Alan P.N. House

The use of ants and other soil and litter arthropods as bio-indicators of the impacts of rainforest clearing and subsequent land use

The present study investigated the impacts of rainforest clearance, and associated subsequent land␣use for pasture, on assemblages of soil and litter arthropods in eastern subtropical Australia. We assessed the utility of soil and litter arthropods as potential bio-indicators of cleared and forested habitats. Arthropods were sampled from 24 sites (12 sites each in rainforest and pasture) using two methods (extraction from litter, pitfall traps). Responses of taxa were analysed at various levels of taxonomic resolution, including ‘coarse’ arthropods (all arthropods sorted to Order/Class), ant genera and ant species. Multivariate analyses of arthropod composition indicated that an increase in the level of taxonomic resolution did not provide a commensurate increase in the sensitivity of assemblage response. Indicator values (IndVals), computed for each taxon, showed that a number of arthropod taxa may have potential as bio-indicators of habitat change. However the use of many of these, especially many ant species found in our study, may be unreliable because even after extensive numbers of sites were sampled, most species showed patchy distributions. To overcome this problem, we generated ‘composite indices’, by combining information from sets of indicator taxa. The utility of these composite indices is discussed.

Effect of fragmentation, habitat loss and within-patch habitat characteristics on ant assemblages in semi-arid woodlands of eastern Australia

The reliability of ants as bioindicators of ecosystem condition is dependent on the consistency of their response to localised habitat characteristics, which may be modified by larger-scale effects of habitat fragmentation and loss. We assessed the relative contribution of habitat fragmentation, habitat loss and within-patch habitat characteristics in determining ant assemblages in semi-arid woodland in Queensland, Australia. Species and functional group abundance were recorded using pitfall traps across 20 woodland patches in landscapes that exhibited a range of fragmentation states. Of fragmentation measures, changes in patch area and patch edge contrast exerted the greatest influence on species assemblages, after accounting for differences in habitat loss. However, 35% of fragmentation effects on species were confounded by the effects of habitat characteristics and habitat loss. Within-patch habitat characteristics explained more than twice the amount of species variation attributable to fragmentation and four times the variation explained by habitat loss. The study indicates that within-patch habitat characteristics are the predominant drivers of ant composition. We suggest that caution should be exercised in interpreting the independent effects of habitat fragmentation and loss on ant assemblages without jointly considering localised habitat attributes and associated joint effects.

Effects of shading and mulch depth on the colonisation of habitat patches by arthropods of rainforest soil and litter

Abstract.  1. Development of foliage cover and a layer of leaf litter are two factors considered important for the successful recolonisation of soil and litter arthropods during the early stages of rainforest restoration; however, this needs to be tested explicitly.

Agricultural matrix provides modest habitat value for ants on mixed farms in eastern Australia

Agricultural development has contributed to the global erosion of biodiversity. The farmed matrix in agricultural landscapes can and must be important for the conservation of biodiversity and provision of ecosystem services, but this assumes that the matrix has biodiversity value. We investigate the contribution of pastures and crops to ant diversity on mixed farms in eastern Australia. Remnant native woodlands, pastures of native grasses, sown pastures of exotic species, and crops were sampled for epigaeic ants on 3 farms using pitfall trapping. Ants were sorted to species and assigned to functional groups. Ant species richness and functionality followed consistent patterns across the three farms. Significant differences in assemblage composition were found between the major habitat types, and in species richness between woodland and non-woodland habitats (native and sown pastures, and crops), which did not contribute appreciably to farm-level biodiversity: 1–10% of species were found only in the farmed matrix. Insect conservation in agricultural landscapes is important for the provision of ecosystem services, including pest control and the maintenance of soil condition. As the farmed matrix makes only a modest contribution to farm-scale biodiversity, appropriate management of the unfarmed parts of the landscape is critical and habitat restoration may be warranted where the level of native vegetation is low. Maintaining a mix of land uses within the production matrix will also be a necessary bet-hedging strategy in a world with changing climates, commodities, community expectations and farming practices.

Effects of isolation on the colonisation of restored habitat patches by forest‐dependent arthropods of soil and litter

Abstract.  1 A novel experimental approach was taken to investigate the effects of distance from rainforest remnants on the recolonisation patterns of ants and other soil and litter arthropods in ‘restored’ habitat patches within a pasture matrix. 2 Experimental habitat patches were created by adding a thick mulch of sterilised woodchips and leaves, and simulating shade using shadecloth, to create conditions similar to those that occur during rainforest restoration. These patches were deployed at five experimental sites in the Maleny plateau of subtropical eastern Australia. Artificial habitat patches were located at varying distances from a rainforest edge at each site, as well as within the rainforest. The experiment also included a test for efficacy of inoculation, which involved translocation of a small quantity of litter (containing live arthropods) from rainforest habitat to isolated habitat patches. 3 The results showed that, after 9 months, there was little colonisation by rainforest‐dependent taxa in any of the experimental plots beyond those closely adjacent to forest patches. Inoculation was unsuccessful in increasing the extent of arthropod establishment. 4 A number of explanations that potentially account for the observed results are suggested. An experimental approach provides an opportunity to test explicitly for factors considered important for the development of biota in restored habitat patches. There are, however, unavoidable limitations associated with the design of experiments that simulate small‐scale analogues of restoration treatments. Avoiding these limitations may require controlled and replicated efforts in experimental restoration over larger areas, based on collaborations between researchers and practitioners.

Water and nutrient availabilities do not affect lignotuber growth and sprouting ability of three eucalypt species of south-eastern Queensland

Shoot biomass and lignotuber size of seedlings of three eucalypt species, Eucalyptus acmenoides Schauer, E. siderophloia Benth. and Corymbia variegata [syn. E. maculata (F. Muell.)K. D. Hill and L. A. S. Johnson], were measured for glasshouse-grown seedlings established under two water and nutrient regimes. Seedlings were subjected to shoot removal (clipping) at ages from 9 to 19 weeks, and transferred to the high water treatment for a further 8 weeks to assess shoot emergence from lignotubers. Seedling shoot biomass was greater in both the high than the low nutrient and water treatments, but lignotuber diameter was not affected significantly. C. variegata seedlings had the largest lignotuber diameters, followed by E. siderophloia and E. acmenoides, respectively. Although growth of shoots was influenced by nutrient availability, results suggest that species differences in the growth of lignotubers was less affected. It is suggested that lignotuber growth was strongly influenced by genotype. More than 70% of C. variegata seedlings clipped at 9 weeks sprouted, compared with only 5 and 10% of seedlings of E. siderophloia and E. acmenoides, respectively. All C. variegata seedlings sprouted after being clipped at 19 weeks, but < 80% of E. siderophloia and < 60% of E. acmenoides sprouted when clipped at the same age. It was concluded that seedlings forming part of the regeneration stratum in dry sclerophyll forests need to be protected from damage for at least 4 months (for C. variegata) or at least 6 months (for E. siderophloia and E. acmenoides) if they are to survive by sprouting from lignotubers.

Climate and exotic pasture area in landscape determines invasion of forest fragments by two invasive grasses.

To date, there has been a focus on biological aspects of invasion rather than landscape-scale processes within human-modified landscapes. Applying a multi-scale approach may improve predictive models of invasion in fragmented landscapes as well as management. We tested a priori models of the relative importance of landscape (10 000 to 30 000 ha), site-scale (<0·3 ha) factors and climate gradients, and their interactions, on the cover of exotic grasses in forest fragments. We tested the models for two exotic pasture grasses Cenchrus ciliaris and Panicum maximum in fragmented agricultural landscapes of subtropical eastern Australia. Mixed-effect models were applied to quantify the multi-scale effects of land use, forest area and fragmentation, vegetation structure, soil and climate attributes and their interactions on the ground cover of the two exotic grasses. We used model averaging to account for model and parameter uncertainty and tested for spatial autocorrelation and the model fit in model residuals. There was strong evidence that the area of exotic pasture grass in the landscape and climate gradients had a strong influence on cover observed at the site scale, but the climate influence was species specific. Cenchrus ciliaris cover was higher in forest sites within landscapes converted to exotic pastures and with high mean minimum temperatures and sites with low canopy cover. In contrast, P. maximum cover was primarily influenced by high mean annual rainfall, with moderate positive effects from area of exotic pasture in the landscape and high minimum temperatures. Synthesis and applications. This study highlights several key issues that need to be considered when prioritizing management of invasive species in fragmented landscapes. First, the propagule supply in the landscape and climate gradients are key factors influencing the spread of exotic grasses into forest fragments. Second, managing canopy cover is critical to enhancing C. ciliaris invasion resistance, but not for P. maximum. We conclude that a multi-scale approach provides the conceptual and applied basis for an improved understanding and management of plant invasions in fragmented landscapes.

The Essential Oils of the Genus Doryphora

ABSTRACT The essential oils of two species within the genus Doryphora have been examined. The principal components of both the leaf oil and bark oil of D. sassafras Endl. were methyl eugenol (27–47%), safrole (15–30%) and camphor (15–19%). The oil obtained from the seed of this species had a similar composition. The leaf essential oil of D. aromatica (F. M. Bail.) L. S. Smith did not contain any aromatic compounds; its major components were sesquiterpene alcohols, with the principal members being α-, β- and γ-eudesmol, spathulenql, elemol and guaiol each in approximately 5–15% amounts.

The Leaf Essential Oil of Haplostichanthus johnsonii F. Muell.

ABSTRACT The essential oil ofHaplostichanthus johnsonii, isolated in 1.5–2% yield on fresh weight of leaves contained 2,3,4,5-tetramethoxyallylbenzene (79%) and much lesser amounts of elemicin (5.9%). The remainder of the oil was accounted for mainly by sesquiterpene hydrocarbons of which α-copaene (5%) and β-elemene (2%) were the major contributors.