Research area
The Yili Valley (42°14′–44°53′N, 80°09′–84°56′E) lies in the
westernmost part of the Tianshan Mountain Range in the Xinjiang
Autonomous Region. The region has an average annual temperature and
precipitation of 10.4°C and 417.6 mm, respectively. Yili Valley can be
thought of as a wet island in the arid area of Xinjiang, as it has an
abundant and unique set of plant species, and the valley is listed as
one of five most important areas of terrestrial biodiversity in China
(Chen, 1993).
Xinyuan County (43°03′–43°40′N, 82°28′–84°56′E) is located in the
hinterland of the Gongnaisi grassland in the eastern part of the Yili
Valley. This site is the main distribution area of A.
artemisiifolia and A. trifida. The average annual temperature
and precipitation are 8.1°C and 480 mm, respectively. We studied the
interspecific competitive ability, seed size, and water demand
differences between the two species in farmland ecotone, residential
area, roadside, and grassland in Xinyuan County, because these four
habitats were the main distribution areas of the two species (Dong et
al., 2017), and there were relatively large differences in water status,
temperature status, and companion species between those four habitats.