Vegetation arcs and litter dams: similarities and differences

Eddy, John A.; Humphreys, Geoff S.; Hart, Diane; Mitchell, P. B.; Fanning, Patricia

doi:10.1016/s0341-8162(98)00055-1

Cited by 41 publications

(38 citation statements)

References 26 publications

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“…5D). This predicted wavelength-slope relationship is consistent with empirical data (5,(8)(9)(10)(11).…”

Section: Pattern Generation From Uniform Vegetationsupporting

confidence: 87%

“…Moreover it is expected, because of the increased run-off on steeper gradients. However, this positive correlation is the opposite of the wavelength-slope relationship found empirically (5,(8)(9)(10)(11).…”

Section: Mathematical Modeling Of Semiarid Vegetationmentioning

confidence: 56%

“…My results therefore suggest that wavelength would increase with slope for patterns arising from the degradation of uniform vegetation, and would decrease with slope following the colonization of bare ground. Because there is now a large amount of data indicating the latter trend (8)(9)(10), I infer that the banded vegetation in this region has developed via colonization of bare ground--at least in the locations providing the data, which are very widespread.…”

Section: Discussionmentioning

confidence: 99%

“…The database of wavelengths is extensive, and some studies also record slope gradient. In 1999 Eddy et al (8) compiled various older data of this type. Both this and a parallel study by d'Herbès et al (9) showed an inverse relationship: longer wavelengths tend to occur on shallower slopes.…”

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confidence: 99%

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Using wavelength and slope to infer the historical origin of semiarid vegetation bands

Sherratt

2015

Proc. Natl. Acad. Sci. U.S.A.

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Landscape-scale patterns of vegetation occur worldwide at interfaces between semiarid and arid climates. They are important as potential indicators of climate change and imminent regime shifts and are widely thought to arise from positive feedback between vegetation and infiltration of rainwater. On gentle slopes the typical pattern form is bands (stripes), oriented parallel to the contours, and their wavelength is probably the most accessible statistic for vegetation patterns. Recent field studies have found an inverse correlation between pattern wavelength and slope, in apparent contradiction with the predictions of mathematical models. Here I show that this “contradiction” is based on a flawed approach to calculating the wavelength in models. When pattern generation is considered in detail, the theory is fully consistent with empirical results. For realistic parameters, degradation of uniform vegetation generates patterns whose wavelength increases with slope, whereas colonization of bare ground gives the opposite trend. Therefore, the empirical finding of an inverse relationship can be used, in conjunction with climate records, to infer the historical origin of the patterns. Specifically, for the African Sahel my results suggest that banded vegetation originated by the colonization of bare ground during circa 1760–1790 or since circa 1850.

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“…5D). This predicted wavelength-slope relationship is consistent with empirical data (5,(8)(9)(10)(11).…”

Section: Pattern Generation From Uniform Vegetationsupporting

confidence: 87%

Section: Mathematical Modeling Of Semiarid Vegetationmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Using wavelength and slope to infer the historical origin of semiarid vegetation bands

Sherratt

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…0.25% in the Sudan [30]). In addition, the inverse relationship between pattern wavelength and the hillslope gradient (see figure 3) has been identified elsewhere [30,[64][65][66]. However, the one model [67] that has been used to study wavelengthgradient correlations predicts the opposite trend: steepness causes larger wavelengths [41,68].…”

Section: Discussionmentioning

confidence: 99%

Local properties of patterned vegetation: quantifying endogenous and exogenous effects

Penny

Daniels

Thompson

2013

Phil. Trans. R. Soc. A.

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Dryland ecosystems commonly exhibit periodic bands of vegetation, thought to form due to competition between individual plants for heterogeneously distributed water. In this paper, we develop a Fourier method for locally identifying the pattern wavenumber and orientation, and apply it to aerial images from a region of vegetation patterning near Fort Stockton, TX, USA. We find that the local pattern wavelength and orientation are typically coherent, but exhibit both rapid and gradual variation driven by changes in hillslope gradient and orientation, the potential for water accumulation, or soil type. Endogenous pattern dynamics, when simulated for spatially homogeneous topographic and vegetation conditions, predict pattern properties that are much less variable than the orientation and wavelength observed in natural systems. Our local pattern analysis, combined with ancillary datasets describing soil and topographic variation, highlights a largely unexplored correlation between soil depth, pattern coherence, vegetation cover and pattern wavelength. It also, surprisingly, suggests that downslope accumulation of water may play a role in changing vegetation pattern properties.

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Shrub encroachment alters the spatial patterns of infiltration

Eldridge¹,

Wang

Ruíz-Colmenero³

2014

Ecohydrology

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Encroachment of open woodlands by shrubs is a global phenomenon associated with marked changes in ecosystem structure and function. We measured sorptivity and steady-state infiltration at two supply potentials under shrubs and grasses and in their interspaces where shrubs were encroaching into grassland. Steady-state infiltration (ponded) and sorptivity were greater at the grassland than the shrubland site, and there was substantially greater infiltration under shrubs (48.2 mm h -1 ) and grasses (50.0 mm h -1 ) than the corresponding interspaces (17.0 and 32.3 mm h -1 for shrubland and grassland, respectively). The difference between grasses and their interspaces was substantially less (1.5-times) than that between shrubs and their interspaces (three-1 times). Shrub encroachment also affected the spatial patterns of infiltration. While the autocorrelation range for shrublands coincided almost exactly with the average width of shrub canopies (3.5 m), the range for grasslands was three-times greater (1.5 m) than the mean grass canopy, indicating a greater connectivity of infiltration in the grasslands than the shrublands. Our study indicates that encroachment by shrubs does not change infiltration under individual plants. Rather, it reduces the interspace infiltration rates significantly, resulting in lower estimated site-level infiltrationrates in shrublands. Our research suggests therefore that it is the shrubland interspaces that are the likely drivers of reduced infiltration rates when grasslands are encroached, rather than increase in the total cover of shrubs per se. Management strategies that result in greater retention of grass cover and minimise the level of interspace disturbances, are likely to result in increased infiltration.

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Vegetation arcs and litter dams: similarities and differences

Cited by 41 publications

References 26 publications

Using wavelength and slope to infer the historical origin of semiarid vegetation bands

Using wavelength and slope to infer the historical origin of semiarid vegetation bands

Local properties of patterned vegetation: quantifying endogenous and exogenous effects

Shrub encroachment alters the spatial patterns of infiltration

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