# Precipitation Dominates the Distribution of Species Richness on the Kunlun-Pamir Plateau
## 3 Results
### Species Richness and Productivity Hypothesis  
The high density of a species is mainly spread in the marginal regions of the Kunlun-Pamir Plateau, characterized by relatively small areas (Figure 5). The dense distribution of species is primarily detected in the frontier areas of the Kunlun-Pamir Plateau, with relatively small but insignificant differences in species' abundance in the central region (Figure 5). The species richness correlated positively with the cumulative DHI based on the FPAR for all four categories, with the Spearman rank correlation coefficients amounting to 0.36, 0.39, 0.39 and 0.08 for mammals, birds, breeding birds and non-breeding birds, respectively. However, there was also a considerable dispersion noticeable. The minimum DHI based on the FPAR predicted that the species richness was higher when the minimum DHI based on the FPAR was larger. In this case, the positive correlation coefficients were 0.19, 0.22, 0.22 and 0.04 for mammals, birds, breeding birds and non-breeding birds, respectively. The scatter plots of the minimum DHI based on the FPAR versus the species richness for the four taxa were similar to those of the cumulative DHI based on the FPAR and variation DHI based on the FPAR. The variation DHI based on the FPAR predicted that  
Figure 3: Spearman rank correlations and scatter plots among the three DHIs derived from various MODIS products. Significant relations: \({}^{***}\)\(p\)\(<\) 0.001.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Cumulative DHI**} & \multirow{2}{*}{**RMSE**} & \multicolumn{2}{c}{**Minimum**} & \multirow{2}{*}{**RMSE**} & \multicolumn{2}{c}{**Variation**} & \multirow{2}{*}{**RMSE**} & \multicolumn{2}{c}{**All DHIs**} & \multirow{2}{*}{**RMSE**} \\  & \(\mathbf{R^{2}}\)**Adj** & & & & & & **DHI \(\mathbf{R^{2}}\)Adj** & & \\ \hline Mammals & 0.12 *** & 7.03 & 0.03 *** & 7.38 & 0.12 *** & 7.04 & 0.14 *** & 6.98 \\ Birds & 0.20 *** & 37.10 & 0.04 *** & 40.59 & 0.19 *** & 37.42 & 0.25 *** & 36.73 \\ Breeding birds & 0.20 *** & 34.95 & 0.05 *** & 38.17 & 0.18 *** & 35.40 & 0.24 *** & 34.66 \\ Non-breeding birds & 0.00 *** & 18.97 & 0.00 *** & 19.01 & 0.00 *** & 18.98 & 0.01 *** & 18.97 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Coefficient of determination between the individual FPAR-based DHIs of the four main taxa. Significant relations: \({}^{**}\)\(p\)\(<\) 0.01; \({}^{***}\)\(p\)\(<\) 0.001.  
the species richness would be higher when there was less variability. However, because most parts of the Kunlun-Pamir Plateau region are bare land and desert steppe, the species richness was higher when the environmental conditions were more variable. Indeed, the variability in the Kunlun-Pamir Plateau region correlated positively with the species richness for all four taxa, with positive correlation coefficients of 0.36, 0.4, 0.4 and 0.08 for mammals, birds, breeding birds and non-breeding birds, respectively. This implies that, for all four taxa, high values of the variability DHI based on the FPAR indicate a high species richness variation.  
Furthermore, the three DHIs based on the FPAR complement each other (Figure 6 and Table 3). A hierarchical partitioning analysis of the multiple regression models showed that all three DHIs based on the FPAR contributed considerably to the explanation of the overall variability in species richness. The cumulative DHI based on the FPAR was the most critical variable in each regression model, followed by the varDHI based on the FPAR and MinDHI based on the FPAR. According to the regression models, birds demonstrate the most explanatory power, and non-breeding birds exhibit the least explanatory power among these four categories (Figure 6).