The critical regions of orchids’ geographical distribution
The SDMs results of the species prediction are usually a continuous value of 0-1 to represent the probability of target species distribution. We set the threshold value as 0.5, thus more than it regarded as suitable for survival, otherwise as not having the conditions for orchids existence. All results were converted into binary data (1 represents existence; 0 represents nonexistence) and projected to the environmental layers via Arcmap GIS. For exploring the orchid lifeforms effect in models, we used spatial overlay technology, fused the suitability map generated based on t-data, e-data, and m-data into a total layer, and compared it with the suitability map of all-data.
Biodiversity conservation of target species chiefly commands the protection of their potentially suitable habitats. Hence the amount of the suitability area within the specific geopolitically unit will become an essential consideration for conservation management to formulate policies and plans. To find out the critical regions of orchids distribution in the Hengduan Mountains, we separately counted their suitability habitat based on the county level. Instead of using a single area ranking to screen, which would confuse the various modeling strategies, we adopted a double-ranking approach to compare the prediction suitability results between models. For each model, one of the screens was based on sequential weights, extracting the counties ranked in the top 30% according to the amount of area. Considering the existence of an enormous difference in the suitable area between counties, another was based on the area weights, we chose some counties at the top of the area sequence, and the sum of them was required to reach 50% of the total suitable habitat area in that column. The double-ranking processing could exclude bias due to modeling differences that made it possible to compare the predicted results under arbitrarily modeled strategies.