Maxent Model Analysis Of Potential Distribution Pattern Evolution Of Xing’an Larch And Mongolian Oak In The Daxingan Mountains Under Climate Change Scenario

Climate affects the geographical distribution of forests on multiple scales,and the impact is likely to intensify in the future.The Greater Khingan Range of China is a permafrost and natural coniferous forest distribution area,and it is also a sensitive area for climate change,but at this stage,there is still a lack of comprehensive research on the changes of geographical distribution patterns of different types of tree species in the future multi-climate model.Therefore,in this study,Larix gmelinii and Quercus mongolica were selected as the main tree species of coniferous and broad-leaved forests in the Greater Khingan Range,combined with field survey data,and the MaxEnt model optimized by R language was used to predict the potential geographical distribution of the current suitability of the two tree species under different climate scenarios,2050 and 2070.Arc GIS and ENMTools software were used to compare and analyze the current geographical distribution pattern of suitable habitat of two tree species from different angles,determine the dominant driving factors affecting the geographical distribution of the two tree species by knife cutting method,and quantify the suitability range of each dominant environmental factor by using the logistic response curve,and then explore the relationship between the suitable distribution of tree species and the demand of climate.In order to compare the response differences of the two tree species to future climate change,regional statistics were used to analyze the changes of the suitable habitat range of the two tree species under the next six climate scenarios,and the trend of distribution centroid migration with climate change was obtained with the help of SDM tools and neighborhood analysis,and the migration distance was calculated.The main conclusions are as follows:(1)For the optimal setting of the FC and RM parameters of the maximum entropy model,1.7 and PQT for Larix gmelinii and 1 and H for Quercus mongolica.After testing,the prediction results of the two tree species models were extremely accurate,and the AUC values of the subjects’working curves were 0.921 and 0.985,respectively.(2)At present,the suitability of Larix gmelinii is excellent,with a total area of about8.11×104km~2,accounting for 97.86%of the study area.The dominant environmental factors influencing the distribution of its habitat in order of contribution are the coldest season average temperature,the suitable range is not higher than minus 19℃;the warmest season average temperature,the suitable range is 12-19℃;the driest season precipitation,the suitable range is 10-28 mm,the cumulative contribution of the three is more than 71%.(3)At present,the ratio of suitable and non-suitable areas of Quercus mongolica in the Greater Khingan Range is about 4:6,with medium and high suitable areas mainly distributed in Huma County and Songling District.The dominant environmental factors in order of contribution rate are annual average temperature,the suitable range is less than8℃;altitude,the suitable range is 166-776m;annual precipitation,the suitable range is415-620mm,the contribution rate is more than 90%.(4)Larix gmelinii is more adaptable to the current habitat environment,its ecological niche width(0.997)is greater than Quercus mongolica(0.925);ecological niche overlap is 0.453,the similarity of the two species to environmental space requirements is low.High latitude Mohe only suitable for Larix gmelinii growth area is the largest,while the latitude of low Gagodaqi more suitable for Quercus mongolica growth,common suitable for both growth area of the largest district and county for Huma.(5)Future climate scenarios of the distribution of the two tree species suitable for the center of mass have the trend of migration to the northwest,the Quercus mongolica south boundary north and east boundary west shift slightly larger than the Larix gmelinii.The suitability of Larix gmelinii gradually decreases,the high habitat area has a tendency to shrink toward the center,and the original habitat area is greatly reduced;while the original habitat area of Quercus mongolica as a whole remains stable,its suitability is significantly increased,and the new habitat area increases with the increase of greenhouse gas emission concentration,and the expansion rate is sharply accelerated.The shrinkage of Larix gmelinii and the expansion of Quercus mongolica forests have become important signs of dry warming in the Greater Khingan Range.