A comparison of some populations of Eucalyptus viminalis Labill. growing on calcareous and acid soils in Victoria,Australia

A study of populations of Eucalyptus viminalis found on both acid and alkaline soils showed that seedlings differ in their tolerance of calcareous soils and their susceptibility to lime chlorosis. Seedlings from an open-forest population on calcareous dunes in the Otway Ranges, Victoria, averaged a significantly greater yield than seedlings of three other populations found on acid soils when all were grown on calcareous soil of pH 6.8. A tall ribbon gum form of E. viminalis, from Paradise gully in the Otways, was the least tolerant of alkaline conditions and showed severe signs of chlorosis and reddening of leaf margins. The latter appeared to be related to high uptake of phosphorus. This population showed rapid growth on a fertile acid loam. The data presented also emphasize the need to consider the variation in soils which can occur at any one site. Population differences were most marked when seedlings were grown on soils of pH near 7.0. Yield was reduced in the Otways calcareous population when seedlings were grown on the more leached soil from swales (pH 6.5) between dunes and on the highly calcareous soil from the dune crests (pH 7.8–8.0). The failure of any of the populations of E. viminalis studied to grow well on soils of high pH suggest that this species is not tolerant of highly calcareous soils. This may in part explain the absence of this species from the drier calcareous areas on the Mornington Peninsula and the Yanakie Isthmus, Victoria. Since seedlings had reduced root development on the soil collected from the Peninsula, E. viminalis may be restricted, in effect because of drought stress, to non-calcareous sites in the eastern part of Victoria.     

Ecological gradients in forest communities on Groote Eylandt,Northern Territory,Australia

Vegetational changes over a series of geological boundaries through an area of managanese mineralization on the western side of Groote Eylandt, have been analysed using pattern analysis techniques. Hierarchical classification of data on the frequency of occurrence of plant species in the transects through each of the vegetational zones gave five ecologically identifable groups. The degree of interrelatedness between the sites was emphasized by ordination of the groups, incorporating minimum spanning analysis. The vegetational groups represent developments under different environmental conditions in which differences in water relations and the presence of an impermeable barrier in the soil profile were important. Comparison of the soil nutrient contents of the sites indicated major differences in the total manganese concentration in the topsoil. Even though manganese levels in Eucalyptus tetrodonta leaf tissue were high, no evidence could be found for an iron-chlorosis induced by a low Fe/Mn ratio. The levels of other nutrients in eucalypt foliage were similar to those measured elsewhere. In each vegetational grouping the frequency of occurrence of termite species varied according to site and food type. The role of termites in nutrient cycling needs to be further studied. The closed-forest maybe the climatic climax on the acid red earth soils since in the absence of fire it extends into the surrounding Eucalyptus tetrodonta open-forest. On the Sandstone and Manganese ares the stable state of the vegetation is likely to be composed of the Australian element of the vegetation modified to various extents by fire.     

Erosion, Geological History, and Indigenous Agriculture: A Tale of Two Valleys

Irrigated pondfields and rainfed field systems represented alternative pathways of agricultural intensification that were unevenly distributed across the Hawaiian Archipelago prior to European contact, with pondfields on wetter soils and older islands and rainfed systems on fertile, moderate-rainfall upland sites on younger islands. The spatial separation of these systems is thought to have contributed to the dynamics of social and political organization in pre-contact Hawai’i. However, deep stream valleys on older Hawaiian Islands often retain the remains of rainfed dryland agriculture on their lower slopes. We evaluated why rainfed agriculture developed on valley slopes on older but not younger islands by comparing soils of Pololū Valley on the young island of Hawai’i with those of Hālawa Valley on the older island of Moloka’i. Alluvial valley-bottom and colluvial slope soils of both valleys are enriched 4–5-fold in base saturation and in P that can be weathered, and greater than 10-fold in resin-extractable P and weatherable Ca, compared to soils of their surrounding uplands. However, due to an interaction of volcanically driven subsidence of the young island of Hawai’i with post-glacial sea level rise, the side walls of Pololū Valley plunge directly into a flat valley floor, whereas the alluvial floor of Hālawa Valley is surrounded by a band of fertile colluvial soils where rainfed agricultural features were concentrated. Only 5% of Pololū Valley supports colluvial soils with slopes between 5° and 12° (suitable for rainfed agriculture), whereas 16% of Hālawa Valley does so. The potential for integrated pondfield/rainfed valley systems of the older Hawaiian Islands increased their advantage in productivity and sustainability over the predominantly rainfed systems of the younger islands.     

The redistribution of soil water by tree root systems

Plant roots transfer water between soil layers of different water potential thereby significantly affecting the distribution and availability of water in the soil profile. We used a modification of the heat pulse method to measure sap flow in roots of Grevillea robusta and Eucalyptus camaldulensis and demonstrated a redistribution of soil water from deeper in the profile to dry surface horizons by the root system. This phenomenon, termed “hydraulic lift” has been reported previously. However, we also demonstrated that after the surface soils were rewetted at the break of season, water was transported by roots from the surface to deeper soil horizons – the reverse of the “hydraulic lift” behaviour described for other woody species. We suggest that “hydraulic redistribution” of water in tree roots is significant in maintaining root viability, facilitating root growth in dry soils and modifying resource availability. Received: 26 January 1998 / Accepted: 15 April 1998     

La flora e le associazioni algali della Sorgente di Salomone (Anterselva,Bolzano). Facies estiva

Abstract

The flora and algal associations of Salomon's spring (Anterselva, Bolzano). Summer facies. – Salomon's spring is situated in Anterselva valley (Bolzano), a characteristic valley of a glacial escavation, having a typical profile formed like a « U » and a wide peat-bog on the bottom. The source springs at 1100 mts above the sea-level from a zone of waste-layer formed by fragments of metamorphic rocks (ortogneiss). Then it gives birth to a small pool from which the water flows very slowly forming a little stream. The spring has a plentiful algal flora rich of species (66, including the varieties too) belonging to the following classes: Cyanophyceae (12), Xanthophyceae (4), Bacillariophyceae (38), Euchlorophyceae (8), Ulothricophyceae (3), Zygophyceae (1).

In the spring are described the following algal associations:

–Diatometum hiemalis, that forms many brown-reddish little flocks on the borders and in the anfractures of the big stones that occupy the source;

–Diatometum hiemalis subass. ceratoneietosum, formed by gelatinous little masses amoung the stalks of some phanerogams forming floating clods at the surface of the spring;

–Melosiretum italicae, the most developed association of the spring, looking like wide islets floating on the surface and filamentous drapings fixed at the stones;

–Homoeothriceto-Chamaesiphonetum, which forms wide blue-coloured casings on many submerged stones;

–Phormidietum membranaceum (Fjerdingstad, 1950, Douglas, 1958; Phormidium community, Fritsch, 1929; Fjerdingstad, 1964), that forms many thick mucous blue-green coloured coats on some of the submerged stones.     

Invertebrate communities on Western Australian eucalypts: A comparison of branch clipping and chemical knockdown procedures

Chemical knockdown and branch clipping procedures were used in wandoo (Eucalyptus wandoo) woodland and jarrah (E. marginata)/marri (E. calophylla) open-forest to sample arboreal invertebrate faunas on three species of Western Australian eucalypts. Jarrah was sampled in both habitats and had significantly lower invertebrate populations and a less diverse fauna than either wandoo or marri. The two procedures provided similar results with respect to the relative abundance of invertebrates on each plant species but the knockdowns sampled a more diverse fauna, including species sheltering in or on bark. Chemical knockdowns underestimated the abundance of sessile invertebrates, such as psyllids. Branch clipping sampled insufficient numbers of large, mobile, or cryptic invertebrates to estimate abundances, but provided a more accurate estimate of the abundance of sessile, leaf-dwelling organisms. Neither procedure provides a complete sample of arboreal invertebrates, but they are complementary. When used in conjunction with each other a more complete estimate of arboreal invertebrate abundance and diversity is obtained. Both procedures can be used concurrently with only a small increase in field time.     

Reproductive traits of two closely related species-pairs on adjacent,different soil types in South African Fynbos

High levels of edaphic endemism and soil-related beta-diversity in Agulhas Plain fynbos communities suggest that reproductive traits of plants growing on different fynbos soils would be related to differences in soil regime. We investigated reproductive traits in two closely related Proteaceae species-pairs growing on adjacent soil types: Protea obtusifolia and Leucadendron meridianum occurring in shallow pockets of limestone-derived soils, and P. susannae and L. coniferum on the adjacent, uniformly deep colluvial sands.We found that species growing on the limestone soil comprised smaller plants, with fewer cones and seeds per plant, than species on the colluvial sands. These differences suggest that the small soil pockets of limestone soil limit plant size, in turn limiting the number of reproductive structures. Annual variation in cones and seed was the same in all species. There were no consistent trends in degree of serotiny, or sex allocation across soil types. The higher cone and seed predation levels of both limestone species than the colluvial sands species were ascribed to the higher plant densities of the former leading to lower insect search times. It was concluded that there were no overall patterns in reproductive traits that could be ascribed to differences in soil regime, other than through size-related effects. Fire regime is likely to have played a more important role in determining reproductive traits.Department of Statistical Sciences, University of Cape Towm     

Establishment and early growth of species in farm plantations near salt seeps

Clearing of native forest has caused a rise in soil watertables and increased the salinity of land and streams in south-western Australia. Reforestation is a possible method of increasing the use of water on cleared catchments, lowering watertables and reducing the output of salt from hillside seeps. One of the first needs is evidence of suitable species for such a project. This paper describes the comparative success of twenty-eight species (mainly Eucalyptus spp.) in establishment and early growth when grown on and near saline seeps during 1976–77. Plantations were located in 850, 500 and 420 mm annual rainfall zones of the Hotham River valley about 150 km south-east of Perth, Western Australia. The sites had saline confined aquifers and seasonal perched watertables which were typical of many landscapes in the region. Though rainfall was below average and only one watering was given, nineteen species had greater than 80% establishment in upslope, midslope and downslope positions. In late winter 1977, 15 months after planting, the leading species were 1–2 metres tall and carried leaf area up to 5.5 m² per tree where current rainfall was highest. The results indicate a high potential for plant establishment and early growth within the rainfall zones. Eucalyptus spp. from many regions of southern Australia were successful at the wettest location. Success at the two driest locations was limited to species from dry climates of southern South Australia and Western Australia. Planting on seep areas decreased the establishment of three species. Eucalyptus wandoo, E. globulus and E. camaldulensis, which performed well on non-seep areas at one or more locations. Implications for a source of further test species and for planting strategy near seeps are discussed.     

Effects of neighbouring vegetation on eucalypt seedlings at two sites subject to different levels of abiotic stress

Abstract In spite of numerous studies on the effect of nutrient levels and/or standing crop on the intensity of resource competition the debate has not been resolved. Field studies that have used natural productivity gradients have generally supported the argument that competitive intensity and resource availability are positively correlated, whereas studies that have used artificial resource gradients have generally refuted the same argument. Here we report the results from study in which both approaches were used within the same system. We studied two species of eucalypt that occupy contrasting parts of the same landscape: Eucalyptus camaldulensis, found mostly along creek lines and in valleys with deep alluvial soils, and Eucalyptus microcarpa, found on hillsides and ridges with shallow soils. We studied the response of seedlings of the two species to the combined effects of competition and manipulated nutrient levels in a glasshouse experiment, and also investigated their responses to removal of neighbouring plants in the field. Eucalyptus microcarpa was less responsive to increased resource availability, which is consistent with one of the principal assumptions of Grime’s C‐S‐R model. In the glasshouse experiment both species of eucalypt responded in a qualitatively similar fashion to the combined effects of resource availability and competition: release from competition resulted in increased growth, but only in pots that received additional resources. In the field we found that neighbouring vegetation could severely limit the establishment of E. camaldulensis but the removal of neighbouring vegetation did not affect the performance of E. microcarpa seedlings. Eucalyptus camaldulensis seedlings suffered high levels of damage from herbivores. Our results thus generally support the predications of the C‐S‐R model, however, they indicate that the effects of competition and herbivory may be heavily confounded.     

Eucalyptus infestation by Leptocybe invasa in Uganda

Very little is known about Leptocybe invasa Fisher & LaSalle, a new fast-spreading alien pest infesting Eucalyptus in several countries. This study examined L. invasa infestation on Eucalyptus germplasms in different agroecological zones of Uganda. The incidence and severity of the pest infestation were higher in hotter and drier agroecological zones than in cooler and wetter zones. There were direct negative relationships between altitude and L. invasa infestation on Eucalyptus species. No infestation was observed on any Eucalyptus species in stands at altitudes ranging from 1938 to 2452 (the maximum encountered) m above sea level. Leptocybe invasa infestation occurred on all Eucalyptus species encountered ( Eucalyptus grandis , Eucalyptus camaldulensis , Eucalyptus saligna , Eucalyptus robusta ), except Eucalyptus maidenii that escaped attack because it was located outside the ecological range of the insect. The incidence and severity of L. invasa infestation was generally higher on clonal hybrids E. grandis  ×  E. camaldulensis than on E. grandis  ×  Eucalyptus urophylla . Research on host germplasms, L. invasa biology and ecology, impact of the pest infestation and possible control strategies are suggested to facilitate the development of sustainable management strategies.     

Local environmental correlates of variability in the organic soils of moorland and alpine vegetation,Mt Sprent,Tasmania

Abstract Data on soils, vegetation and environment were collected between 510 and 1050m a. s. l. on Mt Sprent, southwestern Tasmania, traversing the Gymnoschoenus sphaerocephalus sedgeland-alpine vegetation boundary. One or more of the following horizons were found in almost all soil pits (downwards from the surface to the bed rock) fibric peat, hemic peat, sapric peat, organic sand, sand and clay. Mean total soil depth, mean organic soil depth, mean humification of the soil surface horizon, pH and mean organic content of the surface horizon all decline with altitude, while the redness of the soil and the mean depth of the mineral and gravel layers increase. At four intensively studied sites at 620, 850, 930 and 1040 m the relationships between phytosociological, topographic and water-table variables, and soil characteristics were determined. The pH of the topsoil was significantly positively related to water-table depth at three sites, but there were no other relationships between local environmental variation and soil characteristics that were consistent between most of the four sites, despite a large number of locally significant relationships. The alpine and sedgeland soils differ most markedly in colour, number of horizons and degree of humification of the surface horizon. The vegetation at each site was separated into communities along a drainage gradient. The mesoscale differences in soils seem most likely to be attributable to a vegetation productivity gradient.     

Soil properties affect the availability, movement, and virulence of entomopathogenic fungi conidia against puparia of Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), is the major tephritid pest in the Mediterranean region. This insect may overwinter as pupae inside fruits or in soil. Therefore, infection with entomopathogenic fungi is a potentially useful control technique during the insect’s soil-dwelling stage. Entomopathogenic fungi have an important role in Integrated Pest Management programs as an alternative to conventional chemical control, but they have been usually selected on the basis of laboratory results with little regard to fungal ecology. In this work, we designed several experiments to study the availability and movement of the EF Beauveria bassiana (Balsamo) Vuill. and Metarhizium anisopliae (Metsch.) conidia in 16 soils differing widely in pH, texture, organic matter, and carbonate contents. Experiments of adsorption and drag of conidia by soil particles suspended in CaCl₂ solutions of different ionic strength showed B. bassiana conidia to be retained by clay particles, and this effect disappeared with increasing ionic strength. The availability of M. anisopliae conidia in the suspension tended to be lower for sandy than for clayey soils and was not influenced by ionic strength. Regardless of soil properties, over 90% of the added fungal propagules were recovered from the surface layer of columns of packed soils representing model combinations of texture (sandy or clayey) and pH values (acid or alkaline). However, retention of B. bassiana conidia in the surface layer was higher in clayey than in sandy soils, and the retention of M. anisopliae conidia in the surface layer was higher in sandy than in clayey soils. Finally, neither soil texture nor ionic strength affected the infectivity of conidia of both fungal strains to C. capitata puparia.     

Nutrient requirements of exotic tree species in Zimbabwe

Pot and field experiments were conducted in the greenhouse and at three field sites (Marondera, Domboshawa and Makoholi) in Zimbabwe to examine the effects of soils and fertilizers on nutrient uptake and growth of 6 exotic tree species (Eucalyptus camaldulensis, E. grandis, E. tereticornis, Leucaena leucocephala, Casuarina cunninghamiana, and Acacia holosericea). Plant growth, N and P contents of all species were increased by the application of N, P, K and micronutrient fertilizers. The effect of individual nutrients (N, P, K and micronutrients) and their combination on Eucalyptus species was further investigated in a pot experiment using soil from Domboshawa. Eucalyptus species responded only to N application and no significant interactions were found between N and the other elements. Nutrient uptake results showed that E. camaldulensis and E. tereticornis removed more cations than the N-fixing trees but only in the fertilized treatments. L. leucocephala and C. cunninghamiana were higher in P, but no clear trends were observed for N. Plant growth and nutrient uptake by E. camaldulensis. C. cunninghamiana and A. holosericea were assessed in the field at the three sites. Plant species grown in the Marondera site had greater height and diameter at breast height (DBH) than those in the two other sites. These results followed trends in soil nutrient contents. The analysis of foliage revealed differences in the nutrient concentration of leaves from different trees, but no effect of site was found. The interrelationships between plant characteristics, soil and foliage nutrients were examined. In a pot experiment, mineral N was the only variable correlated with growth response and nutrient uptake, while in the field the only significant correlation was obtained with soil pH.     

Estimating hydraulic conductivity of a sandy soil under different plant covers using minidisk infiltrometer and a dye tracer experiment

The objective of this study was to estimate the hydraulic conductivity of sandy soil under different plant cover at the locality Mláky II at Sekule (southwest Slovakia). Two sites were demarcated at the locality, with mainly moss species at glade site, and pine forest at forest site. The estimation of unsaturated hydraulic conductivity was conducted by (a) minidisk infiltrometer and (b) the analysis of a dye tracer total resident concentration. The latter approach assumed the applicability of the stochastic—convective flow theory in the sandy soil. In the dye tracer experiment, two plots (1 × 1 m each) were established in both sites, and 100 mm of dye tracer (Brilliant Blue FCF) solution was applied on the soil surface. Similar results were obtained in both plots, with more than 70 % area of horizons stained in the depth of 30–50 cm. In some cases, the predicted and measured hydraulic conductivity were found within an order of magnitude, thus revealing similar impact of different plant cover on hydraulic properties of sandy soil studied. In contrast to sandy soils used for agriculture, the influence of the plant/surface humus and topsoil interface extended in the form of a highly heterogeneous matrix flow to the depth of 50–60 cm, where it was dampened by horizontal layering.     

Sorption of dissolved organic matter by mineral soils of the Siberian forest tundra

Because of low net production in arctic and subarctic surface water, dissolved organic matter (DOM) discharged from terrestrial settings plays an important role for carbon and nitrogen dynamics in arctic aquatic systems. Sorption, typically controlling the export of DOM from soil, may be influenced by the permafrost regime. To confirm the potential sorptive control on the release of DOM from permafrost soils in central northern Siberia, we examined the sorption of DOM by mineral soils of Gelisols and Inceptisols with varying depth of the active layer. Water‐soluble organic matter in the O horizons of the Gelisols was less (338 and 407 mg C kg^?1) and comprised more dissolved organic carbon (DOC) in the hydrophobic fraction (HoDOC) (63% and 70%) than in the O horizons of the Inceptisols (686 and 706 mg C kg^?1, 45% and 48% HoDOC). All A and B horizons from Gelisols sorbed DOC strongly, with a preference for HoDOC. Almost all horizons of the Inceptisols showed a weaker sorption of DOC than those of the Gelisols. The C horizons of the Inceptisols, having a weak overall DOC sorption, sorbed C in the hydrophilic fraction (HiDOC) stronger than HoDOC. The reason for the poor overall sorption and also the preferential sorption of HiDOC is likely the high pH (pH>7.0) of the C horizons and the smaller concentrations of iron oxides. For all soils, the sorption of HoDOC related positively to oxalate‐ and dithionite–citrate‐extractable iron. The A horizons released large amounts of DOC with 46–80% of HiDOC. The released DOC was significantly (r=0.78, P<0.05) correlated with the contents of soil organic carbon. From these results, we assume that large concentrations of DOM comprising large shares of HiDOC can pass mineral soils where the active layer is thin (i.e. in Gelisols), and enter streams. Soils with deep active layer (i.e. Inceptisols), may release little DOM because of more frequent infiltration of DOM into their thick mineral horizons despite their smaller contents of reactive, poorly crystalline minerals. The results obtained for the Inceptisols are in agreement with the situation observed for streams connecting to Yenisei at lower latitudes than 65°50′ with continuous to discontinuous permafrost. The smaller sorption of DOM by the Gelisols is in agreement with the larger DOM concentrations in more northern catchments. However, the Gelisols preferentially retained the HoDOC which dominates the DOC in streams towards north. This discrepancy can be explained by additional seepage water from the organic horizons that is discharged into streams without intensive contact with the mineral soil.     

Acclimation of a dominant mangrove plant (<Emphasis Type="Italic">Kandelia candel</Emphasis>) to soil texture and its response to canopy shade

Kandelia candel, a dominant plant species in Hong Kong mangroves, had different growth strategies during its seedling stage for acclimation to various soil types. Leaves of the seedlings grown in sandy soils (coarse texture) were significantly thicker than those in loamy–sandy and silty soils (fine texture). However, leaf weight per unit leaf area of seedlings grown in sandy soils was similar to that in loamy-sandy soils and was 1.60 times that in silty soils. These indicate that K. candel in sandy soils had developed a more loose leaf structure and a xerophilous characteristic during its seedling stage for acclimation to the features of coarse textured soils, which were low water holding capacity and low mineral content. In addition, for young seedlings grown in sandy and loamy–sandy soils, more biomass was allocated to roots than in silty soils, indicating that K. candel seedlings in sandy soils developed stronger roots for anchorage and water absorption; another xerophilous characteristic to acclimate to loose and coarse textured soils. As the plants became more mature, no significant difference in leaf thickness of the saplings was found between loamy-sandy and sandy soils. In order to acclimate to the low water holding capacity in sandy soils, K. candel seedlings had lower physiological activities including lower chlorophyll content; lower activities of root oxidase, nitrate reductase, peroxidase and superoxide dismutase but higher malonaldehyde contents than those in silty soils. Canopy shade is an important factor affecting the growth and physiology of K. candel. The seedling grew worse under the mangrove canopy than that in the open gap, with smaller leaf area, specific leaf area, leaf number and biomass. The seedlings under the canopy eventually died and no saplings were found under canopy shade, implying K. candel is a shade intolerant species and canopy shade might force its newly recruited individuals to expand out of the forest.     

Infestation of Glycaspis brimblecombei (Hemiptera: Psyllidae) on three Eucalyptus species in selected ecological zones in Malawi

The study determined variations in incidence, severity and damage of Glycaspis brimblecombei among Eucalyptus species and ecological zones, and the interaction between Eucalyptus species and ecological zones. Additionally, the study determined variation in pest abundance between the upper, middle and lower parts of the tree crown. The study was conducted in six districts located in four ecological zones in Malawi. Eucalyptus stands established in 2014–2016 or coppices from trees cut in that period were sampled for G. brimblecombei infestation. A significant interaction was found between Eucalyptus species and ecological zones on G. brimblecombei infestation. Significant differences were observed between ecological zones in G. brimblecombei infestation with lowest incidence, severity and damage being found in the cooler ecological zone M. Eucalyptus camaldulensis and Eucalyptus tereticornis showed high susceptibility to G. brimblecombei compared to Eucalyptus grandis. There were no significant differences in abundance between the upper, middle and lower tree crown parts of each Eucalyptus species. Control efforts for this psyllid should focus on breeding and planting of resistant Eucalyptus varieties in specifically recommended sites. The uniform distribution of the pest on different tree crown parts implies that use of contact insecticides on a large scale would be tedious and expensive.     

Controls on microbial CO2 production: a comparison of surface and subsurface soil horizons

Although a significant amount of the organic C stored in soil resides in subsurface horizons, the dynamics of subsurface C stores are not well understood. The objective of this study was to determine if changes in soil moisture, temperature, and nutrient levels have similar effects on the mineralization of surface (0–25 cm) and subsurface (below 25 cm) C stores. Samples were collected from a 2 m deep unsaturated mollisol profile located near Santa Barbara, CA, USA. In a series of experiments, we measured the influence of nutrient additions (N and P), soil temperature (10–35°C), and soil water potential (?0.5 to ?10 MPa) on the microbial mineralization of native soil organic C. Surface and subsurface soils were slightly different with respect to the effects of water potential on microbial CO₂ production; C mineralization rates in surface soils were more affected by conditions of moderate drought than rates in subsurface soils. With respect to the effects of soil temperature and nutrient levels on C mineralization rates, subsurface horizons were significantly more sensitive to increases in temperature or nutrient availability than surface horizons. The mean Q₁₀ value for C mineralization rates was 3.0 in surface horizons and 3.9 in subsurface horizons. The addition of either N or P had negligible effects on microbial CO₂ production in surface soil layers; in the subsurface horizons, the addition of either N or P increased CO₂ production by up to 450% relative to the control. The results of these experiments suggest that alterations of the soil environment may have different effects on CO₂ production through the profile and that the mineralization of subsurface C stores may be particularly susceptible to increases in temperature or nutrient inputs to soil.     

Responses of forest eucalypts to moderate and high intensity fire in the Tingle Mosaic,south‐western Australia: comparisons between locally endemic and regionally distributed species

Responses of three locally endemic (Eucalyptus brevistylis, Eucalyptus jacksonii and Eucalyptus guilfoylei) and three co‐occurring regional eucalypts (Eucalyptus marginata, Eucalyptus diversicolor and Corymbia calophylla) to moderate‐ and high‐intensity fires were examined in granitic terrain of the Tingle Mosaic, south‐western Australia. Significant associations between diameter distributions and community type (CT) for each species (P < 0.001) suggest that fire response will also vary according to the habitat/fire interaction. None of the species were fire sensitive, although responses differed both within and between species, and with CT. All species examined predominately consisted of several cohorts of regeneration within a forest stand. Each species had thick bark and re‐sprouted from crown epicormics following 100% scorch of the mature tree. The quantity and type of regeneration in relation to gaps created by individual dead trees following fire differed between species; for example, E. guilfoylei regeneration was strongly associated with gaps, and C. calophylla with non‐gaps. However, regeneration of the two tall open‐forest species, E. jacksonii and E. diversicolor were not most associated with either gaps or non‐gaps. The very low levels of regeneration of E. brevistylis following fire and the high proportion of stems of E. jacksonii that were hollow butted (40% of stems > 1 m DBHOB) may be factors associated with narrow endemism of these species and may affect the vulnerability of these eucalypts to fire. The interaction of seed availability, intense fires and subsequent rainfall may be critical in the long term survival of these species. Eucalyptus guilfoylei, by contrast, appears well adapted to the increasing levels of disturbance likely in the region where these species occur. The vulnerability of a locally endemic species in a fire‐prone environment is likely to reflect differences to the prevailing adaptations of the dominant species rather than an inherent ability of the species to survive or respond. Management regimes must account for variations in species responses to fire in different CTs if the long‐term survival chances of local endemics are to be enhanced.     

Studies of a vegetation transect through brigalow (Acacia harpophylla) forest in central Queensland

Vegetation and environmental data were collected in 182 contiguous plots along a belt transect, 3.7 km long, in central Queensland through a relatively undisturbed forest dominated by brigalow (Acacia harpophylla). A subset of eighty-nine plots using percentage cover of 128 species was classified using a polythetic agglomerative approach. Dual stand and species ordinations by principal component analysis and reciprocal averaging were also undertaken. The cluster analysis and ordination of unstandardized cover data, grouped stands on the basis of abundance of the predominant canopy species, but only where these species were true dominants such as Macropteranthes leichhardtii did these same groupings appear in the ordination of standardized data. The latter ordination was ecologically more satisfying, but the complementary species ordination was unsatisfactory. The vegetation-species complex was best explained by dual species and stand ordinations using presence-absence data. Reciprocal averaging appeared to produce a marginally better ordination than principal component analysis. An ordination of eleven environmental factors indicated soil profile and presence of gilgai were the most important environmental variables. The ordination was enhanced by varimax rotation which focused on a more homogeneous environmental gradient and coincided more closely with the vegetation ordinations. An ordination using both species and environmental factors substantiated the explanation of the vegetation-environmental complex derived from separate ordinations. The main gradient revealed from the ordinations appeared to be a mesic-xeric gradient stretching from Macropteranthes leichhardtii semi-evergreen vine thicket at the mesic end diverging through various A. harpophylla - dominant communities to A. harpophylla - Eucalyptus melanophloia woodland on duplex soils and Dichanthium affine grassland on clay soils. Six plant communities are defined and described and each related to a particular set of environmental conditions. These communities are bonewood (Macropteranthes leichhardtii) - semi-evergreen vine thicket, brigalow (Acacia harpophylla) - semi-evergreen vine thicket, brigalow (A. harpophylla) continuum (clay soils), Dichanthium affine grassland, brigalow (A. harpophylla) continuum (duplex soils) and brigalow (A. harpophylla) - silver-leaved ironbark (Eucalyptus melanophloia) woodland.