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Articoli di riviste sul tema "Plant-soil relationships – Western Australia"
1
Pate, J. S., W. H. Verboom e P. D. Galloway. "Co-occurrence of Proteaceae, laterite and related oligotrophic soils: coincidental associations or causative inter-relationships?" Australian Journal of Botany 49, n. 5 (2001): 529. http://dx.doi.org/10.1071/bt00086.
Testo completoAbstract (sommario):
This communication presents the hypothesis that certain Australian lateritic and related oligotrophic soils may have been partly derived biotically from soluble iron-rich complexes generated following secretion of low-molecular weight organic acids by phosphate-absorbing specialised proteoid (cluster) roots of proteaceous plants. Subsequent precipitation of the iron is then pictured as occurring onto the oxide rinds of developing laterite after consumption of the organic components of the complexes by soil bacteria. The hypothesis is f irst examined in relation to current theories of origins of laterites and the extent of the coincidences worldwide in past and present times between Proteaceae and oligotrophic soil types of lateritic character. The paper then provides more definitive lines of evidence supporting the hypothesis, based largely on recent studies by the authors in south-western Western Australia. This relates to (a) cases of definitive association in habitats rich in Proteaceae between zones of root proliferation and ferricrete layers in lateritic soils, (b) proximity in soil profiles between ferric deposits and current and ancestral root channels, (c) the recovery of citrate-consuming bacteria from soil profiles and specifically from ferricrete rinds and horizons accumulating sesquioxide organic matter and (d) distribution of iron and phosphorus within plant and soil profile components consistent with ferricrete rinds being generated by rhizosphere-mediated interactions of plants and microbes under conditions of severely limited availability of phosphorus. The mode of functioning of proteoid root clusters is then discussed, especially in relation to exudation of organic acid anions, uptake of phosphorus and the subsequent fate of organic anions and their metal ion complexes in the system. An empirically based scheme is presented indicating flow profiles for phosphorus and iron between soil, ferricrete rinds and bacterial and plant components. We then discuss possible carbon costs to proteaceous plant partners when accessing phosphorus under the nutrient-impoverished conditions typical of heathlands and open woodlands of Mediterranean-type ecosystems of Western Australia. The paper concludes with a critical overview of the hypothesis, particularly its implications regarding possible higher plant: microbial influences shaping soil and landscape evolution in the regions involved.
2
Wong, M. T. F., e R. J. Harper. "Use of on-ground gamma-ray spectrometry to measure plant-available potassium and other topsoil attributes". Soil Research 37, n. 2 (1999): 267. http://dx.doi.org/10.1071/s98038.
Testo completoAbstract (sommario):
The incidence of potassium (K) deficiency is increasing in crops, pastures, and forestry in south-western Australia. Although soil K can be measured using soil sampling and analysis, γ-ray spectrometry offers a potentially cheaper and spatially more precise alternative. This could be particularly useful in precision agriculture, where inputs are applied according to need rather than by general prescription. In a study of topsoils near Jerramungup, Western Australia, strong relationships (r2 = 0·9) were found between on-ground counts of γ-rays derived from 40K (γ-K) and both total K and plant-available K. The success of γ-ray spectrometry in predicting available K relied on a strong relationship (r2 = 0·9) between total K and available K which may not hold in all areas. Although the relationship between γ-K and available K held over the range of 36–1012 mg/kg, crop response to K fertilisers is only expected when the available K content is <100 mg/kg. Estimates of available K from γ-K were unreliable at this lower end of the regression curve. Separate analysis with a subset of the data with available K <100 mg/kg showed a poor relationship between γ-K and available K (r2 = 0·05; d.f. 11). The usefulness of γ-ray spectrometry may therefore be restricted to defining areas where response to fertiliser K may occur, and where further soil sampling and analysis are required to predict the fertiliser requirement. Strong relationships (r2 = 0·9) were also found between γ-K and a range of other soil attributes, including clay, silt, and organic carbon content. These relationships depended on the locally strong relationship between total K and these soil attributes. Since such relationships do not hold everywhere, the utility of γ-ray spectrometry will likewise be limited. Site-specific calibrations are required if γ-ray spectrometry is to be used for soil property mapping.
3
Wong, M. T. F., R. J. Corner e S. E. Cook. "A decision support system for mapping the site-specific potassium requirement of wheat in the field". Australian Journal of Experimental Agriculture 41, n. 5 (2001): 655. http://dx.doi.org/10.1071/ea00191.
Testo completoAbstract (sommario):
The intensely weathered nature of Western Australian cropping soils and the long history of potassium depletion by the farming system has resulted in increased incidence of potassium deficiency in wheat. There is currently no scientifically based method for potassium recommendation in Western Australia. This paper describes the use of site-specific plot-scale field trials carried out in 1995–98 and a crop response model to develop a generally applicable potassium recommendation system. Geographic information system technology was used to extend the uniform potassium recommendation system into a system for mapping spatially variable potassium requirement that takes account of crop demand and soil available potassium. The field trials were carried out on a range of soil types and showed that wheat response to potassium can be described by the Mitscherlich equation. The size of the response was dependent on the soil test value for plant available potassium and the yield of the crop. The latter is mainly dependent on rainfall in the water-limited Mediterranean environment of Western Australia. The relationships between the maximum achievable yield, crop response and soil available potassium values were quantified in order to allow the decision support system to be developed for uniform whole-paddock fertiliser recommendation. Both soil available potassium and yield are very spatially variable in Western Australia and for wheat, the coefficient of variation of yield within the paddock is often of the order of 30%. Soil property variation can be of a similar order. Maps of soil available potassium values and of spatially variable target yield determined either from (i) farmer’s estimate, (ii) yield monitors and (iii) remotely sensed normalised difference vegetation index measurements allow this decision system to map spatially variable potassium requirement. Comparison of the map of potassium requirement with measured spatially variable response to potassium showed that the decision support system performed satisfactorily.
4
Samadi, Abbas, e R. J. Gilkes. "Phosphorus Transformations and Their Relationships with Calcareous Soil Properties of Southern Western Australia". Soil Science Society of America Journal 63, n. 4 (luglio 1999): 809–15. http://dx.doi.org/10.2136/sssaj1999.634809x.
Testo completo
5
Wong, M. T. F., R. W. Bell e K. Frost. "Mapping boron deficiency risk in soils of south-west Western Australia using a weight of evidence model". Soil Research 43, n. 7 (2005): 811. http://dx.doi.org/10.1071/sr05022.
Testo completoAbstract (sommario):
The aim of this work was to develop a risk map for boron (B) deficiency in the grain cropping regions of Western Australia (WA), whilst avoiding the high costs associated with direct B measurements for an area as vast as the south-west of WA. The study firstly determined relationships between 0.01 m CaCl2-extractable soil B levels and readily available data on soil properties and parent materials for Reference Soils of south-west Australia and secondly assembled direct evidence of B deficiency risk from surveys of farmers’ crops and soils and from glasshouse experiments. Across 73 Reference Soils, there was a positive relationship between 0.01 m CaCl2-extractable soil B levels and clay (r 2 = 0.50) and pH (r 2 = 0.43) in the surface horizon. Soils containing <0.5 mg B/kg generally had <5% clay and pH CaCl2 <5.5. Plant and soil analysis surveys in farmers’ fields revealed 10–20% of fields had B levels below tentative critical levels. In a glasshouse experiment, B response in oilseed rape was obtained in 4 sandy acid soils, all developed on sandstone parent materials. From this prior evidence of B deficiency, spatial data layers for surface soil pH, subsurface pH, surface clay level, and geology in south-western Australia were weighted and combined using the Dempster-Shafer weight of evidence model to map B-deficiency risk. The weightings of evidence layers were revised to increase the correspondence between predicted areas of high risk and field areas with measured low B or B deficiency from a validation dataset. The model helps overcome the high cost associated with direct B measurements for risk mapping. A similar approach may have value for mapping risk of other deficiencies of relevance to agriculture.
6
Bolland, MDA, IR Wilson e DG Allen. "Effect of P-buffer capacity and P-retention index of soils on soil test-P, soil test P-calibrations and yield response curvature". Soil Research 32, n. 3 (1994): 503. http://dx.doi.org/10.1071/sr9940503.
Testo completoAbstract (sommario):
Twenty-three virgin Western Australian soils of different buffer capacities (BC) for phosphorus (P) were collected. The effects of BC on the relationships between Colwell soil test P and the level of P applied, yield and soil test P, and yield and the level of P applied were studied. Wheat (Triticum aestivum cv. Reeves), grown for 27 days in a glasshouse, was used. Two methods of measuring P sorption of soils, P buffer capacity (PBC) and P retention index (PRI), were used. The PBC is determined from a multi-point sorption curve. The PRI is a new, diagnostic, one-point, sorption method now widely used for commercial soil P testing in Western Australia. Both PBC and PRI produced similar results. The relationship between soil test P and the level of P applied was adequately described by a linear equation. When the slope coefficient of the linear equations was related to PBC or PRI, there was no relationship. The other two relationships were adequately described by a Mitscherlich equation. When the curvature coefficient of the Mitscherlich equation was related to PBC or PRI, the trend was for the value of the coefficient to decrease with increasing PBC or PRI. Consequently, as the capacity of the soil to sorb P increased the trend was for larger soil test P or higher levels of P application to produce the same yield.
7
Taylor, Miranda J., Keith Smettem, Gabriella Pracilio e William Verboom. "Relationships Between Soil Properties and High-Resolution Radiometrics, Central Eastern Wheatbelt, Western Australia". Exploration Geophysics 33, n. 2 (giugno 2002): 95–102. http://dx.doi.org/10.1071/eg02095.
Testo completo
8
Anderson, Geoffrey, e Richard Bell. "Wheat grain-yield response to lime application: relationships with soil pH and aluminium in Western Australia". Crop and Pasture Science 70, n. 4 (2019): 295. http://dx.doi.org/10.1071/cp19033.
Testo completoAbstract (sommario):
Soil acidity, or more specifically aluminium (Al) toxicity, is a major soil limitation to growing wheat (Triticum aestivum L.) in the south of Western Australia (SWA). Application of calcium carbonate (lime) is used to correct Al toxicity by increasing soil pH and decreasing soluble soil Al3+. Soil testing using a 0.01 m calcium chloride (CaCl2) solution can measure both soil pH (pHCaCl2) and soil Al (AlCaCl2) for recommending rates of lime application. This study aimed to determine which combination of soil pHCaCl2 or soil AlCaCl2 and sampling depth best explains the wheat grain-yield increase (response) when lime is applied. A database of 31 historical lime experiments was compiled with wheat as the indicator crop. Wheat response to lime application was presented as relative yield percentage (grain yield for the no-lime treatment divided by the highest grain yield achieved for lime treatments × 100). Soil sampling depths were 0–10, 10–20 and 20–30 cm and various combinations of these depths. For evidence that lime application had altered soil pHCaCl2, we selected the change in the lowest pHCaCl2 value of the three soil layers to a depth of 30 cm as a result of the highest lime application (ΔpHmin). When ΔpHmin <0.3, the lack of grain-yield response to lime suggested that insufficient lime had leached into the 10–30 cm soil layer to remove the soil Al limitation for these observations. Also, under high fallow-season rainfall (228 and 320 mm) and low growing-season rainfall (GSR) (<140 mm), relative yield was lower for the measured level of soil AlCaCl2 than in the other observations. Hence, after excluding observations with ΔpHmin <0.3 or GSR <140 mm (n = 19), soil AlCaCl2 provided a better definition of the relationship between soil test and wheat response (r2 range 0.48–0.74) than did soil pHCaCl2 (highest r2 0.38). The critical value (defined at relative yield = 90%) ranged from 2.5 mg Al kg–1 (for soil Al calculated according to root distribution by depth within the 0–30 cm layer) to 4.5 mg Al kg–1 (calculated from the highest AlCaCl2 value from the three soil layers to 30 cm depth). We conclude that 0.01 m CaCl2 extractable Al in the 0–30 cm layer will give the more accurate definition of the relationship between soil test and wheat response in SWA.
9
Coates, Fiona, e J. B. Kirkpatrick. "Is Geographic Range Correlated with Climatic Range in Australian Spyridium Taxa?" Australian Journal of Botany 47, n. 5 (1999): 755. http://dx.doi.org/10.1071/bt97066.
Testo completoAbstract (sommario):
The major centres of local endemism and richness at the species level and below in Spyridium Fenzl are located on the southern coast of Western Australia and in south-eastern South Australia. There are only a few Spyridium taxa with ranges that transgress the boundaries of the following four regions: south- western Western Australia; south-eastern South Australia and western Victoria; eastern Victoria, New South Wales and southern Queensland; Tasmania. Synthetic climatic variables were generated for all recorded populations of Spyridium taxa. Variabilities in these were related to the maximum geographic ranges of taxa in Australia as a whole, and within the regions, in order to test the hypothesis that narrow endemism is explained by climatic restriction since the last glacial. In Australia as a whole, local endemics are both narrowly and widely distributed climatically, as are more widespread Spyridiumtaxa, and there were no significant relationships between the climatic and geographic ranges of taxa confined to the Australian mainland regions. However, Tasmanian taxa exhibited a strong positive relationship. Restriction of range as a result of climate change is an unlikely explanation for local endemism in Spyridium in mainland Australia, where topographic and climatic gradients are generally subdued, and which apparently experienced less severe climatic oscillations during the Quaternary. However, this hypothesis cannot be rejected for Tasmania, which experienced more extreme Quaternary climatic fluctuations than the present-day areas of mediterranean climate, and hence more severe fluctuations in the area and location of climatically suitable habitats.
10
O'Rourke, Tiernan A., Tim T. Scanlon, Megan H. Ryan, Len J. Wade, Alan C. McKay, Ian T. Riley, Hua Li, Krishnapillai Sivasithamparam e Martin J. Barbetti. "Severity of root rot in mature subterranean clover and associated fungal pathogens in the wheatbelt of Western Australia". Crop and Pasture Science 60, n. 1 (2009): 43. http://dx.doi.org/10.1071/cp08187.
Testo completoAbstract (sommario):
Pasture decline is considered to be a serious challenge to agricultural productivity of subterranean clover across southern Australia. Root disease is a significant contributing factor to pasture decline. However, root disease assessments are generally carried out in the early part of the growing season and in areas predominantly sown to permanent pastures. For this reason, in spring 2004, a survey was undertaken to determine the severity of root disease in mature subterranean clover plants in pastures located in the wheatbelt of Western Australia. DNA-based soil assays were used to estimate population density in the soil of a variety of soil-borne pathogens known to commonly occur in the Mediterranean-type environments of southern Australia. The relationships between severity of disease on tap and lateral roots and root diameter, root length, nodulation, and total rainfall were determined. The survey showed, for the first time, that severe root disease is widespread in spring across the wheatbelt of Western Australia. There was a positive correlation between rainfall and tap root disease, and between tap root disease and average root diameter of the entire root system. Despite the high levels of root disease present across the sites, the DNA of most root disease pathogens assayed was detected in trace concentrations. Only Pythium Clade F showed high DNA concentrations in the soil. DNA concentrations in the soil, in particular for Phytophthora clandestina and Rhizoctonia solani AG 2.1 and AG 2.2, were higher in the smaller autumn sampling in 2006. This study suggests that the productivity of subterranean clover-based pastures is severely compromised by root rot diseases throughout the growing season in the wheatbelt of Western Australia.
Tesi sul tema "Plant-soil relationships – Western Australia"
1
Dolling, P. J. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia /". Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
Testo completo
2
Collins, Shane. "Residue composition influences nutrient release from crop residues". University of Western Australia. School of Earth and Geographical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0171.
Testo completoAbstract (sommario):
[Truncated abstract] A greater adoption of stubble retention, minimum-till and no-till farming practices for the purposes of conserving soil, water and fertility requires a greater understanding of the complexity of physical and chemical interactions between the soil and crop residues. There is currently insufficient knowledge to allow reliable predictions of the effects of different residue types in different environments on soil fertility and crop growth, owing to the many residue characteristics and environmental interactions that have been shown to affect decomposition or nutrient release. The role of fibre and nutrient composition in nutrient release from crop residues, and implications for residue management techniques, were studied. Canola, lupin and field pea residues, obtained from farmland in Meckering and Northam, Western Australia, were separated into upper and basal stems, leaves, and siliques or pods. This was done to provide materials with a wide range of chemical and physical characteristics, and also allowed consideration of differential residue management of plant organs, such as comparing harvested canola siliques and retained canola stubble. Pre-treatment by chopping and/or humidification was applied to residues to provide some information about the processes of nutrient release. Residues were subjected to simulated rainfall to assess nutrient leaching from plant material, and placed on soil in pots in constant-temperature glasshouse conditions to assess decomposition. Amounts and rates of change of residue fibre and nutrients were determined throughout leaching and decomposition. Energy Dispersive X-ray (EDX) microanalysis was used to assess the location of diffusible ions in air-dried residues and the effects of humidification on nutrient positioning and release. ... However, the release of calcium and magnesium depended on the decomposition of the more recalcitrant components such as cellulose and lignin, as supported by microscopy results showing changes in nutrient distribution following humidification. The proportionality of amounts of calcium and magnesium leached and released during decomposition is likely to suggest a similarity of chemical form more than similarity of function or position of the two elements. Management of crop residues for maximising and optimising the timing of release of different nutrients will need to take into account the placement of different plant types and parts, particle sizes distribution and pre-treatment of material to efficiently manage short- and long-term soil fertility to sustain crops, particularly on degraded soils. Significant nutrient release of potassium, sulphur and magnesium from crop residues can be achieved from surface placement, with the release of potassium and sulphur managed by modifying residue particle size through appropriate harvesting, ploughing or sowing implement selection. High nutrient uptake crops and plant parts where they can be economically viable to grow or separated by the harvesting technique are particularly valuable as sources of nutrients and soil organic matter.
3
Setyawan, Dwi. "Soil development, plant colonization and landscape function analysis for disturbed lands under natural and assisted rehabilitation". University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0117.
Testo completoAbstract (sommario):
[Truncated abstract] Spontaneous plant growth and soil development occur at disturbed sites with their extent and nature being variously affected by soil fertility status, local climate and topographic conditions. Soil-plant interactions can be diverse and site-specific within a disturbed landscape. The main purpose of the present study is to evaluate soil characteristics and landscape indices in relation to natural plant growth and soil development under different conditions and for diverse materials. A comprehensive study has been carried out to evaluate spontaneous soil development and plant colonization on various regolith materials at a railway cutting near Jarrahdale bauxite mine and on various substrates comprising waste rock, weathered regolith and replaced topsoil at Scotia (Norseman, Western Australia) and Kelian (East Kalimantan, Indonesia). At Jarrahdale soil development has occurred slowly over 36 years in relation to morphological changes in surface horizons. Soils at several locations exhibit substantial changes in color, texture and structure. The slow soil development is primarily due to low biomass and litter contributions (˜1 Mg/ha) from colonizing plants (e.g. Dryandra sessilis, Eucalyptus marginata and low shrubs) on the cutting shelf and slow litter decomposition. Nutrient accumulation is up to 5 kg N/ha, and 0.5 kg/ha for P and K. Surface soil samples from Jarrahdale are generally acidic (pH < 5.1) and contain low concentrations of total soil carbon (20 g/kg) and nutrients of total nitrogen (0.73 g/kg), bicarbonate-extractable phosphorus (bic-P) (< 2 mg/kg), bic-K (37 mg/kg) and total exchangeable bases (<1.1 cmol/kg, with 24 % base saturation). Soil properties at the Scotia waste dump are mainly associated with alkaline (mean pH = 9) and saline conditions (EC1:5 = 1.01 dS/m). Exchangeable base values are high with average concentrations of exchangeable Ca of 18 cmol/kg and exchangeable Mg of 6 cmol/kg, thus these elements are not a limiting factor for plant nutrition. Patchy plant growth on the waste dump is mostly related to differences in water availability in the arid region and to salinity such that halophytes (saltbushes Maireana and Atriplex) colonize many parts of the waste dump together with some Melaleuca and Eucalyptus species
4
Dolling, Perry. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia". University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
Testo completoAbstract (sommario):
[Truncated abstract] In southern Western Australia the replacement of deep-rooted native vegetation with annual species has resulted in rising water tables and increased salinity due to insufficient water use. The area has a Mediterranean-type climate where rainfall during summer is generally low but variable resulting in limited plant growth. However, if rainfall does occur it potentially can contribute to to the increased water excess or drainage by increasing the soil water content before the main drainage period in winter. The first study investigated factors controlling soil water content changes during the fallow (December to May) in annual farming systems. This was achieved by examining variation in available soil water storage to a depth of 1.0-1.5 m at three sites within 13 seasons. Reasons for the variation were examined using the Agricultural Production Systems Simulator (APSIM). This study also investigated the relationship between soil water content at the end of the fallow period (1 May) and the amount of drainage below 2.5 m by using APSIM coupled to historical weather records at three locations. At the end of the fallow a mean of 24 mm (or 25%) of rainfall during the fallow was retained in the soil. Losses of soil water during the fallow were due to evaporation (mean of 60 mm), transpiration from plant cover (mean of 12 mm) and drainage below the root zone and run off (combined mean of 13 mm). Soil water accumulation during the fallow period had a significant impact on simulated drainage under wheat in the following growing season. Every 1 mm increase in soil wetness at the end of the fallow resulted in a 0.7-1 mm increase in simulated drainage during the growing season. ... Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The findings of this PhD indicate that lucerne does have a place in Mediterranean-type environments because of its greater water use than current farming practices. However, its use needs to be strategic and the strategy will vary from region to region. For example, in the low rainfall region lucerne sowings need to be matched with high soil water contents and phase length will generally be short (2-3 years). In comparison at high rainfall regions lucerne will need to be grown for longer or combined with other strategies to increase water use.
5
Doole, Graeme John. "Value of perennial pasture phases in dryland agricultural systems of the eastern-central wheat belt of Western Australia". University of Western Australia. School of Agricultural and Resource Economics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0213.
Testo completoAbstract (sommario):
Over the past thirty years, price relativities and technological development have motivated an increase in the area of land allocated to cropping, as opposed to pasture production, throughout the central wheat belt of Western Australia. Nevertheless, reducing the proportion of pasture in these rotations has challenged the future productivity of farming systems in this area. First, the frequent application of selective herbicides for weed control in extended cropping rotations has promoted the development of herbicide resistance in a number of major agricultural weeds. Second, the primary use of annual plants has promoted the development of soil salinisation by allowing a significant proportion of rainfall to recharge saline water tables. The inclusion of perennial pasture phases between extended periods of cropping may mitigate or delay these constraints to production through (a) allowing the use of costeffective forms of non-selective weed control, and (b) through creating a buffer of dry soil that absorbs leakage occurring beneath subsequent crops. This study consequently explores the value of including perennial pasture phases in dryland agricultural systems in the eastern-central wheat belt of Western Australia, accounting for benefits related to herbicide resistance and water table management. A novel computational algorithm for the solution of multiple-phase optimal control problems is developed and used to conduct a conceptual analysis of the value of lucerne (Medicago sativa L.) pasture for managing annual ryegrass (Lolium rigidum Gaudin), the primary weed in wheat belt cropping systems. The competitiveness and fecundity of annual ryegrass provide strong economic incentives to maintain a low weed population, irrespective of herbicide-resistance status. Consequently, the ineffectiveness of selective herbicides primarily reduces the profitability of cropping by motivating the adoption of more costly non-selective forms of weed control. The inclusion of lucerne in land-use rotations is only optimal in the presence of severe herbicide resistance given (a) the low efficiency of alternative weed-management practices available during the pasture phase, relative to selective-herbicide application; (b) the significant cost of establishing this perennial pasture; and (c) the high relative profitability of cereal production in the absence of resistance. The value of lucerne, relative to annual pastures, for weed management is explored in greater detail through the use of compressed annealing to optimise a sophisticated simulation model. The profitability of candidate rotations is also manipulated to account for the long-term production losses accruing to the recharge of saline groundwaters that occurs beneath them. Sequences incorporating lucerne are only more profitable than those that include annual pasture at the standard set of parameter values if (a) annual ryegrass is resistant to all selective herbicides, (b) the water table is so shallow (approximately less than 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, or (c) sheep production is highly profitable. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost. Consistent with intuition, these benefits are reinforced by lower discount rates and higher rates of leakage occurring beneath annual-based systems. Formulation of an effective communication strategy to report these results to producers is justified given the complexity involved in determining the true magnitude of these intertemporal benefits through alternative means, such as field trials.
6
Radomiljac, Andrew M. "Santalum album L. plantations : a complex interaction between parasite and host". Murdoch University, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060818.134603.
Testo completoAbstract (sommario):
This thesis examines a broad spectrum of physiological and silvicultural features of the highly
valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to
its culture in plantations in northern Western Australia. Topics covered include allometry of
host and Santalum when grown as single plant pairings in both field and pot culture, nutritional
interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences
of parasitism on plantation productivity and heartwood induction in young trees.
In Western Australia sandalwood is grown in the nursery for 8 months before establishment in
the field and during this time a pot host is introduced. Survival of Santalurn after field
establishment and its subsequent growth were significantly affected by the time of introduction
of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera
association in the nursery to 109 days prior to field establishment markedly increased early
growth of Salztalum plantations. Introduction at 134 days prior to field establishment was
detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum
seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with
Alternanthera in the nursery prior to field establishment compared with seedlings grown
without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown
with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks
in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio
and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and
Alternanthera DW.
In Western Australia Santalu~n is established in the field with an intermediate host which
nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host
and the intermediate host dies. The relationship between Santalum and several species tested as
intermediate hosts was examined by pairing Santalum seedlings with intermediate host
seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three
N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps),
the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably
between host treatments. Santalum growth was greater and root : shoot ratio lower for
seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or
with no host. The root : shoot ratio of unattached Santalum increased exponentially over time,
whereas for all other treatments it remained relatively constant. An assessment of the value of
the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW.
The host use efficiency of A. trachycalpa was greater than that of the other hosts.
The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria
of Santalzkm were analysed for amino acids, organic acids and sugars to determine which
solutes were available in the host and which were extracted by the Santalum haustoria from
different hosts. There were similarities between Santalum and legume hosts in concentration
and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding
Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis
and dissimilarities between its amino acid composition and that of Santalum. This indicated
substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem
sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate
and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most
common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the
predominant amino acid in the xylem sap of Santalum acurninatum growing in natural
vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in
Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained
variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric
and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic
acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were
particularly evident for the E. camaldulensis : Santalum partnership.
Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those
for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently
more negative than that of corresponding hosts. Net photosynthesis and water use efficiency
was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen
concentrations of foliage of Santalum were higher than their hosts, and higher when on legume
hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage
was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C
values of shoot dry matter of Santalum were poorly correlated with instantaneous water use
efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress
tolerant species.
S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry
matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in
association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of
haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root
nodules of legume hosts were parasitised by a small proportion of Santalum haustoria.
Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that
of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum
was greatest when grown in association with hosts richest in the corresponding element. Net
losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when
Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has
limited ability for uptake of those minerals through its own root system.
To understand the effect of hosts on the productivity of a Santalum plantation a young
plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and
Acacia anuera was selected to study the relationship between host quality and distance of hosts
from Santalunz on Santalum health. The selected plantation showed marked decline in health
and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants
were assessed to select the best predictor of Santalunz crown health. The height and diameter
growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum
crown health. Santaluin crown health and growth increased as host quality increased, and the
distance of host fiom Santalum decreased. An index, which combined host quality and the
distance of the host from that of Santalum, was a better predictor of Santalum crown health
than host distance or quality alone.
The age at which heartwood is initiated in Santalum album under plantation conditions in
Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of
age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections
of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a
plantation. Trees injected with paraquat alone had a significantly greater extension of induced
heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled
water. Eight months after treatment with paraquat or ethrel or a combination of these
chemicals induced heartwood was formed, which had high lipid, and low starch and
polysaccharide concentrations compared to the sapwood. Induced heartwood from both
chemical treatments and their combinations contained total volatile oil and santalol oil (alpha
and beta santalol) concentrations that were equal to or greater than that of naturally formed
heartwood and greater than that of sapwood. Moisture content, and concentrations of K and
Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood.
The thesis concludes with a synthesis of the findings and suggestions for future research, with
special reference to mid-rotation aspects of Santaltrm plantation silviculture.
7
Horsnell, Tara Kathleen. "Quantifying thresholds for native vegetation to salinity and waterlogging for the design of direct conservation approaches". University of Western Australia. School of Environmental Systems Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0082.
Testo completoAbstract (sommario):
A field-based project was undertaken to develop and test a mechanism which would allow for the correlation of the health of vegetation surrounding playa lakes in south-west Australia with the natural variation in salinity and waterlogging that occurs spatially and temporally in natural systems. The study was designed to determine threshold ranges of vegetation communities using moderately extensive data over short temporal periods which will guide the design of potential engineering solutions that manipulate hydrological regimes to ultimately conserve and protect native vegetation. A pair of playa lake ecosystems, surrounded by primary production land, was modelled with hydro-geological data collected from March 2006 to March 2007. The data was used to determine the hydroperiods of vegetation communities fringing playa lakes and provide insight into the areas and species that are most affected by extreme rainfall events which are hypothesised to have a significant, rapid deleterious effect on the ecosystems. The methodology was multi-faceted and included; a detailed topographical survey; vegetation surveys; hydrological and hydro-geological monitoring over a 12 month period. 4 The hydro-geological data and vegetation data was linked with the topographical survey at a high resolution for spatial analysis in a Geographic Information System (GIS) to determine the degree of waterlogging experienced by vegetation communities over the monitoring period. The study has found that the spatial and temporal variability of hydroperiods has been reduced by rising groundwater levels, a result of extensive clearing of native vegetation. Consequently populations are becoming extinct locally resulting in a shift in community composition. Extreme summer rainfall events also have a significant impact on the health of vegetation communities by increasing the duration of waterlogging over an annual cycle and in some areas expanding the littoral zone. Vegetation is most degraded at lower positions in the landscape where communities are becoming less diverse and dominated by salt tolerant halophytic species as a result of altered hydrological regimes. Some species appear to be able to tolerate groundwater depths of less than 2.0 m from the surface, however there are thresholds related to the duration at which groundwater is maintained at this depth. Potential engineering solutions include groundwater pumping and diverting water through drains to maintain sustainable hydroperiods for vegetation in areas with conservation value. The effectiveness and efficiency of the engineering solutions can be maximised by quantifying thresholds for vegetation that include sustainable durations of waterlogging. The study has quantified tolerance ranges to salinity and waterlogging with data collected over 12 months but species may be experiencing a transition period where they have 5 sustained irreversible damage that will result in their eventual mortality. With long-term monitoring, the methodology developed and tested in the study can be used to quantify the long-term tolerance ranges that are important for the application of conservation approaches that include engineering solutions.
8
Poulter, Rachel. "Investigating the role of soil constraints on the water balance of some annual and perennial systems in a Mediterranean environment". University of Western Australia. Faculty of Agriculture, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0018.
Testo completoAbstract (sommario):
This thesis compares the in situ water balance of common annual production systems (wheat, lupin, subclover and serradella) with a grazed perennial system (lucerne) at a site in the Avon Catchment, Western Australia. Using a physically-based water balance approach the value of a plant based solution in redressing the hydrological imbalance that has become a feature of much of the dryland agricultural region of Western Australia is investigated. The effectiveness of lucerne in providing greater available storage for buffering large rainfall events, as compared to the annual systems, is illustrated. Continued transpiration following out-of-season rainfall events maintains a larger available storage capacity. In contrast, the annual systems that are fallow over summer only withdrew a small fraction of water by soil evaporation between rainfall events. Under annual systems, the profile moisture store was sequentially increased to the extent that additional increments of rainfall could potentially contribute to deep drainage. A particular focus of this study has been to investigate the presence of soil constraints to root growth, and to assess how these constraints affect the water balance. A site survey indicated the soil penetration resistance was sufficient to impose a physical constraint to root growth. Published literature on the site shows soil acidity is also at a level imposing chemical constraints to root growth. A root growth model “Rootmodel”, for predicting root growth with and without soil constraints is examined in detail as a method for providing root growth parameters for inclusion into the numerical water balance model, SWIM based on Richard’s equation. Functions developed from “Rootmodel” adequately describe the effect of profile limitations to root growth, such as soil strength, moisture availability and temperature. Recommendations are made for inclusion of a growth suppressing function in “rootmodel” based on the chemical limitation of low pH. The effects of soil acidity on the root growth of several species is investigated experimentally and the resultant root data provided a reference point by which the simplified prediction of root growth built into SWIM could be adjusted using a linear reduction function. A similar linear reduction function is also employed to impose a physical constraint in the form of high penetration resistance.
9
Lucas, Anne. "Water stress and disease development in Eucalyptus marginata (jarrah) infected with Phytophthora cinnamomi". Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040820.13290.
Testo completo
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Bleby, Timothy Michael. "Water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on mine rehabilitation sites in the jarrah forest of south-western Australia". University of Western Australia. School of Plant Biology, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0004.
Testo completoAbstract (sommario):
[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.
Libri sul tema "Plant-soil relationships – Western Australia"
1
Websdane, Kirsten. The impact of smut diseases on rushes and sedges in pre- and post-mining situations: Morphological and ecological aspects of the pathogen and its impact on host reproduction and growth and host population regeneration after fire : results of research carried out as MERIWA Project No. M200 at the Kings Park and Botanical Gardens and the Department of Soil Science and Plant Nutrition, University of Western Australia. East Perth, WA: Minerals and Energy Research Institute of Western Australia, 1995.
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2
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, 1990.
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3
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, 1990.
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4
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, 1990.
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5
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: Dept. of the Interior, Fish and Wildlife Service, 1990.
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6
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, 1990.
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7
Veneman, Peter L. M. Soil-vegetation correlations in the Connecticut River floodplain of western Massachusetts. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, 1990.
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8
Gilkes, R. J. Mineralogy of Darling Range bauxites: Forms of Al in pisolitic ore : results of research carried out as part of MERIWA Project No. 90 in Soil Science and Plant Nutrition, the University of Western Australia. East Perth, WA: Minerals and Energy Research Institute of Western Australia, 1995.
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9
Aylmore, M. G. Mineralogy of Darling Range bauxites in relation to chemical reactivity, new ore types: Results of research carried out as MERIWA Project No. 90 in the Soil Science and Plant Nutrition Department of the School of Agriculture, the University of Western Australia. East Perth, WA: Minerals and Energy Research Institute of Western Australia, 1991.
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10
B, Summerfield Harry, e Intermountain Research Station (Ogden, Utah), a cura di. Edaphic relationships in climax singleleaf pinyon stands of western Nevada. [Ogden, UT]: U.S. Dept. of Agriculture, Forest Service, Intermountain Research Station, 1986.
Cerca il testo completoCapitoli di libri sul tema "Plant-soil relationships – Western Australia"
1
Verboom, W. H., e J. S. Pate. "Relationships between cluster root-bearing taxa and laterite across landscapes in southwest Western Australia: an approach using airborne radiometric and digital elevation models". In Structure and Functioning of Cluster Roots and Plant Responses to Phosphate Deficiency, 321–33. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0243-1_28.
Testo completo
2
Tomanek, G. W. "Some Soil-Vegetation Relationships in Western Kansas". In Forage Plant Physiology and Soil-Range Relationships, 158–64. Madison, WI, USA: American Society of Agronomy, 2015. http://dx.doi.org/10.2134/asaspecpub5.c13.
Testo completo
3
Connell, Karen. "Marketing soil acidity knowledge in Western Australia". In Plant-Soil Interactions at Low pH: Principles and Management, 717–21. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0221-6_114.
Testo completo
4
White, Robert E. "Putting it All Together". In Understanding Vineyard Soils. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780199342068.003.0009.
Testo completoAbstract (sommario):
In reality, there can be no generic definition of an “ideal soil” because a soil’s performance is influenced by the local climate, landscape characteristics, grape variety, and cultural practices and is judged in the context of a winegrower’s objectives for style of wine to be made, market potential, and profitability of the enterprise. This realization essentially acknowledges the long-established French concept of terroir: that the distinctiveness or typicity of wines produced in individual locations depends on a complex interaction of biophysical and human cultural factors, interpreted by many as meaning a wine’s sense of place. As discussed in “Soil Variability and the Concept of Terroir” in chapter 1, because of this interaction of factors that determine a particular terroir, it is not surprising that no specific relationships between one or more soil properties and wine typicity have been unequivocally demonstrated. While acknowledging this conclusion, it is still worthwhile to examine how variations in several single or combined soil properties can influence vine performance and fruit character. These properties are: • Soil depth • Soil structure and water supply • Soil strength • Soil chemistry and nutrient supply • Soil organisms Provided there are no subsoil constraints, the natural tendency of long-lived Vitis vinifera, on own roots or rootstocks, to root deeply and extensively gives it access to a potentially large store of water and nutrients. In sandy and gravely soils that are naturally low in nutrients, such as in the Médoc region of France, the Margaret River region in Western Australia, and the Wairau River plain, Marlborough region, New Zealand, the deeper the soil the better. A similar situation pertains on the deep sandy soils on granite in the Cauquenas region, Chile. However, such depth may be a disadvantage where soils are naturally fertile and rain is plentiful, as in parts of the Mornington Peninsula, King and Yarra Valley regions, Victoria, Australia, and the Willamette Valley region in Oregon (see figure 1.11, chapter 1), because vine growth is too vigorous and not in balance.
5
Blondel, Jacques, e Frédéric Médail. "Biodiversity and Conservation". In The Physical Geography of the Mediterranean. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199268030.003.0039.
Testo completoAbstract (sommario):
The biodiversity of Mediterranean-climate ecosystems is of particular interest and concern, not only because all five of these regions (the Mediterranean basin, California, central Chile, Cape Province of South Africa, western and southern parts of Australia) are among the thirty-four hotspots of species diversity in the world (Mittermeier et al. 2004), but they are also hotspots of human population density and growth (Cincotta and Engelman 2000). This relationship is not surprising because there is often a correlation between the biodiversity of natural systems and the abundance of people (Araùjo 2003; Médail and Diadema 2006) and this, inevitably, raises conservation problems. Within the larger hotspot of the Mediterranean basin as a whole, ten regional hotspots have been identified. They cover about 22 per cent of the basin’s total area and harbour about 44 per cent of Mediterranean endemic plant species (Médail and Quézel 1997, 1999), as well as a large number of rare and endemic animals (Blondel and Aronson 1999). A key feature of these Mediterranean hotspots as a whole is their extraordinarily high topographic diversity with many mountainous and insular areas. Not surprisingly this results in high endemism rates and they contain more than 10 per cent of the total plant richness (see the recent synthesis of Thompson 2005). However, of all the mediterranean-type regions in the world, the Mediterranean basin harbours the lowest percentage (c.5%) of natural vegetation considered to be in ‘pristine condition’ (Médail and Myers 2004; Chapter 7). With an average of as many as 111 people per km2, one may expect a significant decline in biological diversity in the Mediterranean basin—a region that has been managed, modified, and, in places, heavily degraded by humans for millennia (Thirgood 1981; Braudel 1986; McNeill 1992; Blondel and Aronson 1999; Chapter 9). There are two contrasting theories that consider the relationships between humans and ecosystems in the Mediterranean (Blondel 2006, 2008). The first one is the ‘Ruined Landscape or Lost Eden’ theory, first advocated by painters, poets, and historians in the sixteenth and seventeenth centuries, and later by a large number of ecologists.
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Alexander, Earl B., Roger G. Coleman, Todd Keeler-Wolfe e Susan P. Harrison. "Synthesis and Future Directions". In Serpentine Geoecology of Western North America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195165081.003.0031.
Testo completoAbstract (sommario):
Ultramafic rocks come from deep within the earth. Most rocks on the surface of the earth are quite different from them. Unique rocks make unique soils and support special plants. Exploring the links and interactions among these unique rocks, soils, and vegetation is an interdisciplinary endeavor that has been accomplished by experts in three areas. It has helped elucidate serpentine rock–soil–plant relationships and provide a rationale for the unusual soil properties and vegetation associated with ultramafic rocks. Examples from arctic tundra to temperate rainforest and hot desert in western North America provide a framework for the investigation of serpentine geoecosystems around the world. The unusual character of most serpentine vegetation is readily apparent even to an untrained eye. Although a vast number of rock and soil types make up the earth’s surface, few have as dramatic and visible effects on ecosystems as do ultramafic, or serpentine materials. Most ultramafic rocks in western North America have been derived from the mantle of earth via ocean crust. Magnesium is highly concentrated in the mantle and calcium, potassium, and phosphorous are relatively low. Calcium and potassium are further depleted from peridotite in the partial melting of ultramafic rock at the base of the ocean crust. As oceanic plates drift from spreading centers, most of the ocean crust is subducted and returns to the mantle (chapter 2). Only relatively small fragments of ocean crust are added to the continents. Because eukaryotic organisms, from protozoa to plants and animals, have evolved on continental crust, they are adapted to soils with higher concentrations of calcium, potassium, and phosphorus (elements with higher concentrations in continental crust than in ultramafic rocks from the base of the ocean crust) and much lower concentrations of magnesium. Having evolved on continents, plants depend on relatively high ratios of calcium and potassium to magnesium, elements that they use for a wide range of physiological functions. Although there has been a long history of evolutionary adaptation to the chemistry of the continental crust, special adaptations have allowed some plants to colonize the atypical conditions of serpentine.
7
Maltman, Alex. "Weathering, Soil, and the Minerals in Wine". In Vineyards, Rocks, and Soils. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190863289.003.0014.
Testo completoAbstract (sommario):
Weathering of rocks is the crucial first step in making vineyards possible. For where the debris produced by weathering—the sediment we met in Chapter 5—becomes mixed with moist humus, it will be capable of supporting higher plant life. And thus we have soil, that fundamental prerequisite of all vineyards, indeed of the world’s agriculture. So how does this essential process of weathering come about? Any bare rock at the Earth’s surface is continually under attack. Be it a rocky cliff, a stone cathedral, or a tombstone, there will always be chemical weathering—chemical reactions between its surface and the atmosphere A freshly hewn block of building stone may look indestructible, but before long it will start to look a bit discolored and its surface a little crumbly. We are all familiar with an analogy of this: a fresh surface of iron or steel reacting with moisture and oxygen in the air to form the coating we call rust. In his “Guide to the Lakes” of England, William Wordsworth put the effects of weathering far more picturesquely: “elementary particles crumbling down, over-spread with an intermixture of colors, like the compound hues of a dove’s neck.” A weathered rock is one that is being weakened, broken down. The rock fragments themselves are further attacked, which is why stones in a vineyard often show an outer coating of discolored material, sometimes referred to as a weathering rind (Figure 9.1; see Plate 22). If the stone is broken open, it may show multiple zones of differing colors paralleling the outer surface of the fragment and enclosing a core of fresh rock. Iron minerals soon weather to a powdery combination of hematite, goethite, and limonite, and the rock takes on a reddish-brown, rusty-looking color. The great example of such weathering in viticulture is the celebrated terra rossa, but the rosy soils in parts of Western Australia and places further east such as McLaren Vale and the Barossa Valley are also due to iron minerals. Several Australian wines take their names from this “ironstone.”
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Peters, Debra P. C., e Robert P. Gibbens. "Plant Communities in the Jornada Basin: The Dynamic Landscape". In Structure and Function of a Chihuahuan Desert Ecosystem. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195117769.003.0014.
Testo completoAbstract (sommario):
Plant communities of the Jornada Basin are characteristic of the northern Chihuahuan Desert both in structure and dynamics. Although a number of plant communities can be differentiated, five major vegetation types are often distinguished that differ in plant species cover and composition, as well as other factors, such as animal populations, soil properties, and elevation. These five types are black grama (Bouteloua eriopoda) grasslands, playa grasslands, tarbush (Flourensia cernua) shrublands, creosotebush (Larrea tridentata) shrublands, and mesquite (Prosopis grandulosa) shrublands. Similar to many other parts of the Chihuahuan Desert, these plant communities have experienced major shifts in vegetation composition over the past 50–150 years (York and Dick-Peddie 1969). The most dramatic changes in vegetation and associated ecosystem processes have occurred as a result of a shift in life form due to woody plant encroachment into perennial grasslands (Grover and Musick 1990; Bahre and Shelton 1993). This encroachment of shrubs has occurred in many arid and semiarid regions of the world, including the Western United States, northern Mexico, southern Africa, South America, New Zealand, and Australia (McPherson 1997; Scholes and Archer 1997). A number of drivers have been implicated in these grass–shrub dynamics, including various combinations of livestock grazing, small animal activity, drought, changes in fire regime, and changes in climate (Humphrey 1958; Archer 1989; Allred 1996; Reynolds et al. 1997; Van Auken 2000). The causes of shrub invasion are quite variable and often poorly understood, although the consequences consistently lead to the process of desertification (Schlesinger et al. 1990). This chapter describes the characteristics of each vegetation type and the documented changes in each type at the Jornada Basin. We then discuss the key drivers influencing these dynamics. Vegetation in the Chihuahuan Desert region has been classified as desert-grassland transition (Shreve 1917), desert savanna (Shantz and Zon 1924), desert plains grasslands (Clements 1920), desert shrub grassland (Darrow 1944), and shrubsteppe (Kuchler 1964). Desert grassland is often used as a general descriptive name for the area (McClaran 1995), although landscapes at the Jornada and throughout the northern Chihuahuan Desert often consist of a mosaic of desert grasslands, Chihuahuan Desert shrublands, and plains-mesa sand scrub (Dick-Peddie 1993).