Habitat Suitability Evaluation and Regionalization of Juglans cathayensis Dode in Sichuan Province Based on MaxEnt Model

In order to clarify the habitat suitability of Juglans cathayensis Dode in Sichuan province, the MaxEnt model was used to predict its potential distribution area by combining the distribution information and environmental variables. The effects of major environmental variables on the distribution were analyzed, and the accuracy of the prediction model was evaluated using ROC (receiver operating characteristic curve) curve. The results were as follows: (1) The average AUC of the training set was 0.990 after more repetitions, which indicated that the prediction effect of the model was good. (2) Based on the Jackkinfe method and the Person's correlation coefficient method, the most important environmental variables affecting the potential distribution of J.cathayensis Dode were annual mean temperature, preciptitation of warmest season, mean temperature of driest season and mean temperature of coldest season. Altitude had little effect on the potential distribution of wild walnut, and 300~3800m was suitable for the growth of wild walnut. (3) According to the MaxEnt model, the suitable range of average annual temperature was 9.68~18.88 ℃, and mean diurnal range Mean of monthly(max temp - min temp) is 6.16~11.63℃, and Isothermality (Mean diurnal range / Temperature annual range)×100 was 24.68~44.47, and temperature seasonality (standard deviation×100) was 313.04~933.33. The lowest temperature of the coldest month was −7.38~4.76 ℃, and mean temperature of wettest season was 16.52~25.35 ℃, and mean temperature of driest season was −0.9~12.4 ℃, and average temperature of the coldest season was −1.19~10.71 ℃. The annual precipitation was 654.55~5033.77 mm, and the monthly precipitation in the wettest month was 116.94~948.49 mm. The precipitation in the wettest season was 311.69~2158.44 mm, and the precipitation in the warmest season was more than 358.44 mm.