Exploring on the climate regionalization of Qinling-Daba mountains based on Geodetector-SVM model

credible. These findings indicated that the delimitation results objectively revealed the climate characteristics in the QDM. Discussion A new method of the climate regionalization. In this paper, the Geodetector-SVM model was used as a new regionalization method. Compared with commonly used methods of regionalization schemes, this method provides excellent statistical support for the establish- ment of an index system. Based on q-statistics of the Geodetector model, it is easy to judge which index or variable is more critical for regionalization. In this study, four of 14 waiting indexes were selected as the delimitation indexes of the boundary of subtropical and temperate zones and the transition zone. The results of the boundary and the transition zone were also reasonable. Additionally, due to the differences in the sensitivity of explanatory variables to different vegetation types for a specific boundary, different and appropriate vegetation-envi- ronmental indicators can be adopted based on the Geodetector. The Geodetector model can measure the spatial stratified heterogeneity, which satisfies the principle of comprehensive physical regionalization. Three sets of reliable index systems for the boundaries of three cou- ples of vegetation types were acquired based on that model, and redundant information was removed (shown in Fig 3). Moreover, the SVM is a relatively advanced machine learning algo- rithm, which can efficiently mine potential information from the data. In this study, three reli-

able boundaries of the vegetation-climatic zone were acquired and verified by the survey quadrat data. These results demonstrate that the Geodetector-SVM model can be used as an efficient method of climate regionalization. The transitional zone, not the boundary. In previous studies, people were focused on delimiting a clear dividing line between the subtropical and warm temperate zones. However, a gradual transition is noted between the subtropical zone and temperate zone. Thus, different boundaries were proposed in the QDM. The sensitivity of diverse vegetation types to climate is different. Thus, the geographical locations of different zonal vegetation types are different. Therefore, focusing on the transitional zone rather than the boundary is more useful to study the direction and intensity of the spatial variation of natural elements in the QDM. As shown in Fig 5a and 5b, the locations of boundaries of subtropical vegetation and temperate vegeta- tion are slightly different, but their trends tend to be similar. These boundaries constitute the transition zone between the subtropical zone and temperate zone. Moreover, the location is approximately the same as the previous climatic boundaries (Renmeie, Luokaifu Houxueyu) (Fig 5c). The transition zone acts as a buffer zone with a distinct transitional character, and this zone is where the temperature, the precipitation, soil type, vegetation change. The limitations of this study. (1) Although vegetation is an indicator of climate condi-

tions, vegetation exhibit a lag with regard to climate change [51]. Additionally, the relationship between boundaries of three vegetation type couples were exclusively considered, and different time scales were not assessed. Based on the result that regionalization might be too rigid, the dynamic change of the climate cannot be reflected via the exclusive use of single-phase data. With global warming, the transition zone between subtropical and temperate regions should change dynamically [52–54]. In future studies, dynamic regionalization models should be established in the study using the time-series datasets. In the context of global changes, the transition zone is sensitive to environmental changes. Therefore, an in-depth study of the com- position and distribution characteristics of vegetation and climate within the transition zone can provide strong evidence for regional responses that indicate environmental changes [16]; (2) Given the coarse spatial resolution of the Chinese vegetation map (1:1,000,000) and the dif- ficulties encountered when obtaining vegetation survey data throughout the study region, only PLOS ONE Climate regionalization based on Geodetector-SVM model PLOS ONE | https://doi.org/10.1371/journal.pone.0241047 November 2, 2020 13 / 16