Riparian vegetation removal alters consumer - resource stoichiometry in an Australian lowland stream

2012 ◽  
Vol 63 (1) ◽  
pp. 1 ◽  
Author(s):  
Darren P. Giling ◽  
Paul Reich ◽  
Ross M. Thompson
Keyword(s):  
Riparian Vegetation ◽  
Anthropogenic Impacts ◽  
Negative Relationship ◽  
Canopy Cover ◽  
Ecological Impacts ◽  
Molar Ratio ◽  
Freshwater Crayfish ◽  
Resource Quality ◽  
Lowland Stream ◽  
Eastern Australia

Anthropogenic impacts on stream ecosystems generate changes in nutrient and carbon availability which act as stoichiometric challenges to consumers. We tested the hypothesis that removal of Eucalyptus riparian vegetation alters in-stream resource stoichiometry with flow-on effects for a benthic consumer (the freshwater crayfish, Cherax destructor). Sites with high and low riparian canopy cover were selected on a lowland stream in south-eastern Australia. A reduction in riparian vegetation canopy cover was associated with decreased terrestrial detritus (low nutritional quality; high carbon to nitrogen (C : N) ratio) and increased cover of macrophytes and filamentous algae (high quality; low C : N ratio). This resource-quality shift was associated with a small but significant decrease in C. destructor C : N ratio (molar ratio of muscle tissue). This suggests that the animals are deviating from homeostasis and may be in better condition in the stream pools dominated by in-stream productivity. A significant negative relationship between C. destructor length and C : N ratio was observed, suggesting that resource-quality impacts may differ with age. The present study has shown that riparian loss alters stoichiometric interactions in stream benthic ecosystems, with potential consequences for stream processes such as nutrient cycling. Ecological stoichiometric theory should therefore be further utilised to make predictions of ecological impacts in freshwater systems.

Characteristics of refugia used by the threatened Australian growling grass frog (Litoria raniformis) during a prolonged drought

2013 ◽  
Vol 40 (5) ◽  
pp. 385 ◽  
Author(s):  
Nick Clemann ◽  
Michael P. Scroggie ◽  
Michael J. Smith ◽  
Garry N. L. Peterson ◽  
David Hunter
Keyword(s):  
Water Body ◽  
Aquatic Vegetation ◽  
Negative Relationship ◽  
Canopy Cover ◽  
Tree Canopy ◽  
Severe Drought ◽  
Body Type ◽  
Tree Canopy Cover ◽  
Millennium Drought ◽  
Eastern Australia

Context Because they are dependent on water, drought can have a deleterious impact on aquatic-breeding amphibians. One such species, the threatened growling grass frog (Litoria raniformis) occurs in south-eastern Australia, a region that has recently emerged from a decade-long, severe drought. Aims We aimed to identify features of drought refugia that facilitate persistence of L. raniformis, so as to provide guidance to natural-resource managers attempting to conserve populations of this species during drought. Methods We conducted repeat surveys for L. raniformis at 90 water bodies at the end of the ‘millennium drought’. We recorded the following six environmental variables for each water body: origin (natural or not), type (lotic or lentic), proportion of aquatic vegetation cover, conductivity of water, riparian tree-canopy cover and distance to the nearest woodland. We used occupancy models to relate the presence of L. raniformis to these variables, while accounting for uncertain detection. Key results Water-body type (natural or artificial, lentic or lotic) had minimal influence on the probability of occupancy by L. raniformis. We found a strong negative relationship between occupancy and conductivity of water (a surrogate for salinity), and a positive relationship between occupancy and the proportion of aquatic vegetation. We found a negative relationship between detection and the extent of aquatic vegetation, and a mildly negative effect of canopy cover on occupancy. Conclusions Habitat characteristics are more important indicators of the quality of drought refugia for L. raniformis than is the type of water body per se. Consequently, we identified aquatic vegetation and salinity as important targets for management when planning the retention, creation or restoration of habitat to facilitate persistence of L. raniformis during drought. Implications Our results highlighted aquatic vegetation and water-quality parameters that are likely to facilitate the persistence of L. raniformis during drought. Assessing the effectiveness of our recommendations in an experimental framework would ensure that conservation management of this frog can be refined over time.

scholarly journals Dredging fundamentally reshapes the ecological significance of 3D terrain features for fish in estuarine seascapes

2022 ◽  
Author(s):  
Hayden P. Borland ◽  
Ben L. Gilby ◽  
Christopher J. Henderson ◽  
Rod M. Connolly ◽  
Bob Gorissen ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Three Dimensional ◽  
Ecological Impacts ◽  
Fish Diversity ◽  
Urban Landscapes ◽  
Ecological Significance ◽  
Landscape Modification ◽  
Eastern Australia ◽  
Coastal Landscapes ◽  
Terrain Features

Abstract Context Landscape modification alters the condition of ecosystems and the structure of terrain, with widespread impacts on biodiversity and ecosystem functioning. Seafloor dredging impacts a diversity of flora and fauna in many coastal landscapes, and these processes also transform three-dimensional terrain features. The potential ecological significance of these terrain changes in urban seascapes has, however, not been investigated. Objectives We examined the effects of terrain variation on fish assemblages in 29 estuaries in eastern Australia, and tested whether dredging changes how fish associate with terrain features. Methods We surveyed fish assemblages with baited remote underwater video stations and quantified terrain variation with nine complementary metrics (e.g. depth, aspect, curvature, slope, roughness), extracted from bathymetry maps created with multi-beam sonar. Results Fish diversity and abundance were strongly linked to seafloor terrain in both natural and dredged estuaries, and were highest in shallow waters and near features with high curvature. Dredging, however, significantly altered the terrain of dredged estuaries and transformed the significance of terrain features for fish assemblages. Abundance and diversity switched from being correlated with lower roughness and steeper slopes in natural estuaries to being linked to features with higher roughness and gentler slopes in dredged estuaries. Conclusions Contrasting fish-terrain relationships highlight previously unrecognised ecological impacts of dredging, but indicate that plasticity in terrain use might be characteristic of assemblages in urban landscapes. Incorporating terrain features into spatial conservation planning might help to improve management outcomes, but we suggest that different approaches would be needed in natural and modified landscapes.

scholarly journals Foraging loads of red wood ants:Formica aquilonia(Hymenoptera: Formicidae) in relation to tree characteristics and stand age

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2049 ◽  
Author(s):  
Heloise Gibb ◽  
Jon Andersson ◽  
Therese Johansson
Keyword(s):  
Large Diameter ◽  
Negative Relationship ◽  
Small Diameter ◽  
Resource Depletion ◽  
Foraging Efficiency ◽  
Stand Age ◽  
Resource Quality ◽  
Red Wood Ants ◽  
Wood Ants ◽  
Colony Level

Background.Foraging efficiency is critical in determining the success of organisms and may be affected by a range of factors, including resource distance and quality. For social insects such as ants, outcomes must be considered at the level of both the individual and the colony. It is important to understand whether anthropogenic disturbances, such as forestry, affect foraging loads, independent of effects on the quality and distribution of resources. We asked if ants harvest greater loads from more distant and higher quality resources, how individual efforts scale to the colony level, and whether worker loads are affected by stand age.Methods.First, we performed a fine-scale study examining the effect of distance and resource quality (tree diameter and species) on harvesting of honeydew by red wood ants,Formica aquilonia, in terms of crop load per worker ant and numbers of workers walking up and down each tree (ant activity) (study 1). Second, we modelled what the combination of load and worker number responses meant for colony-level foraging loads. Third, at a larger scale, we asked whether the relationship between worker load and resource quality and distance depended on stand age (study 2).Results.Study 1 revealed that seventy percent of ants descending trees carried honeydew, and the percentage of workers that were honeydew harvesters was not related to tree species or diameter, but increased weakly with distance. Distance positively affected load mass in both studies 1 and 2, while diameter had weak negative effects on load. Relationships between load and distance and diameter did not differ among stands of different ages. Our model showed that colony-level loads declined much more rapidly with distance for small diameter than large diameter trees.Discussion.We suggest that a negative relationship between diameter and honeydew load detected in study 1 might be a result of crowding on large diameter trees close to nests, while the increase in honeydew load with distance may result from resource depletion close to nests. At the colony level, our model suggests that very little honeydew was harvested from more distant trees if they were small, but that more distant larger trees continued to contribute substantially to colony harvest. Although forestry alters the activity and foraging success of red wood ants, study 2 showed that it does not alter the fundamental rules determining the allocation of foraging effort.

scholarly journals The value of trophic interactions for ecosystem function: dung beetle communities influence seed burial and seedling recruitment in tropical forests

2016 ◽  
Vol 283 (1844) ◽  
pp. 20161634 ◽  
Author(s):  
Hannah M. Griffiths ◽  
Richard D. Bardgett ◽  
Julio Louzada ◽  
Jos Barlow
Keyword(s):  
Tropical Forests ◽  
Seedling Recruitment ◽  
Anthropogenic Impacts ◽  
Anthropogenic Activities ◽  
Seedling Emergence ◽  
Negative Relationship ◽  
Dung Beetle ◽  
Burial Depth ◽  
Seed Burial ◽  
Emergence Success

Anthropogenic activities are causing species extinctions, raising concerns about the consequences of changing biological communities for ecosystem functioning. To address this, we investigated how dung beetle communities influence seed burial and seedling recruitment in the Brazilian Amazon. First, we conducted a burial and retrieval experiment using seed mimics. We found that dung beetle biomass had a stronger positive effect on the burial of large than small beads, suggesting that anthropogenic reductions in large-bodied beetles will have the greatest effect on the secondary dispersal of large-seeded plant species. Second, we established mesocosm experiments in which dung beetle communities buried Myrciaria dubia seeds to examine plant emergence and survival. Contrary to expectations, we found that beetle diversity and biomass negatively influenced seedling emergence, but positively affected the survival of seedlings that emerged. Finally, we conducted germination trials to establish the optimum burial depth of experimental seeds, revealing a negative relationship between burial depth and seedling emergence success. Our results provide novel evidence that seed burial by dung beetles may be detrimental for the emergence of some seed species. However, we also detected positive impacts of beetle activity on seedling recruitment, which are probably because of their influence on soil properties. Overall, this study provides new evidence that anthropogenic impacts on dung beetle communities could influence the structure of tropical forests; in particular, their capacity to regenerate and continue to provide valuable functions and services.

scholarly journals Canopy cover and anurans: nutrients are the most important predictor of growth and development

2016 ◽  
Vol 94 (3) ◽  
pp. 225-232 ◽  
Author(s):  
Freya E. Rowland ◽  
Sara K. Tuttle ◽  
María J. González ◽  
Michael J. Vanni
Keyword(s):  
Growth And Development ◽  
Large Scale ◽  
Food Resource ◽  
Canopy Cover ◽  
Resource Quality ◽  
Bottom Up ◽  
Growth And Survival ◽  
Primary Producer ◽  
Full Factorial ◽  
Potential Food

Bottom-up effects such as the availability of light and nutrients can have large impacts on primary producer quantity and quality, which is then translated into the growth and development of consumers. The use of “canopy cover” as a bottom-up predictive factor is a broad categorization, as canopy cover controls both the amount of light allowed into a pond and the nutrient load through leaf litter. To test how light and nutrients influence pond ecosystems, we manipulated inorganic nutrients and light in a 2 × 3 full-factorial, large-scale mesocosm experiment. Larval American Bullfrogs (Lithobates catesbeianus (Shaw, 1802)) were reared for 6 weeks at low densities and then assessed for development, growth, and survival at the end of the experiment. We also collected weekly samples of potential food resources (phytoplankton and periphyton) for the estimation of algal production and stoichiometric quality (carbon:nitrogen:phosphorus). Light had strong effects on food resource quality; however, resource quality did not significantly predict tadpole growth or development. Instead, nutrients seemed to be the most important factor as a stimulator of total algal primary production and some unknown pathway, which in turn affected tadpole development. Ours is the first study to investigate canopy cover using a comprehensive causal model, and our results suggest in regards to tadpole growth and development, canopy cover is important mainly as a source of nutrients to ponds.

Do bare-nosed wombat (Vombatus ursinus) mounds influence terrestrial macroinvertebrate assemblages in agricultural riparian zones?

2009 ◽  
Vol 57 (5) ◽  
pp. 329 ◽  
Author(s):  
Philip Borchard ◽  
Ian A. Wright ◽  
Clare McArthur
Keyword(s):  
Canopy Cover ◽  
Soil Surface ◽  
Macroinvertebrate Communities ◽  
Riparian Ecosystems ◽  
Macroinvertebrate Assemblages ◽  
Ecological Variability ◽  
Eastern Australia ◽  
Surrounding Landscape ◽  
Study Sites

Riparian ecosystems contain a complex mosaic of habitat structure types that can support distinct macroinvertebrate communities. Bare-nosed wombats (Vombatus ursinus) are often an integral component of agricultural riparian systems in south-eastern Australia. In these systems, wombats construct large burrow systems and mounds in the stream banks. Wombat mound structures vary markedly from the surrounding landscape and they may influence macroinvertebrate assemblages. We examined this ecosystem-engineering role of wombats as well as the ecological variability within our agricultural riparian study sites on the possible influence on macroinvertebrate assemblages. There were no detectable effects of wombat mounds on the richness or abundance of macroinvertebrates on the soil surface. At the site level, however, macroinvertebrate assemblages were most influenced by litter depth, upper canopy cover, cattle hoof prints and slope. The ecological variables within the study sites strongly affected macroinvertebrate assemblages. These findings reflect an influence of anthropogenic impact on communities of ground-dwelling invertebrates that have been found in other studies. It is possible that a finer resolution of taxa may highlight a unique pattern of macroinvertebrate use of wombat mounds.

scholarly journals Landscape effects on the occurrence of ichthyofauna in first-order streams of southeastern Brazil

2016 ◽  
Vol 28 (0) ◽  
Author(s):  
Gabriela Santos Tibúrcio ◽  
Carolina da Silva Carvalho ◽  
Fabio Cop Ferreira ◽  
Roberto Goitein ◽  
Milton Cezar Ribeiro
Keyword(s):  
Species Richness ◽  
Functional Groups ◽  
Riparian Vegetation ◽  
Riparian Forest ◽  
Vegetation Type ◽  
Canopy Cover ◽  
Southeastern Brazil ◽  
Temperature Conductivity ◽  
Explanatory Variables ◽  
First Order

Abstract Objective In this study we aimed to understand how extrinsic environmental factors measured in the watercourses and the surrounding landscape influence the ichthyofauna of first-order streams. Methods Data were collected within the Corumbataí River Basin, São Paulo, southeastern Brazil, during the dry season of 2012. We sampled the ichthyofauna in 13 stretches of streams distributed across four river sub-basins. The stretches differed in relation to the presence/absence of riparian forest, the predominant type of matrix and the percentage of forest. Response variables were species richness and the occurrence of functional groups and explanatory variables include both local and landscape structures from the surrounding environment. Local variables comprised the following water quality and structural attributes: pH, temperature, conductivity, turbidity, flow rate, depth, width, type of substrate. Landscape variables included presence/absence of riparian vegetation, type of vegetation, type of matrix, percentage of forest and canopy cover. Results A total of 268 individuals were recorded, which were distributed among 12 species. The landscape structure influenced the occurrence of functional groups in first-order streams, especially allochthonous-feeders, nektonic and hypoxia-intolerant species. The presence of riparian forest was the most important predictor. Species richness was negatively related to the presence of riparian vegetation, supporting the hypothesis that degraded landscapes lead to a reduction in diversity. Conclusion The protection of riparian vegetation is critical to the maintenance of ichthyofauna diversity in first-order streams. The presence or absence of riparian vegetation differently affected the occurrence of species depending on their functional characteristics, particularly those related to the tolerance to hypoxia, source of alimentary items and the position in the water column.

scholarly journals Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes

2019 ◽  
Vol 76 (4) ◽  
pp. 1052-1061 ◽  
Author(s):  
Christopher J Henderson ◽  
Ben L Gilby ◽  
Thomas A Schlacher ◽  
Rod M Connolly ◽  
Marcus Sheaves ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Urban Expansion ◽  
Ecological Impacts ◽  
Spatial Context ◽  
Fish Diversity ◽  
Mangrove Forests ◽  
Habitat Types ◽  
Tropical Estuarine ◽  
Eastern Australia ◽  
Close Proximity

Abstract Coastal seascapes are composed of a diversity of habitats that are linked in space and time by the movement of organisms. The context and configuration of coastal ecosystems shapes many important properties of animal assemblages, but potential seascape effects of natural and artificial habitats on nearby habitats are typically considered in isolation. We test whether, and how, the seascape context of natural and urban habitats modified fish assemblages across estuaries. Fish were sampled with underwater videos in five habitat types (mangroves, rock bars, log snags, unvegetated sediments, armoured shorelines) in 17 estuaries in eastern Australia. Different habitats supported distinct fish assemblages, but the spatial context of mangroves and armoured shorelines had pervasive ecological effects that extended across entire estuaries. In most estuarine habitats, fish diversity and abundance was greatest when they were in close proximity of mangroves, and decreased due to the proximity of armoured shorelines. Many cities are centred on estuaries, and urban expansion is often associated with the fragmentation of mangrove forests. Our findings emphasize that these transformations of urban estuarine landscapes are likely to propagate to broader ecological impacts detectable in multiple habitats beyond mangrove forests.

The taxonomy and phylogeny of the 'Cherax destructor' complex (Decapoda : Parastacidae) examined using mitochondrial 16S sequences

2003 ◽  
Vol 51 (2) ◽  
pp. 99 ◽  
Author(s):  
C. M. Austin ◽  
T. T. T. Nguyen ◽  
M. M. Meewan ◽  
D. R. Jerry
Keyword(s):  
Phylogenetic Analysis ◽  
New South ◽  
Mitochondrial Gene ◽  
Haplotype Diversity ◽  
Morphological Plasticity ◽  
Phylogeographic Structure ◽  
Freshwater Crayfish ◽  
Cherax Destructor ◽  
South Wales ◽  
Eastern Australia

This study uses nucleotide sequences from the 16S rRNA mitochondrial gene to investigate the taxonomy and phylogeny of freshwater crayfish belonging to the 'Cherax destructor' complex. The sequencing of an approximately 440-bp fragment of this gene region from freshwater crayfish sampled from 14 locations identified significant haplotype diversity. Phylogenetic analysis found three distinct clades that correspond to the species C. rotundus, C. setosus and C. destructor. C. rotundus is largely confined to Victoria, and C. setosus is restricted to coastal areas north of Newcastle in New South Wales. C. destructor is widely distributed in eastern Australia and shows significant phylogeographic structure, with three well supported clades. None of these clades, however, correspond to species previously recognised as C. esculus, C. davisi or C. albidus. The failure to genetically distinguish these morphologically defined species is consistent with reproductive information and morphological plasticity relating to habitat similar to that documented for other Cherax species.

Sign in / Sign up

Export Citation Format

Share Document