Spatial variation in the ongoing and widespread decline of a keystone plant species
Spatial variation in the ongoing and widespread decline of a keystone plant species
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DOI：
10.1111/aec.12758
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发表时间：
2019-08-01
期刊：
影响因子：
1.5
通讯作者：
McGeoch, Melodie A.
中科院分区：
文献类型：
--
作者：
Dickson, Catherine R.;Baker, David J.;McGeoch, Melodie A.
为应对气候变化，优势植物物种出现大面积枯死现象越来越普遍。气候条件和相关变量（例如蒸散量）会根据地形的复杂性而变化。这种复杂性在提供气候庇护所方面发挥着重要作用。 2008/2009年，亚南极麦夸里岛发生了全岛范围内的垫状植物Azorella macquariensis Orchard（伞形科）枯死事件。这标志着潜在的状态转变的开始，表明这是由蒸气压不足增加所驱动的。八年后，我们量化了该物种所暴露的假定小气候范围内的覆盖和顶枯，目的是解释顶枯模式。我们使用一系列地形代理和其他变量作为拟议的变化驱动因素来测试蒸散量的影响。我们在岛的南部发现了更高的覆盖层和更低的枯萎病。麦夸里埃种群的高空间变化最好用纬度来解释，纬度可能是宏观气候梯度和地质的代表。麦夸里木的覆盖范围和纬度可以最好地解释枯萎病，随着覆盖范围的扩大以及向岛北方向的增加，纬度也随之增加。影响蒸散率的地形变量的效应大小很小。全岛范围内的枯死现象仍然很明显。部分地点与历史数据的比较显示，该岛北部和中部地区的覆盖面积减少，而顶枯最活跃的地区则向南转移。南部的枯死率仍然相对较低。幼苗的存在与枯死无关。这项研究为麦夸里木的覆盖和状况的空间变化提供了经验基线，这两个关键变量是监测这种极度濒危特有植物物种的状况和“覆盖债务”的关键变量。这些发现对于了解未来气候下整个亚南极地区的荒野生态系统和其他白藻物种的反应具有更广泛的意义。
Extensive dieback in dominant plant species in response to climate change is increasingly common. Climatic conditions and related variables, such as evapotranspiration, vary in response to topographical complexity. This complexity plays an important role in the provision of climate refugia. In 2008/2009, an island-wide dieback event of the keystone cushion plant Azorella macquariensis Orchard (Apiaceae) occurred on sub-Antarctic Macquarie Island. This signalled the start of a potential regime shift, suggested to be driven by increasing vapour pressure deficit. Eight years later, we quantified cover and dieback across the range of putative microclimates to which the species is exposed, with the aim of explaining dieback patterns. We test for the influence of evapotranspiration using a suite of topographic proxies and other variables as proposed drivers of change. We found higher cover and lower dieback towards the south of the island. The high spatial variation in A. macquariensis populations was best explained by latitude, likely a proxy for macroscale climate gradients and geology. Dieback was best explained by A. macquariensis cover and latitude, increasing with cover and towards the north of the island. The effect sizes of terrain variables that influence evapotranspiration rates were small. Island-wide dieback remains conspicuous. Comparison between a subset of sites and historical data revealed a reduction of cover in the north and central regions of the island, and a shift south in the most active areas of dieback. Dieback remained comparatively low in the south. The presence of seedlings was independent of dieback. This study provides an empirical baseline for spatial variation in the cover and condition of A. macquariensis, both key variables for monitoring condition and 'cover-debt' in this critically endangered endemic plant species. These findings have broader implications for understanding the responses of fellfield ecosystems and other Azorella species across the sub-Antarctic under future climates.