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Stocking Rate (stocking + rate)

Distribution by Scientific Domains

Earth and Environmental Science	76%
Life Sciences	24%

Kinds of Stocking Rate

high stocking rate

Selected Abstracts

Herbage growth rates on heterogeneous swards as influenced by sward-height classes

GRASS & FORAGE SCIENCE, Issue 1 2009
ahin Demirba
Abstract The contribution of four classes of sward height to daily herbage growth rates of a heterogeneous sward in eight periods throughout a grazing season was investigated in two continuous cattle-grazing systems differing in intensity (moderate stocking rate: MC; lenient stocking rate: LC). At the beginning and end of periods of 12 to 28 d, the compressed sward height (CSH) was measured in exclusion cages at eighteen fixed points per cage to derive daily growth rates for the four classes of sward height. Stratified calibrations were made to relate sward height to herbage mass for each treatment in each period. Quadratic regressions described the relationship between herbage growth rate and initial CSH for each treatment in each period. For scaling up to the scale of the plot, CSH was measured monthly at 100 points per plot. Daily herbage growth rates declined from more than 100 kg dry matter (DM) ha,1 d,1 on both treatments at the beginning of the grazing season to 20 kg DM ha,1 d,1 or less, especially on treatment LC. This was due to the larger area covered by tall herbage on treatment LC than on treatment MC. On treatment MC, daily herbage growth rate was predominantly derived from short sward areas of up to 12 cm in height while sward areas taller than 12 cm contributed most to daily growth rates on treatment LC in early summer. The method used is considered suitable for estimating daily herbage growth rates of different classes of sward height in extensively managed pastures and can easily be adapted to deal with more heterogeneous swards than used in this study. [source]

How does grazing intensity influence the diversity of plants and insects in a species-rich upland grassland on basalt soils?

GRASS & FORAGE SCIENCE, Issue 1 2009
B. Dumont
Abstract The effect of stocking rate on the species richness, abundance and functional diversity of vascular plants, butterflies and grasshoppers was examined in a semi-natural upland pasture in central France. Over a 5-year period, 3·6-ha plots were continuously grazed by Charolais heifers at 1·4 (High stocking rate), 1·0 (Intermediate) and 0·6 (Low) livestock units (LU) ha,1. To evaluate botanical diversity, percentage cover of all plant species was estimated in late July in ten fixed 1 m × 1 m quadrats per plot. Butterflies were counted on three occasions between late June and early August along three fixed 50-m-long transects per plot using the ,Pollard walk', with grasshoppers being recorded on two occasions along the same transects. Diversity patterns of the three taxa were affected by stocking rate. For plants, species abundance changed more than species number. Abundance of forbs became higher under the Low compared with the High stocking rate. Stress-tolerant grasses were also more abundant in plots grazed at the Low stocking rate, while an opposite trend was observed for competitive grasses. Butterflies consistently responded to alterations in vegetation composition, especially to the dynamics of nectar plants. The species richness of grasshoppers also increased in plots at the Low stocking rate. The Low and Intermediate stocking rates were suitable for providing a high diversity of the three taxonomic groups. The results suggested that at least butterfly diversity would peak in vegetation taller than that of vascular plants. [source]

Estimation of nitrogen concentration and in vitro dry matter digestibility of herbage of warm-season grass pastures from canopy hyperspectral reflectance measurements

GRASS & FORAGE SCIENCE, Issue 2 2008
P. J. Starks
Abstract Remote sensing of nitrogen (N) concentration and in vitro dry matter digestibility (IVDMD) in herbage can help livestock managers make timely decisions for adjusting stocking rate and managing pastures during the grazing season. Traditional laboratory analyses of N and IVDMD are time-consuming and costly. Non-destructive measurements of canopy hyperspectral reflectance of pasture may provide a rapid and inexpensive means of estimating these measures of nutritive value. Using a portable spectroradiometer, canopy reflectance was measured in eight warm-season grass pastures in the USA in June and July in 2002 and 2003 to develop and validate algorithms for estimating N concentration and IVDMD of herbage. Nitrogen concentration of herbage was linearly correlated (r = 0·82; P < 0·001) with a ratio of reflectance in the 705- and 1685-nm wavebands (R705/R1685) and IVDMD was correlated with R705/R535 (r = 0·74; P < 0·001). Compared with simple linear regressions of N concentration and IVDMD in herbage with two-waveband reflectance ratios, multiple regression, using maximum r2 improvement, band-depth analysis with step-wise regression, and partial least-squares regression enhanced the correlation between N concentration and IVDMD of herbage and canopy reflectance values (0·81 , |r| , 0·90; P < 0·001). Validation of the prediction equations indicated that multiple regression only slightly improved accuracy of a model for predicting N concentration and IVDMD of herbage compared with simple linear regression of reflectance ratios. Results suggest that the N concentration and IVDMD of herbage of warm-season grass pastures can be rapidly and non-destructively estimated during the grazing season using canopy reflectance in a few narrow wavebands. [source]

The influence of strain of Holstein-Friesian dairy cow and pasture-based feeding system on grazing behaviour, intake and milk production

GRASS & FORAGE SCIENCE, Issue 1 2007
S. McCarthy
Abstract A comparative study of grazing behaviour, herbage intake and milk production of three strains of Holstein-Friesian dairy cow was conducted using three grass-based feeding systems over two years. The three strains of Holstein-Friesian cows were: high production North American (HP), high durability North American (HD) and New Zealand (NZ). The three grass-based feeding systems were: high grass allowance (MP), high concentrate (HC) and high stocking rate (HS). In each year seventy-two pluriparous cows, divided equally between strains of Holstein-Friesian and feeding systems were used. Strain of Holstein-Friesian cow and feeding system had significant effects on grazing behaviour, dry matter (DM) intake and milk production. The NZ strain had the longest grazing time while the HD strain had the shortest. The grazing time of cows in the HC system was shorter than those in both the HS and MP systems. There was a significant strain of Holstein-Friesian cow by feeding system interaction for DM intake of grass herbage and milk production. The NZ strain had the highest substitution rate with the HP strain having the lowest. Hence, response in milk production to concentrate was much greater with the HP than the NZ strain. Reduction in milk yield as a consequence of a higher stocking rate (MP vs. HS system) was, however, greater for the HP and HD strains compared with the NZ strain. The results suggest that differences in grazing behaviour are important in influencing DM intake and milk production. [source]

Comparison of haymaking strategies for cow-calf systems in the Salado Region of Argentina using a simulation model.

GRASS & FORAGE SCIENCE, Issue 4 2005

Abstract Risk and cost estimates, calculated using a weather-driven farm simulation model, were used to evaluate the impact of different haymaking strategies in dryland cow-calf systems such as those in the Salado region of Argentina. Based on a 100-ha farm, each strategy was simulated using twenty sequences of 50 years of random weather. A risk-efficiency methodology was used, using calf live weight sold and considering the economic value of the live weight produced per year minus the cost of haymaking, as a simple measure of profit. The analysis highlighted both production and risk advantages in using hay, especially when a flexible hay management approach was implemented, although some haymaking strategies performed worse than not using hay. When calf live weight sold was considered alone, the risk-efficient set included strategies with large proportions of the areas being harvested (0.42,1.05; paddocks could be cut more that once a year in some of the strategies) and high proportions of hay not being used. The amount of hay for maximizing risk efficiency for profit was notably lower than that for maximizing cattle production. When haymaking costs were included, the proportion of area harvested for risk-efficient profit ranged from 0.28 to 0.52, depending on the target stocking rate. [source]

Selective defoliation by sheep according to slope and plant species in the hill country of New Zealand

GRASS & FORAGE SCIENCE, Issue 4 2003
I. F. López
Abstract The objective of the study was to evaluate the grazing behaviour by sheep in hill country paddocks in New Zealand which had received two long-term fertilization and stocking rate treatments [high fertility,high stocking rate (HH); low fertility,low stocking rate (LL)]. Herbage accumulation and selective grazing were evaluated within low slope (LS), medium slope (MS) and high slope (HS) categories. Transects lines were placed and tillers of Agrostis capillaris and Lolium perenne in the LS category; A. capillaris, Anthoxanthum odoratum and L. perenne in the MS category; and A. capillaris and A. odoratum in the HS category were marked. The leaf length of each marked tiller was measured and used to determine selective grazing over 3 weeks during each season. The highest herbage accumulation rates were during spring and the lowest in summer and winter. The LS category showed the highest herbage accumulation rates and HS the lowest. Except for autumn, the marked tillers were more frequently grazed in the HH than in the LL paddock. During summer, autumn and spring, grazing frequency in the slope categories was in the order LS > MS > HS. During winter sheep did not discriminate between slope category. During summer, autumn and spring, sheep did not selectively graze the species studied but this was not the case during winter. Overall, sheep selectively grazed L. perenne. In all the seasons L. perenne consistently had the longest leaves but within species there was no consistent relationship between leaf length and probability of being grazed. Selective grazing changed through the year according to herbage accumulation rate. Sheep concentrated grazing in the category LS when herbage accumulation rate was high, but they did not discriminate between slope categories in winter when herbage accumulation rate was low. [source]

Extensification of grassland use in the Welsh uplands: sheep performance in years 1,6

GRASS & FORAGE SCIENCE, Issue 2 2001
M. Fothergill
An experiment was established in 1991 on a 25-year-old perennial ryegrass/bent (Lolium perenne L./Agrostiscapillaris L.)-dominated pasture in Wales to study the effects of reducing nutrient inputs to previously fertilized upland pasture. The effects of the removal of applications of (1) N (denoted by CaPK) (2) N, P and K (Ca) and (3) N, P, K, and Ca (Nil) were compared with a treatment which received applications of all four nutrients (CaPKN) over a 6-year period (1991,96) in a randomized block design replicated three times. The experiment was managed under a continuous variable stocking regime (ewes and lambs until weaning and ewes thereafter) maintaining a sward surface height of 4·0 cm throughout the grazing season. Although individual liveweight gain of the lambs was unaffected by the treatments, there was a significant reduction (P < 0·05) in total lamb liveweight gain, ewe stocking rate and length of grazing season as a result of the withdrawal of nutrients. Over the 6 years total lamb liveweight gain was reduced by 17%, 32% and 45% and ewe stocking rate by 21%, 36% and 49% on treatments CaPK, Ca and Nil, respectively, compared with treatment CaPKN. The effect of withdrawing nutrient inputs on ewe stocking rate was progressive and by 1996 the Nil input treatment displayed a 63% reduction compared with the CaPKN treatment and this was also coupled with a 21-day reduction in length of the grazing season. During the post-weaning period, ewes from the Nil input treatment recorded a liveweight loss in 1995 and only a modest liveweight gain in 1996. This coupled with significantly lower body condition scores (P < 0·01) of these ewes in the autumn indicated that the Nil input treatment could lead to reductions in reproductive performance. [source]

Effects of Grazing on Bituminaria bituminosa (L) Stirton: A Potential Forage Crop in Mediterranean Grasslands

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2006
M. Sternberg
Abstract Plant traits of Bituminaria bituminosa, as affected by different intensities of cattle grazing, were studied in a Mediterranean grassland in Israel. B. bituminosa is a widespread Mediterranean perennial legume species that may potentially serve as a fodder crop in Mediterranean grasslands. The aims of the present study were: (i) to evaluate the responses of B. bituminosa to different cattle grazing intensities; (ii) to study functional traits associated with grazing tolerance; and (iii) to evaluate its potential as an alternative forage crop in the region. A total of 100 B. bituminosa plants were monitored in field conditions. During the growing season each individual was sampled five times and the following plant traits were monitored each time: (i) aboveground biomass production, (ii) plant height, (iii) specific leaf area (SLA), (iv) number of flowers, (v) seed mass and size, (vi) tannin concentration in leaves, (vii) total nitrogen in leaves, (viii) fibre concentration in leaves (Neutral Detergent Fiber), and (ix) in vitro dry matter digestibility. The results showed that grazing intensity and history of grazing affected B. bituminosa performance. Plant biomass, height, and flower and seed production were all reduced when plants were exposed to cattle grazing. However, under moderate grazing intensities, its plant cover remained relatively stable indicating a potential tolerance under this stocking rate. The nutritious characteristics of B. bituminosa leaves were good, and the condensed tannins concentration found indicated favourable conditions for digestion. Moreover, the in vitro digestibility studies indicated relatively high values (46,51 %) of digestion. B. bituminosa may be considered as a potential crop for cattle feeding in Mediterranean grasslands. Growing this plant in dense stands in rotational paddocks may provide alternative sources of natural fodder protein, reducing the potential costs of artificial feed supplements. [source]

The impact of cattle ranching on large-scale vegetation patterns in a coastal savanna in Tanzania

JOURNAL OF APPLIED ECOLOGY, Issue 3 2003
M. W. Tobler
Summary 1The success of large-scale cattle ranching in African savanna vegetation has often been limited by problems of bush encroachment and disease (in particular trypanosomiasis spread by tsetse flies). Mkwaja Ranch, occupying an area of 462 km2 on the coast of Tanzania, is a recent example of a large ranching enterprise that failed within the savanna environment. It was closed in 2000 after 48 years of operation. In this paper we describe the main vegetation types of the area (excluding closed forest vegetation) and relate their patterns of distribution to the former use of the ranch for cattle. 2The study area comprised the former ranch and parts of the adjacent Saadani Game Reserve, which had not been grazed by cattle for many years and had never been used for large-scale ranching. Following field surveys, 15 distinct types of grassland and bush vegetation were defined and a vegetation map was created using a Landsat TM satellite image. A multispectral classification using the maximum likelihood algorithm gave good results and enabled all 15 vegetation types to be distinguished on the map. 3Two main spatial trends were detected in the vegetation. One was a large-scale decrease in the cover of bushland from the most intensively used parts of the ranch through more extensively used areas to the game reserve; this trend was attributed to differences in management history as well as to climatic and topographic factors. A second trend was a radial vegetation pattern associated with the enclosures where cattle were herded at night. High amounts of three bushland types [dominated by (i) Acacia zanzibarica, (ii) Dichrostachys cinerea, Acacia nilotica or Acacia mellifera and (iii) Terminalia spinosa] occurred in a zone between 300 and 2500 m from the paddocks, with a peak in bush density at about 900 m (mean value for 18 paddocks). In contrast, bushland dominated by Hyphaene compressa was scarce close to the paddocks and became more abundant with distance. There was also a radial trend in the grassland communities: close to the paddocks there was short grass vegetation containing many ruderals and invasive weedy species, while the tall grassland types with species such as Hyperthelia dissoluta and Cymbopogon caesius occurred further away in the areas less affected by cattle. 4Synthesis and applications. The intensive modern livestock ranching as practised on Mkwaja Ranch proved to be unsustainable both economically and ecologically. In the end, the biggest problem faced by the ranch managers was not controlling disease, as had originally been feared, but preventing the spread of bush on pasture land. The results of our study demonstrate just how severe the problem of bush encroachment was, especially in areas close to paddocks. An important lesson for management is that grazing patterns need to be taken into consideration when determining the sustainable stocking rate for an area. To reduce the risk of bush encroachment in grazing systems with focal points such as paddocks or watering points, stocking rates need to be lower than in systems with a more uniform grazing distribution. [source]

Season of grazing and stocking rate interactively affect fuel loads in Baikiaea plurijuga Harms woodland in northwestern Zimbabwe

AFRICAN JOURNAL OF ECOLOGY, Issue 4 2008
J. Gambiza
Abstract Wildfire is a major disturbance in Baikiaea plurijuga Harms woodland savannas. We tested the hypothesis that the timing and intensity of herbivory influence fuel loads. We used three stocking rates namely light (three cows and four goats ha,1), medium (six cows and eight goats ha,1) and heavy (eleven cows and sixteen goats ha,1) and three times of grazing namely early-, middle- and late-growing seasons. Season of grazing and stocking rate influenced herbaceous phytomass. Phytomass was generally the highest (53.5 g DM m,2) in paddocks grazed during the early growing season and the lowest (27.8 g DM m,2) in those grazed during the late growing season. Phytomass was also generally the highest (40.4 g DM m,2) in lightly stocked paddocks and the lowest (32.7 g DM m,2) in heavily stocked ones. Litter mass was the lowest (160.8 g DM m,2) in paddocks grazed during the early season whereas there were no differences in ungrazed paddocks and those grazed during either mid- or late growing seasons (205.4 g DM m,2). There was a negative relationship between litter mass and stocking rate. Baikiaea Benth. woodlands should be grazed during either the mid- or late-growing season at stocking rates greater than 0.1 LU ha,1 to reduce grass fuel loads. Résumé Les feux de brousse sont une perturbation majeure dans les savanes arborées àBaikiaea plurijuga Harms. Nous avons testé l'hypothèse selon laquelle le timing et l'intensité de la consommation par les herbivores influenceraient la quantité de combustible. Nous avons utilisé trois taux de pâturage: léger (trois vaches et quatre chèvres par hectare), moyen (six vaches et huit chèvres par hectare) et élevé (11 vaches et 16 chèvres par hectare), et trois périodes de pâturage, à savoir au début, au milieu et à la fin de la période de croissance. La période de pâturage et le taux de pâturage influençaient la phytomasse herbacée. La phytomasse était généralement la plus élevée (53.5 g MS m,2) dans les enclos pâturés au début de la saison de croissance, et la plus faible (27.8 g MS m,2) dans ceux qui sont pâturés en fin de période de croissance. La phytomasse était aussi généralement la plus grande (40.4 g MS m,2) dans les enclos légèrement pâturés et la plus basse (32.7 g MS m,2) dans les enclos très pâturés. La biomasse végétale (litière) était la plus faible (160.8 g MS m,2) dans les enclos pâturés au début de la saison, alors qu'il n'y avait pas de différence entre les enclos non pâturés et ceux qui l'étaient au milieu ou à la fin de la période de croissance (205.4 g MS m,2). Il y avait une relation négative entre la masse de litière et le taux de pâturage. Les forêts àBaikiaea Benth. devraient être pâturés en milieu ou en fin de période de croissance, et à des taux plus élevés que 0.1 UFL ha,1, pour réduire la quantité de combustible herbacé. [source]

Control of the Trematode Bolbophorus confusus in Channel Catfish Ictalurus punctatus Ponds Using Salinity Manipulation and Polyculture with Black Carp Mylopharyngodon piceus

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2000
Darrel L. Venable
This study evaluated the use of black carp Mylopharyngodon piceus and salinity manipulation for controlling the infection of channel catfish Ictalurus puncratus by a digenetic trematode (tentatively identified as Bolbophorus confusus). Control methods focussed mainly on the eradication of the intermediate snail host, the marsh rams-horn Phanorbella trivolvis (previously referred to as Helisoma trivolvis), and were evaluated in laboratory tests and field experiments at a commercial catfish culture facility in southern Louisiana that was seriously impacted by the trematode. Introduction of fingerling black carp into catfish ponds at a density of 62 carpha resulted in an almost total elimination of P. trivolvis. The farm is now successfully using a facility-wide stocking rate of 40 carp/ha. Laboratory experiments were conducted to investigate the effect of salinity manipulation using NaCl on free-swimming trematode cercariae, the snail P. trivolvis, and catfish fingerlings infected with the cercariae. A salinity of 2.5 ppt had a detrimental effect on snail survival, growth, and reproduction. Salinity did not have a negative effect on the other two aspects of the trematode life cycle tested (in fact, survival of both cercariae and infected catfish fingerlings showed a positive dependence on NaCl over the 0,2.5 ppt range). A field-experiment was then conducted in catfish ponds maintained at three salinities (2.5, 1.25, and 0.25 ppt) with rock salt, NaCl. Snail densities in ponds at 2.5 ppt salinity were consistently lower than in the other treatments and no trematode infection was noted among snails or catfish in the 2.5 ppt salinity ponds. Both the use of 2.5 ppt NaCl and black carp appear valuable management tools for controlling the digenetic trematode in caffish ponds. [source]

Changes in heathland vegetation under goat grazing: effects of breed and stocking rate

APPLIED VEGETATION SCIENCE, Issue 1 2010
Rafael Celaya
Abstract Questions: How are heathland vegetation dynamics affected by different goat grazing management? Location: Cantabrian heathlands in Illano, Asturias, northern Spain. Methods: During 4 years, vegetation dynamics (structural composition, canopy height and floristic diversity) were studied under three goat grazing treatments with three replicates: high stocking rate (11.7 goats ha,1) with a local Celtiberic breed, and high (15 goats ha,1) and low (6.7 goats ha,1) stocking rates with a commercial Cashmere breed. Results: The relative cover of woody plants, particularly heather species, decreased more while herbaceous cover increased more under local Celtiberic than under Cashmere breed grazing. Within Cashmere treatments, the cover and height of live shrubs decreased more and the herbaceous cover increased more under high than under low stocking rate. Redundancy analysis showed a significant effect of treatment × year interaction on floristic composition. Greater species richness was recorded under local goat grazing, but Shannon diversity index fell in the fourth year on these plots because of dominance by two grass species. Conclusions: Local Celtiberic goat grazing at such a high stocking rate (11.7 goats ha,1) hinders the development of sustainable systems on these heathlands, both in environmental and productive terms, owing to the limitations in soil fertility. Nevertheless, Celtiberic goats could be useful for controlling excessive shrub encroachment and reducing fire hazard. Cashmere goat grazing at high stocking rate promoted the highest Shannon diversity by generating a better balance between woody and herbaceous plants, while shrub dominance was not altered under the low stocking rate. [source]

Grazing without grasses: Effects of introduced livestock on plant community composition in an arid environment in northern Patagonia

APPLIED VEGETATION SCIENCE, Issue 1 2006
Mariana Tadey
Abstract Question: How does grazing intensity affect plant density, cover and species richness in an Patagonian arid ecosystem? Location: Monte steppe ecoregion, SW Argentina. Methods: I analysed the effect of grazing on plant density, cover and species richness using a stocking rate gradient within the same habitat. Six paddocks were used with stocking rates ranging between 0.002 , 0.038 livestock/ha. Plant density, species richness, plant cover and percentage of grazed branches were determined by sampling plots within each paddock. The percentage of grazed branches was used as an independent measurement of grazing intensity. Results: Higher stocking rates were related to lower plant density, species richness and plant cover. The paddock with the lowest grazing intensity had 86% more plants per unit area, 63% more plant cover and 48% higher species richness. The percentage of grazed branches and the quantity of dung increased with stocking rate. Conclusions: Introduced livestock seriously affect native vegetation in the Patagonian Monte. The damage observed in this xerophytic plant community suggests that plant adaptations to aridity do not provide an advantage to tolerate or avoid grazing by vertebrate herbivores in this region. Plant degradation in this arid environment is comparable to the degradation found in more humid ecosystems. [source]

Stocking strategies for production of Litopenaeus vannamei (Boone) in amended freshwater in inland ponds

AQUACULTURE RESEARCH, Issue 1 2008
Bartholomew W Green
Abstract The performance of the Pacific white shrimp Litopenaeus vannamei (Boone) under various stocking strategies was evaluated in earthen ponds filled with freshwater amended with major ions. Six 0.1-ha earthen ponds located in Pine Bluff, AR, USA, were filled with freshwater in 2003 and 2004, and potassium magnesium sulphate added to provide 50 mg K+ L,1 and stock salt added to provide 0.5 g L,1 salinity. In 2003, three ponds either were stocked with PL15 shrimp (39 PL m,2) for 125 days of grow out or with PL25 shrimp for 55 days (23 PL m,2) followed by a 65-day (28 PL m,2) grow-out period. In 2004, ponds were stocked with 7, 13 or 30 PL15 m,2 for 134 days of grow out. Salinity averaged 0.7 g L,1 during both years, and concentration of SO4,2, K+, Ca2+ and Mg2+ was higher, and Na+ and Cl, was lower in amended pond water than in seawater at 0.7 g L,1 salinity. Potassium concentration in amended water was 52,61% of the target concentration. Shrimp yields ranged from 3449 kg ha,1 in 2003 to 4966 kg ha,1 in 2004 in ponds stocked with 30,39 PL15 m,2 for a 125,134-day culture period. At harvest, mean individual weight ranged from 17.1 to 19.3 g shrimp,1. In ponds stocked with PL25 shrimp, yields averaged 988 and 2462 kg ha,1 for the 1st and 2nd grow-out periods respectively. Gross shrimp yield in 2004 increased linearly from 1379,4966 kg ha,1 with increased stocking rate. These experiments demonstrated that L. vannamei can be grown successfully in freshwater supplemented with major ions to a final salinity of 0.7 g L,1. [source]

How does grazing intensity influence the diversity of plants and insects in a species-rich upland grassland on basalt soils?

Effect of livestock breed and grazing intensity on grazing systems: 5.

GRASS & FORAGE SCIENCE, Issue 4 2007
Management, policy implications
Summary This paper explores the management and policy implications of research findings investigating the use of grazing intensity and traditional breeds to achieve biodiversity outcomes on grasslands in four countries of Europe. An economic analysis, based on these research findings, indicated that financial assistance and/or premium prices are required to achieve sustainable grazing systems with a high biodiversity. The research findings suggested that existing agri-environment scheme prescriptions based only on blanket stocking rates are too crude to increase plant diversity, lacking consideration of initial site conditions. Conversely, some invertebrates seem to rapidly benefit from lenient stocking, highlighting the importance of clear goals for agri-environment schemes. Recommendations for an appropriate support package to deliver grazing systems with high biodiversity are presented. [source]

Twenty years of rest returns grazing potential, but not palatable plant diversity, to Karoo rangeland, South Africa

JOURNAL OF APPLIED ECOLOGY, Issue 4 2010
Colleen L. Seymour
Summary 1.,Up to 73% of the world's rangelands are degraded, and increasing demand for meat in developing countries and a growing human population are likely to exert even greater pressures on rangelands in the next 20,50 years. Restoration of rangeland grazing potential and resilience is therefore important, particularly in the face of climate change. 2.,We investigated the influence of past stocking rates (from 1910 to 1987), rainfall, and current grazing regimes (from 1988 to 2008) on plant assemblages, grazing potential, and diversity of palatable species in southern Karoo rangelands, South Africa. 3.,We used herbivore exclusion experiments to test whether resting rangeland for 20 years enables recovery of plant assemblages (where seed sources are present within 50 m), regardless of previous grazing history. Mean annual rainfall over this period was 15% higher than the mean annual rainfall for the preceding 80 years and included two exceptionally wet years. 4.,While rainfall was a primary driver of total vegetation cover, grazing history explained differences in plant species composition: plots with shared historical grazing intensity were more similar than plots with the same grazing regimes between 1988 and 2008. 5.,In historically heavily-grazed exclusion plots, cover of the palatable species Tripteris sinuata (formerly Osteospermum sinuatum) returned to levels comparable to that in both exclusion and lightly-grazed plots with a moderate grazing history. Five palatable species (Pteronia empetrifolia, Tetragonia spicata, Berkheya spinosa, Hereroa latipetala and Ruschia spinosa) failed to re-establish, however, despite the presence of seed-producing plants nearby. Furthermore, only cover of P. empetrifolia increased significantly in historically moderately-grazed plots. Cover of unpalatable plants (e.g. Pteronia pallens) increased in all plots over time. 6.Synthesis and applications. These findings suggest that present species composition of arid shrublands reflects historical management at time scales greater than 20 years. Despite high rainfall enabling the return of grazing potential through recovery of a single forage species, rest alone did not ensure the return of all palatable species, with implications for rangeland resilience. Restoring the full suite of palatable species over management timeframes will require more complex interventions such as reseeding or selective clearing. [source]

Gradients in vegetation cover, structure and species richness of Nama-Karoo shrublands in relation to distance from livestock watering points

JOURNAL OF APPLIED ECOLOGY, Issue 2 2006
SIMON W. TODD
Summary 1Gradients of animal impact known as piospheres tend to develop around artificial watering points, particularly in arid zones. Such grazing gradients represent a potential opportunity for differentiating the long-term effects of livestock activity from other environmental patterns. In this study, the impact of watering point provision on the plant cover, species richness and community structure of Karoo shrublands, South Africa, was investigated in the context of the evolutionary history and current grazing management practices of the region. 2The impacts of watering point provision were investigated by sampling plant cover and composition along transects placed at set distances, ranging from 10 m to 2200 m, from 11 watering points. 3Karoo vegetation cover and structure are relatively resilient to livestock grazing. Karoo plant diversity, as measured by species richness, evenness and dominance, was not as resilient. Twice as many species decreased as increased near watering points. The majority of species that decreased were regarded as being highly palatable to livestock. Heavy grazing, leading to death or repeated reproductive failure, is the most likely mechanism leading to the decline of such species. 4The highly disturbed area immediately adjacent to watering points was dominated by forbs and contained a large proportion of alien species. Adjacent to this was a zone dominated by widespread shrub species of medium to low palatability. Areas most distant from watering points contained a greater proportion of species known to be highly palatable to livestock. The ability of dominant Karoo shrubs to tolerate heavy grazing may have allowed rangeland managers to maintain stocking rates above that which can be tolerated by the majority of species but which are supported by a minority of grazing-tolerant species. 5Synthesis and applications. Highly palatable species are more abundant in areas distant from water points. Larger paddocks therefore provide a refuge for sensitive species that might otherwise be lost from the rangeland as a whole. Species that tend to occur away from watering points represent potentially useful indicators of grazing pressure. The use of these species as indicators of rangeland condition among landowners should be promoted. [source]

Heterogeneous grazing causes local extinction of edible perennial shrubs: a matrix analysis

JOURNAL OF APPLIED ECOLOGY, Issue 2 2001
L.P. Hunt
Summary 1Population modelling and field measurements of births, growth and deaths were used to investigate the long-term change in abundance of Atriplex vesicaria (Chenopodiaceae), a long-lived, palatable, perennial shrub, under sheep grazing. Of particular interest was whether A. vesicaria is at risk of being eliminated throughout grazed paddocks when the recommended practice of continuous grazing at conservative stocking rates is employed. 2Time-invariant matrix population models indicated that the A. vesicaria population was in decline over much of the study paddock, but the rate of decline was greatest nearer to the water point (population growth rate , , 0·8). Time-varying stochastic matrix models projected that the A. vesicaria population would become locally extinct at most sites up to approximately 2200 m from water, occurring first closer to water (within 12,29 years). The population was stable (i.e. , , 1) at sites greater than 2200 m from water over the projection period of 100 years. 3Decreases in adult survival and recruitment made the largest contributions to reductions in the population growth rate. However, there were spatial patterns centred on the water point in the degree to which particular demographic processes contributed to these reductions, because of a grazing gradient and the differential sensitivity of demographic processes to grazing. Thus decreases in recruitment contributed to reductions in the population growth rate at greater distances. Such responses, together with the sensitivity of the population growth rate to these processes, determined the spatial pattern in population growth. 4The results suggest that piospheres (i.e. the zone of impact) continue to expand over many years under set-stocking so that the area around the water point that is devoid of A. vesicaria becomes larger. The process of expansion appears to first involve the inhibition of recruitment, followed by eventual mortality of established shrubs. 5The large contribution of adult survival to the population growth rate in A. vesicaria suggests that minimizing the mortality of established adults should be a priority for management. This is likely to involve resting from grazing at critical times such as during extended dry periods. This may also permit increased levels of recruitment during subsequent moister periods. [source]