Heat wave mitigation of ecosystems in mountain areas — a case study of the Upper Yangtze River basin

Figures & data

Figure 1. Location of the study area.

Table 1. Area type classification standards (Li, Pan, and Han 2008; Chenghu et al. 2009).

Type of land area	Amplitude of landforms (m)
Plain	<30
Hill	30–200
Mountain	>200

Table 2. Indicators for the classification of mountainous areas (Li, Pan, and Han 2008; Chenghu et al. 2009).

Type of mountain area	Indicators
Plain area	Area of the plain is larger than that of the hills and mountains
Plateau area	Area of the plain is larger than that of the hills and mountains, and the range is located in the Qinghai-Tibet Plateau
Hilly area	Area of the hills is larger than that of the plain and mountains
Half-mountain area	Area of the mountains is larger than that of the plain and hills, and the percentage of mountainous area is <60%
Quasi-mountain area	Area of the mountains is larger than that of the plain and hills, and the percentage of mountainous area is ≥60% and <80%
Explicit mountain area	Area of the mountains is larger than that of the plain and hills, and the percentage of mountainous area is ≥80% and <100%
Whole mountain area	Mountainous areas comprise the entire region

Table 3. Comfort classification for the temperature humidity index (THI) (Bostan, Timofte, and Leontie 2011).

THI	Human body sensation degree	Grade
<40	Very cold, very uncomfortable	1
40–45	Cold, uncomfortable	2
45–55	Colder, less comfortable	3
55–60	Cool, comfortable	4
60–65	Cool, very comfortable	5
65–70	Warm, comfortable	6
70–75	Hot, comfortable	7
75–80	Hot, uncomfortable	8
>80	Extremely hot, very uncomfortable	9

Figure 2. Frequency and duration of summer heat waves from 1986 to 2015.

Figure 3. (a) Cumulative frequency and (b) duration of summer heat waves in number of days from 1986 to 2015.

Figure 4. Spatial pattern in monthly mean summer THI from 1986 to 2015 in the months of (a) June, (b) July, and (c) August.

Figure 5. Cumulative number of suitable days during the summer months in 1986–2015.

Table 4. Calculated variations in the total number of suitable days during the summer months from 1986 to 2015.

Suitable days and proportion of summer months	Formula	R^2	P
Suitable days in June	y = −0.0096x + 3.5082	0.0134	<0.1
Suitable days in July	y = −0.0125x + 2.2917	0.0911	<0.1
Suitable days in August	y = −0.004x + 2.5346	0.0039	<0.1

Figure 6. Spatial pattern in the number of average suitable days from 1986 to 2015 in the months of (a) June, (b) July, and (c) August.

Figure 7. Average number of suitable days during the summer months in each type of mountain area from 1986 to 2015.

Table 5. Effects of factors on the suitable days from June to August.

Geomorphological area	Precipitation			Altitude			Topographic Relief			Vegetation Area			Soil Moisture
	June	July	August	June	July	August	June	July	August	June	July	August	June	July	August
Plain area	0.605**	−0.066	−0.142*	0.859**	0.899**	0.887**	0.314**	0.348**	0.345**	−0.119*	−0.128*	−0.123*	0	0	0
Hilly area	0.045	0.016	−0.063**	0.806**	0.683**	0.746**	0.157**	0.157**	0.13**	0.154**	0.130**	0.131**	0.114**	0.015	0.001
Quasi mountain area	−0.108**	0.073	0.178**	0.794**	0.667**	0.712**	0.108**	0.04	0.04	0.135**	0.142**	0.156**	0.100*	0.106**	0.122**
Semi mountain area	−0.083	0.131*	0.138*	0.805**	0.687**	0.729**	0.046	−0.032	−0.014	−0.074	−0.035	−0.047	0.063	0.12	0.121
Explicit Mountain area	−0.200**	0.105**	0.248**	0.798**	0.675**	0.675**	0.675**	0.201**	0.207**	0.127**	0.273**	0.232**	0.179**	0.153**	0.176**
Whole mountain area	0.212**	0.318**	0.485**	0.728**	0.630**	0.683**	0.406**	0.359**	0.374**	−0.031	0.087*	0.067*	0.155**	0.098**	0.126**
Plateau area	0.268**	0.305**	0.451**	−0.415**	−0.127**	−0.291**	0.596**	0.398**	0.481**	−0.156**	−0.135**	−0.142**	0.575**	0.356**	0.466**

*mean P < 0.05, ** mean P < 0.01.

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