separated. The results show that the four methods can accomplish the automatic separation of base-flow. The above separated base-flow hydrograph is smooth. There are four base-flow separation methods， which have different base-flow index， ranging from 0.49 to 0.72. The results of recursive digital filtering method have the highest stability. When the filtering parameter β takes a value of 0.95， it is an optimal parameter of the single parameter digital filtering method. The minimum smoothing method， sliding interval method， local minimum method and single parameter digital filtering method （β=0.95） have high Nash-Sutcliffe efficiency coefficients with the average relative error less than 10%. The base-flow simulated results show that these methods were stable， reliable， accurately and could be used as the optimal separation methods to estimate base-flow in the study area.
The variations of precipitation and runoff in the Yellow River source regions from 1961 to 2010 has been studied. Due to the decrease in precipitation during the wet season （July， August and September） and the increase in temperature， the annual runoff and precipitation in the river source regions had showed an overall non-significant decrease， and the flood peak has disappeared in September since the 1990s. By using the partial correlation method， the relationship between precipitation and runoff with ENSO （El Ni?o-Southern Oscillation）， IOD （Indian Ocean Dipole） and WCI （Westerly Circulation Index） were calculated for July， August and September in each 30-year moving window after removing the co-variate effects among ENSO， IOD， and WCI. It is found that the influence of WCI on the runoff of the Yellow River in wet season is higher than those of the ENSO and IOD， and the increase of the WCI maybe the main driven factor for the Yellow River source precipitation and flood peak decreasing in August and September， respectively.
Viruses play an important role in driving the formation of high biodiversity of ecosystems and the cycling of nutrients and organic matter in ecosystems. As a hot spot of microbial activity in cryosphere， cryoconite holes provide a special habitat for viruses， which drives viruses to survive and adapt to extremely cold habitats. This review presents some of the findings and discussions of viruses in the cryoconite holes on the surface of glaciers in recent years， which relate to the importance of cryoconite holes in the glacial ecosystems， the abundance， productivity and genetic diversity of viruses in cryoconite holes， the interaction between viruses and hosts， and the importance of viruses for the carbon cycle and food web of cryoconite holes. Moreover， this review summarizes the gaps in the current research on viruses in cryoconite holes： viral morphological diversity， viral degradation rate， isolation and culture， and the viruses in cryoconite on glacier surface. This article points out several aspects which need to be focused on in future research， and offers a reference for the further study of the important effects of viruses in cryoconite holes. Based on the former studies， it is put forwards a future prospect of the research on the viruses in cryoconite holes of the Qinghai-Tibet Plateau.
