scholarly journals Localised labyrinthine patterns in ecosystems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. G. Clerc ◽  
S. Echeverría-Alar ◽  
M. Tlidi
Keyword(s):  
Plant Communities ◽  
Short Range ◽  
Bare Soil ◽  
Water Dynamics ◽  
Vegetation Patterns ◽  
Irregular Pattern ◽  
Long Range Interactions ◽  
Uniform Cover ◽  
Spatial Size ◽  
Modelling Approach

AbstractSelf-organisation is a ubiquitous phenomenon in ecosystems. These systems can experience transitions from a uniform cover towards the formation of vegetation patterns as a result of symmetry-breaking instability. They can be either periodic or localised in space. Localised vegetation patterns consist of more or less circular spots or patches that can be either isolated or randomly distributed in space. We report on a striking patterning phenomenon consisting of localised vegetation labyrinths. This intriguing pattern is visible in satellite photographs taken in many territories of Africa and Australia. They consist of labyrinths which is spatially irregular pattern surrounded by either a homogeneous cover or a bare soil. The phenomenon is not specific to particular plants or soils. They are observed on strictly homogenous environmental conditions on flat landscapes, but they are also visible on hills. The spatial size of localized labyrinth ranges typically from a few hundred meters to ten kilometres. A simple modelling approach based on the interplay between short-range and long-range interactions governing plant communities or on the water dynamics explains the observations reported here.

scholarly journals The efficient use of small plots in a fynbos phytosociological study in the northern Cederberg: a quick way to collect plant-environmental data

Bothalia ◽  
1993 ◽  
Vol 23 (2) ◽  
pp. 265-269
Author(s):  
P. J. Mustart ◽  
E. J. Moll ◽  
H. C. Taylor
Keyword(s):  
Plant Communities ◽  
Environmental Data ◽  
Vegetation Patterns ◽  
Environmental Relationships ◽  
Ecological Information ◽  
Small Plot ◽  
Phytosociological Study

A phytosociological survey of selected plant communities in the northern Cederberg was made using small (4-16 m') plot sizes. A satisfactory phytosociological table was obtained, and plant-environmental relationships were inferred from it. The use of small plot sizes enabled ecological information about plant communities to be quickly, easily and efficiently obtained. This method could be of considerable use for establishing and monitoring vegetation patterns.

scholarly journals Plant communities of the Karkas Hunting-Prohibited Region, Isfahan-Iran

2008 ◽  
Vol 54 (No. 8) ◽  
pp. 347-358
Author(s):  
S.J. Khajeddin ◽  
H. Yeganeh
Keyword(s):  
Plant Communities ◽  
Random Sampling ◽  
Dominant Species ◽  
Sampling Method ◽  
Bare Soil ◽  
Cluster Analyses ◽  
Isfahan Province ◽  
Biogeographic Region ◽  
The Impact ◽  
Interesting Area

The Karkas mountainous region is a very interesting area for its big game wildlife and rare species in the Irano-Touranian biogeographic region. It is essential to study the plant communities and the impact of environmental factors, to protect and rehabilitate these ecosystems. The studied region is located in the Isfahan province, central Iran, with the area of about 92 100 ha. The aim of the study was to identify the plant communities of the Karkas Hunting-Prohibited Region. Vegetation cover was sampled using a stratified random sampling method and the entities were preliminarily segmented with the physiognomic-floristic-ecologic method. 10 × 10 m quadrates (100 m<sup>2</sup>) were used to estimate the species cover, litter, stone, gravel and bare soil percentages. Plant communities were classified using cluster analyses and denderogram construction. The results confirmed the importance of the climatic and topographic factors that affect the establishment of the plant communities. Plant habitats in the region are mosaics and cause ecoton formations, so diversities in species combinations increase. The species diversity of the communities was measured using the Shannon coefficient; it varied from 2.26 to 0.39. According to cluster analyses, there are 15 different plant communities, but when the second dominant species were considered, some communities were further divided into sub-communities.

scholarly journals Mountain pastures of Qilian Shan: plant communities, grazing impact and degradation status (Gansu province, NW China)

Hacquetia ◽  
2016 ◽  
Vol 15 (2) ◽  
pp. 21-35 ◽  
Author(s):  
Alina Baranova ◽  
Udo Schickhoff ◽  
Shunli Wang ◽  
Ming Jin
Keyword(s):  
Plant Community ◽  
Plant Communities ◽  
Plant Cover ◽  
Management Strategies ◽  
Detrended Correspondence Analysis ◽  
Gansu Province ◽  
Grazing Impact ◽  
Vegetation Patterns ◽  
Pasture Management ◽  
Nw China

Abstract Environmental degradation of pasture areas in the Qilian Mountains (Gansu province, NW China) has increased in recent years. Soil erosion and loss of biodiversity caused by overgrazing is widespread. Changes in plant cover, however, have not been analysed so far. The aim of this paper is to identify plant communities and to detect grazing-induced changes in vegetation patterns. Quantitative and qualitative relevé data were collected for community classification and to analyse gradual changes in vegetation patterns along altitudinal and grazing gradients. Detrended correspondence analysis (DCA) was used to analyse variation in relationships between vegetation, environmental factors and differential grazing pressure. The results of the DCA showed apparent variation in plant communities along the grazing gradient. Two factors - altitude and exposure - had the strongest impact on plant community distribution. Comparing monitoring data for the most recent nine years, a trend of pasture deterioration, plant community successions and shift in dominant species becomes obvious. In order to increase grassland quality, sustainable pasture management strategies should be implemented.

scholarly journals Methane emission by plant communities in an alpine meadow on the Qinghai-Tibetan Plateau: a new experimental study of alpine meadows and oat pasture

2009 ◽  
Vol 5 (4) ◽  
pp. 535-538 ◽  
Author(s):  
Shiping Wang ◽  
Xiaoxia Yang ◽  
Xingwu Lin ◽  
Yigang Hu ◽  
Caiyun Luo ◽  
...  
Keyword(s):  
Experimental Study ◽  
Soil Temperature ◽  
Plant Communities ◽  
Alpine Meadow ◽  
Pore Space ◽  
Bare Soil ◽  
Chemical Mechanism ◽  
Limited Evidence ◽  
Growing Seasons ◽  
Water Filled Pore Space

Recently, plant-derived methane (CH 4 ) emission has been questioned because limited evidence of the chemical mechanism has been identified to account for the process. We conducted an experiment with four treatments (i.e. winter-grazed, natural alpine meadow; naturally restored alpine meadow eight years after cultivation; oat pasture and bare soil without roots) during the growing seasons of 2007 and 2008 to examine the question of CH 4 emission by plant communities in the alpine meadow. Each treatment consumed CH 4 in closed, opaque chambers in the field, but two types of alpine meadow vegetation reduced CH 4 consumption compared with bare soil, whereas oat pasture increased consumption. This result could imply that meadow vegetation produces CH 4 . However, measurements of soil temperature and water content showed significant differences between vegetated and bare soil and appeared to explain differences in CH 4 production between treatments. Our study strongly suggests that the apparent CH 4 production by vegetation, when compared with bare soil in some previous studies, might represent differences in soil temperature and water-filled pore space and not the true vegetation sources of CH 4 .

An Adaptive Trustworthiness Modelling Approach for Ubiquitous Software Systems

2014 ◽  
Vol 8 (4) ◽  
pp. 44-61 ◽  
Author(s):  
Amr Ali-Eldin ◽  
Jan Van Den Berg ◽  
Semir Daskapan
Keyword(s):  
Information Disclosure ◽  
Short Range ◽  
Software Systems ◽  
Wireless Devices ◽  
Privacy And Security ◽  
Proposed Model ◽  
Disclosure Decisions ◽  
Processing Resources ◽  
Trust Models ◽  
Modelling Approach

With the growing interest in ubiquitous applications, attention should be given to privacy and trust issues. Since these environments are quite dynamic, and interactive where devices possess low computing resources, new trust models are required that suit this environment and help overcome its limitations. In this paper, the authors explore the possibility to settle trust in an adaptive way prior to any information disclosure to enable adaptive privacy and security. The proposed model is simulated in a commercial cluster scenario where users can clear all their payments with their short-range ubiquitous devices. In this domain, the authors assume that the user has to rely on what they call payment disclosure service (PDS) to control his or her disclosure decisions. The proposed model respects the limitations of wireless devices such as limited connectivity and processing resources, while enabling autonomous and secure operations.

Development of lateral interactions in the infant visual system

1992 ◽  
Vol 8 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Samuel Sokol ◽  
Vance Zemon ◽  
Anne Moskowitz
Keyword(s):  
Visual System ◽  
Long Range ◽  
Short Range ◽  
Second Harmonic ◽  
Harmonic Component ◽  
Frequency Component ◽  
Human Infants ◽  
Long Range Interactions ◽  
Harmonic Components ◽  
Inhibitory Interactions

AbstractThe development of lateral inhibitory interactions in the infant visual system, as reflected by the visual-evoked potential (VEP), was studied using a radial, asymmetrical windmill-dartboard stimulus. This contrast-reversing stimulus generates VEP responses with a strong fundamental frequency component and an attenuated second harmonic component (relative to that obtained using a symmetrical stimulus). These two harmonic components reflect distinct phenomena, and appear to be the result of short-range (the fundamental) and long-range (attenuated second harmonic) lateral inhibitory interactions elicited by differential luminance-modulation of contiguous spatial regions. We studied the development of the short-and long-range interactions at 100% and 30% contrast in human infants using both VEP amplitude and phase measures. Attenuation of the second harmonic (long-range interactions) was adult-like by 8 weeks of age while the strength of the fundamental (short-range interactions) was adult-like by 20 weeks suggesting a differential development of long-range and short-range interactions. In contrast, corresponding phase data indicated significant immaturities at 20 weeks of age for both the short-and long-range components.

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