Recolonization dynamics of benthic macroinvertebrates after artificial and natural disturbances in an Australian temporary stream

1991 ◽  
Vol 42 (3) ◽  
pp. 295 ◽  
Author(s):  
SS Brooks ◽  
AJ Boulton
Keyword(s):  
Particle Size ◽  
Species Richness ◽  
Benthic Macroinvertebrates ◽  
Large Scale ◽  
South Australia ◽  
Natural Disturbance ◽  
Small Scale ◽  
Temporary Stream ◽  
Large Scale Disturbance ◽  
Coarse Gravel

The effects of substratum particle size (cobbles, coarse gravel and medium-fine gravel) on recolonization by benthic macroinvertebrates after disturbance was investigated in small plots (0.05 m2) in the Finniss River, an intermittent stream in South Australia. Six weeks after flow resumed, the intermediate particle size (coarse gravel) supported the greatest densities of taxa and individuals. Experimental disturbance reduced species richness by 83% and numbers of individuals by 97%. Rapid recolonizers (e.g. mayfly and stonefly nymphs) showed little substratum specificity and attained predisturbance densities within one day. Slow recolonizers (e.g. chironomid hatchlings) favoured gravel substrata and had not reached predisturbance densities within 4 days. Recolonization of small plots appeared to be by surface movement from neighbouring intact areas. A spate on Day 7 prevented further sampling, destroying all experimental plots, but this permitted a study of macroinvertebrate recolonization following a natural disturbance at a larger spatial scale. The spate reduced species richness by 45% and numbers of individuals by 70%. Vertical migration rather than drift appeared to be the major source of recolonizing fauna. Our data show that results from small-scale experiments can not be extrapolated to large-scale disturbance because the scale of disturbance strongly influences the rate and pathways of recolonization as well as the sources and faunal composition of the recolonists.

scholarly journals Testing biodiversity theory using species richness of reef-building corals across a depth gradient

2019 ◽  
Vol 15 (10) ◽  
pp. 20190493 ◽  
Author(s):  
T. Edward Roberts ◽  
Sally A. Keith ◽  
Carsten Rahbek ◽  
Tom C. L. Bridge ◽  
M. Julian Caley ◽  
...  
Keyword(s):  
Species Richness ◽  
Large Scale ◽  
Coral Species ◽  
Environmental Gradients ◽  
Abiotic Factors ◽  
Empirical Support ◽  
Null Model ◽  
Local Scale ◽  
Small Scale ◽  
Energy Availability

Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

scholarly journals Pharmaceutical Particles Design by Membrane Emulsification: Preparation Methods and Applications in Drug Delivery

2017 ◽  
Vol 23 (2) ◽  
pp. 302-318 ◽  
Author(s):  
Emma Piacentini ◽  
Marijana Dragosavac ◽  
Lidietta Giorno
Keyword(s):  
Drug Delivery ◽  
Particle Size ◽  
Rational Design ◽  
Large Scale ◽  
Drug Loading ◽  
Small Scale ◽  
Scale Production ◽  
Membrane Emulsification ◽  
Preparation Methods ◽  
Promising Tool

Nowadays, the rational design of particles is an important issue in the development of pharmaceutical medicaments. Advances in manufacturing methods are required to design new pharmaceutical particles with target properties in terms of particle size, particle size distribution, structure and functional activity. Membrane emulsification is emerging as a promising tool for the production of emulsions and solidified particles with tailored properties in many fields. In this review, the current use of membrane emulsification in the production of pharmaceutical particles is highlighted. Membrane emulsification devices designed for small-scale testing as well as membrane-based methods suitable for large-scale production are discussed. A special emphasis is put on the important factors that contribute to the encapsulation efficiency and drug loading. The most recent studies about the utilization of the membrane emulsification for preparing particles as drug delivery systems for anticancer, proteins/peptide, lipophilic and hydrophilic bioactive drugs are reviewed.

scholarly journals Distinctive patterns and signals at major environmental events and collapse zone boundaries

2021 ◽  
Vol 193 (10) ◽  
Author(s):  
Melinda Pálinkás ◽  
Levente Hufnagel
Keyword(s):  
Climate Change ◽  
Cluster Analysis ◽  
Species Richness ◽  
Relative Abundance ◽  
Large Scale ◽  
Hierarchical Cluster ◽  
Small Scale ◽  
Total Abundance ◽  
First Order ◽  
Environmental Events

AbstractWe studied the patterns of pre-collapse communities, the small-scale and the large-scale signals of collapses, and the environmental events before the collapses using four paleoecological and one modern data series. We applied and evaluated eight indicators in our analysis: the relative abundance of species, hierarchical cluster analysis, principal component analysis, total abundance, species richness, standard deviation (without a rolling window), first-order autoregression, and the relative abundance of the dominant species. We investigated the signals at the probable collapse triggering unusual environmental events and at the collapse zone boundaries, respectively. We also distinguished between pulse and step environmental events to see what signals the indicators give at these two different types of events. Our results show that first-order autoregression is not a good environmental event indicator, but it can forecast or indicate the collapse zones in climate change. The rest of the indicators are more sensitive to the pulse events than to the step events. Step events during climate change might have an essential role in initiating collapses. These events probably push the communities with low resilience beyond a critical threshold, so it is crucial to detect them. Before collapses, the total abundance and the species richness increase, the relative abundance of the species decreases. The hierarchical cluster analysis and the relative abundance of species together designate the collapse zone boundaries. We suggest that small-scale signals should be involved in analyses because they are often earlier than large-scale signals.

scholarly journals Micromechanical study of potential scale effects in small-scale modelling of sinker tree roots

2021 ◽  
Author(s):  
Xingyu Zhang ◽  
◽  
Matteo Ciantia ◽  
Jonathan Knappett ◽  
Anthony Leung ◽  
...  
Keyword(s):  
Particle Size ◽  
Large Scale ◽  
Scale Effects ◽  
Distinct Element ◽  
Scaling Law ◽  
Scale Model ◽  
Small Scale ◽  
Tree Roots ◽  
Scale Modelling ◽  
Element Method

When testing an 1:N geotechnical structure in the centrifuge, it is desirable to choose a large scale factor (N) that can fit the small-scale model in a model container and avoid unwanted boundary effects, however, this in turn may cause scale effects when the structure is overscaled. This is more significant when it comes to small-scale modelling of sinker root-soil interaction, where root-particle size ratio is much lower. In this study the Distinct Element Method (DEM) is used to investigate this problem. The sinker root of a model root system under axial loading was analysed, with both upward and downward behaviour compared with the Finite Element Method (FEM), where the soil is modelled as a continuum in which case particle-size effects are not taken into consideration. Based on the scaling law, with the same prototype scale and particle size distribution, different scale factors/g-levels were applied to quantify effects of the ratio of root diameter (𝑑𝑟) to mean particle size (𝐷50) on the root rootsoil interaction.

scholarly journals The Promotion/Inhibition of the Seepage Transport of Copper Ions by Suspension-Colloidal Particles with Wide Size Gradation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qingke Nie ◽  
Huawei Li ◽  
Haipeng Yang ◽  
Tengfei Ni ◽  
Sichen Jiang
Keyword(s):  
Heavy Metal ◽  
Particle Size ◽  
Large Scale ◽  
Colloidal Particles ◽  
Copper Ions ◽  
Small Scale ◽  
Average Particle ◽  
Promoting Effect ◽  
Transport Distance ◽  
Retarding Effect

Sand column tests were conducted to investigate the seepage transport of silicon powders (SPs) with two wide particle size ranges (30-2000 nm and 2-70 μm), including the cotransport of SPs and copper ions. The results show that the graded large-scale SP has an obvious inhibiting influence on the transport of copper ions. In contrast, in the presence of the graded small-scale SP, the concentration of copper ions in the effluent tends to increase; i.e., there appears to be a promoting effect. However, after a long transport distance, the presence of SPs, regardless of particle size, has an overall retarding effect on heavy metal pollutants (e.g., copper ions). The promoting effect of the increase in seepage velocity on the concentration of copper ions in the effluent is greater with the graded large-scale SPs than with the graded small-scale SPs. In terms of the microstructural characteristics by metallographic microscopy, the average particle size of the deposited graded small-scale SPs is almost constant at different transport distances, while that of the deposited graded large-scale SPs tend to decrease significantly with increasing transport distance; i.e., notable bed filtration is exhibited in the latter case. This physical mechanism also determines the sequence and rate of the retarding effect of SPs on heavy metal ions under seepage flow.

Facilitating recruitment of Amphibolis as a novel approach to seagrass rehabilitation in hydrodynamically active waters

2010 ◽  
Vol 61 (10) ◽  
pp. 1123 ◽  
Author(s):  
Rachel J. Wear ◽  
Jason E. Tanner ◽  
Sonja L. Hoare
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
South Australia ◽  
Cost Effective ◽  
Belowground Biomass ◽  
Small Scale ◽  
Past Century ◽  
Wastewater Management ◽  
Novel Approach ◽  
High Wave Energy

Worldwide, 29% of seagrass habitats have been lost over the past century. Compared with large-scale losses, successful restoration programs are usually only small scale (a few hectares). One area of significant seagrass loss (>5200 ha) is Adelaide, South Australia. Improvements to wastewater management have raised the possibility of rehabilitation in this area. Traditional methods of seagrass restoration are expensive and have had limited success owing to high wave energy. We investigated a range of biodegradable substrates, mostly made of hessian (burlap), to enhance Amphibolis recruitment as an alternative. After 5 weeks, 16 514 seedlings, or 157 seedlings m–2, had recruited. Survival declined over the following 12 months to 31.4%, and down to 7.2% after 3 years, in part as a result of breakdown of the hessian, and the wave-exposed nature of the sites. During the initial 12 months, above- and belowground biomass increased 2.6- and 6.4-fold, respectively. The technique may represent a non-destructive, cost-effective (<AU$10 000 ha–1) method to restore Amphibolis over large spatial scales and in areas that are hydrodynamically too active for traditional techniques, thus helping ameliorate some of the large-scale losses of seagrasses that have occurred globally.

scholarly journals Unassisted invasions: understanding and responding to Australia’s high-impact environmental grass weeds

2017 ◽  
Vol 65 (8) ◽  
pp. 678 ◽  
Author(s):  
Rieks D. van Klinken ◽  
Margaret H. Friedel
Keyword(s):  
Large Scale ◽  
Propagule Pressure ◽  
Natural Disturbance ◽  
Reproductive Rate ◽  
High Impact ◽  
Expert Advice ◽  
Grass Species ◽  
Natural Environments ◽  
Disturbance Regimes ◽  
Large Scale Disturbance

Alien grass species have been intentionally introduced into Australia since European settlement over 200 years ago, with many subsequently becoming weeds of natural environments. We have identified the subset of these weeds that have invaded and become dominant in environmentally important areas in the absence of modern anthropogenic disturbance, calling them ‘high-impact species’. We also examined why these high-impact species were successful, and what that might mean for management. Seventeen high-impact species were identified through literature review and expert advice; all had arrived by 1945, and all except one were imported intentionally, 16 of the 17 were perennial and four of the 17 were aquatic. They had become dominant in diverse habitats and climates, although some environments still remain largely uninvaded despite apparently ample opportunities. Why these species succeeded remains largely untested, but evidence suggests a combination of ecological novelty (both intended at time of introduction and unanticipated), propagule pressure (through high reproductive rate and dominance in nearby anthropogenically-disturbed habitats) and an ability to respond to, and even alter, natural disturbance regimes (especially fire and inundation). Serious knowledge gaps remain for these species, but indications are that resources could be better focused on understanding and managing this limited group of high-impact species. They require new management approaches, especially to counteract the advantages of ecological novelty, reduce propagule pressure and better direct the large-scale disturbance regimes that continue to shape plant communities across Australia.

Gap dynamics of forest trees: A review with particular attention to boreal forests

2001 ◽  
Vol 9 (1) ◽  
pp. 1-59 ◽  
Author(s):  
J McCarthy
Keyword(s):  
Tropical Forests ◽  
Boreal Forests ◽  
Large Scale ◽  
The United States ◽  
Small Scale ◽  
Gap Dynamics ◽  
Large Scale Disturbance ◽  
Temperate Deciduous ◽  
Gap Disturbance ◽  
Multiple Trees

Small-scale gap disturbance in forests is reviewed. Caused by the death of individual or multiple trees with subsequent fall from the canopy, gaps have been extensively studied in temperate deciduous and tropical forests for the past 20 years. This review considers much of this research with a view to assessing the importance of gap disturbance in boreal forests. Because of the ubiquity of large-scale, stand-initiating disturbances such as landscape-level fires, epidemic insect outbreaks, and periodic extensive windthrow events, gap processes in boreal forests have received little attention. Research in the Scandinavian and Russian boreal forest, as well as in high-altitude boreal "outliers" found in Japan and the United States, is showing that gap disturbance determines forest structure and processes to a greater extent than previously assumed. Boreal forests dominated by the shade-tolerant fir (Abies) – spruce (Picea) complex are particularly well-adapted to the development of long-term, old-growth continuity in the absence of large-scale disturbance. Key words: gap dynamics, disturbance, boreal forests, temperate forests, tropical forests, silviculture.

Predicting species richness and abundance of tropical post-larval fish using machine learning

2020 ◽  
Vol 645 ◽  
pp. 125-139 ◽  
Author(s):  
H Jaonalison ◽  
JD Durand ◽  
J Mahafina ◽  
H Demarcq ◽  
N Teichert ◽  
...  
Keyword(s):  
Machine Learning ◽  
Species Richness ◽  
Large Scale ◽  
Larval Fish ◽  
Juvenile Fish ◽  
Larval Settlement ◽  
Small Variation ◽  
Ecological Impacts ◽  
Small Scale ◽  
Species Richness And Abundance

Post-larval prediction is important, as post-larval supply allows us to understand juvenile fish populations. No previous studies have predicted post-larval fish species richness and abundance combining molecular tools, machine learning, and past-days remotely sensed oceanic conditions (RSOCs) obtained in the days just prior to sampling at different scales. Previous studies aimed at modeling species richness and abundance of marine fishes have mainly used environmental variables recorded locally during sampling and have merely focused on juvenile and adult fishes due to the difficulty of obtaining accurate species richness estimates for post-larvae. The present work predicted post-larval species richness (identified using DNA barcoding) and abundance at 2 coastal sites in SW Madagascar using random forest (RF) models. RFs were fitted using combinations of local variables and RSOCs at a small-scale (8 d prior to fish sampling in a 50 × 120 km2 area), meso-scale (16 d prior; 100 × 200 km2), and large-scale (24 d prior; 200 × 300 km2). RF models combining local and small-scale RSOC variables predicted species richness and abundance best, with accuracy around 70 and 60%, respectively. We observed a small variation of RF model performance in predicting species richness and abundance among all sites, highlighting the consistency of the predictive RF model. Moreover, partial dependence plots showed that high species richness and abundance were predicted for sea surface temperatures <27.0°C and chlorophyll a concentrations <0.22 mg m-3. With respect to temporal changes, these thresholds were solely observed from November to December. Our results suggest that, in SW Madagascar, species richness and abundance of post-larval fish may only be predicted prior to the ecological impacts of tropical storms on larval settlement success.

Butterfly species richness and community composition in forests affected by ENSO-induced burning and habitat isolation in Borneo

2004 ◽  
Vol 20 (4) ◽  
pp. 359-367 ◽  
Author(s):  
Daniel F. R. Cleary ◽  
Arne Ø. Mooers
Keyword(s):  
Species Richness ◽  
Community Composition ◽  
Dominant Species ◽  
Large Scale ◽  
Habitat Isolation ◽  
Butterfly Species ◽  
Continuous Forest ◽  
Large Scale Disturbance ◽  
The Impact ◽  
Burned Forest

Landscape-scale studies of community traits such as species richness and community composition are sorely needed to explore the impact of large-scale disturbance events such as ENSO (El Niño Southern Oscillation)-induced burning and habitat isolation on rain-forest communities. Here we assess butterflies in continuous forest, in unburned isolates surrounded by burned forest and in burned forest, in addition to areas sampled before the most recent (1997/98) large-scale burn event in Borneo. Overall levels of species richness were significantly higher pre-ENSO and in continuous forest than in unburned isolates and burned forest. There was, however, some variation among butterfly families in these patterns, with no significant differences among habitats (continuous forest, isolates and burned forest) for the Hesperiidae and significant differences for the other butterfly families. Patterns of community composition showed that similarity was greater between distant continuous forest and isolates than between either of these and burned forest. Since the unburned isolates were surrounded by the burned forest this indicates that the habitat (burned or unburned) overrides geographical differences. Dominant species that contributed substantially to differences among habitats were often completely absent from either burned or unburned forest. The combined patterns of species richness and community structure suggest that burning affects forest ecosystems by a replacement of dominant species while habitat isolation may affect areas by leading to the local extinction of rare species.

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