Study area
The present study was undertaken at the Lanzhou University Research
Station in Maqu County, Gansu Province, China (101°53′E, 33°58′N, 3500 m
a.s.l.). This area is located in the northeast of the QTP. The climate
is cold and humid, with only a warm season (May to September) and cold
season (October to April) (Sun et al. 2015). There is no absolute
frost-free period throughout the year. The annual average temperature is
about 1.2 °C, and the highest temperatures are from June to August, with
an average of <12 °C; the lowest temperatures (average of −10
°C) are from December to February. The average annual rainfall is
~620 mm, which occurs mainly during the forage growing
season (May to September). These soils are classified as Mat-Cryic
Cambisols based on previous experimental work (Sun et al. 2015), and the
vegetation is characteristic of a typical alpine meadow (Yang et al.
2019). Cyperaceae (Kobresia graminifolia , Kobresia
humilis , and Kobresia pygmaea ) constitute the constructive
species, and Gramineae (Elymus nutans and Poa pratensis ),
Compositae (Saussurea hieracioides , Aster
diplostephioides , and Anaphalis lacteal ), Ranunculaceae
(Saussurea hieracioides , Anaphalis lacteal , Anemone
rivularis , Anemone trullifolia , and Anemone obtusiloba ),
and other associated plants are widely distributed among them, in
addition to scattered Potentilla fruticosa shrubs (Yang et al.
2019). The entire study area has undulating mountains, with steep and
changeable, complex, and fragmented terrain.