scholarly journals Local properties of patterned vegetation: quantifying endogenous and exogenous effects

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120359 ◽  
Author(s):  
Gopal G. Penny ◽  
Karen E. Daniels ◽  
Sally E. Thompson
Keyword(s):  
Soil Depth ◽  
Fourier Method ◽  
Vegetation Pattern ◽  
Aerial Images ◽  
Local Pattern ◽  
Natural Systems ◽  
Pattern Dynamics ◽  
Dryland Ecosystems ◽  
Local Properties ◽  
Gradual Variation

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.

scholarly journals Pattern Dynamics of Vegetation Growth With Saturated Water Absorption

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Li ◽  
Jia-Hui Cao ◽  
Xin-Yue Bao
Keyword(s):  
Water Absorption ◽  
Vegetation Dynamics ◽  
Vegetation Pattern ◽  
Typical Feature ◽  
Water Model ◽  
Absorption Effect ◽  
Vegetation Growth ◽  
Pattern Dynamics ◽  
Saturated Water ◽  
Water Absorption Effect

Regular pattern is a typical feature of vegetation distribution and thus it is important to study the law of vegetation evolution in the fields of desertification and environment conservation. The saturated water absorption effect between the soil water and vegetation plays an crucial role in the vegetation patterns in semi-arid regions, yet its influence on vegetation dynamics is largely ignored. In this paper, we pose a vegetation-water model with saturated water absorption effect of vegetation. Our results show that the parameter 1/P, which is conversion coefficient of water absorption, has a great impact on pattern formation of vegetation: with the increase of P, the density of vegetation decrease, and meanwhile it can induce the transition of different patterns structures. In addition, we find that the increase of appropriate precipitation can postpone the time on the phase transition of the vegetation pattern. The obtained results systematically reveal the effect of saturated water absorption on vegetation systems which well enrich the findings in vegetation dynamics and thus may provide some new insights for vegetation protection.

scholarly journals Breaking the spell of nestedness

2017 ◽  
Author(s):  
Clàudia Payrató Borrás ◽  
Laura Hernández ◽  
Yamir Moreno
Keyword(s):  
Species Coexistence ◽  
Positive Impact ◽  
Bipartite Network ◽  
Degree Sequences ◽  
Natural Systems ◽  
Interacting Species ◽  
Mutualistic Interactions ◽  
Local Properties ◽  
Nested Structure

AbstractMutualistic interactions, which are beneficial for both interacting species, are recurrently present in ecosystems. Observations of natural systems showed that, if we draw mutualistic relationships as binary links between species, the resulting bipartite network of interactions displays a widespread particular ordering called nestedness [1]. On the other hand, theoretical works have shown that a nested structure has a positive impact on a number of relevant features ranging from species coexistence [2], to a higher structural stability of communities and biodiversity [3,4]. However, how nestedness emerges and what are its determinants, are still open challenges that have led to multiple debates to date [5–7]. Here, we show, by applying a theoretical approach to the analysis of 167 real mutualistic networks, that nestedness is not an irreducible feature, but a consequence of the degree sequences of both guilds of the mutualistic network. Remarkably, we find that an outstanding majority of the analyzed networks does not show statistical significant nestedness. These findings point to the need of revising previous claims about the role of nestedness and might contribute to expand our understanding of how evolution shapes mutualistic interactions and communities by placing the focus on the local properties rather than on global quantities.

Integrated Fractional white Noise as an Alternative to Multifractional Brownian Motion

2007 ◽  
Vol 44 (02) ◽  
pp. 393-408 ◽  
Author(s):  
Allan Sly
Keyword(s):  
Stochastic Process ◽  
Brownian Motion ◽  
White Noise ◽  
Gaussian Process ◽  
Discrete Data ◽  
Hölder Exponent ◽  
Scaling Properties ◽  
Multifractional Brownian Motion ◽  
Local Properties

Multifractional Brownian motion is a Gaussian process which has changing scaling properties generated by varying the local Hölder exponent. We show that multifractional Brownian motion is very sensitive to changes in the selected Hölder exponent and has extreme changes in magnitude. We suggest an alternative stochastic process, called integrated fractional white noise, which retains the important local properties but avoids the undesirable oscillations in magnitude. We also show how the Hölder exponent can be estimated locally from discrete data in this model.

Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum

1981 ◽  
Vol 39 ◽  
pp. 410-411
Author(s):  
L. P. Hardie ◽  
D. L. Balkwill ◽  
S. E. Stevens
Keyword(s):  
Growth Medium ◽  
Green Alga ◽  
Natural Habitat ◽  
Iron Limitation ◽  
Natural Environments ◽  
Blue Green Alga ◽  
Marine Cyanobacterium ◽  
Natural Systems ◽  
Thin Sectioning ◽  
Agmenellum Quadruplicatum

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systemsActively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.

Interpersonal pattern dynamics and decision-making in rugby

2007 ◽  
Author(s):  
Passos Pedro ◽  
Araujo Duarte ◽  
Davids Keith ◽  
Diniz Ana ◽  
Gouveia Luis ◽  
...  
Keyword(s):  
Decision Making ◽  
Pattern Dynamics

Variation of the local properties in TmxSe (0.8 < x ≤ 1.0) : 169Tm Mössbauer and X-ray measurements

1982 ◽  
Vol 43 (6) ◽  
pp. 961-971 ◽  
Author(s):  
J.A. Hodges ◽  
G. Jéhanno ◽  
D. Debray ◽  
F. Holtzberg ◽  
M. Loewenhaupt
Keyword(s):  
X Ray ◽  
Local Properties

ESTIMATION OF CONSUMPTIVE USE OF POTATO CROP PIANTED UNDER DRIP IRRIGATION SYSTEM BY USING SWRT TECHNOLOGY

2020 ◽  
Vol 10 (1) ◽  
pp. 271-282
Author(s):  
J.N. Abedalrahman ◽  
R.J. Mansor ◽  
D.R. Abass
Keyword(s):  
Water Consumption ◽  
Drip Irrigation ◽  
Soil Depth ◽  
Irrigation System ◽  
Potato Crop ◽  
Block Design ◽  
Organic Fertilizer ◽  
Control Treatment ◽  
Drip Irrigation System ◽  
Spring Season

A field experiment was carried out in the field of the College of Agriculture / University of Wasit, located on longitude  45o   50o   33.5o   East and latitude 32o 29o 49.8o North, in Spring season of the agricultural season 2019, in order to estimate the water consumption of potato crop using SWRT technology and under the drip irrigation system. The experiment was designed according to Randomized Complete Block Design (RCBD) with three replications and four treatments that include of the SWRT treatment (the use of plastic films under the plant root area in an engineering style), and the treatment of vegetal fertilizer (using Petmos), organic fertilizer (sheep manure), and the control treatment . Potato tubers (Solanum tuberosum L.)  var. Burin was planted for spring season on 10/2/2019 at the soil depth of 5-10 cm. The highest reference water consumption for the potato crop during the season was calculated by Najeeb Kharufa, which was 663.03 mm. The highest actual water consumption for the potato crop during the season for the control treatment was 410.1 mm. The results showed increase in the values of the crop coefficient (Kc) in the stages of tubers formation and tubers filling stage as compared to the vegetative and ripening stages, ranged from 1.37-1.92 for the two stages of tubers formation and tubers filling. The SWRT treatment gave the highest water use efficiency during the season, was 3.46 kg m-3 .

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