Energy-water and seasonal variations in climate underlie the spatial distribution patterns of gymnosperms species richness in China

Studying the pattern of species richness is crucial in understanding the
diversity and distribution of organisms in the earth. Climate and human
influences are the major driving factors that directly influence the
large-scale distributions of plant species, including gymnosperms.
Understanding how gymnosperms respond to climate, topography, and
human-induced changes is useful in predicting the impacts of global
change. Here, we attempt to evaluate how climatic and human-induced
processes could affect the spatial richness patterns of gymnosperms in
China. Initially, we divided a map of the country into grid cells of 50 ×
50 km2 spatial resolution and plotted the geographical coordinate
distribution occurrence of 236 native gymnosperm taxa. The gymnosperm taxa
were separated into three response variables: (i) all species, (ii)
endemic species, and (iii) non-endemic species, based on their
distribution. The species richness patterns of these response variables to
four predictor sets were also evaluated: (i) energy-water, (ii) climatic
seasonality, (iii) habitat heterogeneity, and (iv) human influences. We
performed generalized linear models (GLMs) and variation partitioning
analyses to determine the effect of predictors on spatial richness
patterns. The results showed that the distribution pattern of species
richness was highest in the southwestern mountainous area and Taiwan in
China. We found a significant relationship between the predictor variable
set and species richness pattern. Further, our findings provide evidence
that climatic seasonality is the most important factor in explaining
distinct fractions of variations in the species richness patterns of all
studied response variables. Moreover, it was found that energy-water was
the best predictor set to determine the richness pattern of all species
and endemic species, while habitat-heterogeneity has a better influence on
non-endemic species. Therefore, we conclude that with the current climate
fluctuations as a result of climate change and increasing human
activities, gymnosperms might face a high risk of extinction.