Effects of Cutting and Grazing on Vegetation and Productivity of Shrub-steppe in the Loess Plateau, North-west China

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  • 中国北西部の黄土高原におけるかん木ステップの植生と生産性におよぼす刈取りと放牧の影響

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Abstract

The Loess Plateau, situated in north-west China, has been subjected to degradation of vegetation owing to overgrazing. In order to clarify the effects of grazing and cutting on vegetation and productivity of shrub-steppe, the study was carried out from May in 1989 to October in 1991 in the Pastoral Preserving Zone of Yunwu Mountain. The vegetation was monthly surveyed, and DM weights of dominant species were separately measured. Soil samples were taken at three selected sites and one overgrazed site and these chemical analysis were made. Relative abundance of species was calculated on the base of the total frequency of 7835. Gramineae showed the highest value (26 %), followed by Compositae (24 %) and Leguminosae (12 %). During 3 experimental years, the significant increasers were T i onella ruthenica and Potentilla acaulis, and the significant decreasers were Poa sphondylodes, Agropy n cris atum, Potentilla bifurca and Heteropappus altaicus. Species diversity was apparently lower in the cutting plots than in the other plots. According to the result of ordination by principal component analysis, T igonella ruthenica, Carex spp., Aneurolepidium dasystachys and Thermopsi lanceolata were indicator species under natural recovery from overgrazed condition. Artemisia frigida and Potentilla acaulis were typical species in grazing plots. According to monthly aerial DM productions, Stipa bungeana showed excellent regrowth after cutting or grazing, and contributed to higher aerial DM production. Stipa ungeana showed significantly lower values of important nutritional elements and higher values of neutral detergent fiber than other species. The result of soil analysis suggests that total carbon and phosphorus contents may relate with the rate of the rehabilitation from overgrazed condition of steppes.

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