贺兰山岩羊冬春季取食生境的比较

2003年11～12月和2004年4～6月，在贺兰山设定了25条固定样线，采用直接观察法对岩羊冬春季的取食生境选择进行了研究。结果表明，岩羊冬季对12种取食生境生态因子有选择性，偏爱选择位于山地疏林草原带，优势乔木为灰榆，乔木密度〈4株、高度4～6m，灌木密度〉5株、高度〉1．3m，食物质量〉50g，人为干扰距离〈500m，距裸岩距离〈2m的地方取食。而春季对11种取食生境生态因子有选择性，偏爱选择山地疏林草原带，优势乔木为灰榆，乔木密度〈4株、高度〈6m，灌木密度5～10株、高度1．3～1．7m，食物质量〉100g，海拔高度〈2000m，距水源距离〈500m，隐蔽级50％～75％的地点。冬春季岩羊对植被类型、地形特征、优势乔木、乔木密度、乔木高度、灌木密度、灌木距离、食物丰富度、坡向、坡度、距水源距离、人为干扰距离和隐蔽级的选择存在显著差异。主成分分析表明，冬季第1主成分的贡献率达24．493％，其中绝对值较大的权系数出现在植被类型、优势乔木、乔木高度、乔木距离、灌木密度、灌木高度、海拔高度、距水源距离和人为干扰距离等生态因子：春季第1主成分的贡献率达28．777％，其中绝对值较大的权系数出现在植被类型、乔木距离、灌木高度、灌木距离、食物丰富度、海拔高度和人为干扰距离等生态因子。随着北方地区冬春季食物数量和质量的剧烈变化，贺兰山岩羊对取食生境的利用对策也将发生一定程度的改变，与其他分布区的岩羊相比，贺兰山独特的地理位置和特殊生境使其在取食生境选择上存在很大差异。

Comparison of Seasonal Feeding Habitats by Blue Sheep (Pseudois nayaur) During Winter and Spring in Helan Mountain, China

The selection of feeding habitats of blue sheep (Pseudois nayaur) was studied by the direct observation method in Helan Mountain during winter (from November to December) and spring (from April to June) from 2003 to 2004. We established 25 line transects to collect information on feeding habitats used by blue sheep. Blue sheep in the study area preferred montane savanna forests, habitat dominated by Ulmus glaucescens, medium tree density (<4 individuals/100 m2), moderate tree height (4-6 m), higher shrub density (>5 individuals/100 m2), taller shrub (>1.3 m), higher food abundance (>50 g), moderate distance to human disturbance (<500 m), short distance to bare rock (<2 m). Such characteristic habitats with 12 ecological factors were preferred as feeding areas by blue sheep during winter. Similarly, blue sheep showed a preference for montane savanna, trees dominated by Ulmus glaucescens, and medium tree density (<4 individuals/100 m2) during spring. Nevertheless, blue sheep preferred medium tree height (<6 m), moderate tree density (5-10 individuals/100 m2), medium shrub height (1.3-1.7 m), higher food abundance (>100 g), moderate altitude (<2 000 m), moderate distance to water resource (<500 m), medium hiding cover (50-75%) during spring. Selection of feeding habitat by sheep showed a significant difference in vegetation type, landform feature, dominant tree, tree height, shrub density, distance to the nearest shrub, food abundance, slope direction, slope angle, distance to water resource, and hiding cover between winter and spring. Results of principal components analysis indicated that the first principal component accounted for 24.493% of the total variance among feeding habitat variance during winter, with higher loadings for vegetation type, dominant tree, tree height, distance to the nearest to tree, shrub density, shrub height, altitude, distance to water resource, and distance to human disturbance. In spring, the first principal components explained 28.777% of the variance, with higher loadings for vegetation type, distance to nearest tree, shrub height, distance to the nearest shrub, food abundance, altitude, and distance to human disturbance. In the northern temperate region, the quantity and quality of forage species have experienced great changes between winter and spring; hence the strategy of feeding habitats used by blue sheep varied with the season. Compared with the sheep of other distribution area, different selection of feeding habitat by sheep resulted from special geographical location and unique habitat of Helan Mountain.