Maisey Alex C, Haslem Angie, Leonard Steven W J, Bennett Andrew F
Department of Environment and Genetics La Trobe University Bundoora Vic. Australia.
Research Centre for Future Landscapes La Trobe University Bundoora Vic. Australia.
Ecol Evol. 2022 Jun 2;12(6):e8956. doi: 10.1002/ece3.8956. eCollection 2022 Jul.
Ecosystem engineers that modify the soil and ground-layer properties exert a strong influence on vegetation communities in ecosystems worldwide. Understanding the interactions between animal engineers and vegetation is challenging when in the presence of large herbivores, as many vegetation communities are simultaneously affected by both engineering and herbivory. The superb lyrebird , an ecosystem engineer in wet forests of south-eastern Australia, extensively modifies litter and soil on the forest floor. The aim of this study was to disentangle the impacts of engineering by lyrebirds and herbivory by large mammals on the composition and structure of ground-layer vegetation. We carried out a 2-year, manipulative exclusion experiment in the Central Highlands of Victoria, Australia. We compared three treatments: fenced plots with simulated lyrebird foraging; fenced plots excluding herbivores and lyrebirds; and open controls. This design allowed assessment of the relative impacts of engineering and herbivory on germination rates, seedling density, vegetation cover and structure, and community composition. Engineering by lyrebirds enhanced the germination of seeds in the litter layer. After 2 years, more than double the number of germinants were present in "engineered" than "non-engineered" plots. Engineering did not affect the density of seedlings, but herbivory had strong detrimental effects. Herbivory also reduced the floristic richness and structural complexity (<0.5 m) of forest vegetation, including the cover of herbs. Neither process altered the floristic composition of the vegetation within the 2-year study period. Ecosystem engineering by lyrebirds and herbivory by large mammals both influence the structure of forest-floor vegetation. The twofold increase in seeds stimulated to germinate by engineering may contribute to the evolutionary adaptation of plants by allowing greater phenotypic expression and selection than would otherwise occur. Over long timescales, engineering and herbivory likely combine to maintain a more-open forest floor conducive to ongoing ecosystem engineering by lyrebirds.
改变土壤和地被层性质的生态系统工程师对全球生态系统中的植被群落有着强烈影响。当存在大型食草动物时，理解动物工程师与植被之间的相互作用具有挑战性，因为许多植被群落同时受到工程活动和食草行为的影响。华丽琴鸟是澳大利亚东南部潮湿森林中的一种生态系统工程师，它广泛地改变了森林地面的凋落物和土壤。本研究的目的是厘清琴鸟的工程活动和大型哺乳动物的食草行为对地面植被组成和结构的影响。我们在澳大利亚维多利亚州中部高地进行了一项为期两年的控制性排除实验。我们比较了三种处理方式：有模拟琴鸟觅食的围栏地块；排除了食草动物和琴鸟的围栏地块；以及开放对照地块。这种设计使得能够评估工程活动和食草行为对发芽率、幼苗密度、植被覆盖度和结构以及群落组成的相对影响。琴鸟的工程活动提高了凋落物层种子的发芽率。两年后，“有工程活动”地块中的发芽种子数量是“无工程活动”地块的两倍多。工程活动并未影响幼苗密度，但食草行为有强烈的不利影响。食草行为还降低了森林植被的植物丰富度和结构复杂性（<0.5米），包括草本植物的覆盖度。在为期两年的研究期内，这两个过程都没有改变植被的植物组成。琴鸟的生态系统工程活动和大型哺乳动物的食草行为都影响着森林地面植被的结构。工程活动刺激发芽的种子数量增加两倍，这可能通过允许比其他情况更大的表型表达和选择，有助于植物的进化适应。在较长的时间尺度上，工程活动和食草行为可能共同作用，维持一个更开阔的森林地面，有利于琴鸟持续进行生态系统工程活动。
