Interactions between repeated fire, nutrients, and insect herbivores affect the recovery of diversity in the southern Amazon
Interactions between repeated fire, nutrients, and insect herbivores affect the recovery of diversity in the southern Amazon
复制标题
反复发生的火灾、营养物质和昆虫食草动物之间的相互作用影响了亚马逊南部多样性的恢复
作者：
T. Massad;J. Balch;E. Davidson;P. Brando;Cândida Lahís Mews;Pábio Porto;Raimundo Mota Quintino;S. Vieira;B. M. Junior;S. Trumbore
地表火灾每年烧毁大片热带森林，改变了资源的可用性，生物相互作用，并最终改变了植物多样性。在巴西塞拉多（热带稀树草原）和高身材亚马逊森林之间的过渡森林，我们利用了长期的火灾实验，建立一个析因研究火灾，养分供应和草食动物之间的相互作用，早期植物再生。总体而言，每年五次烧伤减少了再生茎的数量和多样性。群落组成在多次火灾后发生了重大变化，塞拉多常见的物种变得更加丰富。在被烧毁的地区，新兵的数量和多样性减少，但被烧毁的地块接近食草动物与氮添加有14%的增加招募。在燃烧的地块中，当添加氮时，新兵的多样性也增加了50%.磷的添加有关的物种均匀度在燃烧的地块开放给食草动物的增加。草食性减少幼苗存活率整体和增加多样性燃烧地块时，添加营养物质。这最后一个结果支持我们的假设，草食动物的存在和多样性之间的正相关关系将是最强的治疗，有利于草食动物在这种情况下，草食动物是较高的燃烧地块，最初较低的多样性。再生幼苗在不太多样化的地块可能更明显的食草动物，使增加食草动物和更强的信号的负密度依赖。相比之下，草食动物一般减少物种丰富的未烧毁的地块的多样性。虽然这项研究记录了重复烧伤，营养和食草动物之间复杂的相互作用，但很明显，火灾引发了决定新兵多样性和数量的最重要因素的转变。随着森林的演替，这种变化可能会产生长期的影响。
Surface fires burn extensive areas of tropical forests each year, altering resource availability, biotic interactions, and, ultimately, plant diversity. In transitional forest between the Brazilian cerrado (savanna) and high stature Amazon forest, we took advantage of a long-term fire experiment to establish a factorial study of the interactions between fire, nutrient availability, and herbivory on early plant regeneration. Overall, five annual burns reduced the number and diversity of regenerating stems. Community composition changed substantially after repeated fires, and species common in the cerrado became more abundant. The number of recruits and their diversity were reduced in the burned area, but burned plots closed to herbivores with nitrogen additions had a 14 % increase in recruitment. Diversity of recruits also increased up to 50 % in burned plots when nitrogen was added. Phosphorus additions were related to an increase in species evenness in burned plots open to herbivores. Herbivory reduced seedling survival overall and increased diversity in burned plots when nutrients were added. This last result supports our hypothesis that positive relationships between herbivore presence and diversity would be strongest in treatments that favor herbivory—in this case herbivory was higher in burned plots which were initially lower in diversity. Regenerating seedlings in less diverse plots were likely more apparent to herbivores, enabling increased herbivory and a stronger signal of negative density dependence. In contrast, herbivores generally decreased diversity in more species rich unburned plots. Although this study documents complex interactions between repeated burns, nutrients, and herbivory, it is clear that fire initiates a shift in the factors that are most important in determining the diversity and number of recruits. This change may have long-lasting effects as the forest progresses through succession.