Spatial distribution and its limiting environmental factors of native orchid species diversity in the Beipan River Basin of Guizhou Province, China

Understanding the distribution of biodiversity and its determinants,
particularly that of ecologically sensitive ones, has long been intriguing
to the science community and will help formulate conservation strategies
under future climate changes. To this end, we conducted extensive field
surveys on the distribution of orchid flora in the Beipan River Basin in
Guizhou Province, which is one of the biodiversity conservation priorities
in China. The data we acquired, together with those published previously,
were converted into orchid species richness for each of the 3km × 3km grid
cells covering the study region. Redundancy analysis (RDA) and
Geographically Weighted Regression (GWR) were then applied to determine
which of the 30 environmental factors are potentially critical for the
spatial distribution of orchid flora we have observed. Despite a moderate
spatial extent, we found that the Beipan River Basin harbors about 249
native orchid species belonging to 74 genera, equivalent to 14.5% of
orchid flora of China. Orchid species richness in this area follows a
descending gradient from the southeast to the northwest, 70.41% of its
variation among grid cells can be explained by environmental factors and
spatial variables, and spatial variables accounted for 63.90% of the
spatial variation of orchid distribution, indicating that spatial
variables played a dominant role in the distribution of wild orchidaceae
species richness. In addition, the main environmental driver is the mean
temperature of the wettest quarter. Our study provides a good example for
revealing the main drivers of orchid distribution characteristics, and has
a certain reference value for the development of orchid conservation
strategies.