Spelling suggestions: "subject:"soil arcology"" "subject:"soil becology""
21 |
The effect of fire management on chemical and physical properties of rangelandsMagomani, Matimba Israel January 2017 (has links)
The use of fire in rangeland has become standard practice for decades; however, there is no shared understanding of how fire affects soil properties. The exact relationship between fire and soil properties is still yet to be understood. The differences in fire frequency, fire intensity, fire severity, the period between fire and sampling resulted in contradictory results amongst studies. A long-term trial at the University of Fort Hare provides a valuable experimental layout for fire research. The trial was established in 1980 with the aim of investigating the effect of burning frequency on vegetation species composition and biomass production. The objective of this study was however to determine the effect of fire management on soil chemical and physical properties under the long-term burning experiment. The treatments of the study site were: no burn (K), annual (B1), biennial (B2), triennial (B3), quadrennial (B4) and sexennial (B6) burns. A line intercept sampling technique was used to collect the soil samples from the surface (0 to 75 mm) for both chemical and physical analysis. All Burning treatments significantly (p < 0.05) increased the bulk density (Db), soil pH, total cations, Magnesium (Mg) and Calcium (Ca), but reduced the soil porosity and exchangeable acidity when compared to the control. Hydraulic conductivity (Ks), water conducting macroporosity (WCM) and total nitrogen were reduced under more frequent burning treatments (B1, B2), as compared to less frequent burning treatments (B3, B4, B6). The aggregate stability showed an opposite trend. Total organic carbon (TOC) was reduced only under annual burning treatment. Burning frequencies did not impact the extractable Phosphorus (p), Potassium (K), Sodium, soil water repellency and water content significantly (P > 0.05). The risk associated with annual burning showed in this study might facilitate processes such as overflow that lead to soil degradation. Triennial burning in rangeland ecosystem supports soil conservation practices. Further studies that measure the quality of rangeland in triennial burning is necessary.
|
22 |
Biology and chemistry of a meadow-to-forest transition in the Central Oregon CascadesHeichen, Rachel S. 18 April 2002 (has links)
In this study, biological and chemical characteristics were determined for
two high-elevation meadow-to-forest transitions located in the Central Oregon
Cascades. The chloroform fumigation incubation method (CFIM) was used to
determine microbial biomass C(MBC) and the N flush due to fumigation (NF), and
meadow values were compared to forest values for each. Meadow and forest MBC
values were also compared for estimates of MBC determined with microscopy and
these values were compared to CFIM estimates. Net N mineralization and C
mineralization were determined for an 85-d incubation period and used as a
measure of labile C and N. Microbial biomass C and NF were then compared to
these labile pools in order to investigate the relationship between the amount of
each nutrient stored in biomass and the magnitude of the respective labile nutrient
pool for each. Long-term and short-term net N mineralization rates and C/N ratios
were also compared for meadow and forest soils, and the relationship between
these two characteristics was examined.
In general, microbial biomass estimates made with the CFIM method did not
show any significant differences between meadow and forest soils. Mean MBC for
both sites as determined by CFIM was estimated to be 369 and 406 μg C g⁻¹ soil in
meadow and forest soils, respectively. Mean NF was estimated to be 37 and 56 μg
N g⁻¹ soil in meadow and forest soils, respectively. MBC estimates made using
microscopy showed biomass C to be greater in the forest than in the meadow.
Mean MBC as determined by microscopy was estimated to be 529 and 1846 μg C
g⁻¹ soil in meadow and forest soils, respectively. The NF measured as a percentage
of the net N mineralized over 85 d was significantly greater in the forest than in the
meadow soils, but was a substantial percentage in both. The means of these values
were 30 and 166% in meadow and forest soils, respectively. This led to the
conclusion that biomass N may be a very important pool of stored labile N in this
ecosystem. Net N mineralization rates were almost always greater in the meadow
than in the forest soils. Net N mineralization for the 10-d incubations averaged
21 μg N g⁻¹ soil in the meadow and 8 μg N g⁻¹ soil in the forest Rates for long-term
N mineralization averaged 126 μg N g⁻¹ soil in the meadow and 52 μg N g⁻¹
soil in the forest. Net N mineralization rates were correlated with C/N ratios for
both short-term and long-term incubations. / Graduation date: 2002
|
23 |
Serpentine and non-serpentine edaphic ecology and the recovery of Lomatium cookii (Apiaceae), an endangered endemic of southwest Oregon /Silvernail, Ian S. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.
|
24 |
Soil carbon and nitrogen in old-growth forests in western Oregon and Washington /Remillard, Suzanne Marie. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2000. / Typescript (photocopy). Includes bibliographical references (leaves 98-109). Also available online.
|
25 |
How does agricultural management affect the structure and function of arbuscular mycorrhizal fungal communities?Van den Bos, Alexander Arthur January 2015 (has links)
Arbuscular mycorrhizal (AM) fungi form an obligate symbiosis with many wild and cultivated plants. The plant may benefit from improved nutrient uptake (particularly phosphorus) and resistance to drought, pests and disease. Compared to more natural habitats, arable systems support reduced diversity of AM fungi, with community structure shifted in favour of ruderal types. Physical disturbance is an important driver of these differences and reduced tillage systems might facilitate greater utilisation of the AM symbiosis as part of more sustainable production systems. In this study, the structure of root-associated AM fungal communities in barley grown under a range of tillage regimes was characterised, using high-throughput molecular methodology. AM fungal community structure was significantly influenced by tillage intensity, with soils subject to high tillage burden richest in ruderal types. These findings were consistent in both winter and spring barley cultivars. Significant temporal changes in AM fungal community structure suggested an important role for plant growth stage in determining AM fungal community dynamics. Functional differences can occur between fungal species and different fungus-plant combinations, and in the second part of this study the functional consequences of changes in community structure due to tillage were tested in a model system using intact field-soil cores. There were clear differences in AM fungal community structure due to differential physical disturbance. Although no functional effects were observed, this may have been due to the inherent limitations of recreating field conditions in microcosm experiments. The results of this comprehensive assessment of fine-scale spatial variation in AM fungal community structure in an arable system identify tillage as an important driver of AM fungal community dynamics, and plant growth stage is also a key factor which has rarely been addressed. Elucidating the functional significance of these changes remains essential in order to justify future changes to arable management practices.
|
26 |
Some aspects of the mesofaunal population of moorland soils, with particular reference to the influence of certain members on the pedology of such soilsMurphy, Paul W. January 1953 (has links)
No description available.
|
27 |
The ecology of some British podzol formationsDimbleby, G. W. January 1950 (has links)
No description available.
|
28 |
The effect of long-term tillage practices on selected soil properties in the Swartland wheat production area of the Western CapeBotha, Pieter Barend 03 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The effect of long-term tillage on basic soil properties with respect to sustainability was investigated in this dissertation. Over the last three decades soil conservation has become an important prerequisite for sustainable agriculture. The primary aim of this study was to evaluate the effect of different tillage practices on the physical and some of the chemical properties of soil after 37 years of continuous application.
This study was conducted on the Langgewens experimental farm, 18 km north of Malmesbury in the Western Cape. The experiment was initiated in 1975 on a Glenrosa (Haploxeralf) soil form with a gravelly sandy-loam texture. It was treated with four main tillage methods, namely conventional, tine, minimum and no-tillage. Important basic soil properties studied were the electrical conductivity (EC) and total carbon percentage, water stable aggregate percentage, bulk density and hydraulic conductivity. Most of the properties were analysed for the 0-100 mm and 100-200 mm depths. Seasonal bulk density variation for the 0-100 mm soil depth was determined by a Troxler surface gamma-neutron meter for in situ measurement. ANOVA’s and Tukey’s LSD posthoc tests were computed to assess whether significant statistical differences existed between tillage treatments.
No-tillage proved to be beneficial in terms of salinity and had the lowest electrical conductivity, indicating that salts leeched out of the profile. Total carbon content was in general very low and in the 0-100 mm soil depth it decreased in the order of: no (0.92%), minimum (0.86%), tine (0.83%) and conventional tillage (0.51%). Aggregate stability was significantly the lowest under conventional (47.82%) and tine tillage (45.02%) compared to minimum (61.43%) and no-tillage (78.40%) at 0-100 mm depth. This can be explained by the relatively low amount of total carbon in the soil combined with the tillage intensity. The same trend was observed for the 100-200 mm depth. Significant correlation between total carbon content and aggregate stability for the 0-100 mm confirmed that an increase in total carbon in the soil would lead to an increase in aggregate stability. Significant, increased aggregate stability under the no-tillage treatment would therefore indicate that there may be some stable structure present in the soil. Seasonal bulk density variation was the lowest in no-tillage, which supports the manifestations of stable soil structure. More intensive tillage treatments such as conventional and tine tillage initially showed lower bulk densities, but only for the first month. Thereafter it increased to significantly higher values as the season progressed. This was mainly as a result of hardsetting of the soil which is driven by natural processes and rainfall. It is also due to the sandy loam texture that is particularly prone to compaction. Hydraulic conductivity studied for conventional and no-tillage showed significant differences. No-tillage (41 mm.h-1) showed a noticeably higher conductivity, which remained constant compared to conventional tillage (20 mm.h-1) that decreased over time. The main reasons for this increased hydraulic conductivity under no-tillage was higher water stable aggregates and lower bulk density.
In the long term no-tillage thus stimulated structure formation of a Glenrosa soil form that significantly improved soil properties studied. These properties may influence processes such as water infiltration, water storage, run-off and drainage positively, due to soil property interaction. No-tillage, in terms of sustainability, quantified by the soil properties studied, thus proved to be superior compared to conventional and tine tillage but to a lesser extent if compared to minimum tillage. / AFRIKAANSE OPSOMMING: In hierdie tesis word die effek van langtermynbewerking op basiese grondeienskappe met betrekking tot volhoubaarheid ondersoek. Oor die afgelope drie dekades het grondbewaring ‘n belangrike aspek in landbou geword, ten einde volhoubaarheid te verseker. Die primêre doel van hierdie studie was om die effek van verskillende bewerkingspraktyke op die fisiese en chemiese eienskappe van grond na 37 jaar van deurlopende bewerking te ondersoek.
Die studie is uitgevoer op die Langgewens eksperimentele plaas, 18 km noord van Malmesbury in die Wes-Kaap. Die eksperiment is in 1975 geïnisieer op 'n Glenrosa (Haploxeralf) grondvorm met ʼn klipperige sandleem-tekstuur. Dit bestaan uit vier hoof-bewerkingsbehandelings, naamlik konvensionele, tand-, minimum en geenbewerking. Belangrike basiese grondeienskappe wat bestudeer is, is die elektriese geleidingsvermoë (EG) en die totale persentasie koolstof, persentasie waterstabiele aggregate, bulkdigtheid en hidrouliese geleiding. Die meeste van die eienskappe is ontleed op die 0-100 mm en 100-200 mm diepte. Seisoenale bulkdigtheidsvariasie vir die 0-100 mm gronddiepte is bepaal deur 'n Troxler oppervlak gamma-neutron meter deur middel van in situ meting. ANOVA en Tukey se LSD posthoc-toetse is bereken om te bepaal of daar statisties-beduidende verskille tussen die bewerkingsmetodes is.
Geenbewerking het geblyk voordelig te wees in terme van die soutgehalte en het die laagste elektriese geleidingsvermoë gehad, wat daarop dui dat die soute uit die profiel loog. Die totale koolstofinhoud was oor die algemeen baie laag en in die 0-100 mm gronddiepte het dit afgeneem in die volgorde geen- (0.92%), minimum- (0.86%), tand- (0.83%) en konvensionele bewerking (0.51%). Aggregaatstabiliteit was betekenisvol die laagste onder konvensionele (47.82%) en tandbewerking (45.02%) in vergelyking met die minimum (61.43%) en geenbewerking (78.40%) by die 0-100 mm diepte en kan verduidelik word deur die relatief lae totale koolstofinhoud in die grond gekombineer met die bewerkings-intensiteit. Dieselfde tendens is waargeneem vir die 100-200 mm diepte. ‘n Beduidende korrelasie tussen totale koolstofinhoud en aggregaatstabiliteit is vir die 0-100 mm diepte gevind en dit bevestig dat 'n toename in totale koolstof in die grond sal lei tot 'n toename in aggregaatstabiliteit. Betekenisvolle verhoogde aggregaatstabiliteit onder die geenbewerking-behandeling sal dus aandui dat die grond 'n meer stabiele struktuur vertoon. Seisoenale bulkdigtsheidsvariasie was die laagste in geenbewerking en ondersteun die manifestasies van 'n stabiele grondstruktuur. Meer intensiewe bewerkingsbehandelings, konvensionele en tandbewerking het vir die eerste maand ‘n laer bulkdigtheid getoon, waarna dit tot aansienlik hoër waardes gestyg het soos die seisoen verloop het. Dit was hoofsaaklik as gevolg van grondkonsolidering wat gedryf word deur natuurlike prosesse soos reënval en ook as gevolg van die sandleemtekstuur wat veral geneig is tot verdigting. Hidrouliese geleiding is bestudeer vir konvensionele en geenbewerking en het beduidende verskille getoon. Geenbewerking (41 mm.h-1) het 'n merkbare hoër geleidingsvermoë gehad wat konstant gebly het, in vergelyking met konvensionele bewerking (20 mm.h-1) wat met die verloop van tyd afgeneem het. Die vernaamste redes vir hierdie verhoogde hidrouliese geleiding onder geenbewerking is hoër waterstabiele aggregate en ‘n laer bulkdigtheid.
Op die langtermyn het geenbewerking dus struktuurvorming van 'n Glenrosa-grondvorm gestimuleer, wat die grondeienskappe wat bestudeer is, aansienlik verbeter het. Hierdie eienskappe kan prosesse soos waterinfiltrasie, waterretensie, -afloop en -dreinering positief beïnvloed as gevolg van grondeienskapinteraksie. Geenbewerking, in terme van volhoubaarheid, gekwantifiseer deur die grondeienskappe wat bestudeer is, is dus bewys as superieur in vergelyking met konvensionele en tandbewerking, maar tot 'n mindere mate in vergelyking met minimumbewerking. / Water Research Commission
|
29 |
Investigating the impact of herbivory and nitrogen-fixation on savanna plant and soil nutrient dynamicsHattingh, Wesley Neil 20 January 2016 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science
Johannesburg, September 2015 / Plant functional traits provide a means to investigate the diverse ecological strategies employed by plants and a tangible link to assess how the variability in these traits might influence ecosystem processes and functioning. The aim of this dissertation has been to determine how plant and soil nutrient dynamics in a savanna environment are affected by two primary drivers, one a top-down driver, being herbivory by large mammalian herbivores and the other a bottom-up driver, the variable N2-fixation capacity of tree species. To the best of my knowledge this is the most comprehensive study to date to investigate the bioavailability of soil nutrients and the link between these availabilities and plant functional traits. Furthermore this study provides important insight into the use of a novel technology, ion exchange resin capsules in a South African savanna context.
By studying a selection of plant functional traits (nutrient concentrations, ratios as well as specific leaf area, relative chlorophyll content and leaf dry matter content) and soil nutrients (suite of macro- and micronutrients) associated with two species of savanna tree of contrasting N2-fixation capacities, I went about investigating how herbivory differentially influences the nutrient dynamics of this system. Selecting individuals of the N2-fixing Acacia tortilis and the non-N2-fixing Combretum hereroense both inside an exclosure and on the adjacent land allowed me to determine the potential impacts by herbivores. These include both direct impacts from foraging and indirect impacts through the regulation of nutrient input pathways via deposition of dung and urine. The work compiled for this dissertation is based on the experimental work conducted in a mesic savanna system in the Marakele Park (PTY) Ltd. During the course of this dissertation, I investigated herbaceous and woody biomass in relation to protection from and exposure to herbivory, determining any differences in the functional leaf traits between individuals inside and outside the exclosure, if these differences were exhibited in the associated herbaceous biomass as well as a comprehensive assessment of the bioavailability of 15 important micro- and macronutrients using ion exchange resin capsules. These capsules were incubated in the soil over the entire summer rainfall period, providing a
cumulative view of nutrient bioavailability during the growing season. In this work I also demonstrated whether particular nutrients are associated with specific drivers (i.e. herbivory, canopy position or N2-fixation). Furthermore, these results were then looked at together to suggest the mechanism by which herbivory and N2-fixation drive nutrient dynamics and make recommendations on the use of these results in managing savanna systems in the future.
Between the two sites, aboveground herbaceous biomass was significantly greater when protected from herbivores than on the adjacent land. Both exposure to herbivory and N2-fixation capacity were found to alter plant functional traits. Herbivore presence was associated with an increase in herbivore-resistant or structural traits such as C/N, C/P, foliar C and SLA as well as a reduction in N and P content. These less palatable leaves were accompanied by a significantly lower availability of a number of important soil elements, namely NO3-N, inorganic N, P, K, Na, Cu, B, Mg, and S. This suggests a feedback loop between these two components of the ecosystem. N2-fixation capacity is associated with greater concentrations of elements such as N and P and a reduction in traits that are illustrative of a greater structural investment into leaves. Soil nutrient bioavailability however, shows a reduction in certain nutrients when associated with Acacia. A number of nutrients which show a reduction in availability are those which are essential to N2-fixation machinery, namely B and Fe but also lower bioavailabilities of Al and Mg. Finally, Ca, NO3-N, B, Fe, Al and inorganic N were found in greater quantities below the tree canopy than beyond it.
In conclusion both herbivory by large mammalian herbivores and N2-fixation have significant effects on tree health, through their regulation of limiting nutrients and alteration of leaf traits. Given the changes which these drivers are capable of exerting on plant and soil nutrient dynamics, this has important consequences for ecosystem processes and functioning and highlights potential considerations in the long-term sustainable management of savannas.
|
30 |
Arthropods inhabiting pine litter in the South-East of South AustraliaHoward, Geoffrey William. January 1967 (has links) (PDF)
Includes bibliographical references
|
Page generated in 0.0348 seconds