The subalpine and alpine meadow vegetation in Wutai Mountain, North China, distributed in altitude from about 2400 m a.s.l. through to 3061 m a.s.l. at the summit, serves as the largest summer mountainous pasture for cattle grazing around the local area. However, the degradation with different grades owing to overgrazing occurred in the meadow has been observed in both vegetation and soil. Referring to features of vegetation, five grades of meadow degradation relating to different grazing pressure have been recognized in the area through our earlier studies.
This paper,based on the analysis in nutrient composition and palatability of herbage, aimed to determine the effects of grazing intensity on herbage quality of the subalpine and alpine meadow vegetation within Wutai Mountain. In total 85 quadrat (sized in 1m×1 m) data sampled during the field survey in 2006 were involved in the analysis.
The results showed that: (1) According to animals' grazing behavior, the grass species in meadows were grouped into six herbage grades in eating-palatability as, addicted-to, delighted-in, happy-to, just-pick-at, little to and never-touch. In the meadows under conventional interference of grazing, the most palatable herbages (species in the addicted-to and the delighted-to groups) reached 20 species, while in the extremely degraded meadows, those species appeared only down to 13. Also, according to the relative cover of a meadow community, which was classified into five grades in light of meadow degradation owing to grazing, the highest relative average cover emerged at meadows under conventional interference was held by the herbage group of delighted-in eating, reaching up to 45.40%, whereas the highest relative average cover in the extremely degraded meadows went to the herbage group of happy-to eating, as 62.24%. The highest relative average cover composited by herbage groups of happy-to eating and over appeared in the light degraded meadows, accounting to 65.59%. (2) The herbage species in the same palatable level changed in different grades of degraded meadows. For example, in the meadows under conventional interference that were graded at most favorable for cattle grazing, the species composition consisted mainly of Festuca rubra, Kobresia pygmaea and Libanotis condensate, whereas in contrast those most unfavorable for cattle grazing due to overgrazing in the past, the extremely degraded meadows, consisted mainly of Carum carvi, Koeleria cristata and Polygonum aviculare, regarded as unpalatable species. (3) The heavily-intensified grazing increased the contents of crude protein and ash in herbage, but decreased the neutral detergent fiber and acid detergent fiber. Although the herbage quality as referring to its biochemical composition was not much changed or even improved when grazing pressure was intensified, the quantity of herbage available for cattle grazing was decreased, which much reduced the economic gains and even may confine the sustainable use and natural conservation of meadow resources.