放牧对布氏田鼠主要食物选择的影响

Influence of sheep grazing on major food selection by Brandt 'voles(Lasiopodpmys brandtii)

动物的食物选择受食物资源量、质量和喜好度决定。尽管放牧可减少鼠类喜食植物的数量和质量,但其如何影响鼠类的食物选择尚不清楚。本研究于2014年5月至10月,在内蒙古锡林郭勒盟锡林浩特市毛登牧场的大型试验围栏内进行了布氏田鼠的食物选择实验。利用大型实验围栏内5年连续放牧处理所构建的植被变化条件,采用扣笼试验,调查了布氏田鼠对其中3种主要植物的取食情况。研究发现:连续放牧后,糙隐子草的盖度增加,而羊草、克氏针茅盖度降低;糙隐子草的盖度显著高于羊草、克氏针茅,成为各季节的优势植物种类。放牧对布氏田鼠取食羊草、克氏针茅和糙隐子草的绝对取食频次均无显著影响。在季节上,布氏田鼠对克氏针茅和糙隐子草的取食在三个季节均无差异,但布氏田鼠对羊草取食的绝对频次夏季显著高于春季和秋季;布氏田鼠对3种植物的喜好程度依次为羊草>克氏针茅>糙隐子草,但季节和放牧因素不显著影响布氏田鼠对这3种植物的喜好度。结果表明,布氏田鼠的食物选择及食物组成相对稳定,表现为其对放牧或季节因素造成的喜食植物资源量的变化具有很好的适应性,推测是其调整取食努力来实现食物组成的平衡。

Food selection by animals is determined by their food resources,food quality and food preferences. Although livestock grazing can significantly decrease quality and quantity of the preferred-plant by rodents,it is still not clear how rodents respond to livestock grazing in their food selection. During May to October 2014,we conducted a food selection experiment in the Maodeng pasture,Xilinhot of Xilingol League in Inner-Mongolia. Based on vegetation changes in large-scale enclosures after five years livestock grazing experiment,we investigated food selection of the Brandt＇s voles by using cage experiments. We found that grazing increased the coverage of Cleistogenes squarrosa,and decreased the coverage of Leymus chinensis and Stipa krylovii. C. squarrosa was the predominant plant species in the enclosures. Grazing had no significant influence on the absolute feeding frequencies on three plants by Brandt＇s voles. There was no significant difference in feeding frequency of S. krylovii and C. squarrosa between seasons,but the feeding frequency of L. chinensis was highest in summer.The preference ranking of the three plants by voles was： L. chinensis〉 S. krylovii〉 C. squarrosa. However,both seasonal and grazing factors showed no significant impacts on preference index of the three plants by voles. Our results indicate that food selection by Brandt＇s voles was relatively stable under grazing pressure,suggesting they had high capacity for adapting to the changing food resources caused by grazing and seasonal factors. We speculate that Brandt＇s voles achieve the balance of food components by adjusting feeding efforts.