Ecosystem-scale effects of megafauna in African savannas
Ecosystem-scale effects of megafauna in African savannas
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DOI：
10.1111/ecog.01640
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发表时间：
2016-02-01
期刊：
影响因子：
5.9
通讯作者：
Levick, Shaun
中科院分区：
文献类型：
--
作者：
Asner, Gregory P.;Vaughn, Nicholas;Levick, Shaun
自然保护区对于防止狩猎和栖息地退化造成的大规模巨型动物灭绝至关重要。然而，这种保护可能会导致巨型动物种群数量迅速增加。了解植被对巨型动物种群变化的生态系统规模响应，例如稀树草原中的非洲象 Loxodonta africana 的情况，需要长期进行大规模、高分辨率的监测。从 2008 年到 2014 年，我们利用机载光探测和测距 (LiDAR) 技术反复调查了南非克鲁格国家公园超过 1040 万个木本植物冠层的命运，以确定影响树木倒伏率和模式的多种环境、生物和管理因素的相对重要性。我们报告的平均两年树木倒塌率为 8 棵树或 12% ha(-1)，但在空间和时间上损失模式不同。在整个克鲁格，大象密度对树木砍伐的影响仅与土壤和海拔的空间变化相匹配，并且所有三个因素共同主导了整个公园的树木砍伐模式。在决定树木倒塌率方面，大象密度的影响力是火灾频率的两倍，这种模式对于较高的树木（高度 > 2 m）最为明显。我们的研究结果表明，将巨型动物种群限制在保护区内，或将它们重新引入以前或新的栖息地，可以极大地改变宿主生态系统的结构和功能。保护策略需要适应和管理这些巨大的生态变化，以在不损害系统功能的情况下拯救巨型动物免于灭绝。
Natural protected areas are critically important in the effort to prevent large-scale megafaunal extinctions caused by hunting and habitat degradation. Yet such protection can lead to rapid increases in megafauna populations. Understanding ecosystem-scale responses of vegetation to changing megafaunal populations, such as the case of the African elephant Loxodonta africana in savannas, requires large-scale, high-resolution monitoring over time. From 2008 to 2014, we repeatedly surveyed the fate of more than 10.4 million woody plant canopies throughout the Kruger National Park, South Africa using airborne Light Detection and Ranging (LiDAR), to determine the relative importance of multiple environmental, biotic and management factors affecting treefall rates and patterns. We report a mean biennial treefall rate of 8 trees or 12% ha(-1), but with heterogeneous patterns of loss in both space and time. Throughout Kruger, the influence of elephant density on treefall was matched only by spatial variation in soils and elevation, and all three factors co-dominated park-wide treefall patterns. Elephant density was up to two times more influential than fire frequency in determining treefall rates, and this pattern was most pronounced for taller trees (> 2 m in height). Our results suggest that confining megafauna populations to protected areas, or reintroducing them into former or new habitat, can greatly alter the structure and functioning of the host ecosystem. Conservation strategies will need to accommodate and manage these massive ecological changes in the effort to save megafauna from extinction, without compromising system functionality.