Dry Sclerophyll Eucalypt Forest Research Articles

Fire Regime Has a Greater Impact Than Selective Timber Harvesting on Vegetation in a Sub-Tropical Australian Eucalypt Forest

We compared selectively harvested and unharvested areas located among treatments of annual burning since 1952, triennial burning since 1973 and an area that had received no prescribed burning, but with a single wildfire in 2006 (one fire in 72 years), in a dry sclerophyll eucalypt forest, south-eastern Queensland, Australia. Historic fire regime, rather than low-intensity, selective timber harvesting (17% to 37% live tree basal area removed) had a greater impact on a range of vegetation and soil attributes. Plant taxa composition was influenced more by historic fire regime than recent harvesting; of the 25.5% of the variation in taxa composition explained, fire treatments alone accounted for 96.4% of the explained variation and harvesting alone accounted for just 4.8%. Selective harvesting of timber had a predictable influence associated with removal of tree cover and physical impacts associated with extraction of logs. In harvested areas there were increases (p < 0.05) in bare-ground cover and in coarse woody debris volumes and decreases in understorey vegetation height, particularly where woody understorey was present. However, overall, the combined effects of timber harvesting and fire regime were relatively minor. These sub-tropical dry eucalypt forests appear to be resilient to the impacts of combined, but low-intensity disturbances.

Very frequent burning encourages tree growth in sub-tropical Australian eucalypt forest

Frequent fire often has a negative impact of tree recruitment and growth. Tree growth rates, density and recruitment were compared among treatments of annual burning since 1952, triennial burning since 1973 and no burning (1946 to 1996) or single wildfire (1996 to 2018), in a dry sclerophyll eucalypt forest, south-eastern Queensland, Australia. Tree diameter (at breast height, DBH) growth rates were greater in the annually burnt treatment than in the triennially burn and single wildfire treatments over the period from 1974 to 2018, and these differences were also apparent pre-wildfire (period from 1974 to 1996). In the period from 1996 to 2018, the annually burnt treatment had greater DBH growth relative to the single wildfire treatment, but the triennial treatment had intermediate growth rates. Competitive interactions between trees (assessed using plot basal area) also had a negative impact on individual tree growth rates. The impacts of different fire regimes at this site on tree crown health were not apparent (P > 0.05) and there was only limited evidence that differences in growth rates were due to differences in soil nutrients (marginally higher topsoil phosphorus in the frequently burnt treatments, P = 0.075). Greater tree growth rates in the annually burnt treatment may be related to the lower density of understorey woody plants in this treatment and potentially reduced competition for soil moisture. The density of trees (DBH ≥ 10 cm) in 2018 was surprisingly higher in the triennially burnt treatment (381 stems/ha) relative to both the annually burnt (192 stems/ha) and single wildfire (234 stems/ha) treatments. This was largely due a higher level of recruitment over time and a higher density of stems 10–20 cm DBH in triennially burnt plots. Concerns regarding the impacts of frequent prescribed fire on tree recruitment and growth may be unwarranted in these remarkably resilient dry eucalypt forests.

Exploring how fire spread mode shapes the composition of pyrogenic carbon from burning forest litter fuels in a combustion wind tunnel

In this study, solid state 13C nuclear magnetic resonance (NMR) spectroscopy was used to explore the carbon-containing functional groups present in pyrogenic carbon (PyC) produced during different fire spread modes to forest litter fuels from a dry sclerophyll eucalypt forest burnt in a combustion wind tunnel. A replicated experimental study was performed using three different fire spread modes: heading fires (i.e. fires which spread with the wind), flanking fires (i.e. fires which spread perpendicular to the wind) and backing fires (i.e. fires which spread against the wind). In addition to 13C NMR measurements of PyC, detailed fire behaviour measurements were recorded during experiments. Experiments showed that heading fires produced significantly more aryl carbon in ash samples than flanking fires. All other experimental comparisons for burnt fuel samples involving different fire spread modes were statistically insignificant. Principal component analysis (PCA) was used to explore the relationship between 13C NMR functional groups and fire behaviour observations. Results from PCA indicate that maximising the residence time of high temperature combustion and the combustion factor (i.e. the fraction of pre-fire biomass consumed by fire) could be a method for increasing the amount of aryl carbon in PyC. Maximising the amount of aryl carbon could be beneficial for the overall PyC balance from fire, since more recalcitrant carbon (e.g. carbon with a higher aryl carbon content) that is not emitted to the atmosphere has been shown to have longer residence times in environmental media such as soils or sediments.

Urbanisation-related land use change from forest and pasture into turf grass modifies soil nitrogen cycling and increases N<sub>2</sub>O emissions

Abstract. Urbanisation is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanisation influence ecosystem dynamics, making peri-urban environments more vulnerable to nutrient losses. Brisbane in South East Queensland has the most extensive urban sprawl of all Australian cities. This research estimated the environmental impact of land use change associated with urbanisation by examining soil nitrogen (N) turnover and subsequent nitrous oxide (N2O) emissions using a fully automated system that measured emissions on a sub-daily basis. There was no significant difference in soil N2O emissions between the native dry sclerophyll eucalypt forest and an extensively grazed pasture, wherefrom only low annual emissions were observed amounting to 0.1 and 0.2 kg N2O ha−1 yr−1, respectively. The establishment of a fertilised turf grass lawn increased soil N2O emissions 18-fold (1.8 kg N2O ha−1 yr−1), with highest emissions occurring in the first 2 months after establishment. Once established, the turf grass lawn presented relatively low N2O emissions for the rest of the year, even after fertilisation and rain events. Soil moisture was significantly higher, and mineralised N accumulated in the fallow plots, resulting in the highest N2O emissions (2.8 kg N2O ha−1 yr−1) and significant nitrate (NO3−) losses, with up to 63 kg N ha−1 lost from a single rain event due to reduced plant cover removal. The study concludes that urbanisation processes creating peri-urban ecosystems can greatly modify N cycling and increase the potential for losses in the form of N2O and NO3−.

Assessment of Forest Structure Using Two UAV Techniques: A Comparison of Airborne Laser Scanning and Structure from Motion (SfM) Point Clouds

This study investigates the potential of unmanned aerial vehicles (UAVs) to measure and monitor structural properties of forests. Two remote sensing techniques, airborne laser scanning (ALS) and structure from motion (SfM) were tested to capture three-dimensional structural information from a small multi-rotor UAV platform. A case study is presented through the analysis of data collected from a 30 × 50 m plot in a dry sclerophyll eucalypt forest with a spatially varying canopy cover. The study provides an insight into the capabilities of both technologies for assessing absolute terrain height, the horizontal and vertical distribution of forest canopy elements, and information related to individual trees. Results indicate that both techniques are capable of providing information that can be used to describe the terrain surface and canopy properties in areas of relatively low canopy closure. However, the SfM photogrammetric technique underperformed ALS in capturing the terrain surface under increasingly denser canopy cover, resulting in point density of less than 1 ground point per m2 and mean difference from ALS terrain surface of 0.12 m. This shortcoming caused errors that were propagated into the estimation of canopy properties, including the individual tree height (root mean square error of 0.92 m for ALS and 1.30 m for SfM). Differences were also seen in the estimates of canopy cover derived from the SfM (50%) and ALS (63%) pointclouds. Although ALS is capable of providing more accurate estimates of the vertical structure of forests across the larger range of canopy densities found in this study, SfM was still found to be an adequate low-cost alternative for surveying of forest stands.

Establishing turf grass increases soil greenhouse gas emissions in peri-urban environments

Urbanization is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanization influence ecosystem dynamics and how peri-urban environments contribute to climate change. Brisbane in South East Queensland (SEQ) currently has the most extensive urban sprawl of all Australian cities. This leads to substantial land use changes in urban and peri-urban environments and the subsequent gaseous emissions from soils are to date neglected for IPCC climate change estimations. This research examines how land use change effects methane (CH4) and nitrous oxide (N2O) fluxes from peri-urban soils and consequently influences the Global Warming Potential (GWP) of rural ecosystems in agricultural use undergoing urbanization. Therefore, manual and fully automated static chamber measurements determined soil gas fluxes over a full year and an intensive sampling campaign of 80 days after land use change. Turf grass, as the major peri-urban land cover, increased the GWP by 415 kg CO2-e ha−1 over the first 80 days after conversion from a well-established pasture. This results principally from increased daily average N2O emissions of 0.5 g N2O ha−1 d−1 from the pasture to 18.3 g N2O ha−1 d−1 from the turf grass due to fertilizer application during conversion. Compared to the native dry sclerophyll eucalypt forest, turf grass establishment increases the GWP by another 30 kg CO2-e ha−1. The results presented in this study clearly indicate the substantial impact of urbanization on soil-atmosphere gas exchange in form of non-CO2 greenhouse gas emissions particularly after turf grass establishment.

Quantity, composition and water contamination potential of ash produced under different wildfire severities

Wildfires frequently threaten water quality through the transfer of eroded ash and soil into rivers and reservoirs. The ability to anticipate risks for water resources from wildfires is fundamental for implementing effective fire preparedness plans and post-fire mitigation measures. Here we present a new approach that allows quantifying the amount and characteristics of ash generated under different wildfire severities and its respective water contamination potential. This approach is applied to a wildfire in an Australian dry sclerophyll eucalypt forest, but can be adapted for use in other environments.The Balmoral fire of October 2013 affected 12,694ha of Sydney's forested water supply catchment. It produced substantial ash loads that increased with fire severity, with 6, 16 and 34Mgha−1 found in areas affected by low, high and extreme fire severity, respectively. Ash bulk density was also positively related to fire severity. The increase with fire severity in the total load and bulk density of the ash generated is mainly attributed to a combination of associated increases in (i) total amount of fuel affected by fire and (ii) contribution of charred mineral soil to the ash layer. Total concentrations of pollutants and nutrients in ash were mostly unrelated to fire severity and relatively low compared to values reported for wildfire ash in other environments (e.g. 4.0–7.3mg Askg−1; 2.3–4.1 B mgkg−1; 136–154 P mgkg−1). Solubility of the elements analysed was also low, less than 10% of the total concentration for all elements except for B (6–14%) and Na (30–50%). This could be related to a partial loss of soluble components by leaching and/or wind erosion before the ash sampling (10 weeks after the fire and before major ash mobilisation by water erosion).Even with their relatively low concentrations of potential pollutants, the substantial total ash loads found here represent a water contamination risk if transported into the hydrological network during severe erosion events. For example, up to 4Mg of ash-derived P could be delivered into a single water supply reservoir.

Repeated fuel reduction burns have little long-term impact on soil greenhouse gas exchange in a dry sclerophyll eucalypt forest

Fuel reduction burning is a widespread management tool in fire-tolerant forest systems to mitigate wildfire risk, but has the potential to impact soil greenhouse gas exchange processes. Soil disturbance often alters soil carbon dioxide (CO2) and methane (CH4) flux; however, the influence of repeated fuel reduction burning upon these flux processes long-term is still not well understood. In this study we measure soil CH4 flux, soil methanotrophic activity and soil CO2 flux in all seasons from March 2009 to February 2011 in three different fire frequency treatments applied to a dry sclerophyll eucalypt forest (Victoria, Australia) for the last 27 years. The low-intensity fire treatments are forest burnt in autumn (i) every 3 years, (ii) every 10 years, and (iii) not burned (since before 1985). Mean soil CO2 emissions were greater in the burnt as compared to un-burnt treatments. In contrast, soil CH4 oxidation did not show a response to repeated burning and there was no statistical difference in soil CH4 flux among treatments. Furthermore, we did not detect changes in the relationships of soil CH4 flux or soil CO2 flux and key environmental controls. Our results indicate that low intensity fuel reduction burns have no cumulative negative impact on biogeochemical processes related to soil respiration or soil CH4 oxidation.

Resilience of a eucalypt forest woody understorey to long-term (34 - 55 years) repeated burning in subtropical Australia

We investigated the effects of annual burning since 1952, triennial burning since 1973, fire exclusion since 1946 and infrequent wildfire (one fire in 61 years) on woody understorey vegetation in a dry sclerophyll eucalypt forest, south-eastern Queensland, Australia. We determined the influence of these treatments, and other site variables (rainfall, understorey density, topsoil C : N ratio, tree basal area, distance to watercourse and burn coverage) on plant taxa density, richness and composition. The richness of woody understorey taxa 0–1 m in height was not affected by burning treatments, but richness of woody plants 1–7.5 m in height was lower in the annually burnt treatment than in the triennially burnt treatment from 1989 to 2007. Fire frequency and other site variables explained 34% of the variation in taxa composition (three taxon groups and 10 species), of which 33% of the explained variance was explained by fire treatment and 46% was explained by other site variables. Annual burning between 1974 and 1993 was associated with lower understorey densities mainly due to reduced densities of eucalypts 1–7.5 m in height. Triennial burning during the same period was associated with higher densities of eucalypts 0–7.5 m in height relative to the annually burnt and unburnt treatments. Most woody taxa persisted in the frequently burnt treatments through resprouting mechanisms (e.g. lignotuberous regeneration), and fire patchiness associated with low-intensity burning was also found to be important. Persistence of plants <1 m tall demonstrates the resilience of woody taxa to repeated burning in this ecosystem, although they mainly exist in a suppressed growth state under annual burning.

Decomposition of litter in a dry sclerophyll eucalypt forest and a Pinus radiata plantation in southeastern Australia

AbstractThis study of litter decomposition was part of an extensive project examining the partitioning of rainfall, the associated chemistry, and litterfall in a dry sclerophyll eucalypt forest and a Pinus radiata plantation in southeastern Australia. The eucalypt species studied were Eucalyptus rossii, E. mannifera and E. dives. The components tested were Pinus radiata needles, leaves of the three eucalypt species, and the bark of E. rossii and E. mannifera.During the first 16 weeks of the decomposition experiment there was a rapid decrease in the concentrations of potassium, magnesium, sodium and phosphorus; this was attributed to leaching. During this period, concentrations of nitrogen and calcium increased for most components. After this period, decomposition became the dominant process, during which the concentrations of most elements increased. By the end of the experiment there was, compared with the initial values, a marked reduction in concentrations of sodium, magnesium and potassium for all eucalypt and pine litter. Calcium concentrations increased through time, with eucalypt bark showing a mid‐period decline. Phosphorus concentrations decreased for the eucalypt leaves but increased substantially for the pine needles and the eucalypt bark. For all components of both the eucalypts and pines, total nitrogen concentrations rose consistently throughout the decomposition period. This was attributed to the formation of nitrogen‐substituted lignin, which was more resistant to decomposition than the other nitrogen‐containing compounds, as well as some nitrogen being stored in the micro‐organisms responsible for decomposition. Because of loss of fragmented litter from the litter bags after 16 weeks, the weight changes could not be confidently measured after this period. Copyright © 2002 John Wiley & Sons, Ltd.

Tree hollow development in wet and dry sclerophyll eucalypt forest in south-east Queensland, Australia

Summary Tree hollow development was studied in Eucalyptus pilularis (blackbutt) and Eucalyptus microcorys (tallowwood) in wet sclerophyll forests, and Eucalyptus signata (scribbly gum) in dry sclerophyll forest in south-east Queensland, Australia. In all three tree species hollow development appeared to be primarily initiated by fungal infection entering trees through dead branches and/or branch stubs rather than from fire scars. The process of hollow development appeared to commence when the trees were around 100 years old. The size and abundance of hollows increased with the size and age of the tree but there were apparent differences between species. Hollows were found in the majority (>50%) of E. pilularis trees above 100 cm dbh. By contrast most E. microcorys and E. signata larger than 80 cm dbh had hollows. There was a similar difference between species in the numbers of hollows present in trees of different size. E. pilularis trees 100–110 cm dbh had two hollows per tree but this number were present in much smaller E. microcorys or E. signata trees. The rate of growth of E. pilularis is faster than either E. microcorys or E. signata and the rate of hollow formation appears to be dependent on the growth rate of the species. This suggests that hollows begin to develop after comparable times in the different species although the time taken for large hollow development differs between the species. The analyses suggest that the smallest arboreal marsupials and hollow dependent birds could recolonise regrowth E. pilularis trees after about 165 years but hollows suitable for larger animals would not be available for around 210 years. This time frame would be longer for slower growing species of trees. Some of the implications of this work in connection with management practices that aim to ensure the maintenance of hollow-dependent fauna in these forests are discussed.

Effects of three short rotation prescribed fires in spring on surface-active arthropods in dry sclerophyll eucalypt forest of west-central Victoria

Summary The effects of three prescribed low intensity fires varying from means of 80 to 209 kWm−1 within six years on invertebrates in litter/upper soil were assessed. The 8.6 year study was based on 88 934 arthropod specimens, representing 35 ordinal or lower level taxa contained in 3520 pitfall trap samples from a site burnt three times in spring and an unburnt control site within a 30.7 ha area. The three fires had no discernible effect on total taxa, total non-insects, Araneae (spiders), Acarina (mites), Collembola (springtails), total insects and Formicidae (ants), although activity of the Coleoptera (beetles) decreased significantly after the second and third fires while that of the Diptera (flies) increased over the same period. However, as Coleoptera and Diptera activity on the unburnt control site decreased and increased respectively over the same period, it is uncertain whether the changes in activity were due to the fires or other non fire-related environmental factors. Futhermore, these changes in activity resulted from one or two of the spring fires only, and not all three, further questioning whether the fires were the contributing causal factors. Three prescribed low-intensity fires in spring appear therefore, not to impact adversely on the activity of major forest litter arthropod groups, although the situation of the Coleoptera and Diptera is less clear due to similar activity on the unburnt control site in both cases. This therefore suggests that any fuel reduction burning in spring be conducted at intervals of not less than three years in order to minimize any impact on litter arthropods. Where a period of drought has occurred, burning should be delayed until the drought period has ended.

Effects of two short rotation prescribed fires in autumn on surface-active arthropods in dry sclerophyll eucalypt forest of west-central Victoria

The effects of two prescribed low intensity fires (from 73 to 123 kW m −1) within 5 yrs on invertebrates in litter/upper soil were assessed. The 7.8-yr study was based on 98 159 arthropod specimens representing 34 ordinal or lower level taxa contained in 3200 pitfall trap samples from a twice burnt site and an unburnt control site within a 29.9 ha area. The two fires had no discernible effect on total insects, Araneae (spiders), Coleoptera (beetles) and Diptera (flies), though activity of total arthropods and total non-arthropods decreased significantly after the first fire due largely to Collembola (springtails), although within 5 yrs, the activity of these groups had recovered to prefire levels. However, there was no change in activity in these three groups following the second fire, leaving the question open as to whether fire was the cause for the change following the first fire. The activity of Formicidae (ants) increased and Dermaptera (earwigs) decreased following the second fire although effects other than fire are believed to be the cause. As the increase in Formicidae and decrease in Collembola and Dermaptera activity were confined to a single postfire period only, it is not possible to determine whether or not these changes were fire-related. Two consecutive fires in autumn appear to have a minimal effect on activity of major arthropod groups in the forest litter layer. The interval of prescribed fires in autumn should be not less than 5 yrs. Further research is required on families and species comprising the major arthropod groups before precise prescriptions on fire frequency can be formulated. In forest where protracted drought has supervened, a second burn should be delayed until the drought has broken.

Litterfall, litter and associated chemistry in a dry sclerophyll eucalypt forest and a pine plantation in south-eastern Australia: 2. Nutrient recycling by litter, throughfall and stemflow

This paper concerns recycling of the major nutrients (N, P, Ca, Mg, Na and K) by litterfall, throughfall and stemflow in a dry sclerophyll eucalypt forest and a nearby Pinus radiata plantation of similar tree density and basal area. With the exception of Mg, the concentration of these nutrients in eucalypt leaf-fall were substantially higher than in pine needlefall. The eucalypt nutrient input was greater owing to larger mass of litterfall, as well as higher concentrations. There were inverse relationships between N and P concentrations and amount of leaf-fall for the eucalypts and needlefall for the pines. Mg was positively correlated with eucalypt leaf-fall. For the other components and elements the relationships were random. The proportion of particular nutrients recycled by litterfall, and throughfall and stemflow, varied for both forests. For Ca, only 6 and 12%, for eucalypts and pines respectively, was recycled by throughfall and stemflow, compared with 52 and 68% of potassium. The amount of nitrogen recycled differed between the forests, in a way that was consistent with the eucalypts being native to a nitrogen-poor environment. Amounts of floor-litter collected in the eucalypt forest from two fairly distinct layers, the loose and cohesive litter, were similar. The concentrations of Mg and Na were similar in both layers, but the other elements varied substantially. The N concentration of the cohesive litter was more than double that of the loose layer, whereas its P concentration was only 10% of the loose layer value. Selected chemical analyses on the total tree biomass of the eucalypt forest showed that the concentration of elements increased in the order; wood, twigs, fine twigs and leaf, and from large diameter wood to fine twigs. However, the concentration in fine twig and leaf components varied between the elements. For Ca, P and K, the fine twig values were greater than the leaf values, but the reverse applied to the other elements. The concentrations of almost all elements in all components were substantially higher in Eucalyptus mannifera than in E. rossii, E. macrorhyncha and E. melliodora. The nutrient content of the floor-litter was compared with the twig, fine twig and leaf components of the live biomass, i.e. the components most likely to become readily decomposable floor-litter. For all elements except N, the amount in floor-litter was similar to the amount in the biomass components. This was because the concentration of N in the floor-litter was much greater than in these components of the biomass. © 1998 John Wiley & Sons, Ltd.

Litterfall, litter and associated chemistry in a dry sclerophyll eucalypt forest and a pine plantation in south-eastern Australia: 1. Litterfall and litter

Litterfall was measured in a dry schlerophyll eucalypt forest and a nearby Pinus radiata plantation of similar tree density and basal area near Canberra in south-eastern Australia. Total annual litterfall for the eucalypts was 329 g m−2, compared with 180 g m−2 for the pines, with the bark component being 52 g m−2 for eucalypts and zero for pines. Barkfall did not occur for the eucalypts during the drought of 1982–1983 but complete bark shedding occurred during the subsequent very wet year when barkfall was 177 g m−2 for Eucalyptus rossii and 146 g m−2 for Eucalyptus mannifera (9·3 and 7·6 g m−2 of basal area, respectively). Barkfall of E. rossii responded to rainfall in the period autumn to early summer, whereas E. mannifera responded to summer rainfall. In the eucalypt forest floor-litter was stratified into a surface layer where the components were substantially intact, and a cohesive layer where the components were fragmented and bound together by fungal hyphae. The amount and residence times of loose and cohesive floor-litter were 1056 g m−2 and 3·2 years, respectively, for the loose litter layer; and 1164 g m−2 and 3·5 years for the cohesive layer. The litter biomass represented 17% of the estimated total above-ground biomass of 127 tonnes ha−1. A previous study showed roots to be 25% of total biomass, suggesting a total biomass of 167 tonnes ha−1. © 1998 John Wiley & Sons, Ltd.

Estimation of interception capacity of the forest floor

Methods of measuring interception capacity of the understorey (grasses) and litter layer have been developed to estimate the forest floor interception capacity of a 15-year-old Pinus radiata plantation and a native dry sclerophyll eucalypt forest at Lidsdale State Forest, Australia. In this study, interception by various types of forest floor have been measured in the laboratory using a technique of applying artificial rain to undisturbed samples of the forest floor. These laboratory experiments separately measure the interception storage capacity of the pine needle mat, the leaf/twig/bark debris mat in the eucalypt forest, and of the understorey (grasses). The results indicate that the interception storage capacity of all components of the forest floor of both vegetation types were proportional to the mass per unit area of forest floor cover. It was also shown that the interception storage capacity of the pine needle mat and the leaf/twig bark debris mat under eucalypt were proportional to the thickness of the surface debris. For standing grasses the capacity was proportional to the percentage of ground cover. These laboratory results were then used to estimate the forest floor interception storage capacity of two experimental catchments each covered by one of the two forest types. In each case the forest floor was extremely heterogeneous, and so a large number of undisturbed samples were examined. Approximate forest floor interception capacity of the pine catchment was 2.8 mm and of eucalypt was 1.7 mm. The contribution of leaf litter, stem and branch litter, and grass vegetation to the overall interception capacity was similar for both catchments at 47%, 8% and 45%, respectively.

Effects of two spring prescribed fires on epigeal Coleoptera in dry sclerophyll eucalypt forest in Victoria, Australia

The cumulative effects of two low-intensity prescribed fires, applied within 3 years during spring (15 October 1985 and 3 November 1988), were assessed on families and species of surface-active Coleoptera (beetles) in litter of dry sclerophyll mixed eucalypt forest over a 5.7 year period between 26 March 1985 and 26 November 1990. The study was based on 13925 adult specimens, representing 31 families and 105 species, of which 70 species (66.7% of total) are undescribed. The most commonly trapped ‘major’ families were the predominantly predatory Staphylinidae and the decomposer/fungus feeding Nitidulidae and Leiodidae. The specimens were contained in 2240 pitfall trap samples collected from a burnt and an unburnt (‘control’) site adjacent to each other within a 30.7 ha study area. The two fires had no discernible cumulative effect on the activity of the Nitidulidae, the Leiodidae, the pool of 28 rarely trapped ‘minor’ families and the totals of decomposers/fungus feeders. However, short bursts in activity occurred among the first three of these taxa/groups during periods between the two fires. In contrast, activity of the Staphylinidae, the most abundant of all taxa trapped, declined significantly after the second fire relative to pre-first fire levels. This trend accounted for the observed reductions in activity of total Coleoptera, of total predators and of the proportions of Coleoptera in total arthropods. Family and species richness of the Coleoptera remained unchanged following the fires. An undescribed fungus-feeding lathridiid ( Aridius sp.) incurred a short upsurge in activity after the second fire. As only activity (and not diversity and taxon richness) of the Staphylinidae was affected by the fires, it is expected that they will return to pre-fire activity levels when the forest recovers in the absence of further fires. Two short-rotation low-intensity spring fires can therefore be applied in the forest type studied without causing unacceptable adverse impacts on litter-frequenting Coleoptera.

Coleoptera in litter of dry sclerophyll eucalypt forest and the effects of low-intensity prescribed fire on their activity and composition in west-central Victoria

Surface-active Coleoptera (beetles) were monitored in dry sclerophyll mixed eucalypt forest of west-central Victoria near Daylesford, and the effects of a one-off low-intensity prescribed fire appl...

Effects of two short rotation prescribed fires in spring on surface-active arthropods and earthworms in dry sclerophyll eucalypt forest of west-central Victoria

Summary The effects of two prescribed low intensity fires (from 137 to 209 kWm−1) within three years on invertebrates in litter/upper soil were assessed in dry sclerophyll eucalypt forest near Daylesford in west-central Victoria. The 5.9 year study was based on 65 210 arthropod specimens representing 34 ordinal or lower level taxa contained in 2 300 pitfall trap samples, and on in situ counts of earthworms (Annelida) in 2 120 litter/upper soil samples, from a twice burnt site and an unburnt “control” site within a 31.3 ha area. The two fires had no discernible effect on total arthropods, total non-insects, total insects and total arthropod decomposers, though activity of total predators increased significantly after the second fire due largely to the Dermaptera (earwigs). A reduction in activity, up to one year, was recorded after each fire for the commonly trapped Collembola (springtails). Earthworm populations also declined substantially, but recovered to “control” levels within three years of each fire. Activity of the Coleoptera (beetles) was significantly lower after the second fire compared with the first, but there was no difference in activities after the first and second fires relative to the respective pre-fire levels. The Diptera (flies) recorded a drop in activity during winter following the first fire only, and effects other than fire are believed to be the cause. As Collembola and earthworms are major decomposers of forest litter, it appears that two consecutive fires in spring may interrupt the decomposer cycle for up to three years. The effect of fire on the Coleoptera remains uncertain, as levels of activity had declined simultaneously on both the burnt and “control” sites, and it is not known whether this trend was caused by many or few beetle taxa. The practical implications of the results are that any fires prescribed in spring should be applied at intervals of more than three years (and outside protracted drought periods), to minimise adverse effects on the general invertebrate fauna, and on Collembola and earthworms in particular, within litter/upper soil of the type of dry sclerophyll eucalypt forest studied.

Effect of superphosphate addition on N mineralization in some Australian forest soils

Pinus radiata stands are reported to accumulate increased N on addition of phosphatic fertilizers. Field and laboratory studies were initiated to determine if addition of superphoshate increases soil N mineralization in forest soils. In a field experiment, application of 200 kg P ha-1 as superphosphate to trenched plots in a Pinus radiata stand increased accumulated soil mineral-N contents by 122% and 82% above the control on two occasions. Application of 500 kg P ha-1 as superphosphate either alone or in combination with lime (10 Mg ha-1) increased in situ soil net N mineralization in a dry sclerophyll eucalypt forest from 20.7 (control) to 28.3 (+P) and 30.2 (+P+lime) kg N ha-1 yr-1 20 cm-1. Uptake by the vegetation accounted for all of the mineralized nitrogen. In a 180 day laboratory incubation using undisturbed soil columns (0-20 cm) from nine forest sites, seven soils showed a positive response to superphosphate (100 kg P ha-1) addition, with increases in N mineralization ranging from 14% to 117%. The response of N mineralization to superphosphate addition was not related to initial soil organic C, total N or P content in the 0-20 cm layer. However, soil pH and organic C combined to account for 76% of the variation in N mineralization response (P < 0.01). In the 0-5 cm layer of untreated soils, soil organic P content could explain 71% of the variation in net N mineralization. Addition of superphosphate appears to increase N mineralization in several Australian forest soils and the improved availability of N will enhance tree growth rates. The mechanisms underlying the response are still poorly understood and thus also our ability to predict its significance for tree nutrition on specific forest sites.