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Tomicus yunnanensis Kirkendall (Coleoptera: Scolytinae) is a stem-boring pest that endangers Pinus yunnanensis Franch (Pinales:Pinoideae), which seriously affects the ecological environment safety in southwest China. In order to understand the potential distribution pattern and change in the potential distribution of P. yunnanensis and T. yunnanensis, this study used the maximum entropy model to predict the distribution of potentially suitable areas for P. yunnanensis and T. yunnanensis and explored the relationships between their different spatiotemporal distributions based on change analysis. The experimental results show that altitude is the main factor restricting the current distribution of P. yunnanensis. The current suitable areas of P. yunnanensis are mainly distributed in Yunnan, Sichuan and Guizhou. The minimum temperature of the coldest month is the main factor affecting the current distribution of T. yunnanensis. The current suitable areas of T. yunnanensis are mainly distributed in Yunnan, Sichuan and Tibet. Under future climate scenarios, the total suitable areas of P. yunnanensis and T. yunnanensis are expected to increase. The suitable areas tend to move to higher altitudes in the west and higher latitudes in the north. At the same time, this study finds that there is an obvious bottleneck of expansion to northeastern Sichuan near the Daba Mountains. The results of intersection analysis showed that, with future climate change, P. yunnanensis and T. yunnanensis mainly showed lowly suitable (or unsuitable)—lowly suitable (or unsuitable) to moderately (or highly) suitable—and moderate (or high) variation patterns of suitable areas under the SSP1-2.6 climate scenario. These results will provide an important basis for the breeding of P. yunnanensis and controlling T. yunnanensis. [ABSTRACT FROM AUTHOR]

In this study, the distribution information of lemon planting and the surface observation data during 1971-2017 from meteorological stations in Sichuan Province are adopted to reasonably plan the layout of lemon planting in Sichuan Province. Considering the elements of climate, soil and terrain affecting the planting distribution of lemon, 16 ecological factors are selected for the analysis and regionalization of the ecological suitability of lemon planting in Sichuan Province. Specifically, the maximum entropy model is used to establish the model for the relationship between the planting distribution of lemon and one of its potential influencing factors related to the climate. On this basis, dominant climatic factors affecting the planting distribution of lemon are investigated, and the distribution for corresponding suitability grades of these climatic factors are also revealed. The receiver operating characteristic curve is used to verify the simulation accuracy. The Jackknife method and correlation analysis are used to screen dominant climatic factors and analyze their relationship with the existence probability. Based on the ArcGIS platform, the spatial distributions for the regionalization indexes of soil and terrain are analyzed for the soil and terrain suitability regionalization of lemon planting in Sichuan Province. Furthermore, by using the ecological suitability analysis method and considering the weights of various indexes, the ecological suitability regionalization of lemon planting in Sichuan Province is obtained. The results show that the highly suitable regions for lemon planting with an area of 29,000 km2 are mainly concentrated in Guang'an City, Nanchong City, Suining City, Ziyang City, Neijiang City and Zigong City, and some regions scattered in the Sichuan Basin as well. In addition, there are also some highly suitable planting spots for lemon in Panzhihua City. The moderately suitable region covers an area of 39,000 km2, and most of which are distributed in the mountainous areas in eastern part of the basin, such as the Guang'an City, Dazhou City, Suining City and Zigong City. The slightly suitable region with an area of 67,000 km2 is mainly concentrated in the central Sichuan Province, surrounding the highly and moderately suitable regions. The unsuitable region covers an area of 53,000 km2, which is mainly concentrated in plateau and mountainous regions of the western and northern Sichuan Province. [ABSTRACT FROM AUTHOR]

As a region known for its high species richness, southwest China plays an important role in preserving global biodiversity and ensuring ecological security in the Yangtze, Mekong, and Salween river basins. However, relatively few studies focus on the response of tree species richness to climate change in this part of China. This study determined the main tree species in southwest China using the Vegetation Map of China and the Flora of China. From simulations of 1970 to 2000 and three forecasts of future benign, moderate, and extreme climate warming anticipated during 2061 to 2080, this study used a maximum entropy model (MaxEnt) to simulate main tree species richness in southwest China. Regions with a peak species richness at intermediate elevations were typically dominated by complex mountainous terrain, such as in the Hengduan Mountains. Likewise, regions with the smallest richness were low-elevation areas, including the Sichuan Basin, and the high-elevation Sichuan-Tibet region. Annual precipitation, minimum temperature of the coldest month, temperature seasonality, and elevation were the most critical factors in estimating tree species richness in southwest China. During future 2061 to 2080 climate scenarios, tree species tended to migrate towards higher elevations as mean temperatures increased. For climate change scenarios RCP2.6–2070 (benign) and RCP4.5–2070 (moderate), the main tree species richness in the study area changed little. During the RCP8.5–2070 extreme scenario, tree species richness decreased. This study provides useful guidance to plan and implement measures to conserve biodiversity. [ABSTRACT FROM AUTHOR]