高寒草原紫花针茅和醉马草种间竞争对不同放牧强度的响应

Response of interspecific competition between Stipa purpurea and Achnatherum inebrians to different grazing intensities in an alpine steppe

在祁连山北坡中段甘肃马鹿(Cervus elaphus kansuensis)的冬季牧场,利用竞争指数、相对拥挤系数和相对竞争严重度指标,研究放牧强度对高寒草原优势种紫花针茅(Stipa purpurea)和退化草原优势种醉马草(Achnatherum inebrians)种间竞争的作用。结果表明,紫花针茅竞争指数在放牧强度梯度上呈先降低后升高再略有降低的趋势,在放牧强度3.45 AUM·hm^(−2)时最大,醉马草竞争指数在放牧强度梯度上呈先升高后降低再略有升高的曲线变化,在放牧强度3.45 AUM·hm^(−2)时出现谷值;竞争严重度指数在放牧强度梯度上呈先降低后升高再降低的趋势,紫花针茅的竞争严重度指数分别在2.45和4.85 AUM·hm^(−2)时最小和最大,醉马草的竞争严重度指数分别在1.45和3.45 AUM·hm^(−2)时最小和最大;紫花针茅的相对拥挤系数在放牧强度梯度上呈先增大后缓慢降低的曲线变化,醉马草的相对拥挤系数在放牧强度梯度上呈“单峰”曲线,在放牧强度4.85 AUM·hm^(−2)时最大。放牧强度在2.45~3.45 AUM·hm^(−2)时,紫花针茅有较高的竞争指数;放牧强度在2.45 AUM·hm^(−2)左右时,紫花针茅与醉马草的竞争严重度接近,紫花针茅不因醉马草的竞争压力过高而逐渐衰退,有利于草原的可持续放牧利用;放牧强度小于2.45 AUM·hm^(−2)时,紫花针茅和醉马草的拥挤压力均较低,且紫花针茅在竞争中占据优势,因此,祁连山北坡高寒草原适宜的冬季放牧强度为2.45 AUM·hm^(−2)左右。

Competition index,relative crowding coefficient,relative competition severity,and other analyses were used to study the effects of grazing intensity on competition between Stipa purpurea and Achnatherum inebrians in the winter pasture of Gansu Deer Farm located in the middle of the northern slope of Qilian Mountains,China.The competition index of S.purpurea showed a tendency to be initially low before rising and then decreasing slightly based on the grazing intensity gradient,which was largest at 3.45 AUM·ha^(−1).The competition index of A.inebrians showed a curve change,with an initial rise,followed by a decrease,then a slight increase on the grazing intensity gradient.The competition severity index of S.purpurea and A.inebrians both showed a trend featuring a decrease,increase,and decrease on the grazing intensity gradient.The smallest and largest competition severity index of S.purpurea was 2.45 and 4.85 AUM·ha^(−1),respectively.The smallest and largest competition severity index of A.inebrians was 1.45 and 3.45 AUM·ha^(−1),respectively.The relative crowding coefficient of S.purpurea showed a curve change,with an initial increase followed by a slow decrease on the grazing intensity gradient.The relative crowding coefficient of A.inebrians presented a“single peak”curve on the grazing intensity gradient,with a maximum value of 4.85 AUM·ha^(−1).The competition severity of S.purpurea and A.inebrians was very close at 2.45 AUM·ha^(−1).Stipa purpurea did not gradually degraded due to the excessively high competitive pressure of A.inebrians,which was conducive to the sustainable grazing and utilization of grassland.The pressing forces of S.purpurea and A.inebrians were both lower at the light grazing intensity(<2.45 AUM·ha^(−1));S.purpurea displayed an advantage in the competition.Based on the principle of equal emphasis on economic benefits and sustainable utilization,the suitable grazing intensity is approximately 2.45 AUM·ha^(−1)for the alpine grasslands in the Qilian Mountains.