Pyric Herbivory and the Nexus Between Forage, Fire and Native and Introduced Large Grazing Herbivores in Australian Tropical Savannas
Pyric Herbivory and the Nexus Between Forage, Fire and Native and Introduced Large Grazing Herbivores in Australian Tropical Savannas
复制标题
澳大利亚热带稀树草原的火食草食性与草料、火和本地及引进的大型食草动物之间的联系
作者：
A. Reid;B. Murphy;T. Vigilante;D. Bowman
地球上的热带稀树草原通常支持高生物量的各种食草动物，这些食草动物依赖于一种高度波动的资源：高质量的饲料。一年一次的干湿循环、火灾和草食联合收割机结合在一起，影响着牧草的质量和全年的可用性。在澳大利亚北方的热带稀树草原上，一群大型的本地（有袋类）食草动物（wallaroos [Oakranter spp.]）和敏捷的小袋鼠[ Notamacropus agilis ]）与世纪后期引入的非本地大型食草动物争夺资源，特别是牛（野生和管理牛[ Bos spp.]和野生的布法罗[水牛]），现在占主导地位的景观。最近大型节肢动物种群数量下降和牛的负面影响的轶事报道强调，需要更好地了解饲料，火和丰富的本地和引进的大型食草动物之间的复杂关系。的pyric草食动物的概念模型，假定火和草食动物之间的复杂的反馈，并在澳大利亚以外的地区开发，预测本地和引进的大型草食动物都将积极响应火灾后的饲料生产在澳大利亚热带草原，他们共同发生。我们使用放牧围栏，牧草生物量和营养分析和运动传感器相机捕获，以评估在澳大利亚的情况下，无论是牧草的数量和质量的草食动物，季节和火灾活动的影响，以及牧草属性最大的影响大型放牧草食动物丰度的pyric草食动物模型的整体鲁棒性。饲料量，衡量活，死和总草本生物量和比例的生物量活着，是较高的内草食动物围栏，即使在相对较低的密度草食动物。牧草质量，纤维含量，测定，不受草食动物，然而，粗蛋白含量的活草本生物量是更大的草食动物围栏外。近期火灾是牧草数量和质量的所有措施的重要预测。最近发生火灾减少了整体数量（生物量），但提高了质量（减少纤维含量和增加粗蛋白含量）;旱季后期火灾导致饲料粗蛋白含量最高。的pyric草食动物的概念模型的预测是一致的，在澳大利亚北方稀树草原的引进牛和一些大型的macropods的喂养行为的观察，贷款支持全球的一般性的pyric草食动物在火灾易发的草地生物群系。
Earth’s tropical savannas typically support high biomass of diverse grazing herbivores that depend on a highly fluctuating resource: high-quality forage. An annual wet–dry cycle, fire and herbivory combine to influence forage quality and availability throughout the year. In the savannas of northern Australia, a depauperate suite of large native (marsupial) herbivores (wallaroos [ Osphranter spp.] and the agile wallaby [ Notamacropus agilis ]) compete for resources with non-native large herbivores introduced in the late nineteenth century, particularly bovines (feral and managed cattle [ Bos spp.] and feral water buffalo [ Bubalus bubalis ]) that now dominate the landscape. Anecdotal reports of recent population declines of large macropods and negative impacts of bovines highlight the need to better understand the complex relationship between forage, fire and abundance of native and introduced large herbivores. The pyric herbivory conceptual model, which posits complex feedbacks between fire and herbivory and was developed outside Australia, predicts that native and introduced large herbivores will both respond positively to post-fire forage production in Australian savannas where they co-occur. We used grazing exclosures, forage biomass and nutrient analyses and motion-sensor camera-trapping to evaluate the overall robustness of the pyric herbivory model in the Australian context, specifically whether forage quantity and quality are impacted by herbivory, season and fire activity, and which forage attributes most influence large grazing herbivore abundance. Forage quantity, as measured by live, dead and total herbaceous biomass and proportion of biomass alive, was higher inside herbivore exclosures, even at relatively low densities of herbivores. Forage quality, as measured by fibre content, was not affected by herbivory, however, crude protein content of live herbaceous biomass was greater outside herbivore exclosures. Recent fire was an important predictor of all measures of forage quantity and quality. Recent fire occurrence decreased overall quantity (biomass) but increased quality (decreased fibre content and increased crude protein content); late dry season fires resulted in forage with the highest crude protein content. The predictions of the pyric herbivory conceptual model are consistent with observations of the feeding behaviour of introduced bovines and some large macropods in northern Australian savannas, lending support to the global generality of pyric herbivory in fire-prone grassy biomes.