William A. Loneragan

Enhanced soil and leaf nutrient status of a Western Australian Banksia woodland community invaded by Ehrharta calycina and Pelargonium capitatum

Increased nutrient availability can have a large impact in Australian woodland ecosystems, many of which are very poor in nutrients, particularly phosphorus. A study was conducted in an urban Banksia woodland remnant in Perth, southwest Western Australia to test the hypothesis that the soil nutrient status in areas in good condition (GC), poor condition invaded by the perennial grass Ehrharta calycina (PCe), and poor condition invaded by the perennial herb Pelargonium capitatum (PCp), is reflected in the nutrient status of the native and introduced species. Leaf concentrations of P, K, N, Na, Ca, Mg, S, B, Cu, Fe, Mn and Zn of six native (Banksia attenuata, Banksia menziesii, Allocasuarina humilis, Melaleuca systena, Macrozamia fraseri and Conostylis aculeata) and four introduced species (Ehrharta calycina, Pelargonium capitatum, Gladiolus caryophyllaceus and Briza maxima), were measured. Soil pH, electrical conductivity, N (total), P (total), available P, K, S and organic C were assessed beneath all species on all sites. Significantly higher concentrations of soil P (total) and P (HCO3) were found at PCe and PCp sites than GC sites, while PCp sites also had significantly higher soil concentrations for N (total) and S. Principal Components Analysis of the leaf analyses showed (a) individual species have characteristically different nutrient concentrations; (b) the introduced species Ehrharta calycina and Pelargonium capitatum clustered separately from each other and by vegetation condition. Leaf concentrations of P were significantly (P<0.05) higher, and K and Cu were significantly lower in PCe and PCp sites compared with those at GC sites. Introduced species leaf nutrient concentrations were significantly greater than native species for all nutrients except Mn which was significantly lower, with no differences for Mg and B. The results indicate a key role for P in the Banksia woodland, and we conclude that higher levels of available P at invaded sites are having a detrimental impact on the ecosystem. These results provide new knowledge to enhance conservation practices for the management of the key threatening process of invasion within a biodiversity hot spot.

The effects of burning on the understorey composition of rehabilitated bauxite mines in Western Australia : community changes and vegetation succession

Abstract The first 2 years of post-burn vegetation succession of 11–13-year-old rehabilitated bauxite mines in Western Australia is compared to the native jarrah ( Eucalyptus marginata ) forest using the techniques of ordination (CANOCO TM ) and classification (TWINSPAN TM ). Analyses of understorey species density and cover values showed consistent patterns of composition and abundance between the native jarrah forest and the rehabilitated areas, both before and after burning. These patterns resulted from the intentional establishment of high densities of legume species in the initial rehabilitation process and proliferation of high densities of seeding species and non-native eucalypt seedlings following burning of the rehabilitated areas, features not characteristic of native jarrah forest. Burnt sites showed larger changes in species abundance and composition than unburnt control sites as indicated by their relative shift of position in the ordination hyper-space. This shift in position was generally less for sites burnt in spring than sites burnt in autumn. The first two divisions of the site classifications separated the unburnt sites and early spring post-burn sites from the forest and the remainder of the post-burn sites. The species classification showed that each of these groups was associated with a specific suite of species. Pit age (i.e. 11, 12 or 13 years-old at time of burning) was an important determinant of species composition in both the ordinations and classifications. Although species densities recovered more rapidly than live plant cover in the rehabilitated areas following burning, the vegetation of these rehabilitated sites exhibited little evidence of returning to their pre-fire species composition and abundance after 2 years. However, the high species similarity (75–79%) between the pre-burn (including species only present as seed in the topsoil) and post-burn vegetation indicates the importance of the initial floristic composition in determining the potential direction of the post-fire succession.

Pollen Selection by Honeybees in Shrublands of the Northern Sandplains of Western Australia

SummaryCommercial apiarists utilize the Northern Sandplain shrublands of Western Australia as winter honeybee (Apis mellifera L.) maintenance areas. Analyses of pollen loads collected from two hives stationed in these sandplains during June-September 1981 and 1982 showed that, among a total of 44 species exploited by the bees for pollen, the most commonly exploited were Leucopogon conostephioides, L. striatus and Acacia stenoptera. Species flowering locally in abundance were preferred, but some common species were never visited. L. conostephioides was a major source of pollen early in the two study seasons (1981 and 1982), followed later in the season by L. striatus (1981 only) and A. stenoptera (1982 only). A high degree of constancy during foraging forays by individual bees was evident from the finding that 52–79% of the pollen pellets of weekly samples consisted solely of pollen of a single plant species. Pollen of Northern Sandplain species varied considerably in crude protein, amino acid concentratio...

Germination and early survival of Eucalyptus blakelyi in grasslands of the New England Tablelands, NSW, Australia

Establishing native eucalypts in grasslands developed by the historical clearing of forests and woodlands has to overcome significant difficulties brought about by past land use activities and associated environmental changes. Options for establishment include natural regeneration from remnant trees, direct sowing or tree planting. Eucalyptus blakelyi is a significant species on the New England Tablelands, being just north of the central part of its ecological range and is potentially useful for ecosystem rehabilitation, agroforestry and farm forestry. The aims of this series of studies are to determine the effects of cold temperatures resulting from microclimate changes on germination and early survival of E. blakelyi, the level of seed predation by ants, and the effectiveness of site preparation techniques on survival and growth of seedlings planted in grasslands. Germination of local seeds collected from the New England Tablelands was tested under constant and alternating temperatures, either in the dark or under 12 h light/dark cycle. E. blakelyi exhibited optimal germination between 15 and 25 °C with the maximum occurring at 15 °C under constant temperatures, and at 15–25 °C under alternating temperatures. Light had a significant and positive effect on germination under both constant and alternating temperature regimes, although this difference was not significant at temperatures around the optimum. Seedling survival decreased significantly as temperature decreased from −5 to −10 °C, as exposure time to low temperature increased from 1 to 4 h, and as seedling age increased from 1 to 8 weeks. Ant predation was high with 73% of the seeds removed within 7 days. Four site preparation techniques (grazing exclusion, cultivation, burning and fertiliser) were used in a factorial arrangement to examine their interactions and influences on seedling survival and height growth 30 months after establishment. Grazing significantly reduced seedling survival and height, whereas soil cultivation and burning significantly increased them. Survival and height were consistently lower when fertiliser was added to grazed plots across all cultivation treatments including the control. When grazing was excluded, fertiliser significantly reduced survival with cultivated treatments, and increased height only with shallow cultivation (to a depth of 5 cm) while it significantly reduced height with deep cultivation (20 cm). The interactions amongst the various treatments identified that seedling survival and growth were best when grazing was excluded and the site was deep cultivated without the broadcast application of fertiliser. Fire has an additive effect on seedling survival and height growth. The main benefits of this combination of treatments lie in preventing browsing and trampling damage by livestock, reducing competition from the herbaceous layer, removing litter, and possibly alleviating potential allelopathic effects.