Jacqui Stol

Grazing response groups among understorey plants in arid rangelands

. We analysed attributes of the understorey flora in different plant communities along two grazing gradients in arid Australian rangelands. We aimed to determine if there were patterns among species in response to grazing, and easily recognizable ‘indicator response types’ for monitoring grazing-induced change in community composition. Measurements were stratified by vegetation patch type, in woody groves and open patches. Trait selection and analyses followed a hierarchical approach which searched for patterns within major plant life forms. Patch type exerted a dominant influence on both life forms and species attributes, but interacted with grazing. Grazing was associated with loss in differentiation of species composition between patch types, rather than loss in numbers of species overall. Heavy grazing was variously associated with small size, prostrate habit, low meristems, small leaves, coated leaves, high regrowth potential, plasticity in response to grazing, and high fecundity; and light grazing with opposing attributes. Many attributes tended to vary independently of each other and grazing-related attribute syndromes were recognisable only among grasses. This could be because the environmental filters acting on the communities have given rise to many different species with different natural attribute combinations, few of which are closely associated with grazing resistance. For grassy communities ‘large, erect tussocks branching above-ground’ and ‘small, sprawling basal tussocks’ may have potential as response types indicative of light and heavy grazing respectively, but no response types could be identified for herbaceous communities.

Colonisation of native tree and shrub plantings by woodland birds in an agricultural landscape

Tree planting has become a cornerstone strategy for natural resource management in agricultural landscapes, yet its contribution as habitat for woodland birds has not been fully investigated. A case study from the Holbrook region in southern New South Wales was used to assess woodland birds in young plantings of native trees and shrubs. Ground-foraging insectivorous woodland birds were under-represented in the plantings, partly due to a lack of native forb diversity (wildflowers) and leaf litter. Of 69 woodland bird species recorded over a three-year period, 48 species (70%) occurred in planted sites, 59 species (86%) occurred in remnant woodland, and 34 species (49%) occurred in adjacent paddock sites. The greater diversity of birds in planted sites relative to paddock sites was mostly due to understorey birds. The proportion of mist-netted birds recaptured was similar in both planted (15%) and remnant woodland (16%) sites, suggesting that individual birds were staying in planted sites. The proportion of woodland birds showing breeding activity (as measured by the presence of a brood patch) was slightly lower in planted sites (24% of all woodland species) than in remnant woodland (29%). Birds such as the superb fairy-wren, red-browed finch and southern whiteface were more likely to occur in planted sites, suggesting that plantings provide unique, transitional-stage habitat within agricultural landscapes. Restoring native forbs, as part of a broader strategy of woodland management, will help to reverse the decline of ground-foraging insectivorous woodland birds in agricultural landscapes.

Towards climate-resilient restoration in mesic eucalypt woodlands: characterizing topsoil biophysical condition in different degradation states

Background and aimsInvestments in restoring native vegetation must increasingly allow for likely impacts of climate change, requiring re-evaluation of limits to ecological recovery and persistence. Nutrient enrichment and weed invasion are significant limits to restoration in mesic ecosystems, but in a drying climate, limits could shift towards more fundamental ecosystem functions. We used a state and transition framework to identify landuse-related changes in topsoil biophysical characteristics likely to influence climate resilience in mesic temperate eucalypt woodlands.MethodsWe compared topsoil condition in little-modified ‘reference’ states of the native ground-layer (dominated by tall tussock grasses) with four degraded ground-layer states identified in our state and transition framework. We hypothesized that ‘nutrient-depleted’ states (dominated by short tussock grasses) and ‘nutrient-enriched’ states (dominated by exotic annuals) would exhibit characteristics reflecting increased and decreased ecosystem vulnerability to a drying climate respectively.ResultsOur hypothesis that nutrient-depleted states are more vulnerable to a drying climate was supported by their significantly slower soil-water infiltration rates and significantly lower levels of topsoil carbon, clay, micro-invertebrates, microbial activity and modeled water holding capacity than reference states. However, degradation was less pronounced beneath trees, and our prediction regarding enriched states was supported only for carbon.ConclusionsTopsoil biophysical characteristics associated with different ground-layer states are predictable using a state and transition framework. Climate resilience of nutrient-depleted states appears compromised by topsoil biophysical degradation, indicating increasing need for attention in mesic ecosystems predicted to become drier under climate change.

Why non-native grasses pose a critical emerging threat to biodiversity conservation, habitat connectivity and agricultural production in multifunctional rural landscapes

ContextLandscape-scale conservation planning is key to the protection of biodiversity globally. Central to this approach is the development of multifunctional rural landscapes (MRLs) that maintain the viability of natural ecosystems and promote animal and plant dispersal alongside agricultural land uses.ObjectivesWe investigate evidence that non-native grasses (NNGs) in rangelands and other low-intensity agricultural systems pose a critical threat to landscape conservation initiatives in MRLs both in Australia and globally.MethodsWe first establish a simple socio-ecological model that classifies different rural landscape elements within typical MRLs based on their joint conservation and agro-economic value. We then quantify the impacts of eight Australian NNGs (Andropogon gayanus, Cenchrus ciliaris, Eragrostis curvula, Hyparrhenia hirta, Nassella neesiana, Nassella trichotoma, Phalaris aquatica and Urochloa mutica) on different landscape elements and then classify and describe the socio-ecological transformations that result at the MRL scale.ResultsOur data indicate that two broad classes of NNGs exist. The first reduces both conservation and agro-economic value (‘co-degrading’ species) of invaded landscapes, while the second improves agro-economic value at the expense of conservation value (‘trade-off’ species). Crucially, however, both classes cause hardening of the landscape matrix, agricultural intensification, reduced habitat connectivity, and the loss of multi-value land use types that are vital for landscape conservation.ConclusionsNNGs drive socio-ecological transformations that pose a growing threat to landscape-scale connectivity and conservation initiatives in Australia and globally. There is an urgent need for further research into the impacts of NNGs on habitat connectivity and biodiversity within multifunctional landscapes, and the socio-ecological goals that can be achieved when landscape transformation and degradation by these species is unavoidable.