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The Altai Mountain is located at the intersection of cold and arid regions. Climate change and overgrazing directly affect the growth of the grassland ecosystem in this region. This study took the grassland community in the Burqin forest area of the Altai Mountains as an example to analyze the species diversity and productivity of different grassland types based on 50 sampling plots. The relationship between species diversity and the productivity of grassland types at different altitudes was also discussed. The results showed that: (1) In the Burqin forest area, the desert steppe was dominated by Gramineae, Compositae, and Leguminosae. Montane steppe and mountain meadows were dominated by Umbelliferae, Gramineae, and Liliaceae. Gramineae, Ranunculaceae, and Liliaceae were the dominant families in both montane meadows steppe and alpine steppe but occurred in varying proportions. (2) The variation in plant numbers at the family–species level was characterized as montane steppe > alpine meadow > montane meadow steppe > desert steppe > mountain meadows. (3) The similarity in species composition among communities of different grassland types was low. In DS and MM, the number of grasslands and species played a decisive role in determining the biomass. The biomass of MS and AM was determined using the Simpson and Shannon–Wiener indices, and the number of dominant species determined the biomass. The number of grasslands and species did not have a significant impact on the biomass of MMS, which may be due to human factors such as grazing. (4) The dominant species in the grassland at an altitude of 1200–1400 m is prominent. The number of individuals in the dominant species was large and evenly distributed. Margalef peaked at an altitude of 1600–1800 m, but the number of individuals was small, resulting in low biomass and diversity in this range. Most plants survive at an altitude of 2000–2200 m; therefore, in grassland protection and planning management, it is important to consider the specific situation of plant growth under different habitats at different altitudes and make reasonable protection decisions based on local conditions to maintain species diversity and sustainable development of grassland ecosystems. This study provides basic data to support the theoretical basis for the protection and sustainable utilization of grassland resources and the restoration of degraded grasslands in the study region. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic in the Shennongjia area mainly developed carbonate deposits with a small amount of local terrigenous clastic rocks. The Luanshigou, Dawokeng, Kuangshishan and Taizi Formations in the mid-Mesoproterozoic contain relatively mixed deposits. To date, little or no systematic research has been conducted on the mixed sediment types and their main influences. Major controversies continue regarding the source of terrigenous clas-tics and the formation environment of the quartz sandstone of the Taizi Formation. The present study analyzed the sedimentary facies of the Luanshigou and Taizi Formations in the Shennongjia area based on rock type and sedimentary structure. A combination of rock flakes and cathodoluminescence (CL) analysis was used to investigate the mixed sedimentary types and the characteristics and sources of the terrigenous component to clarify the sedimentary background and sedimentary evolution history in the Mesoproterozoic. This analysis showed that the terrigenous detritus was mainly generated from ancient continents, and comprises a large amount of granite with some metamorphic and sedimentary rocks. The assemblages and mixture types in the rocks of the Luanshigou and Taizi Formations are very different, with sedimentary environment, sea level change and tectonic activity being the main influences on the distribution and types of sediment mixes. In the early to middle sedimentary period of the Luanshigou and Dawokeng Formations, the Shennongjia area was adjacent to the ancient land, and tectonic activity was relatively stable at the northern margin of the Yangtze Craton, with gentle terrain and shallow water as indicated by the extensive development of mixed-facies-type deposits. In the late depositional period of the Dawokeng Formation and early depositional period of Kuangshishan Formation, the northern margin of the Yangtze Craton began to enter a period of intense extension, leading to a rise in sea level. The Shennongjia area and the ancient continent were separated into distinct carbonate platforms, as evidenced by clear-water carbonate deposits lacking terrigenous clastic sand. In the late sedimentary period of the Kuangshishan and Taizi Formations, the continuous extension at the northern margin of the Yangtze Craton led to the environment of the Shennongjia area entering a relatively deep-water phase. Early coastal sediments collapsed to form gravity flows to the top of the Shennongjia area, forming intermittently mixed deposits. The sedimentary period of the Luanshigou and Taizi Formations was a significant tectonic evolutionary stage of the Mesoproterozoic. Following the deposition of the Taizi Formation, the Shennongjia area was completely separated from the ancient land with the result that mixed-facies deposition no longer took place. The sedimentary period of the Luanshigou-Taizi Formations was an important period of evolution from a narrow sea to an open ocean basin at the northern margin of the Yangtze Craton. [ABSTRACT FROM AUTHOR]