From structure to function: Understanding shrub encroachment in drylands using hydrological and sediment connectivity
From structure to function: Understanding shrub encroachment in drylands using hydrological and sediment connectivity
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DOI：
10.1016/j.ecolind.2018.11.039
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发表时间：
2019-03
影响因子：
6.9
通讯作者：
L. Turnbull;J. Wainwright
中科院分区：
文献类型：
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作者：
L. Turnbull;J. Wainwright
水文和沉积物的连通性可以帮助我们更好地了解物理和过程为基础的联系如何管理生态地貌反馈，并确定退化可能是明显的位置。在这项研究中，我们调查水文和沉积物的连通性如何影响过渡景观的生态地貌反馈。我们提出了一种新的方法，theRelative Connectivity Index（RCI），量化景观连接明确集成结构措施的景观连接（SC）与功能措施的水文和泥沙连接（FC），来自径流和泥沙输运模型。我们使用RCI计算的径流（RCIH）和沉积物（RCIS），以确定位置和时间时，功能连接超过结构连接阈值-土地退化可能是明显的-并探讨这些阈值是如何受到影响的所有事件的大小和先前的土壤水分含量。我们发现，有非线性增加的RCIH值与灌木覆盖的增加，这表明，生态地貌反馈在修改系统结构和功能的灌木入侵后期阶段变得更加重要。沉积物连通性的障碍似乎直接关系到水文连通性的阈值，虽然雨溅似乎是一个重要的机制，在创建连接的沉积物运输，没有连接的径流。HighRCIH值分布最广泛的最大（45毫米）降雨事件，而highRCIS值在一定程度上观察到在所有阶段的草灌木过渡的降雨事件小到10毫米。虽然特别大的事件具有较低的重现期，但它们似乎在塑造生态地貌反馈方面特别有用，这些反馈可能会推动生态系统状态的灾难性变化。这里使用的指标方法的优势是，它可以识别具有明显生态地貌反馈的区域，这些反馈可以作为生态系统状态发生灾难性变化的潜在触发点，因此，我们展示了如何克服现有方法的静态限制来开发连接性指数。动态RCI允许评估特定系统对可变驱动机制的脆弱性或弹性。因此，RCI可以用来指导管理干预，旨在减少或减轻不良的生态系统状态变化，通过集中在特定的位置/区域与高RCI值，以防止系统结构和功能的进一步机会，并最大限度地提供生态系统服务。
Hydrological and sediment connectivity can help us to understand better how physical and process-based linkages govern ecogeomorphic feedbacks and identify locations where degradation is likely to be pronounced. In this study we investigate how hydrological and sediment connectivity affect ecogeomorphic feedbacks in transitional landscapes. We propose a novel approach, theRelative Connectivity Index(RCI), to quantify landscape connectivity which explicitly integrates structural measures of landscape connectivity (SC) with functional measures of hydrological and sediment connectivity (FC) that are derived from runoff and sediment-transport modelling. We use theRCIcalculated for runoff (RCIH) and sediment (RCIS) to identify locations and times when functional connectivity exceeds structural connectivity thresholds – where land degradation is likely to be pronounced – and explore how these thresholds are affected by rainfall-event size and antecedent soil-moisture content. We find that there are non-linear increases inRCIHvalues with an increase in shrub cover, which suggest that ecogeomorphic feedbacks become more important in modifying system structure and function during late stages of shrub encroachment. Thresholds of sediment connectivity appear to be directly related to thresholds of hydrological connectivity, although rainsplash appears to be an important mechanism in creating connected sediment transport where there is no connected runoff. HighRCIHvalues are most widely distributed for the largest (45 mm) rainfall event, whilst highRCISvalues are observed to some extent across all stages of the grass to shrub transition for rainfall events as small as 10 mm. Whilst particularly large events have a low return period, they appear to be particularly instrumental in shaping ecogeomorphic feedbacks that are likely to drive catastrophic shifts in ecosystem state. The strength of the indicator approach used here is that it enables identification of regions with pronounced ecogeomorphic feedbacks, which act as potential trigger points for catastrophic shifts in ecosystem state, and thus, we demonstrate how the static limitations of existing approaches to developing connectivity indices may be overcome. The dynamicRCIallows the evaluation of the vulnerability or resilience of a particular system to variable driving mechanisms. TheRCIcan therefore be used to guide management interventions aimed at reducing or mitigating undesirable ecosystem state change, by focussing on specific locations/regions with highRCIvalues, to prevent further chances in system structure and function and to maximise the provision of ecosystem services.