Prediction Of Potential Suitable Distribution Of Zanthoxylum Bungeanum Maxim. In The Loess Plateau And Responses To Climate Change

Zanthoxylum bungeanum Maxim.is an important economic tree species in the Loess Plateau area,in order to adjust measures to local conditions and reasonably plan the production layout of Zanthoxylum bungeanum Maxim.industry,actively respond to the habitat changes of Zanthoxylum bungeanum Maxim.under the trend of climate change,and promote the sustainable development of land resources.This study aims at the regional division of Zanthoxylum bungeanum Maxim.planting suitability and its response to future climate change in the Loess Plateau.The ArcGIS spatial analysis and the optimized Max Ent model were combined to build the model based on 48 growth points data of Zanthoxylum bungeanum Maxim.and 10 environmental Variables.Three criteria(AUC,AUC_DIFF and TSS values)were used to evaluate the model performance.Contribution rate,replacement importance value and Jackknife test were used to evaluate the importance of environmental factors on potential distribution of Zanthoxylum bungeanum Maxim.The range of major environmental variables suitable for distribution of Zanthoxylum bungeanum Maxim.was calculated according to the single factor response curve of environmental variables,and quantifying its suitable habitat characteristics.The potential suitable distribution and central point migration of Zanthoxylum bungeanum Maxim.under different greenhouse gases emission scenarios（RCP2.6,RCP4.5and RCP8.5）in the present,the future 2050s and the future 2070s were predicted resptectively.The results are as follows:（1）Precipitation seasonality（bio＿15）,Slope,Organic carbon content（t＿oc）and Mean temperature of coldest quarter（bio＿11）are the most important environmental factors affecting the distribution of Zanthoxylum bungeanum Maxim.in the suitable area of the Loess Plateau,with a cumulative contribution rate of 86.6%.The suitable ranges are as follows:Precipitation seasonality<110%,Slope<15°,Organic carbon content>0.6%,Mean temperature of coldest quarter>-6℃.（2）The potential suitable area of Zanthoxylum bungeanum Maxim.are mainly distributed in the central and southern part of the Loess Plateau,accounting for 54.5%of the area of the Loess Plateau.The unsuitability area is mainly distributed in the northern region,accounting for 45.5%of the loess Plateau area.The suitable areas of high,middle and low grades accounted for 21.27%,12.07%and 21.16%of the total area of the Loess Plateau.（3）Compared with the current period,the potential suitability distribution pattern of Zanthoxylum bungeanum Maxim.in the future climate model has little difference,and its suitability gradually decreases from south to north.Under three different greenhouse gas emission scenarios,the potential suitable area of Zanthoxylum bungeanum Maxim.in the Loess Plateau showed a trend of increasing of suitable area and decreasing of non-suitable area in the future.The increase and loss of potential suitable areas of Zanthoxylum bungeanum Maxim.under future climate scenarios occurred in the middle part of the Loess Plateau.（4）Under the future climate scenario,the center of the potential suitable area of Zanthoxylum bungeanum Maxim.in the Loess Plateau will migrate to the northwest compared with the current period,and the center of the high suitable area will move to the southeast direction,the center of the middle suitable area will move to the west direction,and the center of the low suitable area will move to the north direction.Conclusions:The prediction results of the model are reliable.The distribution of potential suitable areas of Zanthoxylum bungeanum Maxim.in the Loess Plateau is mainly affected by Precipitation seasonality,Slope,Organic carbon content and Mean temperature of coldest quarter.The suitability of Zanthoxylum bungeanum Maxim.in this area gradually decreases from south to north.In the future,the new and lost areas of Zanthoxylum bungeanum Maxim.suitable areas will occur in the middle of the Loess Plateau,and the central point of the suitable area will migrate to the northwest.