Costs and benefits of foraging on grasses varying in canopy structure and resistance to defoliation
Costs and benefits of foraging on grasses varying in canopy structure and resistance to defoliation
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在不同冠层结构和抗落叶能力的草上觅食的成本和效益
DOI：
10.2307/2389988
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发表时间：
1995
影响因子：
5.2
通讯作者：
W. Wright
中科院分区：
文献类型：
--
作者：
A. Illius;I. Gordon;J. Milne;W. Wright
1. 分析了植物组织的垂直分布以及山羊对物理和结构特性不同的五种草的放牧反应，目的是确定这些因素如何影响植物组织的损失和食草动物的收益。
2.草种在冠层结构上的差异比其组织在机械特性上的差异更大。细叶草的分蘖数高于阔叶草，这在很大程度上决定了放牧它们所需的更大的力量和能量。
3.在落叶过程中需要较高咬合力的草中，每次咬合时去除的植物组织比例较低。
4. 据计算，放牧期间的大部分能量消耗是咀嚼所摄入的植被，而不是从草丛中去除植物组织。放牧到草地任何深度时，能量增益超过了预测的能量消耗，因此无法解释为什么动物只从表层去除植物组织。
5. 大型动物比小型动物更接近地面，因此显然较少受到植被物理特性的限制。
6. 边际能量摄入率与更深深度落叶所需的额外力之间的平衡为落叶程度提供了解释。动物所能施加的力存在限制并不能解释咬合深度的确定。
1. The vertical distribution of plant tissues and the grazing responses of goats to five grass species differing in their physical and structural properties were analysed, with the aim of establishing how these affected the loss of tissue from the plant and the gains to herbivores.
2. The grass species varied more widely in canopy structure than their tissues vary in mechanical characteristics. Fine-leaved grasses had higher tiller numbers than broadleaved species and this largely determines the higher forces and energy required to graze them.
3. A lower proportion of plant tissue was removed in each bite taken from those grasses which demanded higher bite forces during defoliation.
4. It is calculated that the great majority of energy expenditure during grazing is in chewing the ingested vegetation, rather than in removing plant tissue from the sward. Energy gain exceeded predicted energy use during grazing to any depth in the sward and could not therefore explain why animals remove plant tissue only from the surface layer.
5. Large animals severed herbage closer to the ground surface than small animals and thus were apparently less constrained by the physical properties of the vegetation.
6. The balance between marginal energy intake rate and the additional force required for defoliation at greater depth offers an explanation for the extent of defoliation. The existence of a limit to the force an animal can apply is not a likely explanation for the determination of bite depth.