川西北地区老芒麦人工草地生长季种群数量和构件对不同放牧强度的响应

Response of Quantity and Components of Elymus sibiricus L.Community in Artificial Grassland in Northwest Sichuan to Different Grazing Intensity in Growing Season

为探讨老芒麦人工草地适宜的放牧强度,在生长季设置对照(扣笼)、轻度、中度和重度4个放牧强度进行划区轮牧试验,采用对角线随机样方取样法对老芒麦种群数量特征和构件特征进行取样调查和室内测定,结果表明:不同放牧强度下老芒麦种群的数量特征(高度、盖度、密度、地上生物量和重要值)随放牧强度的增加显著下降;生长季内随着放牧月份的增加,老芒麦的高度和地上生物量呈抛物线变化,盖度变化不明显,密度和重要值略有下降。老芒麦茎叶比在各放牧强度间变化不显著,叶片数、生殖枝数和叶面积指数随放牧强度的增大显著下降;生长季内叶片数和叶面积指数在7月和8月显著大于其他月份,生殖枝数呈下降趋势,茎叶比9月最大。不放牧时老芒麦种群数量特征和构件特征表现最优,超过轻度(利用率50%)及以上放牧强度时显著影响老芒麦的生长发育,降低老芒麦的优势度。

To inquire into suitable grazing intensity of the artificial grassland of Elymus sibiricus L. , CK（cage）, four grazing intensity, light grazing LG （feed rate 50%）, moderate grazing MG （feeding rate 70%） and heavy grazing HG （feeding rate 90%） , were set, the diagonal random quadrat sampling meth od was adopted, a rotational grazing experiment was conducted in growing seasons, the quantitative char- acteristics and components characteristics of Elymus sibiricus community were investigated and tested, the results showed that ： 1） The height, coverage, density, biomass and important value of Elymus sibiricus L. were significantly decreased with the increase of the grazing intensity （P〈0.05）; In the growing season, the height and biomass of Elymus sibiricus L. changed in an unimodal parabola, coverage did not change significantly, density and important value decreased gradually. 2） The ratio of stem to leaf of Elymus sibiricus L. was not changed significant between grazing intensity, leaf number, reproductive branches number and leaf area index declined with the increase of grazing intensity, exceeded the LG and reached significant level （P〈0.05） ; In growing season, leaf number and leaf area index in July and August were lager than other month（P〈0.05）, the number of reproductive branch was in the order： August（96. 313 branches/m2）;September（63.511 branches/m2）;October（44. 556 branches/m2）, ratio of stem to leaf was the largest in September. When not grazing the number of features and components of Elymus sibiricus L. was in the optimal performance, more than moderate （feeding rate 50%） , significantly influenced the growth and development of Elymus sibiricus L. and and the grazing intensity reduced the dominance of the Elymus sibiricus L.