3.2. The main environmental variables affecting the distribution of Campsis grandiflora
Among the 11 environmental variables, the environmental variables with top three contribution rate of were precipitation of driest month (bio14, 46.1% contribution), precipitation of the warmest quarter (bio18, 14.6% contribution), and mean temperature of the warmest quarter (bio10, 9.2% contribution), accounted for almost 69.9% of the model prediction (Table 3). Considering the importance of permutation, altitude (22.5% contribution), temperature annual range (bio7, 22.1% contribution) and mean temperature of the coldest quarter (bio11, 14.7% contribution) were much higher than others. Meanwhile, the jackknife test showed that the mean temperature of the coldest quarter (bio11), mean diurnal range (bio2), and precipitation of driest month (bio14) were the main variables (Fig. 3).
To summarize, temperature (bio2, bio7, bio10, and bio11), precipitation (bio14, bio18) and altitude played a vital role in predicting the probable distribution of Campsis grandiflora. By the response curve (Fig. 4), we got thresholds (probability of presence > 0.5) for the main bioclimatic parameters. Mean diurnal temperature range ranged from 7.3 to 9.5 ℃, range of annual temperature ranged from 28 to 33 ℃, mean temperature of the warmest quarter ranged from 25.5 to 28 ℃, mean temperature of the coldest season ranged from 5 to 15 ℃, driest monthly precipitation ranged from 30 to 100 mm, precipitation of the warmest quarter ranged from 500 to 720 mm and altitude ranged from 400 to 1200 m.
3.3. Current potential distribution
Campsis grandiflora mainly distributes in northern China, central China, southern China, and eastern China (Fig. 5). Among them, the area of highly suitable habitat mainly distributes in the northeast and southeast parts of Jiangxi and Hunan, the northeast part of Sichuan, and the southeast and northeast part of Hubei, and so on. The area of moderately suitable habitat mainly distributes in the coastal and southern Shandong, western Hunan, eastern Sichuan, and Hubei. The area of poorly suitable habitat mainly distributes in central Yunnan, eastern Guizhou, southern Sichuan, western Guangxi, and northern, western, and eastern Henan.
According to the classification of suitable habitats, the areas of suitable habitat in each province were calculated (Table 3). The suitable distribution area of Campsis grandiflora in China is 238.29×104 km2. The area of highly suitable habitat is 50.05×104 km2, accounting for 21% of the suitable area. The area of moderately suitable habitat is 72.75×104 km2, accounting for 30.53% of the suitable area. The area of poorly suitable habitat is 115.49×104 km2, accounting for 48.47% of the suitable area. Jiangxi, Hunan, Sichuan, Guangxi, and Guangdong have relatively large areas of highly suitable habitat. Among them, the suitable distribution area of Campsis grandiflora in Jiangxi is 10.90× 104 km2, ranking first in China. Sichuan, Hubei, Hunan, and Shandong have larger moderately suitable habitat areas than other provinces. There is no suitable distribution area of Campsis grandiflora in Inner Mongolia, Jilin, Ningxia, Heilongjiang, Taiwan and Xinjiang.
Table 3 The potential distribution areas for Campsis grandiflora under current climatic conditions.
Province municipality autonomous regions
|
Poorly suitable habitat(104km2)10-30%
|
Moderately suitable habitat(104km2)30-50%
|
highly suitable habitat(104km2)≥50%
|
Total suitable habitat(104km2)
|
Beijing
|
0.92
|
0.17
|
0.00
|
1.09
|
Tianjin
|
0.57
|
0.19
|
0.03
|
0.79
|
Hebei
|
7.04
|
0.80
|
0.02
|
7.86
|
Shanxi
|
1.81
|
0.00
|
0.00
|
1.81
|
Inner Mongolia
|
0.00
|
0.00
|
0.00
|
0.00
|
Liaoning
|
2.06
|
0.17
|
0.01
|
2.24
|
Jilin
|
0.00
|
0.00
|
0.00
|
0.00
|
Heilongjiang
|
0.00
|
0.00
|
0.00
|
0.00
|
Shanghai
|
0.18
|
0.10
|
0.03
|
0.31
|
Jiangsu
|
2.79
|
4.20
|
1.06
|
8.05
|
Zhejiang
|
2.93
|
3.48
|
2.21
|
8.62
|
Anhui
|
3.63
|
6.32
|
2.39
|
12.34
|
Fujian
|
3.77
|
2.75
|
3.38
|
9.9
|
Jiangxi
|
1.39
|
2.83
|
10.90
|
15.12
|
Shandong
|
6.43
|
6.57
|
0.46
|
13.46
|
Henan
|
11.02
|
3.35
|
0.21
|
14.58
|
Hubei
|
5.39
|
6.95
|
4.37
|
16.71
|
Hunan
|
3.67
|
6.66
|
8.68
|
19.01
|
Guangdong
|
6.03
|
3.49
|
4.05
|
13.57
|
Guangxi
|
8.36
|
5.70
|
4.48
|
18.54
|
Hainan
|
1.09
|
0.20
|
0.00
|
1.29
|
Chongqing
|
2.41
|
2.89
|
1.97
|
7.27
|
Sichuan
|
9.70
|
7.56
|
4.99
|
22.25
|
Guizhou
|
10.11
|
3.92
|
0.26
|
14.29
|
Yunnan
|
13.70
|
2.59
|
0.47
|
16.76
|
Tibet
|
2.78
|
0.24
|
0.03
|
3.05
|
Shaanxi
|
5.71
|
1.47
|
0.07
|
7.25
|
Gansu
|
1.49
|
0.15
|
0.01
|
1.65
|
Ningxia
|
0.00
|
0.00
|
0.00
|
0.00
|
Xinjiang
|
0.00
|
0.00
|
0.00
|
0.00
|
Taiwan
|
0.51
|
0.00
|
0.00
|
0.00
|
Xianggang
|
0.01
|
0.00
|
0.00
|
0.01
|
Total(China)
|
115.49
|
72.75
|
50.05
|
238.29
|
3.4. Future potentially suitable climatic distribution
In the SSP1-2.6 and SSP5-8.5 climate change scenarios for the 2050s and the 2070s, predictions of the future potentially suitable distributions of Campsis grandiflora are illustrated (Fig. 6).
Our study shows that for the 2050s & SSP1-2.6 case, the moderately suitable habitat area of Campsis grandiflora will be 50.05×104 km2, the highly suitable habitat area of Campsis grandiflora will be 157.85×104 km2, and the total habitat area will be 275.72×104 km2. The total suitable habitat of Campsis grandiflora will mainly be located in the north and east part of Guangdong, northeastern Guangxi, northern and southern Yunnan, eastern Sichuan, northern Chongqing, northern Sichuan, southern and eastern Hubei, southern Shanxi, eastern and southern Henan, central and southern Anhui, western Jiangsu, the east part of Shanghai, west and north part of Zhejiang, west and south part of Fujian, central Shandong, south and east part of Hubei, Jiangxi and Hunan.
For the 2050s & SSP5-8.5 case, the moderately suitable habitat area will be 45.06×104 km2, the highly suitable habitat area will be 148.41×104 km2, and the total suitable habitat area will be 261.62×104 km2. The total suitable habitat will mainly be distributed in northern Guangdong, northern and eastern Guangxi, central and eastern Hunan, eastern Sichuan, eastern Chongqing, eastern Hebei, southern Liaoning, northern and eastern Hunan, northern, southern and eastern of Hubei, southern, and eastern Henan, southern and eastern Anhui, northern and southern Jiangsu, Shandong, Zhejiang, Fujian and Jiangxi.
For the 2070s & SSP1-2.6 case, the moderately suitable habitat area will be 54.54×104 km2, the highly suitable habitat area will be 142.88×104 km2, and the total suitable habitat area will be 273.64×104 km2. The total suitable habitat is not much different from that in the 2050s under SSP1-2.6.
For the 2070s & SSP5-8.5, the moderately suitable habitat area will be 35.57×104 km2, the highly suitable habitat area will be 211.51×104 km2, and the total suitable habitat area will be 302.91×104 km2. The total suitable habitat will mainly be distributed in southern Shaanxi, central and eastern Henan, southern Hebei, southern Hubei, northern Guizhou, Sichuan and Chongqing, Shandong, Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, Guangdong, Guangxi and Hunan. The main distribution area will be larger than the first three climate scenarios, the total suitable area will be the largest, and the highly suitable habitat will be the largest. However, the moderately suitable habitat area will be the smallest.
Table 4 Suitable areas for Campsis grandiflora under different climatic conditions.
Decades Scenarios
|
Predicted area/104km2
|
poorly suitable habitat
|
moderately suitable habitat
|
highly suitable habitat
|
Total suitable habitat
|
current
|
115.49
|
72.75
|
50.05
|
238.29
|
2050s,SSP1-2.6
|
67.82
|
50.05
|
157.85
|
275.72
|
2050s,SSP5-8.5
|
68.15
|
45.06
|
148.41
|
261.62
|
2070s,SSP1-2.6
|
76.22
|
54.54
|
142.88
|
273.64
|
2070s,SSP5-8.5
|
73.83
|
35.57
|
211.51
|
302.91
|
Under SSP1-2.6, the lost area of the Campsis grandiflora is 0.18×104 km2 during the 2050s, the area obtained will be 83.66×104 km2, and unchanged area will be 124.33×104 km2. The increasing area will be mainly distributed in the southern and eastern Hebei, the northern and the southern Shandong, southern Liaoning, northern Anhui, eastern Jiangsu, southern Fujian, western Sichuan, southern Guangxi, southern Guangdong, and Henan.
Under SSP5-8.5, the lost area of the Campsis grandiflora will be 0.07×104 km2 during the 2050s, the increasing area will be 99.18 ×104 km2 and the unchanged area will be 124.33×104 km2. The distribution range of increasing area will be similar to that in SSP1-2.6 for the 2050s.
Under SSP1-2.6, the loss area of the Campsis grandiflora will be 0.12×104 km2 during the 2070s, the area obtained will be 72.48×104 km2 and the unchanged area will be 124.71×104 km2. The distribution range of increased area will be similar to that under SSP1-2.6 in the 2050s.
Under SSP5-8.5, the loss area of the Campsis grandiflora will be 0.14×104 km2 during the 2070s, the area obtained will be 123.41×104 km2 and the unchanged area will be 123.71×104 km2. The increasing areas will mainly be distributed in southern and eastern Hebei, southern Liaoning, southern Shaanxi, northern and southern Shandong, southern Sichuan, northern Guizhou, central of Yunnan, southern Guangxi, southern Zhejiang, eastern Fujian, southern Guangdong, northern Hainan Island, and Hubei.
Table 5 Future changes in suitable habitat area.
Decades Scenarios
|
Predicted area/104km2
|
Loss
|
Gain
|
Unchanged
|
2050s,SSP1-2.6
|
0.18
|
83.66
|
124.33
|
2050s,SSP5-8.5
|
0.07
|
99.18
|
124.33
|
2070s,SSP1-2.6
|
0.12
|
72.48
|
124.71
|
2070s,SSP5-8.5
|
0.14
|
123.41
|
123.71
|