Wind Distortion in Alpine and Subantarctic Plants is Constant among Life Forms but does not Necessarily Reflect Prevailing Wind Direction

Fitzgerald, Nicholas B.; Kirkpatrick, J. B.

doi:10.1657/aaar0016-054

Cited by 12 publications

(15 citation statements)

References 44 publications

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“…The data from the single weather station on Macquarie Island, located at sea level on the northern end of the island, are generally considered unrepresentative of conditions on the plateau (Fitzgerald & Kirkpatrick ). Therefore, we first considered the effect of two macroscale gradients (elevation and latitude) that are well known to serve as proxies for climate conditions, even across relatively short distances of <34 km (Dobrowski ).…”

Section: Methodsmentioning

confidence: 99%

Spatial variation in the ongoing and widespread decline of a keystone plant species

et al. 2019

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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.

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Section: Methodsmentioning

confidence: 99%

Spatial variation in the ongoing and widespread decline of a keystone plant species

et al. 2019

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“…Indeed, even though the compact and hemispherical cushion growth form is considered an adaptation to windy conditions (Hauri 1912) (see also (Hauri and Schröter 1914) and (Spomer 1964)), there has been surprisingly little research examining the impact of wind on cushion plants (e.g. (Ashton and Gill 1965;Fitzgerald and Kirkpatrick 2017;Lynch and Kirkpatrick 1995;Whitehead 1951)).…”

Section: Introductionmentioning

confidence: 99%

“…Airflow patterns may also affect the shape of cushion plants (Boelhouwers et al 2003;Pyšek and Liška 1991;Whitehead 1951), as wind strength (i.e. air flow velocity) influences the height, growth rate and compactness of some cushion-forming species (Lynch and Kirkpatrick 1995) (see also (Fitzgerald and Kirkpatrick 2017;Huntley 1972;Ralph 1978;Ternetz 1902;Whinam et al 2014)). The interaction between cushion plant shape and airflow is probably important in exposed sites because plant survival may be strongly linked to the shape of individuals.…”

Section: Introductionmentioning

confidence: 99%

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

et al. 2020

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Aims The sub-Antarctic cushion plant, Azorella selago, is usually hemispherical when small but frequently crescent-shaped when larger. Spatial variation in wind speed and in air-borne seed and sediment deposition is examined to determine if wind scouring and deposition patterns could contribute to the development of non-hemispherical shapes in cushion plants. Methods Computational fluid dynamic analyses were conducted for hemispherical and crescent-shaped cushion plants parameterizing models with data from A. selago habitats on Marion Island. Numerical data were contextualized with field observations to arrive at a conceptual model for shape development. Results Airflow modelling showed that both wind scouring and seed deposition of the commonly co-occurring grass Agrostis magellanica are greater on the windward side of the plant. By contrast, heavier sediment particles are predominantly deposited on the leeward side of plants, leading to burial of lee-side A. selago stems. This sediment accumulation may initiate the development of the crescent-shape in hemispherical plants by increasing stem mortality on the plant’s leeward edge. Once developed, the crescent-shape is probably self-reinforcing because it generates greater air recirculation (and lower air velocities) which enhances further deposition and establishment of A. magellanica grasses in the lee of the crescent. The conceptual model consists therefore of three stages namely, (1) negligible air recirculation, (2) sediment deposition and grass establishment, and (3) differential cushion growth. Conclusion This conceptual model of plant shape development may explain the occurrence and orientation of crescent-shaped cushion plants and highlights how predicted changes in wind patterns may affect vegetation patterns.

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“…Exposure to wind has clear physiological impacts on plants, whereby, for example, plants typically close their stomata during windy conditions to reduce the rate of transpiration, consequently leading to lower rates of photosynthesis (Grace, 1977; de Langre, 2008). In addition, winds may desiccate the soil, creating a moisture stress for plants (Bertiller et al., 1996; Fitzgerald & Kirkpatrick, 2017), and redistribute litter which has an effect on soil temperature and nutrient content (Fahnestock et al., 2000). Wind may also have a range of mechanical impacts on plants, with, for example, strong winds potentially tearing leaves, causing abrasion and desiccation (Gardiner et al., 2016; Hadley & Smith, 1983, 1986; de Langre, 2008), uprooting individuals (Yang et al., 2014), and causing flowers and fruit to be shed (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, wind is seldom considered as a driver of fine‐scale variation in community patterns (see review by Gardner et al., 2019), and despite technological advances that have improved measurement and modelling of wind conditions, little work has recently examined the influence of wind on plant communities (although, see, e.g. Fitzgerald & Kirkpatrick, 2017; Sun et al., 2019; Sparacino et al., 2020; and Table 1). In addition, the reciprocal effect of vegetation on wind patterns has also attracted limited attention (although see, e.g.…”

Section: Introductionmentioning

confidence: 99%

Exposing wind stress as a driver of fine‐scale variation in plant communities

et al. 2021

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The effects of temperature and precipitation, and the impacts of changes in these climatic conditions, on plant communities have been investigated extensively. The roles of other climatic factors are, however, comparatively poorly understood, despite potentially also strongly structuring community patterns. Wind, for example, is seldom considered when forecasting species responses to climate change, despite having direct physiological and mechanical impacts on plants. It is, therefore, important to understand the magnitude of potential impacts of changing wind conditions on plant communities, particularly given that wind patterns are shifting globally. Here, we examine the relationship between wind stress (i.e. a combination of wind exposure and wind speed) and species richness, vegetation cover and community composition using fine‐scale, field‐collected data from 1,440 quadrats in a windy sub‐Antarctic environment. Wind stress was consistently a strong predictor of all three community characteristics, even after accounting for other potentially ecophysiologically important variables, including pH, potential direct incident solar radiation, winter and summer soil temperature, soil moisture, soil depth and rock cover. Plant species richness peaked at intermediate wind stress, and vegetation cover was highest in plots with the greatest wind stress. Community composition was also related to wind stress, and, after the influence of soil moisture and pH, had a similar strength of effect as winter soil temperature. Synthesis. Wind conditions are, therefore, clearly related to plant community characteristics in this ecosystem that experiences chronic winds. Based on these findings, wind conditions require greater attention when examining environment–community relationships, and changing wind patterns should be explicitly considered in climate change impact predictions.

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Wind Distortion in Alpine and Subantarctic Plants is Constant among Life Forms but does not Necessarily Reflect Prevailing Wind Direction

Cited by 12 publications

References 44 publications

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

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

Exposing wind stress as a driver of fine‐scale variation in plant communities

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