3.2 Main environmental factors affecting distribution of PWD
Table 2. Contributions of the climatic factors to the MaxEnt
model.
The contribution rate of climate factors to the adaptability of PWD in
China is shown in Table 2. The greater the contribution value is, the
greater the influence of this variable on the existence probability of
species. The climate factor with the largest contribution rate was
precipitation of the wettest quarter (bio16, 45.7%), followed by max
temperature of the warmest month (bio5, 27.5%), and coefficient of the
variation of precipitation seasonality (bio14, 16.1%). The cumulative
contribution rate was 89.3%, showing that these factors had the
greatest influence on predicting the probability of PWD. The relative
importance of each variable for predicting the probability of species
existence was obtained based on the jackknife of regularized training
gain in MaxEnt (Fig. 3). When only a single climatic factor was used,
the three climatic factors that had the greatest impact on regularized
training were coefficient of variation of precipitation seasonality
(bio14), precipitation of the wettest quarter (bio16), and mean
temperature of the driest quarter (bio9). In conclusion, the main
climatic factors affecting the potential geographical distribution of
PWD were temperature (max temperature of warmest month and mean
temperature of driest quarter), rainfall (coefficient of variation of
precipitation seasonality and precipitation of the wettest quarter). To
understand the relationship between existence probability of PWD
distribution and dominant environmental factors, a logistic curve
suitable for only a single environmental factor (max temperature of the
warmest month, mean temperature of the driest quarter, coefficient of
the variation of precipitation seasonality, and precipitation of the
wettest quarter) was drawn in the MaxEnt model (Fig. 4). The suitable
range was the probability of existence > 0.5. The suitable
range of max temperature of the warmest month was 31 -
33℃, the suitable range of mean
temperature of the driest quarter was 5.1 - 20℃, the suitable range of
the coefficient of variation of precipitation seasonality was 21 - 64,
and the suitable range of precipitation of the wettest quarter was 450 -
950 mm.
Fig 3. Jackknife test result of climatic factors for PWD.
Fig. 4. Response curves of the main environmental variables
affecting distribution of PWD.