基于MaxEnt模型的不同气候情景下白蜡树中国适生区预测

白蜡树自然分布主要在中国境内，而且也是中国栽培悠久的经济树种，研究其当前和历史的地理分布格局、未来气候条件下的地理分布格局及分布区的宏观动态变化，皆有重要意义。依据采集标本记录的183个分布点和21个环境因子，利用最大熵原理，对10种气候情景下白蜡树在中国的适生分布区及分布区的几何质心进行预测。结果表明:1）最大熵模型模拟效果较高，模拟10次，AUC值=0.915 0±0.005，故可用模型计算出的潜在分布区来预测适生分布区，并基本确定白蜡树的地理分布格局。2）年均温、温度季节变化方差、暖季降雨量和未定义坡度是影响白蜡树适生分布的主导因子。3）根据模型计算出的概率值进行分级得知，白蜡树在当前气候情景下的适生分布范围大概率（0.6<P<最大阈值）位于甘肃、陕西2省交界处，西南腹地（尤其是贵州省），河北、北京、安徽、江苏、浙江的一些地区亦可能分布。4）10种气候情景下白蜡树适生分布区的几何质心皆位于湖北省境内。由适生分布区面积的变化得知，自全新世中期至今白蜡树的适生面积减少约20%，未来高排放浓度场景下其适生分布区面积较当前分布区面积减少得最多。可见，白蜡树在我国适生分布区面积可能呈现缩减趋势，应对其进行保护与合理栽植。

Prediction of Suitable Areas of Fraxinus chinensis in China Under Different Climate Scenarios Based on MaxEnt

The natural distribution of Fraxinus chinensis is mainly in China,and it has been one of the major non-timber trees cultivated in China for a long time.It is of great significance to study the present and historical geographical distribution patterns,the future climatic distribution patterns and the macroscopic dynamic changes of the distribution area.We used the maximum entropy principle and collected 183 distribution points and 21 environmental variables to predict the suitable distribution area and geometric center of mass of F.chinensis in China under ten different climate scenarios.The results were reported as follows.1) The maximum entropy model had an extremely high simulation accuracy with the value of the area under curve (AUC) of 0.9150±0.005 (after 10 simulations).Therefore,the potential distribution calculated by this model could be used to predict the suitable distribution area,and the geographical distribution patterns of F.chinensis could be basically clear.2) Factors such ad the annual mean temperature,temperature seasonality,precipitation of warmest quarter and undefined slope were the dominant variables that influenced the distribution of F.chinensis.3) On the basis of the graded probability values that were calculated by MaxEnt,the probability (0.6<P< the maximum threshold) of the suitable distribution range of F.chinensis in the current climate scenario was known to be located in the border of Gansu and Shaanxi Provinces,the hinterland of southwest China (especially in Guizhou Province),Hebei Province,Beijing,and some areas of Anhui,Jiangsu and Zhejiang Provinces.4) Under ten different climate scenarios,the distribution geometric centroids of F.chinensis were all located in Hubei Province.According to the changes of the suitable distribution,the suitable area of F.chinensis had decreased by about 20% since the Mid-Holocene,and the area of the suitable distribution with RCP8.5 had decreased the most among the other climate scenarios,indicating that the area of suitable distribution of F.chinensis in China may be decreasing,so it should be protected and planted reasonably.