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Ecological Factors Influencing Plant Distribution in the Shadscale Zone of Southeastern UtahIbrahim, Kamal M. 01 May 1963 (has links)
The intimate relationship between vegetation and soil has long been a subject of interest. Ecologists, soil surveyors, and ranchers have recognized that vegetation differences are often accompanied by variation in soil types.
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The Effect of Range Condition and Intensity of Grazing Upon the Daily Intake and Nutritive Value of the Diet of Sheep on Summer Ranges of Northern UtahKothmann, Merwyn Mortimer 01 May 1963 (has links)
The mountainous ranges of the West are commonly used during the summer and have been used in this manner since the settlement of white men over a century ago. Many of these ranges have been mis-managed and are in poor condition. The productivity of these ranges greatly affects the economy of the nation; thus, if ranges in poor condition have a nutritive value lower than ranges in good condition, it results in an economic loss. little work has been done to determine the nutritive value of mountainous summer ranges in good condition compared to similar ranges in poor condition.
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Effects of Foraging Sequence on the Ability of Lambs to Consume Endophyte-Infected Tall Fescue (Alkaloids), Birdsfoot Trefoil (Tannins), and Alfalfa (Saponins)Lockard, Emily 01 December 2008 (has links)
All plants contain primary and secondary compounds. Primary compounds are needed by plants and herbivores for maintenance, growth, and reproduction, while secondary compounds play roles as diverse as protecting plants from ultraviolet radiation, defenses against herbivores, pollination attraction, and stress resistance. Secondary compounds have nutritional and medicinal benefits for herbivores as well, especially when eaten in diverse combinations that complement one another. While complementarities among secondary compounds are an important but little understood area of plant-herbivore interactions, even less is known about how the sequences of eating plants with different compounds affects foraging behavior, though they may be critical. In three trials, I determined if the sequence in which lambs ate endophyte-infected tall fescue (alkaloids), birdsfoot trefoil (tannins), and alfalfa (saponins) affected their foraging behavior.
When lambs grazed on monocultures they spent similar amounts of time grazing regardless of which forage they grazed. Lambs that grazed in a sequence of different forages tended to subsequently eat less alfalfa pellets in pens than lambs that grazed a monoculture, which suggests they better met their nutritional needs on mixtures than on monocultures. Likewise, lambs that grazed a monoculture of alfalfa or fescue spent more time grazing during the first 45 min than in the subsequent 45 min, while lambs that grazed alfalfa during the first 45 min and then fescue spent more time grazing in the subsequent 45 min, suggesting lambs satiate faster when they have fewer choices.
While the foraging sequences I examined generally allowed animals to consume more than they would if they grazed in monocultures, there is still a need to further explore how different plants and foraging sequences influence the level of consumption by livestock of forages on pastures that contain various secondary compounds.
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Grass-counters, stock-feeders, and the dual orientation of applied science: the history of range science, 1895-1960Heyboer, Maarten 06 June 2008 (has links)
According to the predominant image, applied science is a linear, sequential process, the application of science. First scientists or applied scientists develop knowledge that satisfies the epistemic criteria of science, and applied scientists then find ways to use this certified knowledge to solve society's problems. There is, therefore, a sharp distinction between epistemic or scientific criteria and social criteria.
The historical development of the applied ecological discipline called range science or range management demonstrates instead that applied science is a simultaneous process. Range science developed at a time when America increasingly looked to science to solve social, political, and economic problems in the hope that science's ability to predict could provide the basis for organization and rational management. The institutionalization of range science industrialized ranching. Ranchers appealed to a variety of traditional American values in response to this industrialization, but in the new context surrounding ranching those values had become illegitimate.
From the outset, range science acquired a dual orientation toward both the epistemic criteria of science and the social criteria of society. That dual orientation introduced a tension into range science because it was not obvious how range scientists should satisfy both sets of criteria simultaneously.
Researchers in different institutional contexts developed distinct resolutions to that tension. The most significant difference between the institutions were their political objectives and a difference in the power relations between range researchers and their audiences. Those institutional contexts defined the social criteria and provided the background to judge the acceptability of particular resolutions of the tension, in the process providing the motivation and justification for range science. Nevertheless, range science was not just politics by another means because range scientists also satisfied the epistemic criteria of science. The distinction between epistemic and social criteria therefore did not exist in the historical development of range science because range scientists simultaneously satisfied the epistemic criteria of science and the social criteria that flowed from different political objectives and different power relations between researchers and ranchers. / Ph. D.
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Sericea lespedeza (Lespedeza cuneata): seed dispersal, monitoring, and effect on species richnessBlocksome, Carolyn E. January 1900 (has links)
Doctor of Philosophy / Department of Agronomy / Walter H. Fick / Sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] is a rangeland weed of the tallgrass prairie of Kansas. Experiments were carried out during the 2001-2003 growing seasons (June-November) to examine the relationship between sericea lespedeza
and other rangeland species, wildlife use and dispersal of sericea lespedeza propagules, and the relationship between sericea lespedeza stubble height and utilization by livestock.
Sericea lespedeza cover was positively correlated with violet lespedeza (r=0.25)
[Lespedeza violacea (L.) Pers.], heath aster (Aster ericoides L.) (r=0.23) and total forb
cover (r=0.56). Sericea lespedeza composition was negatively correlated with big
bluestem (Andropogon gerardii Vitman.) (r=-0.27) and sideoats grama [Bouteloua
curtipendula (Michx. Torr.)] (r=-0.27) composition and positively correlated with
western ragweed (Ambrosia psilostachya D.C.) (r=0.21) and violet lespedeza (r=0.36)
composition. Sericea lespedeza density was inversely related to forb species richness on
all sites. On half the sites, there was also an inverse relationship between grass species
richness and sericea lespedeza density. Grazed sites had less difference in grass species
richness between high and low levels of sericea lespedeza densities. There was no evidence of an ecological threshold to the detriment of species richness with increasing sericea lespedeza density.
Cattle digestive processes did not affect sericea lespedeza germination. Quail digestive processes enhanced germination of the few seeds that were excreted. Quail diet selection was investigated with a field study. Five out of 49 crops collected contained seed classified as sericea lespedeza. None of these seeds germinated in the greenhouse. Both cattle and quail could potentially disperse sericea lespedeza seed, but voluntary consumption appears to be low for both species, at least during November when other
food is available.
An height-weight table estimating percent utilization for various grazed and ungrazed heights of sericea lespedeza was constructed. Coefficient of determination values were greater than 0.85 between plant height and weight, indicating that the heightweight method was appropriate for estimating sericea lespedeza utilization. Using additional regression analysis, a chart for estimating forage from percent of plants grazed was constructed.
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Comparing hyperspectral reflectance characteristics of Caucasian bluestem and native tallgrass prairie over a growing seasonGrabow, Bethany Susan Porter January 1900 (has links)
Master of Science / Department of Agronomy / Walter H. Fick / Kevin Price / Caucasian bluestem [Bothriochloa bladhii (Retz) S.T. Blake] is a perennial, C4 warm-season bunchgrass that was first introduced in 1929 from Russia as a potential forage crop in the Great Plains. Due to its invasiveness and tolerance of drought and grazing pressure, Caucasian bluestem can out-compete native prairie species. Research has shown that this species, when compared to native tallgrass species in the Flint Hills of Kansas causes decreased cattle weight gains because of its poor forage quality relative to tallgrass prairie species. Traditional methods of plant data measurements and mapping are costly and time consuming. Use of remotely sensed data to map and monitor the distribution and spread of this plant would be most useful in the control of this aggressive invader. Spectroradiometer data were collected over the 2009 growing season to determine if and when Caucasian bluestem was spectrally unique from native tallgrass prairie species. Observations were made from June through September as the plants were going into a senescent state. Reflectance data were measured approximately every two weeks or when clear/near clear sky conditions prevailed. Statistical analyses for differences in spectral characteristics were conducted to determine the optimal spectral bands, indices and timing for discriminating Caucasian bluestem from native tallgrass species. Difference in reflectance for spectral reflectance of bands 760 nm, 940 nm, 1,070 nm, and 1,186 nm were found to be statistically significant on the June 17th and June 30th sampling dates. The following band ratios and indices were found to be significantly different between Caucasian bluestem and native range on the June 17th collection date: Simple Ratio, Modified Normalized Difference Index, Normalized Phaeophytinization Index, Plant Index 1, Normalized Water Difference Index, Water Band Index, Normalized Difference Nitrogen Index, and the Normalized Difference Lignin Index. Findings of this study suggest that Caucasian bluestem can be spectrally discriminated from native tallgrass prairies of the Flint Hills in Kansas if the measurements are collected in mid to late June. Statistical analyses also showed differences between treatments for percent litter, grass, and forb basal cover.
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Restricting dry matter intake of stocker calves and its subsequent effects on grazing, feedlot performance, and carcass characteristicsAnglin, Chad O'Neal January 1900 (has links)
Master of Science / Department of Animal Sciences and Industry / Dale A. Blasi / An experiment was conducted to evaluate the effects of dry matter intake (DMI) restriction on early receiving performance by steers in a drylot and subsequent grazing performance, feedlot performance, and carcass characteristics. During the backgrounding period, crossbred, weanling steers (n = 329; initial BW = 191± 5.52 kg ) were randomly assigned to 1 of 4 DMI levels corresponding to ad libitum, 2.50% of BW (2.50%), 2.25% of BW (2.25%), and 2.00% of BW (2.00%) for 62 d. During the subsequent grazing period, the same steers were randomly assigned to 13 paddocks to graze for 90 d. Paddocks were stocked at 281 kg live weight per hectare. Initial steer BW were similar on each pasture and each backgrounding treatment was equally represented within a paddock. During the feedlot period, steers were finished at a commercial feedlot and were assigned to 1 of 4 pens according to their rank in BW. Entire pens were harvested when average steer BW reached 545 kg. During the backgrounding period, ad libitum-fed steers had greater (P < 0.001) ADG and final BW than other treatments; steers fed at 2.50 and 2.25% of BW had similar ADG and final BW and were greater (P < 0.001) than steers fed 2.00% of BW. During the grazing period, compensatory gain was observed in restricted DMI treatments. Steers fed at 2.00% of BW had greater (P = 0.006) ADG than ad libitum-fed steers but an ADG similar to that of the other restricted DMI treatments. Steers fed ad libitum, 2.50% of BW, and 2.25% of BW had similar final BW and steers fed 2.00% of BW had lesser (P < 0.001) final BW than other treatments. During the feedlot phase, steers fed 2.00% of BW were on feed longer (P < 0.05) than other treatments. Growth compensation during grazing illustrated that restricted feeding immediately prior to pasture grazing can reduce backgrounding costs.
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Evaluation of selected legumes for sustainable weed ecology/soil fertility/livestock management interactions in crop-livestock systems of the moist savannah of NigeriaOwoeye, Lawrence Gbadebo 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This project aimed at enhancing the net benefit in production systems. It took
a holistic approach to evaluate the potential interactions of herbaceous
legumes in relation to weed dynamics, soil fertility and livestock management
in the crop-livestock system in Nigeria. The project was carried out between
2000 and 2002 in two localities. These were the National Animal Production
Research Institute (NAPRI) at Zaria in the northern Guinea savannah and the
International Institute of Tropical Agriculture (IITA) at Ibadan in the derived
savannah. The main experiment was carried out in the northern Guinea
savannah, while the secondary experiments were simultaneously conducted
in the derived savannah and the northern Guinea savannah. The
experimental design for the three experiments reported in this thesis is a splitsplit
plot, fitted into randomised complete block design (RCBD), with four
replications. Main plot treatments were herbaceous legumes, namely Vigna
unguiculata, Arachis hypogaea, Glycine max, Aeschynomene bistrix,
Centrosema pascuorum, Stylosanthes guianensis and natural vegetation.
Sub-plot treatments were management systems (1) M1, 'residues left in the
field'; (2) M2, 'residues taken out of the field' and (3) M3, 'residues fed to
livestock, manure/urine/refused feeds returned'. Sub-plot treatments were
administered in a sequence following rotational fallows of herbaceous
legumes and natural vegetation. However, plots in the secondary
experiments were not subdivided before the cropping of maize in 2002, and
for logistical reasons only two sub-plot treatments, M1and M2, are featured in
this experiment. Herbaceous legumes were established at the start of the rainy season,
approximately in June, in 2000, 2001 and 2002. All herbaceous legumes
received single super phosphate (SSP) at 20kg ha" P20S at planting, while
minimum hand weeding was done to maintain pure legume stands during the
establishment phase. Forage biomass was higher in the derived savannah
than in the northern Guinea savannah. Similarly, higher forage yields were
observed after two consecutive years of legume fallow and natural vegetation,
compared to the first year plots. Grain yield for Glycine max was consistently
higher than for the other two grain legumes in 2001 and 2002.
Chemical analysis of herbaceous legumes and natural vegetation showed that
crude protein values ranged between 11.2% to 17.3% for legumes; that was
significantly (p<0.05) higher than the 8.6% value found for natural vegetation.
Moreover, all herbaceous legumes and natural vegetation, except Arachis
hypogaea, had dry matter digestibility values of more than 30%.
Maize grain and stover yields on herbaceous legumes fallowed plots were
evaluated and compared with those for natural vegetation. Results in 2001,
i.e. after a one-year fallow with legumes, indicated that the dry matter of
maize grain and stover yields in the Stylosanthes guianensis plots were
higher among the forage legumes. Arachis hypogaea gave the highest grain
and stover yields among the grain legumes in the northern Guinea savannah.
Results in 2002, i.e. after a two-year fallow, also showed that the productivity
of maize planted on Arachis hypogaea and Glycine max fallowed plots were
consistently higher across the three management systems tested in the Centrosema pascuorum, Glycine max, Aeschynomene histrix, Vigna
unguiculata and least weight gain was recorded for the natural vegetation.
Objective functions in linear optimisation, or linear combinations in algebra,
used to link dynamic processes in livestock production (Iiveweight gain) with
the dynamic processes in soils (soil nitrogen), weeds (weed biomass),
herbaceous legumes (legume biomass) and crop production (maize grain and
stover yields) under varying management systems took the form:
Management system 1, Y, = f (XI, Xz, x4); Yr= 0
Management system 2, Y, = f (x" x2); Yz = 0
Management system 3, Y, = f (XI, Xz, xl); Yz= f (XI, Xz, X4. x5)
Where
(1)
(2)
(3)
Y1 = Crop in kg; Y2 = Livestock weight gain in kg; X1= Weed in kg; X2 = Soil N
g kg-1; X3 = Livestock compost in kg; N= Herbaceous legumes in kg; X5 =
Maize stover in kg, for the three management systems considered in this
experiment.
Deductions from these equations showed that Aeschynomene histrix
performed better under M1, i.e. when legumes residues were left on the field.
Natural vegetation performed better than the herbaceous legumes under M2,
i.e. when legumes residues were exported out of the field. However, the
presence of manure in M3 enhanced soil fertility in the system and improved
the overall productivity across all the legumes and natural vegetation.
Overall rankings, conducted by pooling all components in the system,
indicated that Glycine max performed best among the legumes, followed by
Stylosanthes guianensis and Arachis hypogaea, which ranked second and viithird
respectively. In relation to the specific legume groups, Stylosanthes
guianensis performed better than the other two forage legumes, while Glycine
max also performed better than the other two grain legumes tested.
We can see from these on-station research results that there are indications
of positive opportunities for improving overall productivity and resources. This
can be done through integrating and complementing crop and livestock
production, to provide a sustainable intensification of agriculture. / AFRIKAANSE OPSOMMING: Die studie is uitgevoer om die potensiële wisselwerking van kruidagtige
peulplante met onkruiddinamika, grondvrugbaarheid en veebestuur te
evalueer. Die hoofeksperiment in die "Northern Guinea Savannah" is vanaf
2000 tot 2002 uitgevoer by die "National Animal Production Research
Institute" (NAPRI) in Zaria, Nigerië. Die twee sekondêre eksperimente is
gelyktydig in Zaria en by die "International Institute of Tropical Agriculture"
(liTA) naby Ibadan in die "Derived Savannah" uitgevoer.
Die eksperimentele ontwerp was 'n dubbel gesplete perseelontwerp gepas in
'n volledig ewekansige blokontwerp met vier herhalings. Die hoofkomponente
was die kruidagtige peulplante naamlik: Vigna unguiculata, Arachis hypogaea,
Glycine max, Aeschynomene histrix, Centrosema pascuorum, Stylosanthes
guianensis en natuurlike plantegroei. Die gekose peulplante is potensieel
aangepas vir uiteenlopende omgewings en word dikwels na verwys as "'n
mandjie van opsies". Subperseel behandelings was (1) peulplant gevestig en
gelaat op die land - M1; (2) peulplant gevestig, geoes en weggeneem uit die
land M2 en (3) peulplant gevestig, geoes, vir vee gevoer,
mis/urine/vermorste voer terug na die land - M3. Die dubbel gesplete perseel
behandelings is toegedien in 'n sekere volgorde nadat die peulplant
rusoes/braak toegepas is. In die eerste jaar is die kruidagtige peulplante
geplant op die hoofperseel van 25m by Sam. In die tweede jaar is die
hoofperseel verdeel in twee persele waar onderskeidelik peulplante en mielies
gevestig is terwyl daar in die derde jaar 'n verdere verdeling was wat gelei het tot
verskillende gewasrotasiestelsels, nl. Peulplant-peulplant-mielies,
peulplant-mielies-peulplant en peulplant-mielies-mielies.
Parameters wat insluit planthoogte, -wydte en persentasie grondbedekking
van die kruidagtige peulplante is tweeweekliks gemeet op vier 1M2 persele
wat ewekansig oor elke hoofperseel versprei is in beide gebiede waar die
studie uitgevoer is.
Resultate het getoon dat die kruidagtige peulplante wat getoets is potensiële
kandidate is vir insluitings in gewas/weiding rotasiesteiseis. Alhoewel
voerproduksie hoër was in die "derived savannah" as in die "northern Guinea
savannah", het die prestasie van die peulplante in die noordelike savannah
gevarieer met die gewasproduksiestelsels. Hoër opbrengste is gerealiseer na
twee opeenvolgende jare van oesrus met peulplante vergeleke met die eerste
jaar waar daar geen residuele effek van die peulplante was nie, en die laaste
jaar wat deur 'n mielie-oes voorafgegaan is. Biomassa opbrengste na twee
jaar van aanhoudende verbouiing was die hoogste vir S. guianensis en die
laagste vir A. hypogea. Ruproteien inhoud van die kruidagtige peulplante het
gewissel van 170 g kg-1 DM in A. hypogea tot 62.4 g kg-1 DM in A histrix.
Graanproduksie deur G. max was deurlopend hoër in 2001 en 2002 vergeleke
met die twee ander graanproduserende peulplante nl. V. unguiculata en A.
hypogea. Die voerproduksie in 2002 was heelwat hoër as die vorige jaar.
Rotasie effekte op mieliegraan en oesreste na peulplante is vergelyk oor die
dubbel gesplete persele (areas met verskillende oesruslengtes) om die ximplikasies
van hulle residuele effek op grondvrugbaarheid verbetering en
onkruid dinamika te bepaal.
Mielie-opbrengs na een jaar van rusoes toon hoër waardes op persele wat
onder kruidagtige peulplante was vergeleke met natuurlike plantegroei. Net
so was die opbrengs deurlopend hoër op persele waar daar graan peulplante
was as waar daar voer peulplante was. Oor die algemeen was die waardes
hoër vir G. max, gevolg deur A. hypogea, A. histrix, C. pascuorum, V.
unguiculata, S. guianensis en die laagste vir natuurlike plantegroei. In terme
van die bestuurstelsels, het persele wat kompos ontvang het (M3) beter as
die ander twee bestuurstelsels presteer (2.6 Mg ha" mieliegraan). Produksie
van mieliegraan en oesreste na twee opeenvolgende jare van mielieverbouing
was die hoogste na G. max (7.2 Mg ha" mieliegraan), gevolg deur die A.
histrix perseel en die laagste op S. guianensis persele. Algemene
waarnemings oor die twee subpersele wat met mielies beplant was in 2002
het getoon dat mielies beter presteer het op persele wat twee opeenvolgende
jare met peulplante beplant was.
Onkruidsamestelling en verspreiding is in beide die peulplante en natuurlike
plantegroei gemeet. Grond vir saadbankontledings is op diagonale transekte
in 0.5m by 0.5m kwadrate gemonster. Grondmonsters is ge-analiseer vir pH,
totale stikstof, organiese koolstof, fosfor, kalsium en magnesium. Hierdie
parameters is gebruik in 'n meervoudige regressie ontleding om hulle effek op
onkruidspesievoorkoms te bepaal. Onkruidgetalle in lande na In rusoes het In deurlopende hoër vlak van
besmetting getoon op die natuurlike plantegroei persele as op die peulplant
persele. Die prestasie in terme van onkruidonderdrukking was in dalende
volgorde: S. guianensis, C. pascuorum, V. ungucuilata, G. max, A. hypogaea
en A. histrix. Die onkruidsamestelling het verskilonder die verskillende
behandelings en dit het ook met tyd verander in dieselfde behandelings.
In Bykomende eksperiment met die peulplante is uitgevoer om hulle effek op
inname en groei van skape, asook die effek op kompos wat gemaak is van
vermorste materiaal en uitskeidings van die skape, te bepaal.
Droë materiaal verteerbaarheid was hoog vir S guianensis, G. max en A.
histrix terwyl die laagste syfer verkry is by A. hypogea (177.6 g kg-1 DM).
Ramme wat met kruidagtige peulplante gevoer is het beter presteer as die
wat met natuurlike plantegroei gevoer is. Ramme wat met A. hypogaea
gevoer is, het In gemiddelde daaglikse toename (GOT) getoon van 85.7 g
daq", gevolg deur S. guianensis, C. pascuorum, G. max, A. histrix, V.
unguiculata en laaste natuurlike plantegroei.
Bykomende ontledings was gemik daarop om objektiewe funksies af te lei
om dinamiese prosesse in vee (massatoename) met dinamiese prosesse in
grond (grond N), onkruid (onkruidmassa), kruidagtige peulplante
(peulplantmassa) en mielies (mieliegraan en oesreste massas) onder
verskillende bestuurstelsels te verbind. In In poging om objektiewe funksies xiivan
die verskillende komponente van die studie te bepaal, is die volgende
lineêre funksies vir die drie bestuurstelsels oorweeg nl.
Bestuurstelsel1. Yl = f (Xl, xz, x.); Yz= 0
Bestuurstelsel 2, Yl = f (Xl, Xz); Yz= 0
Bestuurstelsel3, Yl = f (Xl, X2, Xl); Yz= f (Xl. Xz. x.. les)
Waar
(1)
(2)
(3)
Y1 = Oesopbrengs in kg; Y2 = Daaglikse massatoename in kg; X1 =
Onkruidmassa in kg; X2 = Grond N in g kg-1
; X3 = Kompos in kg; X4 =
Kruidagtige peulplante in kg; X5 = Mieliereste in kg.
Onder bestuurstelsel 1, het A. histrix beter as die ander gewasse presteer,
terwyl natuurlike veld beter presteer het onder bestuurstelsel 2. Dit is 'n
aanduiding dat bestuurstelsel 2 nie volhoubaar is nie. Die derde
bestuurstelsel verteenwoordig volle integrasie van gewas en vee
produksiestelsels. Die teenwoordigheid van mis in die stelsel het
grondvrugbaarheid verbeter en algemene produktiwiteit verbeter.
Hierdie resultate dui aan dat daar geleenthede is om algemene produktiwiteit
te verbeter deur integrasie en komplementering van gewas- en
veeproduksiestelsels om volhoubare intensifikasie van landbou te bereik.
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Rangeland degradation around water-points under different management systemsSmet, Michiel 03 1900 (has links)
Thesis (MScConEcol )--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Over 70% of South Africa is too arid for crop farming and is used for commercial livestock ranching,
communal livestock ranching, or game ranching. These management systems differ from each other
in a number of aspects, e.g. herbivore species, stocking rate, grazing regime, and management
structure. The main question addressed in this study is: to what extent do the three management
systems affect rangeland condition? Following the equilibrium paradigm of vegetation dynamics,
communal livestock ranches are expected to have a greater detrimental effect on rangeland condition
than other management systems because stocking densities and, consequently, herbivore impacts,
are usually far higher than under the other two management systems. However, recent nonequilibrium
theories argue that vegetation dynamics in arid systems are mainly driven by rare and
stochastic rainfall events. Biotic factors, such as grazing and herbivore diversity, are predicted to have
little effect on rangeland condition. This leads to the prediction that herbivore impacts on arid
ecosystems are not density-dependent and, consequently, the high stocking densities commonly
recorded on communal livestock ranches will not cause more rangeland degradation than other
management systems.
Arid and semi-arid rangelands are characterised by high inherent spatial and temporal variation in
vegetation and soil parameters. Hence, differentiating between the effects of grazing management
systems and natural variability caused by abiotic factors, such as rainfall, is difficult. This problem can
be circumvented by examining gradients of grazing intensity radiating from water-points (=
piospheres). I examined changes in vegetation and soil parameters along 500 m-Iong grazing
gradients on ranches in the semi-arid Northem Cape province, South Africa, with the three abovementioned
management systems. Analysis of the vegetation on these ranches demonstrated the
existence of grazing gradients around the water-points. Two characteristic zones described in other
studies were identified, namely the sacrifice zone (almost complete denudation of the vegetation close
to the water-point) and the dense shrub zone (distal to the sacrifice zone). Communal livestock
ranching had a greater negative effect on rangeland vegetation than the two other ranching systems,
particularly with regard to annual grass species diversity, percentage of bare soil, and shrub density.
Within 100 m of the water-points, soil quality was negatively affected by commercial cattle ranching.
Contrastingly, there were no significant effects of the other two management systems on soil quality in
the piosphere. The feeding of supplemental forage and nutrients may explain the greater impact of commercial cattle farming on soil quality. The results of this study are consistent with the predictions
of the equilibrium theory of vegetation dynamics because grazing impacts were density-dependent in
these semi-arid rangelands. However, the results presented here also indicate that forage
supplementation alters the spatial and temporal distribution of livestock in a manner that may have
greater negative impacts on soil quality than density of livestock per se. / AFRIKAANSE OPSOMMING: Meer as 70% van Suid-Afrika is te droog vir gewasverbouing en word gebruik vir kommersiële
veeboerdery, gemeenskaplike veeboerdery of wildboerdery. Die bestuur van dié verskillende
boerderytipes verskil wesentlik van mekaar in verskeie opsigte, ondermeer herbivoorspesies, veeaanskaffingstempo,
weidingstipe en bestuurstruktuur. Die belangrikste vraag wat aangespreek word
in die studie is die volgende: Tot watter mate affekteer die drie verskillende boerderybestuurstipes die
toestand van weivelde? Gesien teen die agtergrond van die ekwilibriumparadigma van plantedinamika,
word verwag dat gemeenskaplike veeboerdery 'n groter impak op die toestand van weiveld
sal hê as ander boerderytipes, omdat veedigtheid en gevolglik herbivoor-impak gewoonlik veel hoër is
as met die ander twee boerderytipes. Onlangse nie-ekwilibria-teorië voer egter aan dat plantedinamika
in ariede gebiede gedryf word deur seldsame en buitengewone reënvalgebeure. Biotiese
faktore, soos weiding en herbivoor diversiteit sal na verwagting min effek hê op die toestand van
weiveld. Hieruit volg die voorspelling dat herbivoorimpak op ariede ekosisteme nie afhanklik is van
digtheid nie, en dat hoë veedigtheid algemeen aangeteken vir gemeenskaplike boerderye, nie rede sal
wees vir groter ver1iese in weiveld nie.
Ariede en semi-ariede weivelde word gekenmerk deur 'n hoë ruimtelike en tydelike veranderinge in
plant- en grondparameters. Gevolglik is dit moeilik om te onderskei tussen die effekte van
weidingsbestuur en natuur1ike veranderings wat veroorsaak word deur nie-biotiese faktore, soos
reënval. Dié probleem kan oorbrug word deur gradiënte van weidingsintensiteit, wat vanaf waterpunte
uitstraal, te ondersoek. Vervolgens het ek binne al drie bg. boerderybestuursisteme veranderinge in
plant- en grondparameters langs SOOm-lange weidingsgradiënte ondersoek op plase in die semiariede
Noord-Kaap provinsie van Suid-Afrika. Plantegroei-analise het getoon dat 'n weidingsgradiënt
rondom waterpunte voorkom. Twee kenmerkende sones is in ander studies geïdentifiseer, nl., 'n
opofferingsone (waar amper alle plantegroei naby waterpunte uitgetrap is) en die digte, struik-sone
(distaal to die opofferingsone). Gemeenskapsveeboerdery het 'n groter negatiewe effek op
plaasgewasse as die ander twee boerderytipes, veral waar dit betrekking het op grasspesie-diversiteit,
persentasie grond sonder plantbedekking en struikdigtheid. Binne 100m vanaf waterpunte, is
grondkwaliteit merkbaar negatief geaffekteer deur kommersiële veeboerdery. Daarteenoor, was daar
geen merkbare effek op die grondkwaliteit naby waterpunte van die ander twee boerderytipes nie.
Aanvullingsvoer kan moontlik die rede wees vir die waargenome, groter impak van kommersiële veeboerdery op grondkwaliteit. Die resultate van die studie strook met voorspellings van die
ekwilibria-teorie van plante-dinamika, daarin dat weidingsimpak digtheidsafhanklik is in hierdie semiariede
plaasgebiede. Die resultate toon ook egter, dat voedingsaanvullings die ruimtelike en tydelike
verspreiding van vee in so 'n wyse verander, dat dit moontlik 'n veel groter negatiewe uitwerking op
grondkwaliteit het as veedighteid per se.
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Rangeland potential, quality and restoration strategies in North-Eastern Ethiopia : a case study conducted in the Southern Afar regionGebremeskel, Kidane 03 1900 (has links)
Thesis (PhD (Agronomy))--University of Stellenbosch, 2006. / Vegetation dynamics and restoration strategies of degraded rangeland were investigated near a
watering point in the Allaidege communal grazing area in Administrative Zone 3 of the Afar
Region in the northeastern lowlands of Ethiopia. The degradation gradient formed by grazing
pressure in the study area was stratified into four different areas based on the vegetation cover;
severely degraded (SD), moderately to severely degraded (MSD), moderately degraded (MD) and
lightly degraded (LD) areas. The study was initiated at the start of the rainy season in June 2003
and lasted untill December 2004. The objectives were to study the effects of the grazing pressure
on plant species composition; on plant biomass production and basal cover; on rangeland forage
quality; on the rangeland soil status and to determine and quantify viable restoration strategies for
forage species in severely degraded rangelands.
The botanical composition of the different degradation areas was determined by making a
250 point wheel point method survey in each of four 30 m x 30 m quadrats in each degradation
area using the nearest plant approach. The botanical composition of each degradation area was
determined by measuring the frequency of occurrence of the different life forms (perennial
grasses, annual grasses and forbs) of the species recorded in the field. Accordingly, a significant
interaction was observed in both seasons between the different degradation areas and life forms
considered. A high abundance of annual grasses was evident in SD and MSD areas in both
seasons. In the MD and LD areas, a three-fold increase in frequency was recorded for perennial
grasses compared to the MSD area in 2003. In 2004, the frequency of annual grasses, forbs and
perennial grasses in the MD area was almost similar to that of the LD area. The abundance of
perennial grasses in the MD and LD areas was two- and five-fold higher compared to perennial
grasses in the MSD and SD areas respectively.
Biomass production was recorded by cutting the vegetation in 1 m x 1 m quadrats in each
grazing area at ground level. The dry matter content of subsamples was determined in order to
calculate the dry matter production of the quadrat. The differences in dry matter yield recorded in
the different degraded areas was not significant for the 2003 season, although an increasing trend
in yield was observed from the SD to MD areas. Significant yield differences were however
recorded when one outlier in the data was excluded from the analysis. The significant differences
occurred between the MD and SD areas where the MD area produced 2.4 t ha-1 more dry matter
than the SD area. Similarly, in 2004 no significant yield difference was observed between the
degradation areas. However, the contribution of different species to dry matter yield varied in the different degradation areas. Setaria verticillata, Sporobolus ioclados and Paspalidium
desertorum were found to be the major species contributing to the dry matter producion in the SD
area, S. verticillata and P. desertorum in the MSD area, Chrysopogon plumulosus and P.
desertorum in the MD area and C. plumulosus and Panicum coloratum in the LD area.
The percentage basal cover was calculated from the number of basal strikes recorded at 1
000 points in each plot of each degradation area using the wheel point method. The total basal
cover percentage did not significantly change along the degradation gradient in any of the
seasons. However, data for both seasons showed an increasing trend of total basal cover
percentage closer to the watering point compared to areas further away from the watering point,
except for the SD area, which had the lowest basal cover percentage. The contribution to
percentage basal cover by some species decreased while it increased for some other species in
grazing areas near the watering point.
Forage quality was investigated by analysing sub-samples of the forage samples taken to
determine biomass production. The forage samples were analysed for neutral detergent fibre
(NDF), acid detergent fibre (ADF), crude protein (CP), lignin, in vitro dry matter digestibility
(IVDMD), phosphorus (P), and calcium (Ca) content. The forage showed a decrease in NDF and
ADF content in areas close to the watering point in both seasons. This decrease in fibre content
was accompanied by an increase in CP content close to the watering point. The increase in CP
was significant for the SD area in both seasons. Although a similar trend was observed in both
seasons, the CP content was found to be significantly higher in 2004 than in 2003. The results of
the lignin analysis were inconclusive if the data of both seasons are considered. It does appear
however as if the lignin content of the forage was generally higher in 2003. The 2 years pooled
average of P content of the forages showed insignificant variation along the degradation gradient.
However, an increase in P concentration of the forages was evident in areas far from the watering
point. Contrary to this, Ca concentration was significantly higher in the SD area compared to
areas further away from the watering point.
Hand clipped forage samples and esophageal collected forage samples were analysed to
compare the quality of the samples. Due to the fact that only two animals were available for
esophageal collection, differences were in most cases not significant at the 5% level, but trends
indicate that animals select higher quality forage than what is assumed based on hand clipping.
Organic carbon (OC) content, total nitrogen (N) content, available phosphorus (P)
content, available potassium (K) content, exchangeable calcium (Ca) and magnesium (Mg)
contents, cation exchange capacity (CEC), total exchangeable bases (TEB), exchangeable sodium percentage (ESP), soil acidity (pH) and base saturation of soils in the different degradation areas
were determined by means of acknowledged laboratory methods. No significant differences in
OC, N, P, K, Ca, Mg and K content of soil in the different degradation areas could be observed.
There was however an increasing trend for OC and N content with distance from the watering
point. Sodium concentration and pH increased significantly in areas close to the watering point.
Cation exchange capacity content of the soil was variable and no clear trend could be established.
Significantly higher TEB and ESP contents were observed in the SD area.
In general, the differences in plant biomass production and basal cover, botanical
composition, forage quality and soil status over the degradation gradient clearly implicates the
negative impact of unrestricted grazing pressure on the rangeland around the watering points.
In the rangeland restoration trial, establishment of three local and three exotic grass
species in the SD area was investigated. Treatments applied included application of inorganic
fertilizer, dry dung organic manure and grass mulch. The mulch treatments caused a significant
yield increase for all the sown species. Among all the species, Ischaemum afrum and Tragus
berteronianus performed better and produced significantly higher dry matter yields than
Enteropogon rupestris, Chloris gayana and Panicum coloratum. In general the study indicated
the importance of mulching when planning to restore degraded rangeland under arid
environmental conditions.
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