Lose the plot: cost-effective survey of the Peak Range, central Queensland

The Peak Range (22˚ 28’ S; 147˚ 53’ E) is an archipelago of rocky peaks set in grassy basalt rolling-plains, east of Clermont in central Queensland. This report describes the flora and vegetation based on surveys of 26 peaks. The survey recorded all plant species encountered on traverses of distinct habitat zones, which included the ‘matrix’ adjacent to each peak. The method involved effort comparable to a general flora survey but provided sufficient information to also describe floristic association among peaks, broad habitat types, and contrast vegetation on the peaks with the surrounding landscape matrix. The flora of the Peak Range includes at least 507 native vascular plant species, representing 84 plant families. Exotic species are relatively few, with 36 species recorded, but can be quite prominent in some situations. The most abundant exotic plants are the grass Melinis repens and the forb Bidens bipinnata. Plant distribution patterns among peaks suggest three primary groups related to position within the range and geology. The Peak Range makes a substantial contribution to the botanical diversity of its region and harbours several endemic plants among a flora clearly distinct from that of the surrounding terrain. The distinctiveness of the range’s flora is due to two habitat components: dry rainforest patches reliant upon fire protection afforded by cliffs and scree, and; rocky summits and hillsides supporting xeric shrublands. Plants endemic to the Peak Range are mainly associated with the latter of these habitats

Vegetation-soil relations in a highly sodic landscape, Yelarbon, southern Queensland

Soil and vegetation data were collected from a sodic-scald near Yelarbon in southern Queensland. The surface of the landscape includes relatively light textured pedestals of the A-horizon with slightly alkaline pH and slopes leading down to scalded basement representing the surface of the strongly alkaline B-horizon. The strongest gradient within the floristic patterns was associated with wetland vegetation in drainage lines, but a secondary and orthogonal gradient was related to soil pH, which was probably a function of lower alkalinity on the more stable and weathered A-horizons. There were few significant differences between soil or vegetation characteristics from plot data comparing parts of the landscape with differing historical grazing regimes. Sites included stock routes heavily grazed between the 1920s and 1970s, and subsequently almost ungrazed; and grazed paddocks that have had moderate use throughout this period. There is clear evidence that the area is naturally active in terms of erosion and deposition during flooding regardless of grazing

This disastrous event staggered me : reconstructing the botany of Ludwig Leichhardt on the expedition from Moreton Bay to Port Essington, 1844-45

Ludwig Leichhardt had to abandon a large and important collection of botanical specimens during his Expedition from Moreton Bay to Port Essington. Here we attempt to assess the significance of the lost collection by identifying the botanical references in his detailed published journal from the journey. From Leichhardt’s description of the plants and their habitats, and with our accurate knowledge of current distribution, it has been possible, in most cases, to identity his botanical references to a single species. In other cases there is lower degree of certainty. Well over one hundred of the species recorded in Leichhardt’s journal would have been new to science at the time if specimens had survived. The record does identify some potential locations for species that would represent range extensions and suggests an indigenous status for a number of plant species that where previously considered exotic. Certainly Leichhardt was a talented botanist and his significant contribution to Australian natural science should be recognised

Managed livestock grazing is compatible with the maintenance of plant diversity in semidesert grasslands.

Even when no baseline data are available, the impacts of 150 years of livestock grazing on natural grasslands can be assessed using a combined approach of grazing manipulation and regional-scale assessment of the flora. Here, we demonstrate the efficacy of this method across 18 sites in the semidesert Mitchell grasslands of northeastern Australia. Fifteen-year-old exclosures (ungrazed and macropod grazed) revealed that the dominant perennial grasses in the genus Astrebla do not respond negatively to grazing disturbance typical of commercial pastoralism. Neutral, positive, intermediate, and negative responses to grazing disturbance were recorded amongst plant species with no single life-form group associated with any response type. Only one exotic species, Cenchrus ciliaris, was recorded at low frequency. The strongest negative response was from a native annual grass, Chionachne hubbardiana, an example of a species that is highly sensitive to grazing disturbance. Herbarium records revealed only scant evidence that species with a negative response to grazing have declined through the period of commercial pastoralism. A regional analysis identified 14 from a total of 433 plant species in the regional flora that may be rare and potentially threatened by grazing disturbance. However, a targeted survey precluded grazing as a cause of decline for seven of these based on low palatability and positive responses to grazing and other disturbance. Our findings suggest that livestock grazing of semidesert grasslands with a short evolutionary history of ungulate grazing has altered plant composition, but has not caused declines in the dominant perennial grasses or in species richness as predicted by the preceding literature. The biggest impact of commercial pastoralism is the spread of woody leguminous trees that can transform grassland to thorny shrubland. The conservation of plant biodiversity is largely compatible with commercial pastoralism provided these woody weeds are controlled, but reserves strategically positioned within water remote areas are necessary to protect grazing-sensitive species. This study demonstrates that a combination of experimental studies and regional surveys can be used to understand anthropogenic impacts on natural ecosystems where reference habitat is not available

Quantifying the impact of Gambusia holbrooki on the extinction risk of the critically endangered red-finned blue-eye

Managing competing endangered and invasive species in spatially structured environments is challenging because it is often difficult to control invasive species without negatively impacting the endangered species. Effective management action requires an understanding of the factors affecting the presence and absence of each species so that promising sites for relocation of endangered species combined with eradication of invasive species can be identified. We investigate competing hypotheses about the factors affecting occupancy of the critically endangered red-finned blue-eye (Scaturiginichthys vermeilipinnis; hereafter 'RFBE'), a native Australian fish with a global distribution that is restricted to a group of shallow artesian springs. RFBE are threatened by competition with invasive mosquito fish (Gambusia holbrooki ), which are steadily colonizing the springs, resulting in local extinctions of RFBE in most cases. While hypotheses about the influences of Gambusia on RFBE exist, none have been tested with a quantitative model. We used a spatially-structured two-species occupancy modeling approach to examine the occupancy dynamics of these fish and tested competing hypotheses on how Gambusia occupancy affected RFBE. Gambusia occupancy had a strong negative effect on RFBE occupancy and colonization potential; increasing the probability of local extinction at a spring and decreasing the persistence probability of RFBE in a spring by 8.0%± 2.7% (mean ± 1 SE). We found strongest support for the hypotheses that elevation and spring area influence colonization, and that spring area influences patch extinction probability. Using colonization and local extinction estimates for both species, we identify promising sites for eradication of Gambusia and relocation of RFBE

Potential aboveground biomass in drought-prone forest used for rangeland pastoralism

The restoration of cleared dry forest represents an important opportunity to sequester atmospheric carbon. In order to account for this potential, the influences of climate, soils, and disturbance need to be deciphered. A data set spanning a region defined the aboveground biomass of mulga (Acacia aneura) dry forest and was analyzed in relation to climate and soil variables using a Bayesian model averaging procedure. Mean annual rainfall had an overwhelmingly strong positive effect, with mean maximum temperature (negative) and soil depth (positive) also important. The data were collected after a recent drought, and the amount of recent tree mortality was weakly positively related to a measure of three-year rainfall deficit, and maximum temperature (positive), soil depth (negative), and coarse sand (negative). A grazing index represented by the distance of sites to watering points was not incorporated by the models. Stark management contrasts, including grazing exclosures, can represent a substantial part of the variance in the model predicting biomass, but the impact of management was unpredictable and was insignificant in the regional data set. There was no evidence of density-dependent effects on tree mortality. Climate change scenarios represented by the coincidence of historical extreme rainfall deficit with extreme temperature suggest mortality of 30.1% of aboveground biomass, compared to 21.6% after the recent (2003-2007) drought. Projections for recovery of forest using a mapping base of cleared areas revealed that the greatest opportunities for restoration of aboveground biomass are in the higher-rainfall areas, where biomass accumulation will be greatest and droughts are less intense. These areas are probably the most productive for rangeland pastoralism, and the trade-off between pastoral production and carbon sequestration will be determined by market forces and carbon-trading rules

Vegetation and environmental patterns on soils derived from Hawkesbury Sandstone and Narrabeen substrata in Ku-ring-gai Chase National Park, New South Wales

[Abstract]: The vegetation patterns in the Central Coast region of New South Wales have been extensively studied with respect to single environmental variables, particularly soil nutrients. However, few data are available on the effects of multiple environmental variables. This study examines the relationships between vegetation and multiple environmental variables in natural vegetation on two underlying rock types, Hawkesbury sandstone and Narrabeen group shales and sandstones, in Ku-ring-gai Chase National Park, Sydney. Floristic composition and 17 environmental factors were characterized using duplicate 500 m2 quadrats from fifty sites representing a wide range of vegetation types. The patterns in vegetation and environmental factors were examined through multivariate analyses: indicator species analysis was used to provide an objective classification of plant community types, and the relationships between vegetation and environmental factors within the two soil types were examined through indirect and direct gradient analyses. Eleven plant communities were identified, which showed strong agreement with previous studies. The measured environmental factors showed strong correlations with vegetation patterns: within both soil types, the measured environmental variables explained approximately 32 - 35% of the variation in vegetation. No single measured environmental variable adequately described the observed gradients in vegetation; rather, vegetation gradients showed strong correlations with complex environmental gradients. These complex environmental gradients included nutrient, moisture and soil physical and site variables. These results suggest a simple 'nutrient' hypothesis regarding vegetation patterns in the Central Coast region is inadequate to explain variation in vegetation within soil types

Agricultural legacy, climate, and soil influence the restoration and carbon potential of woody regrowth in Australia

Opportunities for dual restoration and carbon benefits from naturally regenerating woody ecosystems in agricultural landscapes have been highlighted recently. The restoration capacity of woody ecosystems depends on the magnitude and duration of ecosystem modification, i.e., the ''agricultural legacy.'' However, this legacy may not influence carbon sequestration in the same way as restoration because carbon potential depends primarily on biomass accumulation, with little consideration of other attributes and functions of the ecosystem. Our present study simultaneously assesses the restoration and carbon potential of Acacia harpophylla regrowth, an extensive regrowth ecosystem in northeastern Australia. We used a landscape-scale survey of A. harpophylla regrowth to test the following hypotheses: (1) management history, in combination with climatic and edaphic factors, has long-term effects on stem densities, and (2) higher-density stands have lower restoration and carbon potential, which is also influenced by climatic and edaphic factors. We focused on the restoration of forest structure, which was characterized using stem density, aboveground biomass, stem heights, and stem diameters. Data were analyzed using multilevel models within the hierarchical Bayesian model (HBM) framework. We found strong support for both hypotheses. Repeated attempts at clearing Brigalow (A. harpophylla ecosystem) regrowth increases stem densities, and these densities remain high over the long term, particularly in high-rainfall areas and on gilgaied, high-clay soils (hypothesis 1). In models testing hypothesis 2, interactions between stem density and stand age indicate that higher-density stands have slower biomass accumulation and structural development in the long term. After accounting for stem density and stand age, annual rainfall had a positive effect on biomass accumulation and structural development. Other climate and soil variables were retained in the various models but had weaker effects. Spatial extrapolations of the HBMs indicated that the central and eastern parts of the study region are most suitable for biomass accumulation; however, these may not correspond to the areas that historically supported the highest biomass Brigalow forests. We conclude that carbon and restoration goals are largely congruent within areas of similar climate. At the regional scale, however, spatial prioritization of restoration and carbon projects may only be aligned where carbon benefits will be high. © 2010 by the Ecological Society of America

Major and trace element geochemistry of El Chichón volcano-hydrothermal system (Chiapas, México) in 2006-2007: implications for future geochemical monitoring

Isotopic, major and trace element composition studies for the crater lake, the Soap Pool and thermal springs at El Chichón volcano in November 2006-October 2007 confirm the complex relationship between annual rainfall distribution and crater lake volume and chemistry. In 2001, 2004 and 2007 high volume high-Cl lake may be related to reactivation of high discharge (>10 kg/s) saline near-neutral water from the Soap Pool boiling springs into the lake, a few months (~January) after the end of the rainy season (June-October). The peak lake volume occurred in March 2007 (~6 x 105 m3). Agua Tibia 2 thermal springs discharge near the foot of the SW dome but their chemistry suggests a lower temperature regime, an enhanced water-rock interaction and basement contribution (evaporites and carbonates), anhydrite leaching from the 1982 pyroclastic deposits, rather than dome activity. New suggestions of crater lake seepage are evidenced by the Agua Caliente thermal springs. Existing models on the “crater lake-Soap Pool spring” and the deep hydrothermal system are discussed. Chemical changes in the deep geothermal aquifer feeding the thermal springs may predict dome rise. Future volcanic surveillance should focus on spring chemistry variations, as well as crater lake monitoring