不同放牧率对大针茅种群结构的影响

 采用连续放牧的方式研究了不同放牧率对大针茅(Stipa grandis)种群结构的影响。研究结果表明：在一定放牧率范围内，单丛分蘖密度随着放牧率的增加而增加，超过这个范围，单丛分蘖密度下降；单位面积生殖枝数、结实数和种子重随放牧率的增加而下降，种子千粒重在轻度和中度放牧率下最大；不同年龄株丛的分蘖密度存在很大差异，老龄株丛的分蘖密度最大，其次是成年株丛，幼龄株丛最小；轻度和中度放牧率能够刺激成年和老龄株丛分蘖，增加其单丛分蘖密度；老龄株丛在种群的有性生殖中占有重要地位，其生殖枝数目高于成年株丛。

INFLUENCE OF GRAZING RATE ON POPULATION STRUCTURE OF STIPA GRANDIS

The experiment on the influence of continuous grazing rates on population structure of Stipa grandis was conducted over two years. The following results were obtained. Within the certain scope of grazing rates, the tiller density per bunch increased along with the increase of grazing rate, and decreased outside the scope. The numbers of reproductive shoots and seed, and the weight of seed per unit area decreased with increased grazing rate, while the weight of 1000 seeds was highest under light and moderate grazing. There was a significant difference in tiller density among different age groups, in which the highest tiller density occurred in senior bunches; tiller density was lowest in juvenile bunches, while adult bunches showed intermediate tiller density. The light and moderate grazing rates can punctuate the adult and senior bunch tillering, and increase their tiller density. Senior bunches possessed an important position in the sexual reproduction of the population, and the number of reproductive shoots present was higher than that of adult bunches.