The effects of isolation, habitat fragmentation and degradation by livestock grazing on the use by birds of patches of Gimlet Eucalyptus salubris woodland in the wheatbelt of Western Australia

1998 ◽  
Vol 4 (2) ◽  
pp. 155 ◽  
Author(s):  
G. W. Arnold ◽  
J. R. Weeldenburg
Keyword(s):  
Western Australia ◽  
Structural Characteristics ◽  
Canopy Cover ◽  
Livestock Grazing ◽  
Individual Species ◽  
Native Vegetation ◽  
Frequency Of Occurrence ◽  
Large Species ◽  
Passerine Species ◽  
Frequency Of Occurence

The numbers of species, and the frequency of occurrence of individual species, in patches of Gimlet Eucalyptus salubris woodland in remnants of native vegetation in the central wheatbelt of Western Australia were recorded over a year. These values were examined in relation to the structural characteristics of the patches and the biogeographic attributes of the remnants (i.e., size and various indices of isolation from other native vegetation). There were five patches in large remnants (>100 ha) and 24 patches in small remnants (0.5?27.0 ha). Most of the small remnants were grazed by livestock and had lost much or all of the shrub understorey. The Galah Cacatua roseicapilla and Port Lincoln Ringnecked Parrot Platycercus zonarius were found in all patches, but the remaining large species of birds (Australian Raven Corvus coronoides,Pied Butcherbird Cracticus nigroregularis, Crested Pigeon Ocyphaps lophotes, and Yellow-throated Miner Manorina flavigula) were found more frequently in patches in small remnants. Conversely, with the exception of the Striated Pardalote Pardalotus striatus, small passerine species were found less frequently in patches in small remnants. Remnant size was significantly negatively correlated with frequency of occurrence of six of the eight common large species, indicating that these species concentrated in patches in small remnants, and significantly positively correlated with frequency of occurrence of two of four small passerine species. Having taken out the effect of remnant area, a stepwise regression procedure was used to see whether other biogeographic attributes of the remnants or habitat structure in the patches influenced the frequency of occurrence of individual species and species richness. As area of native vegetation within a 5 km radius increased so did the frequency of occurrence of the Galah and Port Lincoln Parrot, indicating that local numbers of the species affects their presence. Of the large birds only the Yellowthroated Miner was influenced by patch structural attributes whereas all species of small passerines showed responses to various structural attributes of the patches. Frequency of occurrence of the Striated Pardalote and the number of species of small passerines in a patch decreased with increasing distance to the nearest native vegatation. Overall frequency of occurence of small passerines increased with the number of linear strips of native vegetation linked to a remnant. In this study a majority of the small remnants were too small to support resident birds. The Gimlet patches, if used, would be part of a home range. Loss of the shrub understorey through grazing and loss of canopy cover through tree deaths had a significant impact on numbers of species of small passerines using the Gimlet patches. The conservation value of the patches in small remnants would be enhanced by increasing remnant size and by the linking of remnants to nearby native vegetation.

Allometry of pharmacokinetics and pharmacodynamics of the muscle relaxant metocurine in mammals

1995 ◽  
Vol 268 (1) ◽  
pp. R85-R91 ◽  
Author(s):  
G. A. Gronert ◽  
D. L. Fung ◽  
J. H. Jones ◽  
S. L. Shafer ◽  
S. V. Hildebrand ◽  
...  
Keyword(s):  
Muscle Relaxant ◽  
Bimodal Distribution ◽  
Active Species ◽  
Individual Species ◽  
Effect Compartment ◽  
Large Species ◽  
Pharmacokinetics And Pharmacodynamics ◽  
Size Dependent ◽  
Physiological Time ◽  
Allometric Analysis

We investigated the effects of body size on the pharmacokinetics and pharmacodynamics of the renally cleared muscle relaxant metocurine. We hypothesized that pharmacokinetics of the drug would change allometrically in proportion to physiological time [infinity Mb0.25, where Mb is body mass] and that pharmacodynamics would be independent of size because of the highly conserved structure of the acetylcholine receptor. Metocurine effects during general anesthesia were examined in 17 rats, 8 cats, 6 dogs, 5 pigs, 7 sheep, and 12 horses. Allometric analysis demonstrated size dependence for pharmacokinetics, which were affected by physiological time (Mb0.25). Pharmacodynamics were size independent, except for the value for effect compartment concentration associated with 50% twitch paralysis (IC50). Data from individual species had a bimodal distribution that was significant: pigs and sheep were more sensitive than other large species, and their IC50 appeared size independent. IC50 was size dependent in more active species (horse, dog, cat, rat). Although the mechanism is unknown, we speculate that this trend might relate to receptor density within the end plate. Thus pharmacokinetics changed in proportion to physiological time, and pharmacodynamics were in part size independent.

scholarly journals A Case Study Balancing Predetermined Targets and Real-World Constraints to Guide Optimum Urban Tree Canopy Cover for Perth, Western Australia

Forests ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1128
Author(s):  
Jackie Parker ◽  
Greg D. Simpson
Keyword(s):  
Western Australia ◽  
Canopy Cover ◽  
Tree Canopy ◽  
Urban Trees ◽  
Conceptual Tool ◽  
Urban Tree ◽  
Tree Canopy Cover ◽  
Urban Tree Canopy ◽  
Social Environmental

Trees in urban settings are becoming increasingly important as mediators to emerging challenges that transect social, environmental, and economic factors. Trees provide shade; absorb and store atmospheric carbon and other pollutants; reduce local temperature fluctuations; provide essential inner-city fauna habitat; assist in reducing over-land stormwater flow; provide amenity; and provide many more social, environmental, and economic benefits. To secure these benefits, tree canopy cover targets are commonly employed by land managers; however, such targets are rarely quantified against the characteristics and limitations of individual urban centers. Through the generation and interrogation of qualitative and quantitative data, this case study of Perth, Western Australia presents a new conceptual tool that integrates eleven factors found to influence the capacity and opportunity for a city to support urban tree canopy cover. This tool is designed to capture and causally weigh urban tree canopy considerations based on individual city characteristics, collective values, and identifiable constraints. The output of the tool provides an “optimum” tree canopy cover result (as a percentage of the urban fabric) to better inform canopy cover targets and recommendations for urban tree strategic planning and management. This tool is valuable for urban land managers, city planners, urban designers, and communities in effective planning, management, valuation, and investment regarding urban trees as a sub-set of urban green infrastructure.

The influence of plant diversity on the resilience of harvester termites to fire

1995 ◽  
Vol 2 (3) ◽  
pp. 279 ◽  
Author(s):  
Max Abensperg-Traun ◽  
Dion Steven ◽  
Lyn Atkins
Keyword(s):  
Western Australia ◽  
High Intensity ◽  
Experimental Studies ◽  
Grazing Pressure ◽  
Livestock Grazing ◽  
Floristic Diversity ◽  
Long Term Effects ◽  
Burnt Area ◽  
Food Species

The harvester termites in floristically rich mallee-heath of southern Western Australia appear resilient to high-intensity fire. This contrasts with the temporary extinction of harvesters occupying a narrow food niche in floristically simple, intensely burnt spinifex Triodia angusta grassland in tropical Western Australia. The present study examines the effects of high-intensity fire on harvester termites Drepanotermes tamminensis in vegetation of intermediate floristic diversity and compares its findings with these earlier studies. We sampled 20 mounds (termitaria) in both an unburnt and (adjacent) burnt stand of Allocasuarina campestris shrubland. Although partially regenerated three years after the fire, 40% of mounds in the burnt area were abandoned, contrasting with 10% in the unburnt stand. No harvested chaff was found in any of the abandoned mounds. The extent of mound occupation by D. tamminensis was considerably lower, and ant invasion higher, in the burnt stand. These findings are consistent with the hypothesis that high floristic diversity enhances the resilience of harvester termites to fire. The most likely mechanism is the availability of a range of plant (food) species with different regenerative responses to high-intensity fire. The death of spinifex and the associated harvester termites after fire may be atypical. We argue, however, that temporary extinction of harvester populations in arid Australia may not be exceptional, particularly where fire coincides with drought and high livestock grazing pressure. Rigorous experimental studies are necessary to enhance our understanding of the long-term effects of fire on harvester termite populations in different vegetation types and climatic zones.

Woody plant seedling distribution under invasive Lantana camara thickets in a dry-forest plot in Mudumalai, southern India

2011 ◽  
Vol 27 (4) ◽  
pp. 365-373 ◽  
Author(s):  
Geetha Ramaswami ◽  
R. Sukumar
Keyword(s):  
Lantana Camara ◽  
Dry Forest ◽  
Southern India ◽  
Individual Species ◽  
Forest Plot ◽  
Tree Seedlings ◽  
Frequency Of Occurrence ◽  
Dispersal Mode ◽  
Seasonally Dry ◽  
Seedling Distribution

Abstract:Lantana camara, a shrub of Central and South American origin, has become invasive across dry forests worldwide. The effect of the thicket-forming habit of L. camara as a dispersal and recruitment barrier in a community of native woody seedlings was examined in a 50-ha permanent plot located in the seasonally dry forest of Mudumalai, southern India. Sixty 100-m2 plots were enumerated for native woody seedlings between 10–100 cm in height. Of these, 30 plots had no L. camara thickets, while the other 30 had dense thickets. The frequency of occurrence and abundance of seedlings were modelled as a function of dispersal mode (mammal, bird or mechanical) and affinities to forest habitats (dry forest, moist forest or ubiquitous) as well as presence or absence of dense L. camara thickets. Furthermore, frequency of occurrence and abundance of individual species were also compared between thickets and no L. camara. At the community level, L. camara density, dispersal mode and forest habitat affinities of species determined both frequency of occurrence and abundance of seedlings, with the abundance of dry-forest mammal-dispersed species and ubiquitous mechanically dispersed species being significantly lower under L. camara thickets. Phyllanthus emblica and Kydia calycina were found to be significantly less abundant under L. camara, whereas most other species were not affected by the presence of thickets. It was inferred that, by affecting the establishment of native tree seedlings, L. camara thickets could eventually alter the community composition of such forests.

Spatial distributions of plankton in Shark Bay, Western Australia

1985 ◽  
Vol 36 (3) ◽  
pp. 421
Author(s):  
WJ Kimmerer ◽  
AD McKinnon ◽  
MJ Atkinson ◽  
JA Kessell
Keyword(s):  
Western Australia ◽  
Deep Sea ◽  
High Salinity ◽  
Individual Species ◽  
Initial Increase ◽  
Zooplankton Abundance ◽  
Spatial Distributions ◽  
Shark Bay ◽  
Abundance Patterns ◽  
Net Phytoplankton

The zooplankton of Shark Bay, Western Australia, shows an unusual pattern of abundance, with an initial increase from the ocean to the central bay, and a decrease of four orders of magnitude into the hypersaline region. The daytime zooplankton abundance in Hamelin Pool, at a salinity of >60 mg 1-1, is of a similar magnitude to that of the deep sea, and 100-fold below typical surface oceanic values. Night abundances are higher, but still well below surface oceanic values. The diverse oceanic community of net phytoplankton and zooplankton is replaced at intermediate salinities by a less diverse bay community, dominated by diatoms and several small copepods. At high salinities, the phytoplankton are mostly dinoflagellates and the zooplankton are mainly demersal forms. The abundance patterns for individual species can be attributed to intolerance of high salinity, although the pattern of total abun- dance is apparently due to extreme nutrient limitation in the hypersaline waters.

scholarly journals The Role of Red Squirrels (Tamiasciurus Hudsonicus) in Shaping Spatial Patterns of Serotiny in Lodgepole Pine (Pinus Contorta) Forests

2011 ◽  
Vol 34 ◽  
pp. 139-145
Author(s):  
Matt Talluto ◽  
Craig Benkman
Keyword(s):  
Seed Predation ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Canopy Cover ◽  
Ecosystem Processes ◽  
Tamiasciurus Hudsonicus ◽  
Individual Species ◽  
Red Squirrels ◽  
Long Term Storage ◽  
Sapling Density

Understanding the effects of individual species on community- and ecosystem-level processes is of critical importance in ecology. Recent work has demonstrated that variation in genetically controlled traits within foundation species can have large implications for ecosystem processes. Identifying these traits and the selective pressures on them is crucial in understanding how ecosystems are structured and how the systems will respond to disturbance. Serotiny, the long-term storage of seeds in the canopy, is thought to be an adaptation to stand replacing fire. Seeds from serotinous plants are released following a fire, and the proportion of serotinous trees determines sapling density following a fire. The effects of serotiny are not limited to the serotinous species, as sapling density is an important determinant of plant community structure and ecosystem processes (including primary productivity and nutrient cycling). Seed predation may select against serotiny, however, no studies have addressed how the relative strengths of selection from fire and seed predation combine to produce the spatial pattern of serotiny on the landscape. Here, we report on an ongoing study of the effects of selection from seed predation in lodgepole pine (Pinus contorta), a serotinous North American conifer. Red squirrels are negatively associated with serotiny at broad geographic scales, and may select against the serotinous trait. This project examined the correlation between red squirrel density and the frequency of serotiny in lodgepole pine forests and the mechanisms underlying potential selection against serotiny by red squirrels. Specifically, we tested whether this correlation was present at landscape scales, whether the fitness of serotinous trees was reduced in the presence of red squirrels, and what factors controlled the density of red squirrels. Preliminary results indicate that serotiny and squirrel density is negatively correlated, but only at low elevations. In the presence of squirrels, we observed significantly lower cone survival in serotinous trees, suggesting reduced fitness. Squirrel density was strongly affected by several measures of forest structure, including species composition, overhead canopy cover, and tree size (mean DBH).

scholarly journals Stopover Habitats of Landbirds During Fall: Use of Edge-Dominated and Early-Successional Forests

The Auk ◽  
2004 ◽  
Vol 121 (4) ◽  
pp. 1040-1055
Author(s):  
Paul G. Rodewald ◽  
Margaret C. Brittingham
Keyword(s):  
Habitat Use ◽  
Small Diameter ◽  
Canopy Cover ◽  
Lower Percentage ◽  
Spatial And Temporal Variation ◽  
Individual Species ◽  
Fruit Availability ◽  
Mature Forest ◽  
Forest Interior ◽  
Successional Forests

Abstract Despite much interest in the conservation of landbirds during migratory stopover periods, relatively few studies have examined spatial and temporal variation in habitat use and identified important habitats for migrating landbirds in North America. We surveyed migrant landbirds in five habitats (mature forest interior, mature forest-agricultural edge, mature suburban forest, mid-successional pole-stage forest, and early successional shrub-saplingstage forest) in central Pennsylvania from late August to early October, 1997–1999. We used abundances of individual species and migrant guilds, species richness, and fruit availability to assess relative habitat quality for fall migrants and measured structural characteristics associated with migrant habitat use. Of 15 species that differed in abundance among habitats, species that breed in mature forest (n = 10) were typically broadly distributed among habitats during stopover, with highest abundance in edge-dominated forests (forest-agricultural edge and suburban forest) and lowest abundance in pole-stage forests. Mature-forest-breeding migrants also regularly used early successional forests, where as many individuals were recorded as in forest interior. Shrub-sapling-breeding species (n = 5) generally were more narrowly distributed among habitats and were most abundant in early successional and edge-dominated forests. We detected among-year differences in relative use of habitats by mature-forest-breeding species, which suggests that the relative quality of stopover habitats may vary from year to year. Fruit availability was highest in shrub-sapling and forest-agricultural edge habitats and was positively associated with abundance of primary frugivores in all three years, indicating that fruit may be driving habitat selection by that guild. Mature-forest-breeding migrants were positively associated with forests that had more understory vegetation and lower percentage of canopy cover (i.e. more tree-fall gaps), which suggests that migrants selected sites with greater vertical and horizontal habitat heterogeneity. Migrating shrub-sapling-breeding species were positively associated with small-diameter stems (0–2.5 cm) and negatively associated with percentage of canopy cover (i.e. characteristics of breeding habitats). Consistently high use of mature edge-dominated and early-successional forests by a wide diversity of landbird species during fall stopover indicates the potential importance of those habitats for migratory landbird conservation.

scholarly journals Effects of livestock grazing on flocks of seed-eating birds in the central Monte desert, Argentina

2019 ◽  
Vol 97 (7) ◽  
pp. 606-611
Author(s):  
A. Zarco ◽  
V.R. Cueto ◽  
M.C. Sagario ◽  
L. Marone
Keyword(s):  
Structural Characteristics ◽  
Resource Depletion ◽  
Cattle Grazing ◽  
Livestock Grazing ◽  
Foraging Efficiency ◽  
Monte Desert ◽  
Management Actions ◽  
Animal Populations ◽  
Nuclear Species ◽  
Seed Eating

Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smaller flocks; (ii) reduces the density of nuclear species, decreasing the group cohesion in large flocks; (iii) makes large flocks less attractive by increasing individual competence for food. Our results provide evidence that cattle grazing affect the interactions of seed-eating birds and suggest the importance of understanding flocking behavior to bring about management actions.

Effects of Impoundment and Diversion on the Crustacean Plankton of Southern Indian Lake

1984 ◽  
Vol 41 (4) ◽  
pp. 613-637 ◽  
Author(s):  
K. Patalas ◽  
A. Salki
Keyword(s):  
Water Levels ◽  
Predatory Fish ◽  
Individual Species ◽  
Main Body ◽  
Large Species ◽  
Total Abundance ◽  
River Inflow ◽  
Cladoceran Species ◽  
Crustacean Plankton ◽  
The Mean

Planktonic crustaceans in Southern Indian Lake were surveyed in 1972 before impoundment, during 1975 when water levels rose above the recorded high level, and then annually from 1977 to 1980 after full impoundment and diversion. Synoptic data were collected in each of these years in midsummer during July or August from a set of 53 stations covering all regions of the lake. Vertical hauls were made at each station using twin nets of 77-μm mesh and 25-cm mouth diameter. In 1972, the crustacean plankton fauna of Southern Indian Lake was composed mainly of 15 copepod and 15 cladoceran species. At least 25 of these species were truly pelagic, while 5 were littoral. Cyclopoids comprised 46% of total crustacean abundance, calanoids 33%, and cladocerans 21%. Dominant species within these three groups were Cyclops bicuspidatus thomasi (37.6% of total abundance), Diaptomus ashlandi (20.1%), and Chydorus sphaericus (8.9%). Total abundance averaged 76 individuals (ind)∙L−1, comparable to more southerly waters such as Lake Ontario (80 ind∙L−1) and Lake Winnipeg (53–108 ind∙L−1) (K. Patalas. 1975. Int. Ver. Limnol. Verh. 19: 504–511). Throughout the lake, total crustacean abundances varied from 10 ind∙L−1 near the Churchill River inflow to between 100 and 200 ind∙L−1 in a few well protected areas. From 50 to 100 ind∙L−1 occurred within the main body of Southern Indian Lake. In 1975, an unusually high water year, lake mean plankton abundance was 61 ind∙L−1. Following diversion in 1976, no dramatic changes in species composition were observed. However, the mean abundance of crustaceans decreased to 40–46 ind∙L−1 during the period 1977–80. Regional zooplankton responses were varied. No significant changes occurred in areas adjacent to the Churchill River inflow, with pre- and post-diversion densities being 35 and 36 ind∙L−1, respectively. In the main water bodies north of the diversion route, abundances declined by 60% and biomass by 50%. A 2–3 °C drop in northern basin water temperatures, related to diversion, reduced growth rates by approximately 20% and resulted in a 60% decline in crustacean production. Not all groups of crustaceans responded similarily to impoundment and diversion. Lakewide average numbers of cladocerans declined from 16 to 4 ind∙L−1 and the area of their distribution was reduced particularly in northern regions of the lake following impoundment. Cyclopoids declined from 35 to 16 ind∙L−1 but showed no change in their distribution. These reductions were related to decreased water temperatures, lower midsummer chlorophyll a concentrations, and decreased water transparencies. The mean abundance of calanoids as a group did not change, but the abundance and distribution of individual species were variably altered. Smaller calanoid species showed either no change or a decrease in their numbers and distribution. Larger species, e.g. Limnocalanus macrurus, Senecella calanoides, and Diaptomus sicilis, were significantly more abundant and widespread following diversion. Similar increases in Mysis relicta were also observed. These large species, preferred food items for both whitefish and cisco, are cold stenotherms, inhabiting deeper water layers. Their increased abundance is likely associated with decreased water transparency offering better protection against predatory fish, decreased water temperature creating more favorable conditions, and increased water depth enlarging the volume of deeper waters suitable for these species.

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