2.1 Plant and soil materials
Grass seeds of drooping
wildryegrass, crymophila bluegrass, Kentucky bluegrass, Chinese fescue
and Siberian wildryegrass
(Elymus sibiricus ) were harvested in September 2019 and provided
by Tongde Forage Seed Production Base (35°15′N, 100°38′E) of Qinghai
Province, which is located at the eastern Tibetan Plateau. Crop seeds of
hulless barley (Hordeum vulgar var. nudum ), oat
(Avena sativa ), wheat (Triticum aestivum ), quinoa
(Chenopodium quinoa ) and rape (Brassica napus ) which have
been harvested in 2019 were acquired from the Academy of Agriculture and
Forestry Sciences, Qinghai University. These crops can grow well in the
agricultural area of the province. All seeds were stored in the
refrigerator at 4°C before experiment. Plants of drooping wildryegrass
were collected in early August 2019, when the plant growth was in peak
period. Robust whole drooping wildryegrass plants with roots were dig
out with a small shovel. The plants were cut into aerial parts and below
ground parts on site. The root zone soils were collected by shaking the
roots parts. All plant and soil materials were put in plastic bags and
kept in a refrigerator and taken back to the laboratory for experiment.