Effects of grazing on a Leymus chinensis grassland on the Songnen plain of north-eastern China

A field study was carried out in 1989 to quantify the effects of grazing on soil and plant properties in a Leymus chinensis grassland on the Songnen plain of north-eastern China. Five intensities of grazing were examined using 15 sample plots in each. Soil bulk density and pH increased with grazing intensity, while soil moisture and organic matter decreased. As the canopy covers of more palatable plants, such as L. chinensis and legumes, diminished, those of less palatable plants, such as Suaeda corniculata and Aeluropus littoralis, increased significantly. Changes in floristic composition were reflected primarily in decreases in the numbers of perennial mesophytes (such as L. chinensis, Calamagrostis epigeios and legumes), and increases in annual grasses (especially Chloris virgata) and halophytes (such as S. corniculata and Puccinellia tenuiflora), with halophytes becoming dominant under heavy grazing. Species diversity was greatest at the intermediate grazing intensities and least in the lightly grazed plots. Plant community biomass decreased significantly as grazing intensity increased-by as much as 47% (aboveground) and 53% (below-ground). Overgrazing appears to be the principal reason for deterioration of this grassland. (C) 1997 Academic Press Limited.