The suitable distribution of alpine plant Sorbus tianschanica and its environmental driving factors

气候变化是影响物种分布的决定性因素之一, 研究高山植物天山花楸的适宜分布及其对未来气候变化的可能响应, 为了解西北地区高山植物类群的生态适宜性及其对未来气候情景的响应提供参考案例。利用天山花楸51个自然分布点和10个环境因子, 整合GIS空间分析和MAXENT模型, 分析基准气候(1970-2000)及未来气候下(2050时段, 基于RPC4.5情景)其在西北地区的适宜分布范围与空间分布特征。利用多元环境相似度面和最不相似变量分析研究区未来气候相比基准气候的波动情况, 利用环境变量贡献值、置换重要性值及刀切法明晰影响天山花楸分布的关键环境因子。利用GIS工具和R软件ggplot2程序包分析基准和未来气候下天山花楸适宜分布区内关键因子变化的数值范围。研究结果表明：(1)基准气候下, 天山花楸的适宜面积占研究区总面积的13%, 主要集中在阿尔泰山西段、准噶尔西部山地、天山西段及祁连山中段的高海拔山地等区域；(2)加入归一化植被指数显著提高了天山花楸模型模拟的准确性, 最干月降水量(0-18mm)、最湿月降水量(6-127mm)和平均气温日较差(8.2-16.3℃)主要限制了天山花楸的适宜分布；(3)相对基准气候, 2050时段下受降水因子影响, 天山花楸的适宜分布在阿尔泰山、准噶尔西部山地、天山及祁连山区域略有扩增, 适宜分布区的质心将向北迁移。本研究的结果表明天山花楸在西北地区的适宜生境面积较小而且破碎, 在未来气候情景下仅在局部适宜山地呈破碎化扩张, 而且将预测的该植物的适宜分布区与其适宜的海拔数值范围叠合分析后, 仅占研究区面积的4%, 但对该植物尚未建立自然保护区, 本研究结果建议将阿尔泰山西段、准噶尔西部山地、天山西段及祁连山中段作为天山花楸中风险保护区域, 将河西走廊东部、青海南山作为高风险保护区域。;Climate change is one of the key factors affecting species distribution. In order to understand the ecological suitability of alpine plant in taxa Northwest China and their responses to future climate scenarios, the suitable distribution of Sorbus tianschanica and its possible response to future climate change were studied. In this study, 51 natural distribution sites and 10 environmental factors of Sorbus tianschanica were used to integrate GIS spatial analysis and MAXENT model to analyze the suitable distribution area and spatial characteristics of Sorbus tianschanica in Northwest China under baseline climate (1970-2000) and future climate (2050 period, based on RCP 4.5 scenario). Based on the multivariate environmental similarity surface and the least similar variables, the future climate fluctuations in the study area compared with the baseline climate were analyzed. The key environmental factors affecting the distribution of Sorbus tianschanica were identified by integrating the contribution value of environmental variables, the replacement importance value and the knife cutting method. GIS tools and R software ggplot2 package were integrated to analyze the numerical range of the changes of key factors in the suitable distribution area of Sorbus tianschanica in the future climate. The results show that: (1) under the baseline climate, the suitable area of Sorbus tianschanica accounts for 13% of the total area of the study area, which is concentrated in the western part of Altay, the western part of Junggar, the middle and western part of Tianshan, Bogda Mountain, Qilian Mountain, South Mountain of Qinghai, and parts of Pamir Plateau and north part of Karakoram Mountain; (2) The accuracy of the model simulation is significantly improved by adding the Normalized Vegetation Index. The distribution of Sorbus tianschanica is mainly limited by the driest monthly precipitation, the wettest monthly precipitation, and the daily range of average temperature. Regarding the suitable distribution range, the driest monthly precipitation is 0-18 mm, the wettest monthly precipitation is 6-127 mm, and the daily range of average temperature is 8.2-16.3 ℃; (3) Compared with the baseline climate, influenced by precipitation factors in 2050, the suitable distribution of Sorbus tianschanica in Altai Mountain, western Junggar Mountain, Tianshan Mountain, and Qilian Mountain will expand slightly, and the center of mass of suitable distribution area will move northward. The results of the study show that the suitable habitat area of Sorbus mandshurica in Northwest China is small and fragmented. In the future climate scenario, only the local suitable mountains will be fragmented and expanded. The predicted suitable distribution area of Sorbus tianschanica and its suitable altitude range only account for 4% of the study area. However, there is no nature reserve for this plant. It is suggested that the western part of Altay, the western part of Junggar, the western part of Tianshan Mountain and the middle part of Qilian Mountain should be taken as the risk protection areas of Sorbus tianschanica, and the eastern part of Hexi Corridor and the southern mountain of Qinghai should be taken as the high risk protection areas. The suitable and most suitable distribution area of the plant predicted in this study is helpful to guide the protection of the Sorbus tianschanica.