Autumn Burning Research Articles

The effect of long-term fire treatments on invertebrates: results from experimental plots at Cathedral Peak, South Africa

This study examined the impacts of different burning regimes (fire frequency and season) and fire history (time since last burn) on invertebrate morphospecies richness and abundance. The study was carried out in the Brotherton experimental plots at Cathedral Peak in the KwaZulu-Natal Drakensberg. Pitfall traps targeting epigaeic invertebrates were set for one week, and soil cores were collected for extraction of hypogaeic invertebrates in 21 plots. A total of 2585 individual specimens from 219 morphospecies were identified. Mean morphospecies richness was consistently highest in blocks burnt in autumn, and higher for biennial burns or two years since last burn for epigaeic, winged and wingless invertebrates, but this was not the case for soil invertebrates which showed little real response to fire. Fire season and frequency significantly influenced epigaeic and winged invertebrate species richness and abundance, with autumn burning and a fire return period of two years favouring richness and abundance. However, the small size of the plots and their proximity and a runaway fire in 2000 could have influenced results and could also result in relatively homogenous communities.

Herbaceous Vegetation Responses (1992–2004) to Restoration Treatments in a Ponderosa Pine Forest

Ecological restoration treatments are widely applied in southwestern ponderosa pine forests to convert them to an open canopy structure similar to that found at the time of Euro-American settlement. An experiment was initiated in northern Arizona in 1994 to evaluate long-term ecosystem responses to 3 restoration treatments: 1) thinning from below (thinning), 2) thinning from below plus forest floor manipulation with periodic prescribed burning (composite), and 3) an untreated control. Results focus on total herbaceous and functional-group standing crop response to these restoration treatments. Pretreatment data were collected in 1992 and posttreatment responses were measured from 1994 through 2004. Total herbaceous standing crop was significantly higher on the 2 treated areas than on the control over the entire posttreatment period, but did not differ between the thinning and composite treatments. Plant functional groups responded differently to treatments and to drought. In general, the graminoid standing crop responded within several years after the initial treatments and continued to increase through time, until a series of severe droughts reduced standing crop to pretreatment levels. C3 graminoids dominated the standing-crop response, of which bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey ssp. elymoides) was the primary contributor. C4 graminoids had a minimal response to restoration treatments, possibly because they were less abundant before the experiment began or because they were adversely affected by autumn burning. Legumes and forbs exhibited a 4‐5 year lag before responding to the thinning and composite treatments. Annual and biennial plants showed a large biomass increase approximately 5 years after implementation of the composite treatment. The restoration goal of optimizing herbaceous standing crop must be weighed against the competing goals of increasing the abundance of specific functional groups, increasing biodiversity or rare plants, and managing invasive plant species.

Herbaceous Vegetation Responses (1992-2004) to Restoration Treatments in a Ponderosa Pine Forest

Ecological restoration treatments are widely applied in southwestern ponderosa pine forests to convert them to an open canopy structure similar to that found at the time of Euro-American settlement. An experiment was initiated in northern Arizona in 1994 to evaluate long-term ecosystem responses to 3 restoration treatments: 1) thinning from below (thinning), 2) thinning from below plus forest floor manipulation with periodic prescribed burning (composite), and 3) an untreated control. Results focus on total herbaceous and functional-group standing crop response to these restoration treatments. Pretreatment data were collected in 1992 and posttreatment responses were measured from 1994 through 2004. Total herbaceous standing crop was significantly higher on the 2 treated areas than on the control over the entire posttreatment period, but did not differ between the thinning and composite treatments. Plant functional groups responded differently to treatments and to drought. In general, the graminoid standing crop responded within several years after the initial treatments and continued to increase through time, until a series of severe droughts reduced standing crop to pretreatment levels. C3 graminoids dominated the standing-crop response, of which bottlebrush squirreltail (Elymus elymoides (Raf.) Swezey ssp. elymoides) was the primary contributor. C4 graminoids had a minimal response to restoration treatments, possibly because they were less abundant before the experiment began or because they were adversely affected by autumn burning. Legumes and forbs exhibited a 4-5 year lag before responding to the thinning and composite treatments. Annual and biennial plants showed a large biomass increase approximately 5 years after implementation of the composite treatment. The restoration goal of optimizing herbaceous standing crop must be weighed against the competing goals of increasing the abundance of specific functional groups, increasing biodiversity or rare plants, and managing invasive plant species.

Rosa rugosa Thunb. ex Murray

Rosaceae, Rosoideae, Rosa L.; subgenus Eurosa Focke; section Cinnamomeae (DC.) Rehder. Japanese Rose. Rhizomatous multi-stemmed erect deciduous shrub, strongly suckering, mature clones forming impenetrable thickets. Rhizomes woody, with orange-brown cortex and triangulate scale leaves. Rhizome branches and suckers emerge from axillary buds subtended by scale leaves. In addition, suckers may arise from buds on the roots. Stems erect, sometimes arching, to 1.5( − 2) m, often much branched, tomentose when young, densely prickly. Cortex light yellowish brown. Prickles subulate, slender and straight, of all sizes down to acicles. Larger prickles tomentose, at least near the base, and usually glabrous in the apical part. Leaves alternate with (5–)7–9 leaflets contiguous on the rachis. Leaflets nearly equally sized, 2–5 × 1.5–3 cm, leathery and robust, widely elliptical, acute, with broadly cuneate or rounded base. Adaxial side dark green, conspicuously bullate or rugose, rather shiny. Abaxial side green-grey, tomentose to pubescent, with sessile pale glands, and with reticulate nervation. Leaf margin bluntly and simply crenate-serrate, involute, edge of teeth often deflexed. Petiole and rachis densely pubescent, and with many unequal subulate prickles. Stipules pale green, densely pubescent, 2.5 × 1–1.5 cm, divergent, the free part broadly ovate or deltoid. Flowers usually solitary or few together, 6–9 cm across, fragrant, nectarless. Sepals 2–3 cm, entire, with a broad, expanded tip, appressedly pubescent, aciculate and glandular (sometimes with stipitate glands), erect on the hip, persistent. Petals five, bright purplish-pink, sometimes white ( R. rugosa f. alba (Ware) Rehder). Stamens 200– 250 per flower, and styles often more than hundred. Styles pilose; stigmas in a large, domed head, sunk in the narrow, concave disc; disc 2.5–4 mm across; orifice large, at least half the diameter of the disc. A hypanthium (hip) encloses the achenes. It is depressed globose, 1.5–2 cm long and 2–2.5 cm wide, with a distinct neck below the sepals, dull green to orange when unripe, becoming glossy and brilliant red when ripe, most often smooth. Pedicel of the same length as the hip, tomentose, often with gland-tipped acicles, erect in flower, curved in fruit so that the hip points downwards. Achenes with a woody-bony pericarp enclosing the seed. Achenes broadly ovoid, obtusely angular, 4.0–6.0 mm long and 2.0–2.6 mm wide and 1.8–2.2 mm thick, with a distinct suture on both ventral and dorsal sides, hilum basal. Achene surface more or less lustrous, orange-brown. Mean seed (achene) mass is 6.6 mg. The albumen is oily. No subspecies of R. rugosa have been recognized in the British Isles. Despite the many cultivated varieties of the species, mainly forms close to the wild type are seen naturalized. However, naturalized clones may be confused with R. × hollandica (syn. R. × kamtchatica ). This taxon differs morphologically from R. rugosa by having soft-textured, dull leaflets, without prominent veins, less prickly stems, conspicuously glandular sepals, and smaller flowers and hips (Rutherford 1990). Taxonomic position: Rosa L., subgenus Eurosa Focke (syn. subgen. Rosa ), section Cinnamomeae (DC) Rehder (syn. sect. Rosa ; sect. Cassiorhodon Dumort.). Section Cinnamomeae is central in the subgenus Eurosa , which contains all but four of the approximately 150 Rosa species in the world. The diploid species of this section, including R. rugosa , are probably basal in the reticulate evolutionary series from diploid species to irregular polyploid species within this genus (Erlanson 1938; Grossi et al . 1998). Originally introduced as a garden and landscape ornamental, and widely used as rootstock for other cultivated roses, R. rugosa can be found in many different cultivated settings. Now a well-established naturalized alien occurring scattered throughout Britain and invasive in fixed dunes and other coastal habitats.

Effects of timing of prescribed fire on the demography of an invasive plant, spotted knapweed Centaurea maculosa

Summary Prescribed burning is a key tool used in prairie and savanna restoration projects. The timing and frequency of prescribed fires are important variables to consider because they can differentially affect the survival of individual plant species, including noxious exotic species. We used annual censuses and population matrix analysis to evaluate the demographic consequences of burning on populations of the invasive species spotted knapweed Centaurea maculosa in a Michigan, USA, prairie restoration experiment. We compared spring, summer and autumn burns at two frequencies: annually (2000–03) and in alternate years (2001, 2003). We examined the effects of different seasons and frequencies of prescribed fire on the survival, growth and reproduction of C. maculosa populations, and used life‐table response experiments and elasticity analyses to determine how season of fire affects population growth rates. We found that annual summer burning was the only treatment that significantly reduced overall population growth rates. The life‐table response experiment analysis indicated which life stages contributed the most to changes in population growth rates under the different treatments. The summer burn treatments reduced population growth by reducing reproduction. The different burn treatments altered the elasticity structure of populations, but in general reproduction of adults as well as survival of non‐reproductive adults and juveniles remained important in all treatments. This indicates that future attempts to control C. maculosa should focus on combinations of treatments targeting these life stages. Synthesis and applications. Management decisions regarding prescribed burning in grassland restoration projects should consider the responses of individual species already present in the system. In particular, it is important to consider the effects of burning on noxious invasive species that may or may not have different life histories and responses to fire compared with native species. Population matrix modelling provides a more complete picture of the effects of management on population responses compared with other measures based only on community composition and relative abundance. Depending on the goals of a restoration, non‐traditional management options, such as summer burning in mid‐west USA prairies, may be effective management tools for the control of invasive species.

Grasstree (Xanthorrhoea preissii) recovery after fire in two seasons and habitats

To distinguish fire-stimulated growth from the underlying growth patterns imposed by season, we measured leaf production of Xanthorrhoea preissii Endl. (Xanthorrhoeaceae). We compared unburnt with spring- and autumn-burnt sites in forest and woodland habitats. Following fire, X. preissii responded with accelerated leaf production, regardless of season. Rapid leaf production during the initial flush of growth was partly at the expense of starch reserves in the stem, at least after autumn fire. Although this initial flush was relatively short-lived after fire in both seasons (12–32 weeks), the effect of fire on leaf production was sustained for up to 20 months, accompanied by a significant reduction in leaf longevity. Mean maximum leaf production rate was higher for spring-burnt grasstrees (up to 6.1 leaves day–1) than those burnt in autumn (up to 4.5 leaves day–1), associated with seasonally optimal growing conditions in late spring–early summer. Similarly, the timing of autumn burns in relation to declining temperature with the approach of winter appeared to dictate how rapidly grasstrees recovered. The consequences of fire season could have implications for the reproductive success of X. preissii.

Response of a Native Perennial Grass Stand to Disturbance in California's Coast Range Grassland

Abstract To assess the potential for enhancing an existing stand of native perennial grasses on a California Coast Range Grassland site, we experimentally manipulated the seasonal timing and presence of grazing for 3 years (1994 through 1996) and of autumn burning for 2 years (1994 and 1995) and measured species cover for 6 years (1993 through 1998). We subjected the species matrix to classification (TWINSPAN) and ordination (CCA) and tested the ordination site scores as well as diversity indices with linear mixed effects models. Four distinct plant community groups emerged from the classification. Two of these were dominated by annual grasses and two by perennial grasses. No treatment effects were observed on diversity. For composition, temporal and spatial random effects were important mixed effects model parameters, as was the fixed effect covariate, pre‐treatment CCA site score, indicating the importance of random environmental variation and initial starting conditions. Incorporation of these random effects and initial condition terms made for more powerful tests of the fixed effects, grazing season, and burning. We found no significant burning effects. Grazing removal imparted a shift in plant community from more annual‐dominated toward more perennial‐dominated vegetation. Individual perennial grass species responded differently according to genus and species. Nassella spp. increased gradually over time regardless of grazing treatment. Nassella pulchra (purple needlegrass) increase was greatest under spring grazing and N. lepida (foothill needlegrass) was greatest with grazing removal. Danthonia californica (California oatgrass) had little response over time under seasonal grazing treatments, but increased with grazing removal. Under relatively mesic weather conditions it appears that grazing removal from Coast Range Grasslands with existing native perennial grass populations can increase their cover. However if N. pulchra is the sole existing population, spring season‐restricted grazing should be equally effective at enhancing cover of the native grass species.

Effects of Season of Burning on the Microenvironment of Fescue Prairie in Central Saskatchewan

The microenvironmental effects of spring, summer and autumn burns were investigated for a small area of fescue prairie in Saskatchewan over two growing seasons. Maximum fire temperature in all burns exceeded 300°C at a height of 5-10 cm in the canopy. At a depth of 1 cm in the soil, temperature increased to 40°C during the summer burn, but was unaffected by burns at other seasons. Spring-burned grasses recovered to the same height as the unburned control plot by the end of the first summer. Grass height was similar in all plots by the end of the second growing season, but aboveground biomass in all burned plots was about half that of the control. Graminoid leaf area index at the end of the second growing season ranged from 0.65 in the control plot to 0.27 in the autumn burn. Surface albedos dropped to about 0.03 immediately after burning and took about 3 months to return to the pre-burn values near 0.20. By mid-June of the second year, albedos were similar in all plots. Soil temperatures at 50 cm depth in the burned plots were higher than in the control during the first summer and lower during the winter. The greatest winter snowpack (73 mm water equivalent) accumulated in the control, compared to 48, 35 and 25 mm in the spring, summer and autumn burned plots, respectively. In the first growing season the greatest demand for water occurred in the spring plot followed by the summer, control and autumn plots. In the second season water demand did not differ significantly among plots, reflecting the similarities in plant cover. The microenvironmental effects of a single burning episode in fescue prairie disappear rather quickly, so that there is little long-term impact on the vegetation.

Burning causes long-term changes in soil organic matter content of a South African grassland

The effects of burning a native grassland on soil organic matter status was investigated on a long-term (50 years) field experiment where different times and frequencies of burning were compared. Significant decreases in organic C were observed only in the surface 0–2 cm layer and only under annual and biennial winter burning and biennial and triennial autumn burning. Burning in spring did not significantly affect organic C content presumably because substantial amounts of litter decomposed and/or were incorporated into the soil by faunal activity prior to burning. Total N content was decreased substantially to a depth of 6 cm by all burning treatments and as a result, the C:N ratio of soil organic matter was widened. In addition, the amount of potentially mineralizable N, as measured by either aerobic incubation or plant N uptake in a pot experiment, was much reduced. Burning also induced a decrease in light fraction and hot water-extractable C in the 0–2 cm layer but an increase in these parameters, and in microbial biomass C and root density, in the 4–10 cm layer. This was attributed to burning causing a decrease in above-ground litter inputs but increased turnover of root material below the surface. Despite the decrease in organic C and total N content with increasing soil depth, potentially mineralizable N showed the opposite trend. This unexpected finding was confirmed at a nearby site under native grassland and contrasted with decreasing potentially mineralizable N with depth which was measured under a fertilized kikuyu grass dairy pasture. The wide C:N ratio of litter from native grassland, in association with the decreasing size and activity of the microbial biomass with depth results in greater N immobilization (thus less net mineralization) occurring in soil samples taken from close to the soil surface.

Vegetation Dynamics from Annually Burning Tallgrass Prairie in Different Seasons

Traditional perception of how tall grass prairie responds to fire at times other than late spring is either anecdotal or extrapolated from studies that lack spatial or temporal variability. Therefore, we evaluated patterns of change in vegetation cover, species richness, diversity, and aboveground biomass production on 2 different topographic positions from ungrazed watersheds that were burned annually for 8 years in either autumn (November), winter (February), or spring (April). Topoedaphic factors influenced the response patterns of some species to seasonal fire, although differences were primarily in the rate of change. Annual burning in autumn and winter produced similar trends through time for most species. Big bluestem (Andropogon gerardii Vitman) cover increased with all burn regimes, whereas indiangrass [Sorghastrum nutans (L.) Nash] increased only with spring burning. Repeated autumn and winter burning eventually increased perennial forb cover, with the largest increases occurring in heath aster [Symphyotrichum ericoides (L.) Nesom], aromatic aster [S. oblognifolium (Nutt.) Nesom], tall goldenrod (Solidago canadensis L.), and legumes. Species richness increased (P < 0.001) through time with spring and winter burning, but was similar among all burn treatments after 8 years of annual fire. Average grass and forb biomass did not differ among burn seasons on either topographic position, although interannual biomass production fluctuated inconsistently with time of burn. Our findings contrast with many of the conventional views of how tallgrass prairie vegetation responds to seasonal fire and challenges traditional recommendations that burning should only occur in late spring.

Vegetation dynamics from annually burning tallgrass prairie in different seasons

Traditional perception of how tallgrass prairie responds to fire at times other than late spring is either anecdotal or extrapolated from studies that lack spatial or temporal variability. Therefore, we evaluated patterns of change in vegetation cover, species richness, diversity, and aboveground biomass production on 2 different topographic positions from ungrazed watersheds that were burned annually for 8 years in either autumn (November), winter (February), or spring (April). Topoedaphic factors influenced the response patterns of some species to seasonal fire, although differences were primarily in the rate of change. Annual burning in autumn and winter produced similar trends through time for most species. Big bluestem (Andropogon gerardii Vitman) cover increased with all burn regimes, whereas indiangrass [Sorghastrum nutans (L.) Nash] increased only with spring burning. Repeated autumn and winter burning eventually increased perennial forb cover, with the largest increases occurring in heath aster [Symphyotrichum ericoides (L.) Nesom], aromatic aster [S. oblognifolium (Nutt.) Nesom], tall goldenrod (Solidago canadensis L.), and legumes. Species richness increased (P &lt; 0.001) through time with spring and winter burning, but was similar among all burn treatments after 8 years of annual fire. Average grass and forb biomass did not differ among burn seasons on either topographic position, although interannual biomass production fluctuated inconsistently with time of burn. Our findings contrast with many of the conventional views of how tallgrass prairie vegetation responds to seasonal fire and challenges traditional recommendations that burning should only occur in late spring.

The effects of burning on the understorey composition of 11–13 year-old rehabilitated bauxite mines in Western Australia – Vegetation characteristics

Alcoa of Australia Limited has been rehabilitating bauxite mines in the jarrah (Eucalyptus marginata) forest of Western Australia for more than 30 years. Mines rehabilitated in the early 1980s using out-dated methods have built up substantial fuel loads that may be reduced through prescribed burning. The vegetation response of 11–13 year-old rehabilitated bauxite mines to fire regimes differing in intensity and season over the first two years of post-burn succession is compared to the native jarrah forest. A total of 243 species from 137 genera and 56 families were identified in the native forest reference sites and in the 11–13 year-old rehabilitated areas before and after burning. The vegetation of the pre-burn rehabilitated areas was very different to that of the native jarrah forest. While total live plant cover, Acacia density, non-native eucalypt seedling density, weed density and the evenness index were similar between the two areas, total plant density, live Acacia cover, the proportion of weeds, native species numbers and diversity were significantly different. However, the greatest difference between the vegetation of the pre-burn rehabilitated sites and the native jarrah forest was the higher dominance of seeding species (plants killed by fire) in rehabilitated areas. In contrast, native jarrah forest was dominated by resprouting species (plants that survive fire). Burning the rehabilitated sites was successful in making the areas more similar to the forest in terms of total plant density, live Acacia cover and native species numbers but decreased their similarity in terms of live plant cover, Acacia density, non-native eucalypt seedling density, weed density and evenness. The vegetation response of the rehabilitated areas to different seasons of burning showed that autumn burning led to a greater increase in plant establishment than spring burning. Autumn burning also resulted in an undesirable increase in the density of non-native eucalypt seedlings that was not observed following spring burning. Although burning these 11–13 year-old rehabilitated sites will increase similarity to the native forest, it is unlikely that they will resemble the native jarrah forest without further management intervention.

Grasshopper response to a 40-year experimental burning and mowing regime, with recommendations for invertebrate conservation management

Grasshopper assemblages were sampled in 44 plots in each of three adjacent sites in a 40-year-old southern tall grassland experimental area in South Africa. Specific plots received particular mowing and/or burning treatments over the 40-year period. Grasshopper responses to vegetation type, and to different burning and mowing practices, were site-specific, despite the close proximity of sites. This suggests that grasshopper assemblage composition is not entirely deterministic and depends on the trajectory of plant succession. Grasshopper species richness and abundance decreased from annually to triennially burnt plots, and increased in plots mown once per year to plots mown three times per year. Burning in the first week of August (winter) was more favourable for grasshopper assemblages than burning in autumn or after the first spring rains. Mean grasshopper species richness was highest in plots mown after the first spring rains, and the mean number of individuals was highest i n plots mown early in summer. When annually burnt plots were compared with annually mown plots, grasshopper abundance and species richness were highest in the burnt plots. A rotational winter burning programme, which is practical under African conditions, is recommended for the conservation of grasshoppers and other invertebrates.

Fuel characteristics, vegetation structure and fire behaviour of 11–15 year-old rehabilitated bauxite mines in Western Australia

Summary Bauxite mines rehabilitated in the early 1980s in Western Australia have built up substantial fuel loads that may be reduced through prescription burning. Fuel characteristics, vegetation structure and fire behaviour of 11–15 year-old rehabilitated bauxite mines were examined. Fuel loads were high in all pre-burn rehabilitation areas (23.4–35.1 t ha−1) although large ranges in fuel load estimates of sample plots (6.3–49.3 t ha−1) indicated the heterogenous nature of the fuel distribution that led to heterogeneity in fire behaviour. The vegetation structure of the rehabilitated areas differed from that of the native jarrah forest due to a lower proportion of live to dead plant material and the presence of a prominent mid-storey layer composed of dead Acacia plants. This mid-storey layer contributed 45% of the total fuel load and led to increased flame heights and subsequent higher levels of crown scorch regardless of the soil and litter moisture conditions. Seven prescription burns were carried out between 1994 and 1996 encompassing a range of fire intensities and seasons of burning. Autumn burns were generally of higher intensity than spring burns due to the drier nature of the fuel following summer drought. Re-accumulation of fuel in the first year following burning was rapid (6.4–9.5 t ha−1) but had levelled off by the second year (6.1–10.3 t ha−1). Vegetation structure of rehabilitated areas one and two years after burning indicated that the prescription burns had removed the mid-storey layer of senescent Acacia material and stimulated an increase in the proportion of live plant material, particularly following autumn burning. Maximum soil temperatures recorded by heat-sensitive crayons exceeded 200°C in the autumn burns and were generally well below 100°C in the spring burns. Hard-seeded species would have been stimulated to germinate in the top 2–5 cm following autumn burning and only in the top I cm following spring burning. Some seeds in the top 1 cm of soil may have been killed in the autumn burns. The fire management of rehabilitated areas will have to be different to that of the native jarrah forest due to differences in fuel characteristics, vegetation structure and fire behaviour of these two sites.

The effect of burning, soil scarification and seeding on the understorey composition of 12 year-old rehabilitated bauxite mines in Western Australia

Summary The effect of burning, soil scarification and seeding on 11 to 13-year-old rehabilitated bauxite mines was examined to assist the development of a prescription for increasing establishment of native tree and understorey species. Scarified and non-scarified treatments were investigated following burning in autumn and spring, and in no burn areas. All treatments were seeded with a mix containing jarrah (Eucalyptus marginata), the native overstorey dominant, and 37 understorey species. Plant response was measured as the density of all plants, weeds, eastern Australian eucalypts, acacias and jarrah as well as native species numbers and the Shannon-Weiner diversity index. Nearly all of these measures were significantly higher in the burnt compared to the unburnt treatments. Species numbers, total plant density. Acacia density and jarrah density were higher following autumn burning than spring burning. However, the density of eastern Australian eucalypt seedlings was also significantly increased by autumn burning which has undesirable implications if the native overstorey dominant, jarrah, is to be established in these areas. Seeding an understorey species mix significantly increased species richness, particularly in burnt areas. Soil scarification significantly increased diversity in the autumn treatments. Burning rehabilitated sites in spring with no soil scarification appears to be the best prescription to minimise the abundance of eastern Australian eucalypts observed following autumn burning, while seeding an understorey seed mix on these areas will increase species richness.

Tree species response to prescribed burns in rehabilitated bauxite mines in Western Australia

Summary The response of fourteen tree species to autumn and spring prescribed burns was assessed in 11 to 13-year-old rehabilitated bauxite mines. Of the 578 trees recorded, 2.8% were killed, a further 14.7% resprouted basally (no resprouts above 2 m) while the remainder resprouted aerially (73.2%) or were not scorched (8.5%). This is indicative of the high tolerance to fire of all species recorded in this study. The most fire tolerant species were Eucalyptus calophylla, E. patens, E. botryiodes and E. maculata. The most susceptible species were E. accedens and E. wandoo. Increased fire tolerance was related to increased bark thickness and larger stem diameter. Rough-barked species were more resistant to fire than smooth-barked species. Tree mortality and the incidence of basal resprouting was higher following autumn burning than spring burning. Based on these findings, it would appear that spring burns are more favourable than autumn burns to the survival and growth of tree species in rehabilitated areas.

Aspects of the distribution, phytosociology, ecology and management of Danthonia popinensis D.I. Morris, an endangered wallaby grass from Tasmania

Danthonia popinensis is a recently discovered, nationally endangered tussock grass, originally known from only one roadside population at Kempton, Tasmania. Six populations have been recorded, all from flat land with mildly acid non-rocky soils, and all in small toadside or paddock remnants, badly invaded by exotic plants. However, one site has recently been destroyed through roadworks. The species germinates best at temperatures of 10°e, indicating a winter germination strategy. Autumn burning at Kempton resulted in an increased cover of D. popinensis two years after the burn, but also resulted in an increased cover of competitive exotics. The future of the species needs to be secured by ex situ plantings, as almost all of its original habitat has been converted to crops or improved pasture.

Prescribed Burning of Thinning Slash in Regrowth Stands of Karri (Eucalyptus diversicolor) .1. Fire Characteristics, Fuel Consumption and Tree Damage

'Fire characteristics, fuel consumption and fire-caused tree damage were investigated for ten low to moderate intensity fires in thinning slash fuel in 22-year-old karri (Eucalyptus diversicolor F. Muell) regrowth in Western Australia. Eight fires were burnt in spring and two in autumn. Most fires consumed greater than 80 per cent of dead fuel &lt; 25 mm in diameter and between 40 per cent and 80 per cent of the litter layer. The total amount of litter and dead fuel &lt; 100 mm in diameter consumed during burning ranged from 24 to 79 t ha-1 (31-89 per cent). Actual and percentage consumption of fuel &lt; 100 mm diameter were inversely related to the moisture content of the litter profile. Fireline intensities determined from flame length estimates ranged from 90 kW m-1 to 2820 kW m-1. Damage to retained trees included stem wounding, crown death and complete death of the stem. Burning in spring when the litter profile was moist resulted in damage to the lower stems of up to 80 trees ha-1, with damage affecting an average of 3 m2 ha-1 of the retained basal area of 19.5 m2 ha-1. The incidence of stem damage following spring burning was considerably greater when the litter layer was dry. Autumn burning resulted in extensive stem damage and tree mortality and is not therefore recommended. Log debris within 1 m of trees significantly increased the probability of fire-caused damage, and wounds tended to be larger on trees that had debris nearby. The incidence of damage from burning was directly related to the quantity of fuel consumed and heat release per unit area, but was not significantly correlated with fireline intensity. A prescription for burning thinning slash during spring conditions is presented.

Water Relations and Growth of Bromus inermis Leyss (Smooth Brome) Following Spring or Autumn Burning in a Fescue Prairie

-Bromus inermis Leyss (smooth brome) is an invasive perennial grass in Fescue Prairie in North America. Prescribed burning is a potential method of controlling this exotic, but its responses to burning in this grassland are not known. This study was conducted to determine the impacts of a single burn in the autumn or spring on the growth and water relations of B. inermis in Fescue Prairie in central Saskatchewan. In 1 yr, leaf xylem water potential and stomatal conductance were lower in plants burned in the autumn than the reference and the spring burn. In another year they were generally similar among the burns and reference. Regardless of water stress following burning, tiller densities, standing crop and the leaf area indices of B. inermis were not significantly different among the reference, autumn and spring burns. Because B. inermis is apparently resistant to fire effects and native species are suppressed by burning, fire may increase B. inermis in Fescue Prairie. Unlike grasslands dominated by C4 species, a single burn in autumn or spring while plants are dormant is not expected to reduce B. inermis in the C3-dominated Fescue Prairie.

Long term effects of rotation, tillage and stubble management on wheat production in southern NSW

A long term field experiment began in 1979 at Wagga Wagga, N.S.W., to compare the sustainability of a range of rotation, tillage and stubble management systems on a red earth. This paper reports yield, yield components and grain protein of wheat for 1979-90. Rotations considered were alternating lupin-wheat (LW), lupin-wheat-wheat (LWW), continuous wheat (WW) with and without N fertilizer (100 kg N/ha), and alternating sub-clover-wheat (CW). Soil N supply at the start of the experiment was high following many years of sub-clover based pasture. From 1979 to 1983, there was a negative grain yield response to N fertilizer and no response to a legume in rotation except in the drought of 1982 when low yields were recorded from LW. Thereafter, a positive grain yield response was usually produced to N fertilizer in WW rotations, until 1989 and 1990, when these crops displayed aluminium toxicity sym ptoms. Overall, average grain yields from legume rotations were higher than WW with added N fertilizer. Since 1983, LW rotations consistently produced higher mean grain yields than CW, but mean grain protein and total N uptake were lower. Yields and N uptake by the second wheat crop in a LWW rotation indicated little carryover of benefits from the lupins. Slightly higher mean grain yield and harvest index, but lower mean grain protein, were produced by direct drilling, compared with cultivation before sowing, following lupins or sub-clover. However, retaining stubble rather than burning in autumn consistently reduced grain yields. There was no evidence that early burial of wheat stubble following summer rain, rather than incorporation in autumn, improved grain yield or total N uptake. The build-up of giant brome grass and diseases, particularly where stubble was retained and crops direct-drilled, casts some doubt on the long term sustainability of these short term rotations in this environment.