Studies in the ecology of the Riverine Plain. V. Plant density response of species in a Danthonia caespitosa grassland to 16 years of grazing by Merino sheep

1969 ◽  
Vol 17 (2) ◽  
pp. 255 ◽  
Author(s):  
OB Williams
Keyword(s):  
Plant Density ◽  
Grazing Pressure ◽  
Individual Species ◽  
Published Data ◽  
Merino Sheep ◽  
Unique Nature ◽  
Feral Animals ◽  
Stocking Rates ◽  
Permanent Quadrats

The species density of 252 permanent quadrats set in plots which were ungrazed and lightly, moderately, and heavily grazed, in a Danthonia caespitosa Gaudich. grassland, was measured on seven occasions between October 1949 and October 1965. The field data were analysed by means of a Response Index and a Grazing Pressure Index to give the grazing responses of 41 individual species. Those species favoured either by grazing or by non-grazing are listed, and their performance examined in relation to published data on the dietary selection exercised by Merino sheep. The present D. caespitosa grassland is a disclimax one resulting from the grazing of domestic and feral animals, and most species have already come into equilibrium with the total environment. It is suggested that the observed reductions in plant density, size, and the seed crop of annual species in the grazed plots was not followed by the elimination of any species because stocking rates applied in the experiment were no more severe than those which brought about the development of the grassland. The possible unique nature of long-term exclosures in a disclimax grassland is noted.

Observations on the regeneration of shrubs and woody forbs over a ten year period in grazed quadrats on Mileura Station, Western Australia.

1979 ◽  
Vol 1 (3) ◽  
pp. 215 ◽  
Author(s):  
SJJF Davies ◽  
TFM Walsh
Keyword(s):  
Species Diversity ◽  
Western Australia ◽  
Individual Species ◽  
Stocking Rate ◽  
Merino Sheep ◽  
Reverse Trend ◽  
Average Rainfall ◽  
Stocking Rates

Observations are reported on the regeneration of shrubs within grazed quadrats in inland Western Australia (26' 22's; 117' 20'~). The observations showed that in a ten year period of slightly above average rainfall, an increase in number of individual plants occurred in 24 out of 30 species of shrubs. No change occurred in four species and a decrease in numbers was observed in two species. Figures are given of the stocking rate of merino sheep on each quadrat in each year. Although no overall differences in amount of regeneration was observed in quadrats subjected to different stocking rates, within the range of rates occurring in this study (6.9 to 13.7 ha per sheep) individual species did show trends indicating different rates of regeneration under different stocking rates. Eremophila fraseri regenerated faster in quadrats experiencing high stocking rates than in those experiencing low ones and the reverse trend was shown by Solanum ashbyae and Acacia tetragonophylla. The Eremophila is considered unpalatable to stock whereas both the Solanum and the Acacia are eaten by sheep. Such trends could lead, eventually, to changes in species diversity in the area. The results of these observations suggest that the regeneration of rangeland shrubs is not incompatible with commercial stocking rates at Mileura.

Stocking rate trials in Ankole, Uganda: I. Weight gain of Ankole steers at intermediate and heavy stocking rates under different managements

1974 ◽  
Vol 82 (3) ◽  
pp. 497-506 ◽  
Author(s):  
G. N. Harrington ◽  
D. Pratchett
Keyword(s):  
Weight Gain ◽  
Grazing Pressure ◽  
Stocking Rate ◽  
Rotational Grazing ◽  
Brachiaria Decumbens ◽  
Continuous Grazing ◽  
Weight Gains ◽  
The Cost ◽  
Stocking Rates

SUMMARYA series of stocking rate trials running for differing periods between 1961 and 1972 are summarized. Weight gains of steers grazed at 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal on Cymbopogon/Hyparrhenia/Themeda pasture are detailed. Subtreatments included continuous and rotational grazing and the removal of the unpalatable Cymbopogon afronardus.Weight gains at 0·6 ha/animal were higher than a linear relationship between stocking rate expressed as animals/ha and weight gain would predict. This was ascribed to the dominance of the high quality grass Brachiaria decumbens at this grazing pressure.Rotational grazing was less productive than continuous grazing, because C. afronardus increased more rapidly under this management, but there was less soil erosion. Removal of C. afronardus increased cattle growth rates and gains/ha by over 40% at 0·6 ha/animal. The cost of clearing this weed should be recovered in 2 years from a commercial cattle ranch. A grazing pressure of ca. 0·8 ha/animal is expected to maximize long-term profits on C. afronardus-free Ankole rangeland and in 3 years in this trial average gains of 0·29 kg/day/animal were achieved. This was an annual production level of 131 kg/ha/annum, which compared with 53 kg/ha at 2·4 ha/animal and 143 kg/ha at 0·6 ha/animal.

Changes in pH and organic carbon were minimal in a long-term field study in the Western District of Victoria

2002 ◽  
Vol 53 (2) ◽  
pp. 115 ◽  
Author(s):  
J. W. D. Cayley ◽  
M. R. McCaskill ◽  
G. A. Kearney
Keyword(s):  
Organic Carbon ◽  
Average Rate ◽  
Perennial Grass ◽  
Subterranean Clover ◽  
Grazing Pressure ◽  
Rate Of Change ◽  
Stocking Rate ◽  
Mean Values ◽  
Stocking Rates

Changes in soil pH from a long-term experiment at Hamilton, Vic., associated with time, fertiliser application, and stocking rate were assessed. The pH was measured in a 1 :5 suspension of soil in water (pHW) from 1980 onwards and in a 1:5 suspension of soil in 0.01 M CaCl2 (pHCa) from 1984 onwards. Topsoils (0–10 cm) were sampled regularly from 1980 to 1999, and the soil profile to a depth of 80 cm in 1994. The site was sown to perennial ryegrass, phalaris, and subterranean clover in 1977. Treatments fertilised with different amounts of superphosphate were grazed by sheep at stocking rates of 7–19 dry sheep equivalents (DSE)/ha. Average applications of phosphorus (P) ranged from 0.5 to 38.7 kg P/ha.year. The pHCa of the topsoil in 1984 was 4.9. It decreased at an average rate of 0.005 pHCa or 0.008 pHW units/year, with little variation due to fertiliser or stocking rate. Measurements in 1994 revealed subtle but statistically significant (P < 0.01) trends in soil pHCa that were associated with grazing pressure, inputs of fertiliser, and whether or not areas sampled were used by the sheep for camping. The top 0–5 cm of soil was slightly less acidic (+0.07 pHCa units) in the camp areas compared with non-camp areas. Below 5 cm to a depth of 80 cm, camp areas were more acidic (–0.19 pHCa units). At the highest stocking rates, heavier applications of superphosphate were associated with greater subsoil acidity: –0.06 pHCa units per 100 kg phosphorus (P) applied. There was no relationship at medium stocking rates. At low stocking rates, higher P applications were associated with more alkaline subsoils. Net removal of product from 1979 to 1994 (wool and meat removed from plots and excreta transferred to camps) was estimated to be equivalent to 140–380 kg/ha of lime over this 15-year period. The organic carbon (OC) content of the topsoil did not change over 20 years of records from 1979, and was unaffected by inputs of P. In 1994, the OC content of the 0–5 cm layer of topsoil was greater than the 5–10 cm layer (mean values 5.5% and 3.8% respectively; P < 0.001). The OC content of camp areas was higher than that of non-camp areas, this difference being more pronounced in the 0–5 cm layer (P < 0.01). It was concluded that the rate of change of pH was slow because of the high pH buffering capacity of the soil, the small amount of alkalinity removed in product, and the generally high perennial grass content of the pastures. Soils shown to be at greatest risk of acidification from this study were those under camp areas, and where high fertiliser rates were applied to pastures with a low perennial grass content. Rotational grazing should diminish these problems by reducing the concentration of excreta in camp areas, and favouring perennials over annuals in both camp and non-camp areas. Inputs of lime may eventually be needed to compensate for the acidifying effect of product removal.

Available phosphorus, sulfur, potassium, and other cations in a long-term grazing experiment in south-western Victoria

2002 ◽  
Vol 53 (12) ◽  
pp. 1349 ◽  
Author(s):  
J. W. D. Cayley ◽  
M. R. McCaskill ◽  
G. A. Kearney
Keyword(s):  
Nutrient Status ◽  
Grazing Pressure ◽  
Available Phosphorus ◽  
Plant Responses ◽  
Single Superphosphate ◽  
Soil P ◽  
Olsen P ◽  
Western Victoria ◽  
Stocking Rates

Relationships between amounts of superphosphate applied to pasture and stocking rate on available nutrient status were assessed from 1979 to 2000 on a chromosol derived from basalt at Hamilton, Victoria. The pastures were stocked with sheep at low, medium, or high grazing pressures in factorial combination with 6 levels of superphosphate. Overall annual amounts of single superphosphate (8.8% P, 11% S, 19% Ca) applied ranged from 0.4 to 36 kg P/ha. Potassium chloride (KCl) was applied to all plots periodically. Average stocking rates ranged from 7 to 19 dry sheep equivalents (DSE)/ha. The nutrient status of plots was monitored by sampling the soil to a depth of 10 cm, avoiding the areas used by the sheep for camping. In 1994, samples of topsoil (0–5 cm and 5–10 cm) were taken from the camp areas and non-camp areas in each plot in order to assess 'plant-available' P, S, and extractable cations. Changes in P and S with depth to 80 cm in high and low grazing pressure treatments were also assessed. The influence of cumulative P applied on Olsen P varied with time and grazing pressure. During the first 12–15 years, the Olsen P of high grazing pressure plots was greater than that of low grazing pressure plots, but subsequently the reverse has been the case. Plant-available S also increased where more superphosphate had been applied. Levels were greater than 7 mg S/kg soil except at the lowest level of superphosphate, indicating that forms of P fertiliser with less S could be used here. After initial applications of KCl, this fertiliser was not applied for 8 years. During this time the K status fell from 270 to 120 mg K/kg soil, just above where plant responses to K are likely, emphasising the need to monitor the K status of productive pastures on these soils. Levels of exchangeable Mg2+ fell as more superphosphate was used, whereas levels of Ca2+ rose. The Olsen P of soil deeper than 10 cm was always less than 5 mg P/kg soil. P supply to deep-rooted pasture plants may thus be limiting when the topsoil is dry. These results, together with published assessments of animal production at this site, show that for pastures fertilised annually, the Olsen P associated with the most profit varied from 7 mg P/kg soil at 7 ewes/ha (10.5 DSE/ha), to 14 mg P/kg soil at 18 ewes/ha.

Long-term changes in soil fertility and pasture production under no, low and high phosphorus fertiliser inputs

2011 ◽  
pp. 37-42 ◽  
Author(s):  
A.D. Mackay ◽  
M.G. Lambert
Keyword(s):  
Soil Fertility ◽  
Published Data ◽  
Research Station ◽  
Pasture Production ◽  
Ongoing Research ◽  
Hill Country ◽  
Fertiliser Application ◽  
Farm Business ◽  
Stocking Rates

Many hill country farmers have struggled to maintain fertiliser inputs in recent years. The long-term fertiliser and sheep grazing farmlet study at the AgResearch Ballantrae Hill Country Research Station provides invaluable insights into the benefits of continued annual inputs of phosphorus (P) fertiliser on production levels and the farm business, and also the implications to the production system when fertiliser is withheld. Since detailed monitoring stopped in 1990, the fertiliser treatments have been maintained, along with nominal sheep stocking rates and grazing practices. Occasional measurements of soil fertility have also been made on the farmlets that have received either no fertiliser inputs for 30 years, a low annual fertiliser input (125 kg superphosphate (SSP)/ha/yr), or a high input (375 kg SSP/ha/yr) for 35 years. In this paper changes in sheep stocking rate and soil fertility are reported and compared with earlier published data from this longterm site. This field study provides a valuable resource for ongoing research into nutrient requirements and cycling in hill land environments, and a visual demonstration of the continued importance of fertiliser application as a driver of hill country production. Keywords: Livestock production, P fertiliser, Olsen P, long-term sites

Update on the Boundaries of the Curly Birch Range

2020 ◽  
pp. 9-21
Author(s):  
L.V. Vetchinnikova ◽  
◽  
A.F. Titov ◽  
◽  
Keyword(s):  
Population Size ◽  
Natural Populations ◽  
Forest Tree ◽  
Published Data ◽  
Population Approach ◽  
Key Factors ◽  
History Of ◽  
Individual Trees ◽  
Karelian Birch

The article reports on the application of the best known principles for mapping natural populations of curly (Karelian) birch Betula pendula Roth var. carelica (Mercklin) Hämet-Ahti – one of the most appealing representatives of the forest tree flora. Relying on the synthesis and analysis of the published data amassed over nearly 100 years and the data from own full-scale studies done in the past few decades almost throughout the area where curly birch has grown naturally, it is concluded that its range outlined in the middle of the 20th century and since then hardly revised is outdated. The key factors and reasons necessitating its revision are specified. Herewith it is suggested that the range is delineated using the population approach, and the key element will be the critical population size below which the population is no longer viable in the long term. This approach implies that the boundaries of the taxon range depend on the boundaries of local populations (rather than the locations of individual trees or small clumps of trees), the size of which should not be lower than the critical value, which is supposed to be around 100–500 trees for curly birch. A schematic map of the curly birch range delineated using this approach is provided. We specially address the problem of determining the minimum population size to secure genetic diversity maintenance. The advantages of the population approach to delineating the distribution range of curly birch with regard to its biological features are highlighted. The authors argue that it enables a more accurate delineation of the range; shows the natural evolutionary history of the taxon (although it is not yet officially recognized as a species) and its range; can be relatively easily updated (e.g. depending on the scope of reintroduction); should be taken into account when working on the strategy of conservation and other actions designed to maintain and regenerate this unique representative of the forest tree flora.

scholarly journals Parenteral Nutrition and Oxidant Load in Neonates

Nutrients ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 2631
Author(s):  
Kandeepan Karthigesu ◽  
Robert F. Bertolo ◽  
Robert J. Brown
Keyword(s):  
Parenteral Nutrition ◽  
Storage Temperature ◽  
Oral Feeding ◽  
Published Data ◽  
Short Term ◽  
Antioxidant Defences ◽  
Term Survival ◽  
Nutrient Sources ◽  
Short Term Survival

Neonates with preterm, gastrointestinal dysfunction and very low birth weights are often intolerant to oral feeding. In such infants, the provision of nutrients via parenteral nutrition (PN) becomes necessary for short-term survival, as well as long-term health. However, the elemental nutrients in PN can be a major source of oxidants due to interactions between nutrients, imbalances of anti- and pro-oxidants, and environmental conditions. Moreover, neonates fed PN are at greater risk of oxidative stress, not only from dietary sources, but also because of immature antioxidant defences. Various interventions can lower the oxidant load in PN, including the supplementation of PN with antioxidant vitamins, glutathione, additional arginine and additional cysteine; reduced levels of pro-oxidant nutrients such as iron; protection from light and oxygen; and proper storage temperature. This narrative review of published data provides insight to oxidant molecules generated in PN, nutrient sources of oxidants, and measures to minimize oxidant levels.

Psychotic disorders in young adults with perinatally acquired HIV: a UK case series

2020 ◽  
pp. 1-7
Author(s):  
I. Mallik ◽  
T. Pasvol ◽  
G. Frize ◽  
S. Ayres ◽  
A. Barrera ◽  
...  
Keyword(s):  
Mental Health ◽  
Young Adults ◽  
Young People ◽  
Case Series ◽  
Psychotic Episode ◽  
Published Data ◽  
Growing Up ◽  
Term Care ◽  
Perinatally Acquired

Abstract Background Increasing numbers of children with perinatally acquired HIV (PaHIV) are transitioning into adult care. People living with behaviourally acquired HIV are known to be at more risk of psychosis than uninfected peers. Young adults living with PaHIV face numerous risk factors; biological: lifelong exposure to a neurotrophic virus, antiretroviral medication and immune dysfunction during brain development, and environmental; social deprivation, ethnicity-related discrimination, and migration-related issues. To date, there is little published data on the prevalence of psychotic illness in young people growing up with PaHIV. Methods We conducted a retrospective case note review of all individuals with PaHIV aged over 18 years registered for follow up at a dedicated clinic in the UK (n = 184). Results In total, 12/184 (6.5%), median age 23 years (interquartile range 21–26), had experienced at least one psychotic episode. The presentation and course of the psychotic episodes experienced by our cohort varied from short-lived symptoms to long term illness and nine (75%) appear to have developed a severe and enduring mental illness requiring long term care. Conclusion The prevalence of psychosis in our cohort was clearly above the lifetime prevalence of psychosis in UK individuals aged 16–34 years, which has been reported to be 0.5–1.0%. This highlights the importance of clinical vigilance regarding the mental health of young people growing up with PaHIV and the need to integrate direct access to mental health services within the HIV centres providing medical care.

Persistence and growth of Lotononis bainesii–Digitaria decumbens pastures: 1. Sheep stocking rate

1983 ◽  
Vol 101 (1) ◽  
pp. 1-7 ◽  
Author(s):  
A. Pott ◽  
L. R. Humphreys
Keyword(s):  
Bulk Density ◽  
Soil Bulk Density ◽  
Grazing Pressure ◽  
Stocking Rate ◽  
Digitaria Decumbens ◽  
Heavy Grazing ◽  
Cotton South ◽  
Seed Reserves ◽  
Stocking Rates

SUMMARYSheep were grazed for 2 years at stocking rates of 7, 14, 21 and 28/ha on a pasture comprising Lotononis bainesii and Digitaria decumbens cv. Pangola at Mt Cotton, south–east Queensland. There were six replicates of each treatment grazed in rotation with 3 days' grazing followed by 15 days' rest.The initial dominance of lotononis was lost after 6 months of grazing and lotononis failed to persist satisfactorily at any stocking rate. Demographic studies showed that lotononis behaved as a short-lived plant, predominantly annual, with some vegetative perennation as stolon-rooted units under heavy grazing. Soil seed reserves varied from 5800 to 400 m2 at the lightest and heaviest stocking rates respectively. Lotononis failed to regenerate under Pangola shading or inopportune high grazing pressure. Soil bulk density (0–7 cm) increased from 1·2 to 1·4 g/cm3 according to stocking rate.

Species Responses to Grazing and Environmental-Factors in an Arid Halophytic Shrubland Community

1987 ◽  
Vol 35 (2) ◽  
pp. 135 ◽  
Author(s):  
RB Hacker
Keyword(s):  
Environmental Factors ◽  
Soil Salinity ◽  
Large Scale ◽  
Chemical Properties ◽  
Grazing Pressure ◽  
Aerial Photographs ◽  
Small Scale ◽  
Factors Affecting ◽  
Species Responses

Species responses to grazing and environmental factors were studied in an arid halophytic shrubland community in Western Australia. The grazing responses of major shrub species were defined by using reciprocal averaging ordination of botanical data, interpreted in conjunction with a similar ordination of soil chemical properties and measures of soil erosion derived from large-scale aerial photographs. An apparent small-scale interaction between grazing and soil salinity was also defined. Long-term grazing pressure is apparently reduced on localised areas of high salinity. Environmental factors affecting species distribution are complex and appear to include soil salinity, soil cationic balance, geomorphological variation and the influence of cryptogamic crusts on seedling establishment.

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