Heavy grazing led to the decrease of competitive intensity relationships
among dominant populations of clustered grasses in a desert steppe
Abstract
Stipa breviflora (Stipa breviflora Griseb.) and Cleistogenes songorica
(Cleistogenes songorica (Roshev.) Ohwi) are two dominant species in the
critically important desert steppe of northern China. Under the
interference of grazing, the two species will have the phenomenon of
plant cluster fragmentation to varying degrees. Therefore, when the two
plant populations appear in the same plant community, what changes will
happen in the inter-specific relationship during grazing has important
guiding significance for its regulation of plant community and function.
To study this, we observed populations of wild S. breviflora and C.
songorica in field under a suite of grazing intensities and at a variety
of scales. The density changes of dominant species S. breviflora and C.
songorica in desert steppe in Inner Mongolia were studied under four
grazing intensities (no grazing, CK, 0 sheep·ha-1·half year-1, light
grazing, LG, 0.93 sheep·ha-1·half year-1, moderate grazing, MG, 1.82
sheep·ha-1·half year-1, heavy grazing, HG, 2.71 sheep·ha-1·half year-1)
and six scales (5 cm×5 cm, 10 cm×10 cm, 20 cm×20 cm, 25 cm×25 cm, 50
cm×50 cm and 100 cm×100 cm). Results showed that grazing changes the
relationship between dominant species. With the increase of grazing
intensity, the densities of S. breviflora and C. songorica increased,
and the increase was more obvious with the increase of scale. Under
heavy grazing conditions, the dominant populations of clustered grasses
in Inner Mongolia desert steppe resisted the interference of
high-intensity grazing by reducing inter-specific competition ability
(increasing inter-specific affinity).