Annual Fire Research Articles

Integrated shrub management in semi-arid woodlands of eastern Australia: effects of chemical defoliants applied after an initial disturbance

Previous fire experiments using artificial fuel have shown that annual fires, especially those applied in the autumn, can effectively control coppicing understorey shrubs in semi-arid woodlands. Such frequent fire is impossible to apply under natural conditions given the limited time available for sufficient herbage fuel to accumulate. Preliminary screening studies were therefore undertaken to test the hypothesis that chemical sprays applied at concentrations less than those normally recommended could be used to mimic high-frequency experimental fires. The effectiveness of 11 chemicals (7 arboricides and 4 dessicants) applied at a range of concentrations was assessed on one site by spot-spraying 5-year-old coppice regeneration of Eremophila mitchellii (budda or false sandalwood) and E. sturtii (turpentine). Chemical activity was assessed by regularly monitoring leaf effect, i.e. by rating the degree of leaf discolouration, scorching, blackening and ultimately leaf fall, over the ensuing 12 months following treatment. Arsenal� and Roundup CT� induced the highest shrub mortalities across all size classes while mortality rates were consistently higher for E. mitchellii than for E. sturtii. A second experiment involved 5 chemicals (4 arboricides and 1 dessicant) applied in a similar manner to 7-year-old seedlings of Cassia nemophila (syn. Senna nemophila) (punty bush). Significant damage to foliage (> 80% leaf effect) of all 3 shrub species was recorded 2 months after treatment with either Roundup CT� or Roundup� (i.e. either 450 or 360 g/L glyphosate respectively), as well as with Arsenal� (250 g/L imazapur + 60 g/L isopropylamine) but only at the highest concentration (i.e. 100% of the 'recommended' rate). In some lower concentration treatments, leaf effect was still increasing 6 months after treatment. In a second series of screening experiments involving 1- and 2-year-old coppices sprayed in autumn and spring, significant interaction occurred between coppice age and season of spraying when averaged over both Eremophila species. At lower concentrations (i.e. 12.5 and 25% of maximum recommended rate), autumn application of Roundup CT� was more effective than spring application, especially once regeneration was 2 years old. Gramoxone� was also most effective at all rates above 12.5% of the maximum when applied in the autumn to two-year-old coppice. However, Garlon� (600 g/L triclopyr) and Tordon 50-DA(r) (50 g/L picloram + 200 g/L 2,4-D) were more effective when applied to 1-year-old coppice in the spring. Overall, the most effective low-concentration treatment was Roundup CT� applied in the autumn to two-year-old coppice. Low-concentration treatment of one-year-old coppice with Roundup CT� and Arsenal� was also consistently more effective when carried out in the autumn (80–90% leaf effect). The probability of shrub mortality was inversely related to coppice biomass with smaller coppices clearly more vulnerable to the added pressure imposed by secondary chemical treatment, independent of application rate.

Arthropod responses to experimental fire regimes in an Australian tropical savannah: ordinal‐level analysis

AbstractFire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long‐term effect on ordinal‐level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal‐level resilience also occurs in Australia’s tropical savannahs. The data are from a multidisciplinary, landscape‐scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15–20 km2 compartments subjected to one of three fire regimes, each with three replicates: ‘early’ (annual fires lit early in the dry season), ‘late’ (annual fires lit late in the dry season), and ‘unburnt’ (fires absent during the five‐year experimental period 1990–94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated‐measures ANOVA. There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass‐layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal‐level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia.

The effect of fire on the diversity and abundance of wood-living beetles in a miombo woodland, Tanzania

SYNOPSIS Weekly sampling was carried out using window flight traps for three and a half successive years, between 1995–1998 to determine the effects of annual fires on the occurrence, abundance, and diversity of wood-living beetles in a miombo woodland at Kitulangalo, Morogoro, Tanzania. A total of 9515 specimens representing 78 species in 19 families were trapped, 4617 in burnt areas, and 4898 in unburnt areas. Most species were recorded in all seasons except 10 that occurred only during the dry season. Overall species diversity and abundance were not significantly different (p<0,05) between burnt and unburnt sites, though abundance was slightly higher in unburnt areas. Conversely species diversity was slightly higher in burnt areas. Five of the 10 most common insect species showed significant population abundance differences (p<0,05) between burnt and unburnt areas. Three insect species namely, Aneurihinu nigrosinuatus (Anthribidae), Chrysobothris dorsata (Buprestidae), and Heterobostrychus brunneus (Bo...

Methane uptake by a selection of soils in Ghana with different land use

We measured the oxidation of atmospheric methane in tropical soils in Ghana covering a moisture gradient from the moist forest zone to the savanna zone at the onset of the rainy season. Land use at the sites covered undisturbed (forest and savanna) and cultivated soil, including burning. Generally, the methane oxidation rates in the tropical forest and savanna soils were low (range from 9 to 26 μg CH4 m−2 h−1) compared to, for example temperate forest soils. In the savanna soil, annual fire had decreased soil methane oxidation rates to 5 μg CH4 m−2 h−1 compared to 9 μg CH4 m−2 h−1 at a site not subjected to fire for 6 years. In paired sites of moist forest and arable soils, methane oxidation rates were lower by &gt;60% in the arable soils. Methane oxidation rates in three arable soils in the savanna zone soils ranged from 7 to 11 μg CH4 m−2 h−1 before the first rain but increased to 23–28 μg CH4 m−2 h−1 after the rain. These rates are comparable to other reports from arable soils in tropical and temperate regions. Thus arable agriculture and, to a lesser extent, biomass burning decreased methane oxidation rates by the investigated soils.

Defining grassland fire events and the response of perennial plants to annual fire in temperate grasslands of south-eastern Australia

Many species-rich Themeda triandra grasslands in south-eastern Australia have been burnt annually in summer as a land management practice for decades. The characteristics of annual fires (maximum surface temperatures, maximum soil temperature changes at 10 mm depth, Byram fire intensity and duration of surface heating) were compared to fires that occur less frequently (2, 4 or 7-year inter-fire interval). The impacts of annual summer fires on seed survival, perennial plant dynamics and flowering were also documented at two sites over two years.

GRAZING OPTIMIZATION AND NUTRIENT CYCLING: POTENTIAL IMPACT OF LARGE HERBIVORES IN A SAVANNA SYSTEM

Using a model, we test the prediction that herbivory can result in grazing optimization of primary production in a nitrogen-limited system where large losses of nitrogen occur in annual fires. The model is based on the nitrogen budget of the humid savanna of Lamto, Ivory Coast, estimated from field data. At present, the ecosystem contains few herbivores, but buffalo and kob populations are increasing. We show that grazing optimization through recycling of nitrogen would occur at Lamto in the short term (i.e., several decades) if the percentage of nitrogen lost from the system out of the amount ingested by herbivores is <24%, and in the long term (i.e., several centuries) if it is <19%. When 25% of nitrogen is lost by herbivores, primary production is maintained at a high level up to very high consumption rates. Because losses due to herbivores are likely to be lower than these values in this particular ecosystem, we conclude that grazing optimization is likely to occur in the Lamto savanna.

Preventing Halloween arson in an urban setting: a model for multisectoral planning and community participation.

Arson is a violent crime and a public health problem that causes injuries and deaths, destroys homes, and destabilizes neighborhoods. During the late 1970s, pre-Halloween pranks in Detroit, Michigan, turned destructive when hundreds of fires were set deliberately throughout the city; in 1984, a record of 810 fires were set during the Halloween period. In 1985, a city wide anti-arson campaign that involved the mobilization and training of thousands of community volunteers was begun in Detroit. This report describes the multiple components of the anti-arson intervention from 1985 through 1996 and changes in the incidence of Halloween fires. Both the decrease in annual Halloween arson fires after the intervention began and the inverse relationship between the number of volunteers and the number of fires suggest a causal effect. This study illustrates the capacity of an urban community to mobilize its residents and stakeholders, the importance of community participation and multisectoral partnerships in program planning and implementation, and the challenges faced in retrospectively evaluating an apparently successful, complex, community-based intervention.

Pollen and charcoal in lake sediments compared with historically documented forest fires in southern Switzerland since AD 1920

Charcoal in unlaminated sediments dated by 210Pb was analysed by the pollen-slide and thin-section methods. The results were compared with the number and area of forest fires on different spatial scales in the area around Lago di Origlio as listed in the wildfire database of southern Switzerland since AD 1920. The influx of the number of charcoal particles &gt; 75 µm2 in pollen slides correlates well with the number of annual forest fires recorded within a distance of 20-50 km from the coring site. Hence a size-class distinction or an area measurement by image analysis may not be absolutely necessary for the reconstruction of regional fire history. A regression equation was computed and tested against an independent data set. Its use makes it possible to estimate the charcoal area influx (or concentration) from the particle number influx (or concentration). Local fires within a radius of 2 km around the coring site correlate well with the area influx of charcoal particles estimated by the thin-section method measuring the area of charcoal particles larger than 20 000 µm2 or longer than 50 µm. Pollen percentages and influx values suggest that intensive agriculture and Castanea sativa cultivation were reduced 30-40 years ago, followed by an increase of forest area and a development to more natural woodlands. The traditional Castanea sativa cultivation was characterized by a complete use of the biomass produced, so abandonment of chestnut led to an increasing accumulation of dead biomass, thereby raising the fire risk. On the other hand, the pollen record of the regional vegetation does not show any clear response to the increase of fire frequency during the last three decades in this area.

FIRE, N AVAILABILITY, AND PLANT RESPONSE IN GRASSLANDS: A TEST OF THE TRANSIENT MAXIMA HYPOTHESIS

In tallgrass prairie, periodic spring fires often result in enhanced aboveground net primary productivity (ANPP) that exceeds the productivity of either annually burned or unburned sites. This study evaluated two alternate hypotheses for the “pulse” in productivity following an infrequent fire: (1) enhanced ANPP results from increased net N mineralization rates due to the removal of surface litter and elevated soil temperatures following fire (the enhanced mineralization hypothesis) or (2) enhanced ANPP results from a transient release from both light and N limitation during a nonequilibrium period as a switch from energy to N limitation occurs (the transient maxima hypothesis). The former hypothesis predicts greater N availability following an infrequent fire, relative to either annually burned or unburned prairie. The latter predicts that N availability following an infrequent fire will decline to intermediate levels, relative to unburned and annually burned prairie, and continue to decline with successive annual fires. To test these hypotheses, I measured inorganic soil N, net N mineralization rates, and plant productivity and N content at Konza Prairie in sites with several different burn histories (unburned, annually burned, infrequently burned). Inorganic soil N and cumulative net N mineralization rates were greatest on the unburned sites, lowest in annually burned sites, and intermediate in infrequently burned sites. Net N mineralization rates and plant tissue N content both declined with successive spring burning. These results did not support the enhanced mineralization hypothesis but indicated that enhanced ANPP following an infrequent fire resulted from an accumulation of inorganic and mineralizable N in the absence of fire which, under conditions of adequate light availability, was utilized following a spring fire. This is consistent with the transient maxima hypothesis and suggests that nonequilibrium responses to multiple, variable resources (light, energy, N) are an important aspect of tallgrass prairie ecosystem dynamics.

97/04342 Availability of the Fire Clay (Hazard No.4) coal in part of the Eastern Kentucky Coal Field: Grab, S. F. et al. Proc. Annu., Int. Pitsburgh. Coal Conf., 1996, 13, (1), 198–203

The Fire Clay (Hazard No. 4) coal is one of the most heavily mined beds in the Eastern Kentucky Coal Field, which is part of the Appalachian Basin. Available resources for the coal were calculated for an area of 15 7.5-minute quadrangles that accounts for 43% of current annual Fire Clay coal production. This study differs from previous coal-availability studies in t hat a single coal bed was analyzed across several 7.5-minute quadrangles rather than multiple coals in a single quadrangle being analyzed. Original Fire Clay coal resources for the study area are estimated at 1.7 billion tons (Bt). Coal mined or lost in mining is estimated at 449 million tons (Mt), resulting in 1.3 Bt of remaining Fire Clay resources. Of the remaining resources, 400 Mt are restricted from mining, mostly because of coal considered too thin (less than 28 in., 71 cm) to economically mine with present market conditions and mining technology. The total coal available for mining in the study area is 911 Mt or 51.7% of the original resource. Of the 911 Mt, 75% is less than 42 inches (1.06 m) in thickness, and most of this resource is below drainage.

Natural regeneration potential and early development of Shorea robusta Gaertn.f. forest after regeneration felling in the Bhabar-Terai zone in Nepal

In Nepal, the natural Shorea robusta (local name ‘sal’) dominated forests have been subject to selection felling, encroachment, uncontrolled grazing and annual forest fires for the past 30–50 years, and the forest cover has declined by about 1.3% per annum. The aim of this study was to obtain information on the natural regeneration potential of the Shorea robusta forests, when these forests are treated with different types of regeneration fellings, and when the areas are protected from grazing and forest fire. The study was conducted in a mature irregular ‘Moist Bhabar Sal’ forest. The main species were Shorea robusta, Terminalia tomentosa, Lagerstroemia parviflora, Sysigium cuminii and Ficus sp. The experiment consisted of three different regeneration felling methods: (1) regeneration felling with 75 sheltertrees ha −1; (2) regeneration felling with 25 sheltertrees ha −1; (3) regeneration fellings without sheltertrees. These areas were fenced and protected from fire and grazing. A control area was fenced and protected in the same forest. Bushes and advanced growth were cleaned from the harvested areas with only the smallest seedlings remaining (height less than 50 cm). The removal of Lantana camara and Eupatorium odoratum was done in the treated areas 14 months after the felling. Permanent plots were measured one growing season after the felling, and again 12 months later. The number of Shorea robusta seedlings was high after the felling, varying from 74500 to 91000 seedlings ha −1. During the dry period between the measurements, 4.2–10.2% of the seedlings died back, but an analysis of variance did not reveal any significant differences. The height development of the dominant 2000 seedlings ha −1 during the second growing season was the fastest in the area without sheltertrees (127 cm), and the lowest in the control area (81 cm). The results of the area without sheltertrees differed significantly from all the other treatments in Tukey's HSD test of means; other significant differences were not observed. Differences in diameter growth were more distinct than those for height; the growth in the area without sheltertrees was almost four times the growth in the control area. Significant differences were detected between all treatments, except between the areas where 25 and 75 sheltertrees were left. The die-back of Shorea robusta seedlings was not a problem in the treatment areas. Removal of old crop and protection led to the fast growth of already recruited seedlings.

Landscape characteristics of disturbed shrubsteppe habitats in southwestern Idaho (U.S.A.)

1. Abstract We compared 5 zones in shrubsteppe habitats of southwestern Idaho to determine the effect of differing disturbance combinations on landscapes that once shared historically similar disturbance regimes. The primary consequence of agriculture, wildfires, and extensive fires ignited by the military during training activities was loss of native shrubs from the landscape. Agriculture created large square blocks on the landscape, and the landscape contained fewer small patches and more large shrub patches than non-agricultural areas. In contrast, fires left a more fragmented landscape. Repeated fires did not change the distribution of patch sizes, but decreased the total area of remaining shrublands and increased the distance between remaining shrub patches that provide seed sources. Military training with tracked vehicles was associated with a landscape characterized by small, closely spaced, shrub patches. Our results support the general model hypothesized for conversion of shrublands to annual grasslands by disturbance. Larger shrub patches in our region, historically resistant to fire spread and large-scale fires because of a perennial bunchgrass understory, were more fragmented than small patches. Presence of cheatgrass (Bromus tectorum), an exotic annual, was positively related to landscape patchiness and negatively related to number of shrub cells. Thus, cheatgrass dominance can contribute to further fragmentation and loss of the shrub patch by facilitating spread of subsequent fires, carried by continuous fuels, through the patch. The synergistic processes of fragmentation of shrub patches by disturbance, invasion and subsequent dominance by exotic annuals, and fire are converting shrubsteppe in southwestern Idaho to a new state dominated by exotic annual grasslands and high fire frequencies.

Fine root biomass distribution and productivity patterns under open and closed canopies of tropical forest ecosystems at Kodayar in Western Ghats, South India

Standing crop, rates of production and distribution of very fine (≤ 1 mm), fine (> 1 − ≤ 3 mm) and coarse (> 3 mm) roots were estimated for one year (August 1993–August 1994) under open and closed canopies of Tropical forest ecosystems at Kodayar in the Western Ghats of India. In the moist deciduous forest very fine root biomass was significantly higher under the open canopies (309 g m −2) than in the closed canopies (222 g m −2). While in the semi-evergreen and evergreen forest ecosystems closed canopies (Site II: 318, Site III: 315 and Site IV: 275 g m −2) were comparatively higher in very fine root biomass than the open canopies (264, 278 and 239 g m −2). A similar trend was observed in the fine root productivity also. Under the closed canopies, total fine root standing crop biomass was significantly higher under the evergreen forest (1847–2021 g m −2) compared with others (1081 g m −2 and 1298 g m −2). Root production and standing crop biomass showed a seasonal pattern of maximum during the rainy season and minimum in the dry season. Necromass fraction ranged between 52–132 g m −2 and the maximum was in the dry period. Localized disturbances such as canopy openings contributed towards the reduction of fine root biomass. Due to the annual wild fire and the consequent grass community dominance in the moist deciduous forest (Site I), greater standing crop of very fine root biomass and net primary productivity was observed. Further, the study revealed that the fine root biomass and production increased significantly due to litter accumulation ( P < 0.05) and the soil moisture ( P < 0.01) at the ground level. The above results are discussed in the light of understanding the fragility of tropical forests and their management.

Fire Impact on Groundlayer Flora in a Sand Forest 1990-1994

-Groundlayer response to prescribed fire was monitored in a central Illinois sand forest between 1990 and 1994. The first of three annual fires resulted in a significant increase in richness and cover of herbaceous species, and a minor decrease in woody cover. Successive fires maintained or slightly increased herb richness and cover, but did not change woody cover. Before burning, the forest understory was dominated by dense shrubs (7489% cover) over a sparse herb layer (4-18% cover). After the first fire, herb cover increased over fourfold to 48-57%, and to 65-66% after the second fire. Fire nonsignificantly reduced woody cover by some 20%, primarily due to a reduction in Parthenocissus quinquefolia (Virginia creeper), but did not affect frequency of woody vegetation. Species richness increased over 50% after the first fire, from 6.2-7.0/M2 to 9.8-10.8/M2, due to the increased frequency of herbaceous, and especially annual, species. Most of the postfire increase in herbaceous cover was due to Eupatorium rugosum (white snakeroot), which increased from 3X higher than preburn levels. The alien biennial Alliaria petiolata was maintained in a reduced condition by repeated fires, but in the absence of fire doubled in cover every 2 yr, from 4.6% in 1990 to 8.6% in 1992 to 17.0% in 1994.

Fire and topographic effects on decomposition rates and N dynamics of buried wood in tallgrass prairie

Decay rates and N dynamics of wood in soils of annually burned and unburned tallgrass prairie were measured over a 3-y period. Wooden dowels were placed at upland, mid-slope and lowland sites in two annually burned and two unburned watersheds. After 3 y, an average of only 15% of initial wood mass remained in burned watersheds, while 34% remained in unburned watersheds. Topographic position also significantly affected decay rates, with dowels decaying faster in the shallow-soil, upland sites and slope sites than in the deep-soil, lowland sites. This pattern is opposite of that generally observed for plant productivity (i.e. greater at lowland sites compared to uplands), and suggests that the controls of belowground decomposition and plant productivity are dissimilar. Dowels in both burned and unburned watersheds showed significant increases in N concentration over 3 y. Topographic position did not affect N concentration in the residual dowel material. Burn treatment, however, did affect N concentration, with dowels decomposing in burned watersheds having a higher average N concentration (0.5% after 3 y exposure) than dowels in unburned watersheds (0.43%). Relatively rapid decay rates resulted in net release of N, despite increased N concentration in the residual material. Faster net N release on the annually burned watershed was due to faster mass loss, since there were no differences in the rate of increase in N concentration per unit mass lost. Surface soil temperatures on burned prairie following spring fire usually exceed those on unburned prairie. However, average monthly summer soil temperatures (May–August) at a 10 cm depth in burned and unburned plots during the study were not statistically different and could not explain decay rate differences. Additionally, one of our unburned watersheds was accidentally burned during the first year of the study. Surprisingly, there were no significant differences in rates of wood decay between that watershed and the other unburned watershed. This suggests that indirect effects of annual fire (i.e. changes in the composition of soil flora and fauna) may override the short-term effects of fire (i.e. changes in soil temperature and moisture) on belowground decomposition in tallgrass prairie.

Biomass and Density Responses in Tallgrass Prairie Legumes to Annual Fire and Topographic Position

Biomass and Density Responses in Tallgrass Prairie Legumes to Annual Fire and Topographic Position

Effect of annual fire on tallgrass prairie legumes (1996)

Total legume density was significantly higher in annually burned prairie (8.0 stems/m2) than in unburned prairie (3.0 stems/ m2). Densities of six species were higher (P<.05) in burned than in unburned prairie, whereas only one legume species decreased from annual fire. Total legume biomass did not differ between burned (11.3 g/m2) and unburned prairie (10.5 g/m2). Most legume species either are favored by fire or are fire tolerant, and their persistence in annually burned grassland suggests that they may play an important role in the nitrogen budget of tallgrass prairie.

Single-Tree Selection Silviculture Affects Cavity Resources in Mixed Deciduous Forests in Thailand

Thailand's forest ecosystems contain a diverse vertebrate fauna and >30% of the species are thought to use cavities in trees. Forest management practices may significantly alter cavity availability for hole-nesting vertebrates. The effects of single-tree selection systems, commonly used in Thailand, on tree cavity abundance have not been extensively studied in any forest ecosystem, and no studies have been conducted in Thailand. We measured the effects of single-tree* selection harvest on cavity availability in mixed deciduous forests. We compared tree and cavity densities in unlogged and logged forests (5 stands in each type) in Huai Kha Khaeng Wildlife Sanctuary (HKKWS) in western Thailand. Tree densities (t = 2.89, 8 df, P = 0.02), cavity-tree densities (t = 4.27, 8 df, P = 0.003), and cavity densities (t = 4.44, 8 df, P = 0.004) were greater in unlogged than in logged stands. Ninety-two percent of cavity trees were alive; dead trees were uncommon, probably because of annual ground fires. Alangium salviifolium, Lagerstroemia spp., and Vitex spp. were the taxa most likely to form cavities, accounting for >30% of all trees and 66% of the cavities in unlogged habitats. Logging reduced tree densities of Vitex spp., but did not affect tree densities of Lagerstroemia spp. or A. salviifolium, nor cavity densities in Lagerstroemia spp. and Vitex spp. However, logging reduced cavity densities in A. salviifolium. Single-tree selection cutting reduced cavity abundances in these mixed deciduous forests. Maintenance of cavity-forming species and leaving more large-diameter trees may be required to maintain habitat for cavity-dependent wildlife.

Mycorrhizas in the Kakadu region of tropical Australia

Bioassays were used to provide estimates of both the distribution and abundance of mycorrhizal fungus propagules in soils from mine sites and natural habitats in tropical Australia. These bioassays measured mycorrhizal formation by bait plants that were grown in intact cores of soil collected along a transect at each site. The mine sites included, had sparse, patchy or dense vegetation cover on waste-rock materials that would initially have been devoid of mycorrhizal fungus propagules. The natural habitats included eucalypt savanna sites which had been subjected to hot annual fires for 4 years or remained unburnt. Propagules of vesicular-arbuscular mycorrhizal (VAM) and ectomycorrhizal (ECM) fungi occurred in all sites, but were sporadically distributed in highly disturbed areas, where they were associated with patches of vegetation. Both the relative abundance and frequency of occurrence of inoculum of VAM and ECM fungi increased with vegetation cover in older disturbed sites. Propagules of VAM fungi were substantially more numerous in some mine site habitats with dense vegetation cover, than in adjacent natural habitats. The presence of substantial amounts of phosphorus, released from weathering rock, in mine waste rock materials may have reduced the requirement of plants for mycorrhizal associations during vegetation establishment in mine sites. In woodland sites, hot annual fires appeared to restrict ECM fungi to infrequent patches in the surface horizon, while ECM fungus inoculum was much more frequently detected in soil from the unburnt site. These fire regimes apparently had less effect on the distribution or quantity of VAM fungus inoculum.

Estimating australian forest fire danger under conditions of doubled carbon dioxide concentrations

The most appropriate indices with which to quantify Australian bushfire danger are the McArthur fire danger meters. These meters use meteorological information to produce a fire danger index that is directly related to the chance of a fire starting - and to the severity of a fire once it has started. The Mark 5 forest-fire danger meter uses air temperature, relative humidity and wind speed, plus a drought factor that is calculated using daily rainfall and temperature information. Three years of daily data generated from the CSIRO four-level general circulation model, and thirty years of daily data generated from the CSIRO nine-level model were used to estimate the daily McArthur forest fire danger index for simulations corresponding to present conditions, and to those corresponding to doubled atmospheric CO2. The performance of these models with respect to fire danger was tested by comparing the fire danger index for Sale (in the Eastern part of Victoria, South-eastern Australia) calculated from analysis of daily climatological data with the modelled annual cumulative forest fire danger index for the grid point that was representative of Sale. Data from both models for all Australian grid points were also examined. Both models predict an increase in fire danger over much of Australia for their doubled CO2 scenarios. The results from the models confirm that annually averaged daily relative humidity is the single most important variable in the estimation of forest fire danger on an annual basis, yet the models tend to produce relative humidities that are slightly too low so that the fire danger is overestimated. A simple one-box model of evaporation indicates that the value of relative humidity to be expected under an altered climatic regime depends on the modelled relation between actual and potential evaporation, the present values of relative humidity and evaporation rate, as well as on the expected changes in wind speed.