FIGURE 4 Contribution value of environmental variables to
predicting result of the MaxEnt model
3.4 Potential geographical distribution of
species
HSI is an important or key factor that affects the survival and
development of species. It refers to the potential ability of a habitat
to support the survival of a particular species. The results of the
study revealed that potential distribution areas of species
appears
to be decreasing with the improvement of habitat suitability (Figure 5),
which indicated that the remaining natural habitat suitable for species
was becoming less and less. In addition, the research results also
indicated that the species with a larger potential distribution areas
were Echinocodon lobophyllus , Gymnadenia crassinervis ,Rhodiola atuntsuensis and Aristolochia delavayi . Their
potential distribution areas were 44,963.53 km2,
30,830.51 km2, 22,481.77 km2 and
22,396.28 km2, respectively, accounting for 56.36%,
38.64%, 28.18% and 28.07% of the total area of Northwest Yunnan
(Table 3; Figure 6). The species with smaller potential distribution
areas were Diphylax uniformis , Paris dulongensis andTerminalia myriocarpa . Their potential distribution areas were
2,137.05 km2, 1,054.28 km2 and
826.33 km2, respectively, occupying only 2.68%,
1.32% and 1.04% of the total area of Northwest
Yunnan (Table 3; Figure 6). Generally,
the
potential distribution areas of each species were relatively
concentrated. The HSI values of the mid-western, mid-eastern and
northern regions of the study area were between 0.40 and 1.00, which
were deemed the main concentration area of the potential distribution of
species. Furthermore, the area of high suitability plaques (i.e., Sum
area of high suitability level
habitats, where 0.40 ≤ HIS < 0.60) was larger than the area of
optimal suitability plaques (i.e., Sum area of optimal suitability level
habitats, where 0.60 ≤ HIS < 1.00) (Table 3; Figure 6).