The orchid’s geographical distribution pattern in the Hengduan
Mountains
Mapping the suitability of orchids with all conditions (see Appendix
S2.4), we intend to provide a reference for the conservation of orchids
in the Hengduan Mountains.
A wide range of suitable habitats for orchids existed in the Hengduan
Mountains, both in the all-layer and in the total layer, with the area
of suitable habitats ranging from 58510 km2 to 187226
km2 (the differences caused by different models), with
the lowest suitable area accounting for 9.77% (R-total) and the highest
reaching 31.25% (G-all) of the total area of the study area.
Suitability maps displayed noticeable geographic distribution centers.
The primary distribution center was located in the northeastern part of
the study area in the mountainous region with a north-south vertical
distribution, while another center was located in the eastern part of
the study area which was a mountainous region. Such a distribution
pattern likewise coincided with terrestrial orchids, which were widely
distributed in the study area, varying in area from 55808
km2 (R-t) to 160956 km2 (G-t),
accounting for 9.31% and 26.86% of the total area, respectively, with
the presence of two geographic centers. The situation was completely
changed for mycoheterotrophic and epiphytic orchids, firstly, they were
less widely spread than terrestrial orchids. The suitable area range of
mycoheterotrophic orchids was 2742 km2 (R-m) to 77071
km2 (G-m), accounting for 0.46% and 12.86% of the
study area, respectively. The suitable area interval for epiphytic
orchids was 3468 km2 (R-e) to 30637
km2 (G-e), which accounted for 0.58% and 5.11% of
the study area, respectively. Although the distribution pattern of
mycoheterotrophic to that of terrestrial orchids, they tended to be
found in the northeastern mountains of the study area (especially in M-m
and R-m), while the distribution pattern of epiphytic orchids was more
prominent, with the southern to the southwestern part of the study area
being the preferred region.
Using spatial analysis, we counted the suitable area of counties for all
suitability maps and performed the same double-ranking (see Appendix
S3.3), this enables us to avoid the bias of prediction results caused by
the different modeling approaches used. The results indicated equally
that the terrestrial orchids were almost consistent with the whole
orchid ranking priority counties and area weighting counties, and the
crucial areas were located in Muli, Yangyuan, Wenchuan, Jiuzhaigou, and
Pingwu counties, and the sorting priority county for mycoheterotrophic
orchids was the same as the first two, but the area weighting county was
Jiuzhaigou County as far as the integrated model results were concerned.
Epiphytic orchids also showed different results, and the suitable area
ranking priority counties were located in the south to the southwest
part of the study area, and the area weighting analysis result was
Tengchong County (see Fig. 5).