Academic literature on the topic 'Soils Composition Victoria Hotham'

Subalpine grasslands in the Mt Hotham area, Victoria, are a common feature of cold-air drainage valleys at elevations of 1260–1660 m. Here, the pooling of cold air prevents trees from establishing and results in a distinct grassland community, composed of tussock grasses and a wide variety of intertussock species. Despite their common occurrence in the region, such grasslands have yet to be fully described. This study focused on identifying the floristic composition of subalpine grasslands across 51 sites in the vicinity of Mt Cope, Dinner Plain and Mt Hotham. The vegetation was sampled from 172, 20-m2 quadrats which were analysed by multivariate ordination techniques. Environmental variables were quantified (i.e. soil depth, pH, aspect, slope, biomass, grazing intensity, altitude). Analysis revealed that the grassland sites varied greatly in their composition and richness. There was a gradual rather than abrupt change in species composition across grassland sites, thought to be related to both the geographic proximity of the sites and environmental factors such as geology. The following five grassland types were identified from the entire data set and defined primarily by the dominant species: Poa hiemata, Poa costiniana, Poa sieberiana, Poa labillardierei and Themeda triandra. Vector-fitting revealed significant correlations between the location of the quadrats in ordination space and altitude, biomass, pH and soil depth. Both increasing altitude and biomass were associated with the P. costiniana grasslands and some of the P. hiemata grasslands. The P. hiemata grasslands were widely distibuted across altitudes and geology (i.e. basalt and metamorphic). The lower-altitude grasslands (P. labillardierei, P. sieberiana, T. triandra) were associated with increasing pH and increasing soil depth. These grasslands were of limited extent and usually occupied small areas within larger grasslands dominated by P. hiemata or P. costiniana. The floristic composition of the Hotham grasslands (1260–1630 m a.s.l.), when compared with previously published data from the higher-elevation subalpine grasslands of both the Dargo High Plains (1450–1680 m a.s.l.) and Bogong High Plains (>1700 m a.s.l.), showed that there was no distinct differentiation between grasslands of these areas. However, there was a suggestion of gradual floristic change across this geographic range. This study highlights the need for ongoing conservation of grasslands in the Hotham area, particularly those at lower altitudes (1260–1450 m a.s.l.), which represent the upper limits of many temperate grassland species.

Dissolved organic carbon (DOC) is important to microbial activity and nutrient cycling, and its concentration is sensitive to pH. Despite the importance of alkaline soils to agricultural production in southern Australia, few studies have documented the concentrations of soil organic carbon (C) and DOC or described the effects of soil properties and management practices on DOC in these soils. A survey of 33 paddocks from the Eyre Peninsula and mid-North regions of South Australia and north-western Victoria demonstrated significant variation in pH, soil organic C and DOC. Carbon stocks in the surface 30cm were 40–55tC/ha and were lowest in paddocks from Victoria. Soils from South Australia had higher DOC concentrations in the top 20cm than soils from Victoria. Principal component analysis suggested variation in DOC was increased by high pH, electric conductivity and the concentration of exchangeable Na, and was reduced by the concentration of exchangeable Ca and clay content. Mid-infrared Fourier transform infrared spectroscopy identified regional differences in the composition of soil organic C, with high amounts of charcoal in Eyre Peninsula soils. Farm management practices had little effect on soil organic C but influenced DOC. Grain yield and DOC concentration were inversely related across and within regions which appeared to be related to the intensity of cropping having opposite influences on yield and DOC. Compared with international data, DOC concentrations were high relative to the amount of soil organic C and, in contrast to many previous studies, DOC in all regions increased with depth.

Measurement of dispersible clay is important for the diagnosis of structural stability problems in soil. However, clay dispersibility is known to change with water content and time. The purpose of the present study was to determine how incubation of sodic soil under different water content regimes influences clay dispersibility. Two topsoils (depth 0-0·1 m), one sodic [exchangeable sodium percentage (ESP) 9 · 7] and the other non-sodic (ESP 3·8), were collected from an experimental pasture at Kyabram, Victoria, and 2 soils, a sodic topsoil (depth 0-0·1 m, ESP 6·9) and the corresponding subsoil (depth 0·2-0 m, ESP 25·7), were collected from a cropped field at Two Wells, South Australia. The soils were incubated for 264 days in a split-plot design. The main treatments were soil type and incubation water content: continuously air-dry, continuously wet (-50 kPa), or with wet/dry cycles. The subtreatment was water content at analysis: air dry or wet (-50 kPa). Clay dispersion was greater when measured on wet soils than dry soils, irrespective of water contents during the prior incubation. Electrical conductivity increased, and sodium adsorption ratio (SAR), pH, and organic carbon content decreased as a function of the time for which the soils were wet. In the Kyabram soils that were wet when analysed, easily dispersible clay content increased with SAR. Decreases in moderately dispersible clay under the wetting/drying regime were not related to electrolyte composition, and were attributed to particle rearrangement and cementation. The decreases in clay dispersibility with time occurred despite net losses of carbohydrate and aliphatic materials. An implication of the work is that the decomposition of soil organic matter, even in the absence of fresh additions, may reduce clay dispersion in sodic soils by altering electrolyte concentration and composition.

The aim of this work was to study the trace metals transfer between soil aquifers and the immediate sediments of the selected wetlands of Lake Victoria. The study covered five trace metals Pb, Cd, Cu, Zn and Mn as these are associated with vehicular traffic and with the combustion of fossil fuels which could both be significant sources of pollution within the wetlands of Lake Victoria basin. Three types of trace metal analyses from various locations of Katonga, Simiyu and Nyando catchments of Lake Victoria were performed: total concentrations, the concentrations in the non-residual fraction and the concentration in the exchangeable fraction. The soil characteristics: texture, pH and organic matter contents, were studied in relation to Cation Exchange Capacity (CEC) to assess the rate of movement of the metals between the soil and the wetland sediments. Eventually, the potential retention and leaching capacity of trace metals within the catchment soils and its possible impact on the composition of the receiving sediments of the wetlands were studied. The comparison between Nyando and Simiyu wetlands showed high variations in the soil characteristics and hence in leaching capacity of the studied metals. In general most areas in Nyando wetland required some measures to improve the CEC of the soil for higher agricultural productivity. Key Words: Trace metals; fractionation; CEC; leaching capacity; soil properties DOI: 10.3126/jowe.v3i0.2222 Journal of Wetlands Ecology, (2009) Vol. 3, pp 68-76

The use of destocking as a means of promoting pasture recovery was evaluated on two important rangeland types of the semi-arid tropics of north west Australia. Recovery on eroded calcareous red soils was substantial within five years. Standing biomass and species composition, particularly the contribution of the major forage grass Enneapogon spp., was then similar to areas in good condition. However, an exotic shrub, Calotropls procera, invaded the area during the study. Grazing limited its increase to 200 bushes ha-1 compared to unstocked areas where it increased to 1,000 bushes ha-1. Destocking had no effect on cracking clay soils in good condition, dominated by Chrysopogon fallax and Iseilema fragile. An index based on similarity measures of herbage standing biomass, followed closely the course of recovery of the eroded calcareous soil during the period. There is a need for range condition assessment and the development and application of appropriate pasture management strategies for the whole district.

Natural communities have the capacity to regenerate themselves, and this functional ecosystem attribute must be regarded as a key indicator of success for revegetation programmes. The accumulation of species (and individuals) as dormant propagules in a soil seedbank, representing potential future states for the vegetation, is one possible index of revegetation success. Here, we investigate the soil seedbanks for five natural vegetation (Box-Ironbark forest) remnants, a topsoil stockpile and three revegetated mine-site areas associated with gold mining at Stawell (Victoria, Australia). The revegetation efforts largely date from 1987 and, in terms of their composition and structure, are relatively similar to natural vegetation remnants. Soil samples were treated with heat or smoke (plus control) and were monitored for seedling emergence, species composition and density in the glasshouse for 150 days. Seedling densities in treated seedbank samples were high (2 200 to 17 500 seedlings m-2) while species richness was low, ranging from 10 to 20 species per sample. Exotic species made up 22?61 % of emergents and 33?50% of species observed. Correlation of seedbank composition and density with chemical attributes of soils, and with above ground (extant) vegetation at sites showed few significant relationships. Total species richness and the proportion of exotic species varied significantly between natural bushland remnants and revegetation areas. Richness was highest, and the proportion of exotic species was lowest in natural bushland samples. Total emergent numbers and the density of exotic emergents did not vary significantly between remnant bushland and revegetation areas. Declining vigour of some woody species in revegetation sites that are well represented in the seedbank, including Acacia pycnantha and A. genistifolia, indicates that the reintroduction of fire might be an appropriate management practice to facilitate long-term recovery of a functional community on these revegetated surfaces, but the potential for the establishment of weed species from the seed-bank following fire may pose a challenge to management.

Concentrations of major ions (Cl−, NO3−, SO42−, Na+, K+, Mg2+, Ca2+) were measured in melting snow and water samples from streams and lakes in ice-free areas throughout northern Victoria Land. Most ions in snow and terrestrial water derive from the marine environment and their concentrations are extremely variable in space and time, especially in water systems without melting snow and ice. The distance from the sea, snow sublimation, changes in water inflow, evaporative concentrations, weathering and drainage processes in the catchment, nesting seabirds and aquatic microbiota are among factors which most influence ion composition variability. Comparisons with data from twelve years ago in the same lakes indicate that the warming trend detected at Terra Nova Bay station during this period did not affect the biogeochemistry of water systems. Waters from a lake which recently experienced a lowering of the water level showed a remarkable increase in SO42− concentrations. We hypothesized that the differential mobility of sulphate salts in the Antarctic soils, the biosynthesis of sulphur compounds in the lake, and the progressive decrease of the water volume are factors involved in the increase of SO42− concentrations.

Soil seedbanks play a key role in the post-fire recruitment of many plant species. Seedbank diversity can be influenced by spatial variability (e.g. geographic location), environmental variability (e.g. soils) and temporal disturbance heterogeneity (e.g. time since fire, TSF) across the landscape. Unlike for aboveground vegetation, relationships between these factors and soil seedbank diversity remain largely unknown. Partitioning the influence of spatial and environmental variability from that of TSF, and explaining how these factors interact with seedbank diversity, will assist conservation managers in their application of prescribed burning. We germinated soil seedbank samples from sites ranging from 1 to 75 years since fire in a heathy-woodland ecosystem across the Otway Ranges in Victoria, Australia. We also measured spatial and environmental variability across sites to partition the influence of these variables and TSF on propagules available for recruitment. We found weak positive relationships between seedbank richness and TSF; however, these relationships varied across the landscape. We found composition did not change considerably over time, suggesting, in this ecosystem, pre-fire age is not strongly influencing propagules available for recruitment post-fire. Our results suggest that spatial and environmental variability influence seedbank composition more than TSF.

Relationships between changes in soil pH and changes in other soil chemical properties were examined using data from a survey of 107 pasture sites from across Victoria. At each site, soil samples (0-5, 5-10, 10-15 and 15-20 cm depths) were taken from the pasture and an adjacent undisturbed (reference) area for chemical analysis. Changes in soil chemical properties were inferred from differences between pasture and reference soils. Increases in extractable Al and extractable Mn and decreases in the sum of exchangeable cations were associated with decreases in pH. Changes in soil organic C, total soil N and total soil P were not associated with changes in pH but were related to pasture composition at each site. Increases in total soil P and exchangeable Ca, and decreases in exchangeable Mg were partly attributed to the application of superphosphate. Decreases in electrical conductivity are discussed in relation to vegetation and salinization.