Antagonistic interactions between competition and insect herbivory on plant growth
Antagonistic interactions between competition and insect herbivory on plant growth
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DOI：
10.1111/j.1365-2745.2004.00847.x
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发表时间：
2004-02-01
影响因子：
5.5
通讯作者：
Cahill, JF
中科院分区：
文献类型：
--
作者：
Haag, JJ;Coupe, MD;Cahill, JF
1虽然大量的理论研究表明，竞争和草食动物在其对植物生长的影响中应该表现出各种各样的相互作用，但经验研究表明，主要的相互作用只是倍增的。2为了确定竞争和草食动物之间的相对强度和相互作用，我们在天然草地上进行了一项田间实验研究，使用了四个焦点物种：3竞争和植食对植物生长、生物量分配和存活的影响因种而异。当影响存在时，邻近植被减少植物生长和存活，食草昆虫减少相对生物量分配到根和增加植物死亡率。4虽然减少由杀虫剂应用引起的食草对植物生物量几乎没有直接影响，它确实与竞争相互作用，影响四个物种中的三个物种的生长。草食性降低了金鸡菊的竞争强度，但增加了亚麻的竞争强度。对于金鸡菊和向日葵来说，植食性和竞争对植物生长的综合影响小于简单乘法反应的预期。5我们认为发现了相互作用，因为我们使用了一种实验设计，即修改邻居和焦点植物上的昆虫密度，考虑到直接和间接效应的确定。6我们认为竞争和植食性之间的拮抗作用可能因为食草动物通过伤害邻近植物改变了竞争环境，或者因为邻近植物的存在通过将食草动物负载分配到更大量的植物生物量上而促进了焦点植物的生长。7虽然作为一个孤立的因素，在这个系统中竞争比昆虫食草更激烈，食草动物可以改变竞争相互作用的强度，因此不能仅通过测量强度来确定其重要性。这一结果强调，这两个生态过程并不是真正离散的，并进一步表明，同时操纵多个生态过程的研究是必要的。
1 Although substantial theoretical work suggests that competition and herbivory should exhibit a wide variety of interactions in their effects on plant growth, empirical studies have shown that the predominant interactions are simply multiplicative.2 To determine both the relative strengths of, and interactions between, competition and herbivory, we conducted a field experimental study in a native grassland using four focal species: Koeleria macrantha, Coreopsis tinctoria, Linum lewisii and Helianthus petiolaris.3 The effects of competition and herbivory on plant growth, biomass allocation and survival varied among species. When effects were present, neighbouring vegetation reduced plant growth and survival, and insect herbivores decreased relative biomass allocation to roots and increased plant mortality.4 Although reduced herbivory caused by insecticide application had little direct effects on plant biomass, it did interact with competition to affect growth for three of the four species. Herbivory reduced the strength of competition experienced by Coreopsis, but increased it in Linum. For both Coreopsis and Helianthus, the combined effects of herbivory and competition on plant growth were less than expected from a simple multiplicative response.5 We suggest that interactions were found because we used an experimental design that modified insect densities on both neighbours and the focal plant, allowing for determination of both direct and indirect effects.6 We suggest that the antagonistic interactions between competition and herbivory may have occurred because herbivores altered the competitive environment by harming the neighbouring plants, or because the presence of neighbours facilitated focal plant growth by distributing herbivore loads over the greater amount of plant biomass available.7 Although as an isolated factor competition is more intense in this system than insect herbivory, herbivory can alter the strength of competitive interactions and thus its importance cannot be determined by measuring intensity alone. This result emphasizes that these two ecological processes are not truly discrete, and further suggests that studies that simultaneously manipulate multiple ecological processes are needed.