Trees in a grazing landscape: vegetation patterns in sheep-grazing agro-ecosystems in Southern Queensland

The modification of natural woodland tree densities through tree removal or clearing has been used by landholders to increase native grass production for livestock grazing. This paper describes studies that aim to determine if vegetation management by graziers affect floristic composition, species richness and plant cover (including production attributes) in the Traprock wool-producing region of southern Queensland, Forty-seven sites were sampled across the study area according to vegetation type (ironbark/gum woodland and box woodland), density of mature trees (low: 6 trees/ha, medium: 6-20 trees/ha, and high >20 trees/ha), and the presence or absence of woody regrowth in the understorey to determine vegetation patterns, A subset of 18 sites was selected to establish grazing exclusion experiments in both vegetation types under varying mature tree densities. This paper describes the general patterns in vegetation under differing mature tree densities and provides preliminary results of the 12-month grazing exclusion experiments

Different landscape factors explain establishment and persistence of river red gum (Eucalyptus camaldulensis) in agricultural landscapes of southeast Queensland

Riparian and floodplain ecosystems in production landscapes are considerably degraded and under continued pressure from surrounding land use. However, little is known about how remnant ecosystems respond to land use and hydrological factors in small non-riverine wetlands. River red gum (Eucalyptus camaldulensis) is a dominant tree species within these scattered remnants, which provides critical ecological functions for the remaining biodiversity. In this study, we investigated how different life stages of E. camaldulensis responded to land use and hydrological variables in the Condamine catchment of south east Queensland. We used logistic regression to develop models for different life stages of E. camaldulensis in two regions with differing land use intensity histories. Broad regional differences and land use practices at smaller scales best explained differences in E. camaldulensis occurrence for younger life stages, while hydrology (groundwater and connectivity to rivers) and land use practices (dryland agriculture and grazing) best explained differences in older life stages. The results indicate that different factors are important in determining the establishment and persistence of E. camaldulensis and that land use practices at the regional scale are key factors in determining the establishment and potential future persistence of E. camaldulensis in floodplain wetlands

Chronic groundwater decline: a multi-decadal analysis of groundwater trends under extreme climate cycles

Chronic groundwater decline is a concern in many of the world’s major agricultural areas. However, a general lack of accurate long-term in situ measurement of groundwater depth and analysis of trends prevents understanding of the dynamics of these systems at landscape scales. This is particularly worrying in the context of future climate uncertainties. This study examines long‐term groundwater responses to climate variability in a major agricultural production landscape in southern Queensland, Australia. Based on records for 381 groundwater bores, we used a modified Mann-Kendall non-parametric test and Sen’s slope estimator to determine groundwater trends across a 26-year period (1989–2015) and in distinct wet and dry climatic phases. Comparison of trends between climatic phases showed groundwater level recovery during wet phases was insufficient to offset the decline in groundwater level from the previous dry phase. Across the entire 26-year sampling period, groundwater bore levels (all bores) showed an overall significant declining trend (p0.05). Spatially, both declining and rising bores were highly clustered. We conclude that over 1989–2015 there is a significant net decline in groundwater levels driven by a smaller subset of highly responsive bores in high irrigation areas within the catchment. Despite a number of targeted policy interventions, chronic groundwater decline remains evident in the catchment. We argue that this is likely to continue and to occur more widely under potential climate change and that policy makers, groundwater users and managers need to engage in planning to ensure the sustainability of this vital resource

Riparian woodlands in crisis? Disturbance ecology on the Condamine floodplain

The Condamine River, at the headwaters of the Murray-Darling basin, drains one of the most intensively-farmed landscapes in eastern Australia. Riparian woodland remnants on the floodplain sections of the upper Condamine are widely recognised as being in generally poor condition, with evidence of significant dieback and limited recruitment of canopy species, as well as widespread invasion by the introduced perennial herb Phyla canescens (lippia). These communities, in keeping with most remnant ecosystems of agricultural landscapes, are poorly understood in terms of their diversity, function and dynamics (resilience) under altered disturbance regimes. This research investigates the condition (health and function) of Eucalyptus tereticornis/camaldulensis riparian woodland communities of the Condamine floodplain in relation to selected natural and anthropogenic disturbance factors (e.g. climate variability, changes in land- and wateruse, weed invasion) operating at a range of spatial and temporal scales. The study takes a multi-dimensional approach aimed at developing an integrated understanding of key drivers and mechanisms of ecosystem change in these environments. It also investigates the potential of simple conceptual tools (e.g. State-and-Transition and Bayesian Belief Network approaches) to model system dynamics and predict outcomes of future climate and land and water management scenarios, including environmental flow restoration

Managing pest species under climate change: risks and opportunities

Human activity is driving significant changes in global and regional climate systems through the enhanced greenhouse effect (IPCC 2007). Global climate models predict that this anthropogenic forcing will alter both mean climate parameters and the frequency and magnitude of extreme meteorological events (e.g. heat waves, severe storm events and droughts). Such changes may have significant destabilizing effects, decoupling existing relationships between species, altering species distributions and challenging current management regimes. However, they may also provide significant management opportunities. Many pest species are expected to expand their geographical range in a warmer, more extreme, climate. Despite this, there is likely to be great variation both in pest species responses to changing climatic conditions and impacts on ecological and production systems, and in the effectiveness of current pest management strategies. This implies a need for ongoing monitoring and assessment of pest species responses to environmental change and management at local and regional scales. It also indicates a need for research aimed at identifying potential tipping points (or critical thresholds) in relation to significant meteorological events. This presentation will focus on the role of risk assessment in decision-making for pest species management under uncertainty. Probabilistic modelling approaches, such as Bayesian Belief networks, provide a valuable adjunct to monitoring and evaluation programs. They facilitate the synthesis of current knowledge (including expert opinion), highlight critical knowledge gaps, and provide a basis for both targeted research and adaptive management. Integrated modelling to predict invasive species response to management under variable climatic conditions can be used to identify key opportunities for management which will contribute disproportionately to effective pest species control. Pest species management programs under future climatic regimes are likely to require the capacity for more adaptive and strategic response, and will need to be supported by flexible investment strategies which enable timely (adaptive) responses at critical periods

Endophytic fungi associated with Australian orchids

Australia is rich in orchid flora with over 1000 native species currently recorded. A significant proportion of Australia’s terrestrial orchids are critically endangered, endangered or threatened. Threats to many orchid species include habitat destruction, degradation and fragmentation from increased urbanisation, overgrazing, altered fire regimes and unfortunately, excessive collecting by orchid fanciers. Conservation efforts for Australian orchids include both ex situ and in situ approaches. Ex situ efforts involve the growth of orchid species under horticultural conditions and long term storage of plant and associated fungal material in laboratories and herbaria. In situ approaches include re-establishing plants in the wild and protection of current populations through management initiatives

Technical report: vegetation changes following the short-term exclusion of grazing in the Traprock region

[Summary]: This study is the continuation of earlier research examining the effects of vegetation management on woodland communities in the Traprock region and will contribute to an understanding of the ‘biodiversity potential’ of managed land units on properties (including open paddocks, scattered treed areas, and remnant woodland). A number of grazing exclosures were established on selected properties with the aim to monitor biodiversity changes over-time following the removal of grazing. Eighteen study sites across 10 properties in the Traprock region were selected for this study. The experimental design consisted of: 2 vegetation types (grassy box (Eucalyptus melliodora, E. microcarpa, or E. moluccana) woodland (L) and ironbark (E. crebra) /gum (E. dealbata) (U) woodland); 3 mature (overstorey) tree densities (20 trees/ha [high](H), and; 3 exclosures (full exclosure (1) [2.5m complete fence], partial exclosure (2) [1.5m three-wire fence], open (3) [corner makers]). Exclosure plots were erected in January/February 2005 and sampled in April 2005 (two months after exclosure establishment) and again in February 2006 (12 months after exclosure establishment). Within each 6 x 6 m exclosure plot, a central 2 x 2 m quadrat was sampled for plant species cover (determined subjectively). Above-ground vegetation (‘biomass’) was clipped in a 0.25m2 sample and dry weight determined. Overstorey cover and recruitment were determined within each 6 x 6 m exclosure plot. Stand structural characteristics, including foliage projective cover of distinct strata, and cover of litter, logs and rocks, and general habitat condition were also determined at each site. Patterns in floristic composition were determined using non-metric Multidimensional Scaling (nMDS). Two-way crossed Analysis of Similarity (ANOSIM) determined whether there were significant differences in floristic composition between exclosure types and mature tree density classes. nMDS was also used to assess patterns in cover data for growth forms. Two-way crossed Analysis of Variance (ANOVA) was used to determine if groups (density class, exclosure type and the interaction of density and exclosure) differed significantly for total, native, exotic, growth-form, perennial, and annual species richness and above-ground biomass. In addition, Spearman-rank correlations were performed to determine if biomass and estimates of ground cover covaried. A total of 151 plant species was recorded across all treatments with an average richness across treatments of 17 species per 4m2. No differences were apparent in overall plant composition (cover) between the exclosure treatments one year following grazing exclusion (ANOSIM, pr > 0.05). nMDS ordinations show no distinction between exclosure treatments, but patterns were observed in mature tree density treatments within vegetation types as found in previous research. Stand structure (cover of strata) showed much the same pattern as floristic composition. There were generally no detectable differences (p > 0.05) in plant above-ground biomass between exclosure treatments, although significant differences between tree density classes was indicated with a significantly higher plant biomass in low density treatments compared to high density for both vegetation types. Correlation results showed that estimates of grass cover provide a good indication of above-ground biomass (p<0.05). There were some differences between density classes for growth-form species richness, exotic species richness and annual species richness, however exclosure treatments did not differ. Overall, there were no differences in total or native species richness between groups. While the distinction between vegetation type and mature tree density is observed in species composition, plant biomass and species richness, the exclusion of grazing (native and exotic) has not significantly altered composition after 12 months. The patterns in floristic composition are associated with different mature tree densities and vegetation type, which are consistent with earlier findings. There is some evidence to suggest that plant above-ground biomass has responded to the removal of grazing in open paddock areas, although this is not consistent across mature tree density treatments. It is suggested that a longer period of exclusion will be necessary to detect changes (if any) in plant species composition

Ephemeral wetlands: their ecological function and resilience and climate change

Ephemeral systems dominate the landscape in Australia, although they are often undervalued both intrinsically, and in terms of their contribution of ecosystem services to the broader landscape compared to other wetland systems. In the face of climate change, a lack of understanding of how ephemeral systems function and their ecological resilience, the ability of the system to adapt to significant (directional) change, represent significant knowledge gaps. Ephemeral systems in inland Queensland are highly dynamic, with species generally well adapted to relatively unpredictable climates. However, ecosystem degradation through the direct impacts of land use such as eutrophication, grazing, salinity, erosion, and indirect interferences on flow rates and hydroperiod has greatly simplified these systems and reduced their resilience and hence their ability to adapt to climate change. Decreased resilience in ephemeral wetlands coupled with inadequate knowledge of how these systems function, could have serious implications for the future sustainability of agricultural landscapes. In order to address these issues a sound understanding of the ecological and social factors important for maintaining these systems resilience to degradation and climate change needs to be developed. This presentation describes a proposed study examining aspects of ephemeral wetland ecological function and resilience to climate change

Retaining trees in a grazing landscape: impacts on ground cover in sheep-grazing agro-ecosystems in southern Queensland

In low-input, low-productivity grazing systems, the modification of natural woodlands through overstorey tree and woody regrowth removal are management options used by graziers to increase native grass production for livestock grazing. This paper describes studies that determine if vegetation management by graziers affect floristic composition, species richness and plant cover in the Traprock wool-producing region of southern Queensland. Forty-seven sites in the region were sampled according to vegetation type (ironbark/gum woodland and box woodland), density of mature trees (low: 6 trees/ha, medium: 6-20 trees/ha, and high: >20 trees/ha), and the presence or absence of woody regrowth in the understorey to determine vegetation patterns. A subset of 18 sites was selected to establish grazing exclusion experiments in both vegetation types under varying mature tree densities. Here we describe the general patterns in vegetation under differing mature tree densities and provide some preliminary results of the 4-year grazing exclusion experiment. While grass production is low under high overstorey tree densities, no differences between medium tree densities and open paddock areas is apparent, suggesting retaining trees in a low-input, low-productivity grazing system can provide biodiversity benefits without adversely impacting upon production