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.