放牧调控对短花针茅种群年龄及叶性状的影响

草食动物对植物种群结构和功能的调控机制是放牧生态学研究的重要内容。本研究以内蒙古锡林郭勒盟苏尼特右旗荒漠草原的长期放牧控制实验为平台,通过研究荒漠草原建群种短花针茅种群年龄动态与其相应叶性状,以期揭示荒漠草地放牧调控下植物响应机制。结果显示,1)短花针茅种群基径小于4 mm部分植株存活数少;适度放牧处理短花针茅各年龄阶段频度与不放牧基本一致,重度放牧处理龄级Ⅲ的频度和比例分别下降了0.79,0.73;2)短花针茅种群龄级Ⅰ与龄级Ⅱ的短花针茅频度和比例较高,龄级Ⅲ相对较低,属于比较稳定的种群;Godron指数显示短花针茅年龄结构的稳定性重度放牧>适度放牧>不放牧;3)放牧调控下,叶高、叶长、叶干重、叶直立度、叶长宽比为年龄型敏感性状,自然叶宽、完全叶宽、叶卷曲度、叶干物质含量为年龄型保守性状;4)相关分析认为自然叶宽和叶干物质含量与各年龄型敏感性状基本呈协同变化;叶卷曲度与叶干重负相关(P<0.05),与叶直立度呈正相关(龄级Ⅲ、龄级Ⅰ)。研究认为,短花针茅种群在亚稳定下,通过控制种群年龄及叶性状,来完成其生活史对放牧调控的适应。

Effect of grazing on Stipa breviflora age dynamics and leaf traits

The regulation mechanism of plant population structure and function by herbivores is an important part of grazing ecology.A long-term grazing study in Xilingol was used to reveal the mechanisms of the regula-tion of plant responses to grazing through population age dynamics and leaf traits of Stipa breviflora in desert grassland.The result showed that few S .breviflora plants with base diameter of less than 4 mm survived. There was little difference between moderate grazing and no grazing.The frequency and proportion of age classⅢ plants was reduced 0.79 and 0.73 respectively by heavy grazing.S .breviflora population were relatively stable.Two way ANOVA showed that leaf height,leaf length,leaf dry weight,leaf erectness and leaf length-width ratio were sensitive to grazing in different age classes.By contrast,leaf width,leaf rolling index and leaf dry matter content were not affected by age class.Correlation analysis suggested that leaf width and leaf dry matter content changed synergistically with the age sensitive traits.Leaf rolling index was significantly nega-tively correlated with leaf dry weight,and was positively related with leaf erectness (e.g.age class Ⅲ and classⅠ).The study suggested that S .breviflora completed its life history and adapted to grazing by controlling population age and leaf traits in a metastable state.