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The aim of this paper was to review the formation mechanism and restorative measures of the black-soil-type degraded grassland ecosystem of the source area of Yangtze and Yellow Rivers, Qinghai-Tibetan Plateau. The relationship among plants, animals, soil, climate change, human activity and the black-soil-type degraded grassland was analyzed based on a review of literature and report of previous investigations conducted by the authors. Degradation of the black-soil-type grassland was caused by a set of complex factors such as altitude range, district characteristics and weather conditions, which existed for a long period of time. Livestock overgrazing and climate dryness were the dominant factors that caused the degradation of the grassland in question. In addition, damages done by rodents, especially pikas ( Ochotona curzoniae), via burrowing through the turf and gnawing at herbs have sped up the formation process of the degradation of the black-soil-type grassland. Furthermore, with the inflation of the population in the last 20 years, the influence of human activity on grassland degradation cannot be neglected. Based on the different successive stages of degradation of the black-soil-type grassland ecosystem, different restorative measures were suggested. The lightly and moderately degraded grasslands should be kept away from disturbance, such as fencing closure, weeding, fertilizing, using rodenticide, decreasing stocking rate, optimizing population structure stocked and slaughter ages; whereas the artificial and semi-artificial grassland establishment required to restore ecosystems should be applied to heavily and extremely degraded grasslands. [ABSTRACT FROM AUTHOR]

The source region of the Yangtze River (SRYR) is located in the hinterland of the Tibetan Plateau (TP). Due to the harsh climate environment, there are few meteorological stations in its territory, and the measured meteorological data are also less. To overcome the impact of lack of measured meteorological data, the China Meteorological Forcing Dataset (CMFD) was used to couple with the meteorological data, to make the meteorological data more representative of the average climate state of the SRYR. Furthermore, we used the Soil and Water Assessment Tool (SWAT) to verify interpolation effect of meteorological data. Then the six global climate models (GCMs) were integrated through deep learning (DL) algorithm to make it closer to the changes in weather data after correction. The future water resource changes of SRYR were obtained by coupling the SWAT model with the integrated meteorological data. The results show that the CMFD dataset has a high precision in the SRYR, and that the average relative error (RE), coefficient of determination (R2), Nash–Sutcliffe efficiency (Ens) with the measured temperature and precipitation are 10.66%, 0.99, and 0.93, respectively. The CMFD dataset can be used for meteorological data integration. After the meteorological data integration, the Ens between simulated runoff and observed runoff increased from 0.64 to 0.70, and the RE reduced from 13.4 to 10.3%. Under the future climate scenario, the runoff in the SRYR shows a decreasing trend, the average annual runoff decreased by 11.89%, and the distribution of runoff during the year changes is even more dramatic. This shows that the SRYR faces the risk of water resources reduction, which will bring challenges to water resources management in the SRYR. This study provides a new idea for meteorological data correction. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is particularly sensitive to the influences of climate change. As indicators of climate change, lakes on the TP play a key role in the Earth's climatic system. Lake Yazi (LY), Lake Tuohepingco (LT) and Lake Changtiao (LC) in the Tuohepingco Basin are three inland lakes on the plateau. The extents of LY, LT and LC were obtained using object-based image analysis for remote sensing and 22 images from Landsat satellites (from September to December between 1972 and 2015). Inter-annual changes in the extent of LY, LT and LC were then analyzed. The results show that the total area of the three lakes underwent a change from shrinkage to expansion between 1972 and 2015. In general, there was a trend toward shrinkage during 1972-1999, distinct expansion during 2000-2007 and slight expansion during 2008-2015. Moreover, we found that 14 other lakes have also expanded dramatically since 2000. Lakes at 30°N and 35°N (LY, LT and LC are also located in this region) exhibited the same dramatic period of expansion between 2000 and 2005. In other words, 2000 appears to be a critical transition point for changes in lake size on the TP. Lakes at the same latitudes in the Tibetan Plateau interior may have a similar period of dramatic expansion after 2000. The warming-triggered deglaciation or permafrost degradation, increased precipitation and decreased evapotranspiration may be the influencing factors of lake expansion in the Tuohepingco Basin. Temperature showed relatively higher correlation with lake extent, while precipitation and evaporation were slightly correlated with lake area. Given the importance of wetlands to human society, these are no trivial issues, and we now need accelerated research based on long-term and continuous remote sensing. [ABSTRACT FROM AUTHOR]

Glaciers on the Tibetan Plateau are undergoing an accelerating retreat under climatic warming, with the immediate result of glacial lake outburst floods (GLOFs) becoming increasingly frequent. Glacial lakes in the southeast of the Tibetan Plateau are densely distributed. Due to the difficulties associated with field investigations of glacial lakes, including remote locations and harsh weather conditions, methods which combine remote sensing, geographic information systems and hydrodynamic modeling (HEC-RAS) with field investigation were developed to assess regional glacial lake variation and hazard. The methods can be divided into three levels. At the first level, multi-temporal satellite images were used to (1) study the variation of glacial lakes for the whole region during recent decades, as well as (2) qualitatively identify potentially dangerous glacial lakes (PDGLs). The second level is an in-depth evaluation of the degree of danger for selected PDGLs by ground-based surveys, and then verification of the first-level results. At the third level, the one-dimensional (1D) hydrodynamic model HEC-RAS was used to simulate the inundation characteristics of hypothetical outburst of PDGLs. The three levels downscale from the whole study area to individual PDGLs, and thus assess the hazard of glacial lakes progressively. The methods were then applied to a region of southeastern Tibet-the Boshula mountain range-to analyze the variation of glacial lakes and assess potential hazards posed by GLOFs. Since these methods employ easily accessible data and instruments, the application in other regions is promising. [ABSTRACT FROM AUTHOR]

Climate change has greatly influenced the permafrost regions on the Qinghai-Tibet Plateau (QTP). Most general circulation models (GCMs) project that global warming will continue and the amplitude will amplify during the twenty-first century. Climate change has caused extensive degradation of permafrost, including thickening of the active layer, rising of ground temperature, melting of ground ice, expansion of taliks, and disappearance of sporadic permafrost. The changes in the active layer thickness (ALT) greatly impact the energy balance of the land surface, hydrological cycle, ecosystems and engineering infrastructures in the cold regions. ALT is affected by climatic, geographic and geological factors. A model based on Kudryavtsev's formulas is used to study the potential changes of ALT in the permafrost regions on the QTP. Maps of ALT for the year 2049 and 2099 on the QTP are projected under GCM scenarios. Results indicate that ALT will increase with the rising air temperature. ALT may increase by 0.1-0.7 m for the year 2049 and 0.3-1.2 m for the year 2099. The average increment of ALT is 0.8 m with the largest increment of 1.2 m under the A1F1 scenario and 0.4 m with the largest increment of 0.6 m under the B1 scenario during the twenty-first century. ALT changes significantly in sporadic permafrost regions, while in the continuous permafrost regions of the inland plateau ALT change is relatively smaller. The largest increment of ALT occurs in the northeastern and southwestern plateaus under both scenarios because of higher ground temperatures and lower soil moisture content in these regions. [ABSTRACT FROM AUTHOR]