This paper reviewed the main expedition and scientific investigation activities on the Tibetan Plateau (TP) before 1949. The history of scientific investigations on the TP can be divided into four stages: (1) The investigations in ancient times were mainly sporadic records of geographical phenomena in some parts of the TP by Chinese monks and Western Christian missionaries. (2) In the late Qing Dynasty, foreign and Chinese scholars and explorers, mainly Westerners, carried out preliminary scientific investigations. (3) 1912-1949, Chinese scholars began to take part in sino-foreign investigation teams to explore the TP. (4) Chinese scholars led scientific investigations in some regions during the Period of the Republic of China. The expedition on the TP mainly focused on geographical description, data collection, and single-subject investigation and research before the Qing Dynasty, which changed to the measurement of geographical elements with simple scientific instruments and in-depth research on a certain topic (such as vegetation) in some regions during the Period of the Republic of China. A remarkable feature of the investigations by Chinese scholars on the TP during the Period of the Republic of China was that they changed from cooperation with Western scientists in joint scientific investigations to independent investigation of geography, geomorphology, geology, meteorology, climate and plants. Some achievements by Chinese researchers have spread worldwide, which expanded the domestic and international understanding of the TP.

The Tibetan Plateau (TP), also known as the roof of the world and the Asian Water Tower, is an important ecological security barrier for China. Since 1949, scientific expedition and research on the TP has always been a major scientific and technological task at the national strategic level. This paper reviewed the scientific expedition and research activities carried out by Chinese scientists on the TP from 1949 to 2017, before the initiation of the Second Tibetan Plateau Scientific Expedition and Research (STEP). These activities can be divided into four stages: (1) Regional and thematic scientific expedition and research carried out from the early 1950s to the late 1960s, which obtained important scientific data, laid the foundation for the large-scale expedition and research starting from the 1970s. (2) The first comprehensive scientific expedition and research on the TP during 1973-1992, which investigated the full range of TP covering an area of 2.6 million km², collected a large number of first-hand scientific data, filled in the gaps in some areas and disciplines of the TP research, and had significant scientific and societal impacts. (3) Scientific question-oriented expedition and research from the early 1990s, promoted by national and international scientific projects, has achieved a milestone transformation from static to dynamic processes, from qualitative to quantitative analyses, and from single discipline to multi-disciplinary integration on TP research. (4) Since its founding in 2003, the Institute of Tibetan Plateau Research, Chinese Academy of Sciences has been leading multi-disciplinary research teams, and conducted institutionalization and group-oriented expedition and research in field observations, laboratory systems and international networks. At present, the STEP is being carried out and the reviewing of the fruitful achievements in the past will inspire the STEP team to be actively involved in the TP research.

Tibet is recognized as the key repository and focal area for future hydropower development in China because of its high capacity for hydropower storage; however, frequent occurrence of geological hazards in this region have posed great challenges to us. Priority should be given to the effects of geological hazards on the suitability of areas in Tibet for hydropower development. Based on the maximum entropy model, the susceptibility of potential development areas to three typical geological hazards (debris flow, avalanche, and landslide) was calculated using data of landforms, hydrometeorology, and vegetation coverage of Tibet. Furthermore, hydropower development suitability was evaluated by considering distribution of potential hydropower storage alongside geological hazard susceptibility. The results show that the Qiangna-Bangxin section of the Great Bend of the Yarlung Tsangpo River has the highest suitability and would be a prime development target. The Mali-Linka and Zhonglinka-Chawalong sections in the middle reaches of the Nujiang River, the Tiantuo-Bitu section of the Weiqu River, the Chaya-Cuowa, Rumei-Yanjing, and Muxie-Gobo sections in the upper reaches of the Jinsha River, the Motuo-Lijia and Xiaru-Penji sections in the lower and upper reaches, respectively, of the Yarlung Tsangpo River, and the Pengqu River Basin in the Himalayas are all highly suitable for hydropower development. However, these areas also show high susceptibility to geological hazards, so they should be developed with caution. The Renbu-Qushui section in the middle reaches of the Yarlung Tsangpo River, the Zhongyu-Yigong section of the Yigong Tsangpo River, the southern section of the Chayu River, and the lower reaches of the Langqin Tsangpo River show moderate suitability and low hazard susceptibility, and thus present future development opportunities. Therefore, other areas are not suitable for hydropower development. This study presents an effective suitability evaluation method for hydropower development in Tibet, and its results provide a scientific basis for hydropower planning and site selection in this region.

The existing human activity suitability evaluation of land resources in China has the defects of insufficient theoretical support in terms of basic data accuracy, elevation and slope classification and suitability grade judgement. When it is applied empirically, there are some problems such as excessive evaluation factors, difficulty in obtaining indicator data, and low altitude of applicable regions. In this paper, we constructed a technical evaluation framework applicable to the Qinghai-Tibet Plateau, and established a grid-scale evaluation model for construction land suitability and cultivated land suitability after selecting key parameters that vary with topographic elevation and slope. And then we proposed a generalized algorithm for key parameters such as atmosphere density, air temperature, slope suitability for construction, and soil erosion resistance of sloping cultivated land. With Milin County in southeastern Tibet as an example, the empirical research has been carried out according to the interval of 100 m in elevation and 1° in slope. In addition, grid precisions of 30 m, 50 m, 100 m, 250 m, 500 m, and 1000 m are tested. This article obtains four conclusions: (1) The construction land suitability and cultivated land suitability can be classified into five levels: suitable, relatively suitable, moderately suitable, less suitable, and unsuitable. Under the grid precision of 30 m, the five levels of construction land suitability account for 1.26%, 2.92%, 2.12%, 2.77%, and 90.93%, respectively. Compared with 30 m, the area ratio results of 50 m, 100 m and 250 m have the errors of ±0.34%, ±0.34% and ±1.11%, respectively. Similarly, the area ratio of each level of cultivated land suitability with a 30 m grid precision is 0.72%, 3.07%, 2.62%, 1.35%, and 92.25%, the errors between it and the results under grid precision of 50 m, 100 m, and 250 m are ±0.52%, and the errors of 500 m and 1000 m grid precisions for both construction land suitability and cultivated land suitability are relatively larger than those of the other grid precisions. (2) Current construction lands (i.e., settlements of cities, towns and villages, industrial and mining lands) in the study area are mainly distributed in areas with levels of relatively suitable, suitable, and moderately suitable according to the distribution ratio. Under grid precisions of 30 m, 50 m, and 100 m, the total land areas of these three levels account for 95.96%, 95.96%, and 94.74%, respectively. Current cultivated land and plantation land are distributed in areas with levels of relatively suitable, moderately suitable, and suitable, accounting for more than 96% of different grid precisions. (3) The empirical research shows that evaluation method, quantitative model, and parameter algorithm for evaluating the human activity suitability of land resources in the Qinghai-Tibet Plateau are feasible and applicable. In the actual evaluation, the grid precision should be controlled within 100 m, and the maximum cannot exceed 250 m. (4) This study established a corresponding pedigree between construction land suitability and cultivated land suitability and topographic elevation and slope that can be applied to the Qinghai-Tibet Plateau. Meanwhile, some professional defects are analyzed of available land resources evaluation methods in major function-oriented zoning and "Double Evaluations" of territorial spatial planning in China when applied to the Qinghai-Tibet Plateau.