Response of suitable area of highland barley in the Tibetan Plateau to climate change based on Maximum Entropy Model analysis

Given very sensitive response of Tibet Plateau to climate change, studying the impact of long-term climate change on the suitable areas of highland barley cultivation in this plateau can provide a reference for plateau agriculture's response to climate change, so as to optimize the spatial pattern of such cultivation. By taking 205 highland barley samples from the Tibetan Plateau as the research object and using ArcGIS software and the Maximum Entropy Model, this study simulates and predicts them. To obtain the main environmental factors affecting the distribution of barley on the Tibetan Plateau. And under the influence of climate change, the distribution range and spatial pattern of highland barley on the Tibetan Plateau will change during the ancient(the last interglacial、last glacial maximum、mid-holocene), contemporary(1970—2000), and next 100 years about two scenarios that SSP126 and SSP585. This study finds the following results: (1) The most critical environmental factors affecting the distribution of highland barley across the plateau include: annual precipitation, annual average temperature, average temperature in the driest quarter, and altitude. In unstable and extremely dry and cold climate, altitudes would determine the suitable areas for highland barley. (2) From the last interglacial period to the mid-Holocene and then to the present era, the suitable areas for highland barley have gradually expanded to Hehuang Valley in the northeast section of Tibetan Plateau, the western Sichuan region in the southeast margin of the plateau, and the one-river and two-river basins in the southern Tibetan Valley. In the future, the suitable areas for highland barley will further expand towards the central and northern parts of the plateau, while the southeastern suitable areas will be decreased. (3) Under the conditions of climate change, the centroid of the suitable growth areas for barley is moving towards high latitude and altitude regions, and the upper suitable limit of altitudes will increase by 207m in the future. In combination with results from other research, it can be concluded that from the last glacial period to the Holocene, the expansion of suitable barley-planting areas was constrained by dual effects, i.e., climate warming and humidification, while affected by human settlements on the plateau and the spread of agriculture and animal husbandry. From the present to the next 100 years, the expansion of the potential suitable areas for barley cultivation may be facilitated by the increase in altitude limits caused by climate warming, while the reduction of the potentially suitable areas may be driven by certain climate change events caused by temperature fluctuations, finally exceeding the optimal temperature range for barley's development.