Grassland-herbivore interactions: How do grazers coexist?

被引:48
作者
Farnsworth, KD
Focardi, S
Beecham, JA [1 ]
机构
[1] Macaulay Inst, Aberdeen AB15 8QH, Scotland
[2] Ist Nazl Fauna Selvatica, I-40064 Ozzano Dell Emilia, Italy
关键词
competition; facilitation; livestock; rangeland; sustainability; sward structure;
D O I
10.1086/324114
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
We develop a new approach to modeling grazing systems that links foraging characteristics (intake and digestive constraints) with resource dynamics via the probability of encounter with different grass heights. Three complementary models are presented: the generation of a grass height structure through selective grazing; investigating the conditions for consumer coexistence; and, using a simplified resource structure, the consequences for consumer abundance. The main finding is that coexistence between grazers differing in body size is possible if a single-resource type becomes differentiated in its height structure. Large grazers can facilitate food availability for smaller species but with the latter being competitively dominant. The relative preference given to different resource partitions is important in determining the nature of population interactions. Large-body and small-body grazer populations can interact through competitive, parasitic, commensalist, or amensalist relationships, depending on the way they partition the resource as well as their relative populations and the dynamics of resource renewal. The models provide new concepts of multispecies carrying capacity (stock equilibrium) in grazed systems with implications for conservation and management. We conclude that consumer species are not substitutable; therefore, the use of rangeland management concepts such as "livestock units" may be inappropriate.
引用
收藏
页码:24 / 39
页数:16
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