2.1 Study area
We carried out this study in metropolitan Shenyang, Liaoning Province,
northeast China
(41o11’51”
~
43o02’13”N,122o25’09”
~ 123o48’24”E, Fig. 1A). Shenyang
city is a capital city of Liaoning province and had an estimated 2017
population of 5,864,912 people (Chinese Census Bureau, 2017). The urban
built-up area of Shenyang is within the third beltway and about 758.6
km2. Shenyang is an inland city with an average
altitude of 51 meter, belonging to the temperate semi-humid continental
climate zone. Its average annual temperature and annual precipitation
are 8.6℃ and 721.9 millimeter respectively. There are 7 districts and 76
subdistricts within the third beltway of Shenyang city (Fig. 1B).