K. pygmaea
As the
ratio
between aboveground and belowground biomass decreases with livestock
grazing intensity (Cao et al., 2010), grazing can also stimulate root
production, increase soil compactness
(Fan
et al., 2020), decrease water infiltration
(Dai
et al., 2019), increase the density of dead roots in the core areas of
mini-patches, and expand the area of bare mini-patches
(Lin,
2017). Thus, the aforementioned asexual reproductive strategy of the
dominant species can lead to two results under increasing grazing
intensity: increase in bare areas, and the internodes becoming even
shorter as the mattic epipedon further thickens
(Zhu,
2002).
In alpine Kobresia meadows, the formation of mattic epipedon is
an adaptive response to livestock trampling and grazing disturbance (Hou
et al., 2004). The thickening of mattic epipedon due to overgrazing can
affect soil nutrient and water availability and thus change the growth
and composition of the plant community. For example, as the niche of
Gramineae-type plants (including Gramineae and Cyperaceae functional
groups) narrows, the resulting empty resource spaces can be occupied by
poisonous
or
inedible plants that are resistant to trampling and grazing (Lin, 2017).
In this manner, the vegetation could maintain high productivity during
the growing period and reduced the utility of the pasture for livestock
production. This strategy allows a damaged alpine meadow to recover its
functional ecology via
a
new succession process and thereby to adapt to overgrazing. Prior
research calculated that it would take 70–80 years for black-soil
beach-type grassland to recovery toK.
pygmaea meadow in an area with no grazing
(Chen,
2016).
An alpine meadow could also maintain relatively stable productivity when
Gramineae had been reduced as the remaining resources were used by
subdominant, poisonous, and inedible species, particularly in heavily
disturbed ecosystems. This leads to different plant communities forming
in the same topographic and climatic environment and ultimately
large-scale multi-stable coexistence (Cao et al., 2007). Therefore, the
degradation of alpine meadows to areas with lower edible grass
productivity is also a self-regulating process that prevents the
occurrence of heavy disturbances.
K.
pygmaeameadows
occur across a wide region of the Qinghai-Tibet
Plateau
and can tolerate substantial livestock grazing intensity.
This
characteristic was dependent on the steady condition maintained by
Cyperaceae plant functional groups, without which these meadows lost
their utility for livestock grazing. Therefore, K. pygmaeameadows were considered the
last
line of defense against alpine meadow degradation and were the key to
improving alpine meadow productivity.