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Bridging ecology and physics: Australian fairy circles regenerate following model assumptions on ecohydrological feedbacks
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-09-21 , DOI: 10.1111/1365-2745.13493 Stephan Getzin 1, 2 , Todd E. Erickson 3, 4 , Hezi Yizhaq 5 , Miriam Muñoz‐Rojas 3, 4, 6 , Andreas Huth 2 , Kerstin Wiegand 1
中文翻译：
架起生态与物理学的桥梁：澳大利亚神仙界按照生态水文学反馈的模型假设进行再生
更新日期：2020-09-21
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-09-21 , DOI: 10.1111/1365-2745.13493 Stephan Getzin 1, 2 , Todd E. Erickson 3, 4 , Hezi Yizhaq 5 , Miriam Muñoz‐Rojas 3, 4, 6 , Andreas Huth 2 , Kerstin Wiegand 1
Affiliation
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- So‐called fairy circles (FCs) comprise a spatially periodic gap pattern in arid grasslands of Namibia and north‐west Western Australia. This pattern has been explained with scale‐dependent ecohydrological feedbacks and the reaction‐diffusion, or Turing mechanism, used in process‐based models that are rooted in physics and pattern‐formation theory. However, a detailed ecological test of the validity of the modelled processes is still lacking.
- Here, we test in a spinifex‐grassland ecosystem of Western Australia the presence of spatial feedbacks at multiple scales. Drone‐based multispectral analysis and spatially explicit statistics were used to test if grass vitality within five 1‐ha plots depends on the pattern of FCs that are thought to be a critical extra source of water for the surrounding matrix vegetation. We then examined if high‐ and low‐vitality grasses show scale‐dependent feedbacks being indicative of facilitation or competition. Additionally, we assessed facilitation of grass plants for different successional stages after fire at fine scales in 1‐m2 quadrats. Finally, we placed soil moisture sensors under bare soil inside the FC gap and under plants at increasing distances from the FC to test if there is evidence for the ‘infiltration feedback’ as used in theoretical modelling.
- We found that high‐vitality grasses were systematically more strongly associated with FCs than low‐vitality grasses. High‐vitality grasses also had highly aggregated patterns at short scales being evidence of positive feedbacks while negative feedbacks occurred at larger scales. Within 1‐m2 quadrats, grass cover and mutual facilitation of plants was greater near the FC edge than further away in the matrix. Soil moisture after rainfall was lowest inside the FC with its weathered surface crust but highest under grass at the gap edge, and then declined towards the matrix, which confirms the infiltration feedback.
- Synthesis. The study shows that FCs are a critical extra source of water for the dryland vegetation, as predicted by theoretical modelling. The grasses act as ‘ecosystem engineers’ that modify their hostile, abiotic environment, leading to vegetation self‐organization. Overall, our ecological findings highlight the validity of the scale‐dependent feedbacks that are central to explain this emergent grassland pattern via the reaction‐diffusion or Turing‐instability mechanism.
中文翻译：
架起生态与物理学的桥梁：澳大利亚神仙界按照生态水文学反馈的模型假设进行再生
- 所谓的仙女圈（FCs）在纳米比亚和西澳大利亚西北部的干旱草原上具有空间周期性的缺口格局。这种模式已经用与规模有关的生态水文反馈和反应扩散（或图灵机制）进行了解释，该模型在基于过程的模型中使用，该模型植根于物理和模式形成理论。但是，仍然缺乏对建模过程的有效性进行详细的生态测试。
- 在这里，我们在西澳大利亚的多刺草原草地生态系统中测试了多尺度空间反馈的存在。基于无人机的多光谱分析和空间显式统计数据用于测试5个1公顷土地中草的活力是否取决于FC的模式，而FC的模式被认为是周围基质植被至关重要的额外水源。然后，我们检查了高活力草丛和低活力草丛是否显示依赖尺度的反馈来指示促进或竞争。此外，我们在1m 2的小尺度上评估了火灾后草木在不同演替阶段的促进作用四边形。最后，我们将土壤湿度传感器放置在FC间隙内裸露的土壤下以及与FC距离越来越远的植物下，以测试是否有证据证明理论建模中使用了“入渗反馈”。
- 我们发现，与低活力草相比，高活力草与FC的系统相关性更高。高活力草在短尺度上也具有高度聚集的模式，这是正反馈的证据，而负反馈则在较大尺度上发生。在1到2个正方形中，在FC边缘附近的草被和植物的相互促进大于在基质中更远的地方。降雨后，土壤内部的水分最低，其表层风化，而在间隙边缘的草丛下最高，然后向基质下降，这证实了入渗反馈。
- 综合。研究表明，正如理论模型所预测的，FCs是干旱地区植被的重要额外水源。草是“生态系统工程师”，可以改变其不利的非生物环境，从而导致植被自组织。总体而言，我们的生态学发现突显了规模依赖性反馈的有效性，这是通过反应扩散或图灵不稳定性机制解释这种新兴草地格局的关键。
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