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.