Inter-fire Period Research Articles

Fire interval and post-fire climate effects on serotinous forest resilience

BackgroundClimate change is eroding forest resilience to disturbance directly through warming climate and indirectly through increasing disturbance activity. Forests characterized by stand-replacing fire regimes and dominated by serotinous species are at risk when the inter-fire period is insufficient for canopy seed bank development and climate conditions for recruitment in the post-fire growing season are unsuitable. Although both factors are critical to serotinous forest persistence, their relative importance for post-fire regeneration in serotinous forests remains poorly understood. To assess the relative effects of each factor, we established plots in severely burned knobcone pine (Pinus attenuata Lemmon) forests in Oregon and California, USA, representing a range of past fire intervals (6 to 31+ years). Specifically, we evaluated effects of fire interval and pre-fire canopy seed bank (proxies for seed supply) and post-fire climate on three metrics of post-fire tree regeneration (seedling density, probability of self-replacement, percent population recovery).ResultsSeed supply consistently had the strongest effect on post-fire regeneration. Between 6- and 31-year fire intervals, post-fire seedling density increased from 1000 to 100,000 seedlings ha−1, while probability of self-replacement increased from ~ 0 to ~ 100% and percent population recovery increased from 20 to 2000% of the pre-fire population, respectively. Similarly, increasing the canopy seed bank by two orders of magnitude increased seedling density and percent population recovery by two orders and one order of magnitude, respectively, and increased the probability of self-replacement by > 50%. Greater post-fire climatic moisture deficit exacerbated the effect of seed supply; an additional 4–6 years between fires was required under high moisture stress conditions to reach similar regeneration levels as under low moisture stress conditions.ConclusionThe overriding effect of seed supply—strongly driven by pre-fire stand age—on post-fire regeneration suggests that altered fire frequency (an indirect effect of climate change) will have a profound impact on serotinous forests. Although direct effects of hot and dry climate are lower in magnitude, they can alter forest recovery where seed supply nears a threshold. These findings reveal how fire interval and climate combine to determine changes in forest cover in the future, informing management and vulnerability mapping.

Demographic processes underpinning post-fire resilience in California closed-cone pine forests: the importance of fire interval, stand structure, and climate

The resilience of serotinous obligate-seeding plants to fire may be compromised if increasing fire frequency curtails time available for canopy seed bank accumulation (i.e., immaturity risk), but how various drivers affect seed availability at the time of fire is poorly understood. Using field data from California closed-cone pine (Pinus attenuata and P. muricata) stands, we assess two critical demographic processes during the inter-fire period—reproductive capacity and mortality. At tree- and stand-levels, we test how these processes are affected by stand age and are mediated by biotic and abiotic factors. We found that stand age was the key driver of reproductive capacity; older stands had a greater proportion of reproductively mature individuals and greater closed cone density. Stand density mediated the effect of age; greater stand density resulted in greater closed cone density and a lower proportion of reproductively mature individuals, but reproductive capacity in low- and high-density stands converged over time. Increased moisture stress reduced the stand-level proportion reproductively mature trees but had no effect on closed cone density. Mortality was strongly associated with density-dependent thinning and increased in stands with high moisture stress. Reproductive capacity began to increase sharply 10 years post-fire and by 20 years immaturity risk was low. However, prior to 20 years, low-density stands with high moisture stress may be more susceptible to immaturity risk. Understanding these relationships is critical to predicting serotinous population persistence under changing climate and disturbance conditions.

Seed structure and physiology in relation to recruitment ecology in Leucospermum (Proteaceae) in fynbos

Development of embryo envelopes in Leucospermum cordifolium (Salisb. ex Knight) Fourcade is presented in a detailed anatomical study, and their structure interpreted ecologically. To support interpretation results for at least six other species of Leucospermum are reviewed, confirming that L. cordifolium is representative of this shrubby group occurring in fynbos, a fire-prone Mediterranean-type vegetation subject to summer drought. The fate of the water-permeable seed coverings subsequent to dispersal is followed in seeds stored experimentally underground. The testa at maturity effectively excludes oxygen in intact soil-stored seeds, thus creating a less common type of physical dormancy which we term ‘anoxia PY’ (oxygen-impermeable physical dormancy). We postulate ‘fire-mediated desiccation-scarification’ testa breakage on a large scale in freshly dispersed (by ants) soil-stored young-seeds, dynamically regulated by drying of different testa layers through fire heat shock (but also by post-fire ambient climate heat), thus alleviating anoxia PY in, and causing undelayed germination of, a major part of the young-seed bank within the ensuing winter germination season. Concurrently a patchy disturbance pattern within a lesser portion of the young-seed cohort causes uneven underground desiccation-scarification by fire, resulting in variable degrees of oxygenation and thus temporally extended (erratic) germination of young-seeds. Both of these strategies are primary long term fitness traits in Leucospermum. By contrast the persistent older-seed cohort, stored underground during the inter-fire period, may become weathered by soil and climate factors (‘soil-mediated abrasion’), which alleviates anoxia PY in old seeds. Thermodormancy of these embryos (physiological dormancy, PD) is enforced in unburnt vegetation by two narrow habitat-dependent daily temperature requirements (~10°C × 20°C), and these have specific ecological functions. The complex Leucospermum system includes balanced adaptive responses to multiple selective pressures. We propose a coherent mechanistic profile for this fynbos genus, synthesising data partly from the literature of other fire-prone ecosystems.

Do dormancy-breaking temperature thresholds change as seeds age in the soil seed bank?

AbstractIn fire-prone ecosystems, many species regenerate after fire from persistent soil seed banks. Species with physically dormant (PY) seeds have dormancy broken by fire-related heat. The magnitude of post-fire recruitment, to predict response to varying fire severity, is commonly estimated by testing dormancy-breaking temperature thresholds of fresh PY seeds. However, seeds spend years in the soil during the inter-fire period, and determining whether dormancy-breaking thresholds change over time is essential to accurately predict population persistence. Germination of four south-eastern Australian PY species from the Fabaceae family (Acacia linifolia, Aotus ericoides, Bossiaea heterophylla and Viminaria juncea) were studied. Dormancy-breaking temperature thresholds vary inter-specifically and the species represented either high or low dormancy-breaking threshold classes. Freshly collected seeds, and seeds that had been buried in the field or stored in dry laboratory conditions for 6 and 18 months were subjected to a fire-related range of heat treatments (40–100°C). Seed ageing increased germination response to heat treatments, effectively lowering the dormancy-breaking thresholds of three species. The fourth species, A. linifolia, initially had a relatively large non-dormant fraction which was lost as seeds aged, with older seeds then displaying PY broadly similar to the other study species. Patterns of threshold decay were species-specific, with the thresholds and viability of low-threshold species declining more rapidly than high-threshold species. The non-dormant fraction did not increase over time for any of our study species. Instead of increasing their non-dormant fraction, as is common in other vegetation types, these fire-prone PY species displayed a change of dormancy-breaking temperature thresholds. This is an important distinction, as maintaining dormancy during the inter-fire period is essential for population persistence. While changes in sensitivity to dormancy-breaking treatments have previously been reported as seeds age, our study provides the first test of changes to temperature thresholds, which increases the range of germination response from the seed bank under varying fire severity.

Predicting time-windows for full recovery of postfire regenerating Pinus halepensis Mill. forests after a future wildfire

A regeneration predictor (RP) has been elaborated to forecast the minimal inter-fire period, required for full recovery (assumed at 1,000 mature stems ha−1, a typical value for a dense pine forest) of an even-aged, postfire regenerating Pinus halepensis population after a subsequent wildfire, in the future. The study has been conducted in three Aleppo pine forests of northern Euboea Island, Greece. Postfire field surveys of sapling growth, sapling density and reproductive dynamics (cone-bearing population fraction, annual cone and seed production per sapling, canopy seed bank build-up) were carried out for three, consecutive growing seasons (years). Additional postfire parameters, with values estimated from literature data, have been also included in order to devise the RP. In the cases of the three populations studied, the application of this RP provides time-windows for full recovery after a recurrent fire, as short as 10–15, 8–11 and 7–11 years, respectively (values corresponding to best and worst scenarios). It is suggested that in even-aged, postfire regenerating Aleppo pine populations, the minimal inter-fire period required for full recovery can be predicted by monitoring a few selected variables, namely (a) sapling density, (b) vegetative to reproductive shift dynamics, and (c) cones/sapling and germinable seeds/cone, for at least 2 years (either consecutive or 2–3 years apart) at a postfire age of 7–12 years.

Ecological structure of burnt-wood flora and stages of their overgrowth in plain pine forests of Altai krai

The ecological structure of burnt-wood flora largely depends on natural and climatic conditions and geographical location. Secondary postfire successions in plain pine forests pass rather quickly, and burnt woods are at the stage of the development of communities of patient plants in 10 years. Pyrophyte plants acquire great significance in the development of vegetation of burnt wood. The development of zonal types of vegetation does not occur in 10 years. A decrease in interfire periods results in the fact that plant communities are under the constant influence of the pyrogenic factor in plain pine forests.

Seedling establishment along post-fire succession in Mediterranean shrublands dominated by obligate seeders

Seedlings are expected to be particularly sensitive to the environmental conditions at the time of establishment. Within succession, environmental conditions vary over time and a species will have a better chance to regenerate on a particular place depending on the intrinsic traits that determine its regeneration niche. We examined the regeneration niche and the pattern of seedling establishment along succession of the main species present in a Mediterranean shrubland. The establishment of Cistus albidus, Rosmarinus officinalis and Ulex parviflorus was monitored for three years using seasonal cohorts in three different stages along a successional gradient (post-fire, building and mature). There was a flush of establishment immediately after fire in all species. After this event, there was a decline in establishment as succession progressed, until practically no seedling establishment was found at mature stages. The presence of a thick litter layer probably precluded seedling establishment at this stage. The establishment of Cistus was very closely tied to the post-fire environment, while recruitment of Rosmarinus and Ulex also occurred in the building stage. In contrast to what has been reported in other Mediterranean shrublands, recruitment in our study area was not restricted solely to post-fire stages, and shrubs also recruited opportunistically when open gaps in the canopy were available along succession. The differences in preferred micro-sites for the establishment suggest a differentiation in regeneration niches and a particular set of environmental conditions where the different species would be particularly competitive through succession. Thus, Cistus regenerates mostly in highly perturbed environments, whereas Ulex and Rosmarinus benefit from environments with longer inter-fire periods.

Fire Effects on Demography of the Invasive Shrub Brazilian Pepper (Schinus terebinthifolius) in Florida Pine Savannas

Fire is a common disturbance in savanna ecosystems that may either facilitate or impede non-native plant invasions. Although fire can create recruitment opportunities for non-native plants, it can also prevent their invasion if it exerts strong negative effects on their demographic processes. Some savannas may, therefore, be able to resist invasion provided the natural, frequent-fire regime remains intact. We examined the effects of fire on the demography of the invasive shrub Brazilian pepper, Schinus terebinthifolius Raddi., which is invading fire-prone slash pine savannas of southern Florida. We studied survivorship, growth, and reproduction of low-density populations of Brazilian pepper in a pine savanna within Everglades National Park to investigate whether fire might suppress Brazilian pepper in the early stages of invasion. We found a significant decrease in Brazilian pepper survivorship following fire, particularly among small individuals. We further found that fire reduced fecundity of surviving Brazilian pepper individuals for at least two years. However, resprouting individuals that survived fire had high relative growth rates the following year, which could facilitate population recovery during inter-fire periods. We used a simple population simulation to show that a low-density cohort of Brazilian pepper may be rapidly eliminated from pine savannas with fire-return intervals of four years or less, but individuals may persist for > 50 years with fire-return intervals of eight years or more. Our study suggests the need to maintain the historical frequent-fire regime in pine savannas in order to prevent their invasion by fire-intolerant shrubs such as Brazilian pepper.

Genetic structure of seedling cohorts following repeated wildfires in the fire‐sensitive shrub Persoonia mollis ssp. nectens

Summary 1 Increased fire frequency is seen as a key threat to plant populations in Mediterranean-type ecosystems across the globe. Short inter-fire periods may exhaust soil-stored and fire-stimulated seed banks of fire-sensitive species, reducing actual and effective population sizes and eroding genetic diversity. 2 Here we used microsatellite genotyping to investigate the genetic impacts of repeated wildfires and, in particular, the contribution of above-ground genetic processes (seed and pollen dispersal) to the genetic structuring and composition of post-fire recruits in an isolated population of the fire-sensitive shrub Persoonia mollis ssp. nectens. 3 We tested the hypothesis that limited pollen and seed dispersal, in combination with the potentially patchy effects of fire at a fine scale within populations, would generate a highly structured population, a decline in genetic diversity after each fire and genetic heterogeneity between successive cohorts. 4 Wildfires killed all 25 adult plants in 1997 and, in 2001, killed all of the 476 seedlings remaining from the 1997 seedling cohort. Although there was no possibility of replenishment of the seed bank in the interval between fires, a second cohort of 381 seedlings emerged after the 2001 fire. 5 We found no evidence that successive fires produced either a decline in genetic diversity, as measured by allelic richness or expected heterozygosity, or the genetic differentiation of adult and successive seedling cohorts (Pairwise FST = −0.0125 to 0.0009). The seedling cohorts displayed less genetic structuring than anticipated. Spatial genetic structure was low, ranging from Sp = 0.02 in the 1997 seedlings to Sp = 0.06 in the 2001 seedlings, and using parentage analysis, we found that seedlings clustered under dead adults rarely reflected simple seed shadows. 6 Synthesis. Overall, we found that a numerically large seed bank with a bet-hedging strategy of staged seed germination, in combination with genetic mixing achieved by both pollen and seed dispersal, provides a powerful buffer against the negative impacts of frequent fire in P. mollis ssp. nectens.

A spatial model of coexistence among three Banksia species along a topographic gradient in fire‐prone shrublands

Summary A spatially explicit, rule‐based model for three co‐occurring Banksia species was developed to investigate coexistence mediating processes in a fire‐prone shrubland in western Australia. Fecundity, recruitment, mortality and other biological data for two non‐sprouting (B. hookeriana, B. prionotes) and one resprouting (B. attenuata) species were available from 15 years of empirical field studies. Without interspecific competition, each species could persist for a wide range of fire intervals (10 to > 20 years). The resprouting species performed better under shorter fire intervals (10–13 years), while both non‐sprouting species were favoured by longer (15 to > 20 years) fire intervals. These results conform with those obtained from single‐species, non‐spatial population models. When interspecific competition for space was included in the model, all three species exhibited optima at shorter fire intervals and with a narrower range than in isolation. The three species did not co‐occur under any fire regime. At intermediate fire frequencies (11–13 years), B. hookeriana excluded the other species, while for longer intervals between fires B. prionotes became dominant. The introduction of temporal (stochastic) variability in fire intervals (drawn from a normal distribution) failed to produce coexistence, unless spatial variability as a spatial ignition gradient was also included. The spatial arrangement of the non‐sprouters observed in the field was then reproduced. Observed patterns of coexistence and spatial distributions of all species occurred when a spatial establishment gradient for the resprouter species was included in the model (individuals of B. attenuata are known to produce more seeds in swales than on dune crests and recruit seedlings here more frequently). Coexistence appears to be highly dependent upon the mean interfire period in combination with subtle gradients associated with fire propagation and recruitment conditions. Variation around the mean fire interval is less critical. When the system is modelled over a long time period (1500 years) coexistence is most strongly favoured for a narrow window of mean fire intervals (12–14 years).

Competitive interactions between overstorey proteas and sprouting understorey species in South African mountain fynbos

Abstract. Previous studies in the mountain fynbos of South Africa have demonstrated that short fire cycles favour the establishment of dense covers of understorey sprouters while longer fire intervals enable the establishment from seed of overstorey proteas and the formation of a overstorey. One consequence of these differences between fire cycle lengths is the effect that understorey sprouters and an overstorey protea canopy have on species richness. In the case of short fire intervals, species richness is decreased while longer intervals between fires allow species richness to decrease or increase depending on the patchiness of the overstorey canopy. Such results are suggestive of competitive effects between understorey sprouters and overstorey canopy proteas. In this study, data were collected from several pyric successional stages in mountain fynbos to study the effect of overstorey proteas on the growth and flowering of understorey sprouters since the last fire. Data were also collected to determine the effect that understorey sprouters had on the establishment and fecundity of overstorey protea species. Competitive interactions between overstorey proteas and sprouting understorey species were evident at all the sites studied. The vegetative growth and seed production of understorey sprouters, which grew under a canopy of overstorey proteas during the current interfire period, were significantly lower than that for plants growing in the open. In addition, the postfire growth and seed production of understorey sprouters were significantly lower for individuals, which grew under an overstorey protea canopy during the previous fire cycle, than for those individuals which grew in the open. The fecundity of overstorey proteas, which grew near understorey sprouters, was lower than that of plants which grew in the open. This effect was evident for up to the first 15 years after a fire. However, not all understorey sprouters affected the overstorey proteas equally. Also, seedlings of overstorey proteas established significantly less successfully in close proximity to understorey sprouters after a fire than in the open or under proteas. Finally, the results demonstrate that complex species‐specific, understorey–overstorey interactions are important in mountain fynbos. For example, some overstorey species depend on trophically similar species to reduce potential competition from understorey sprouters for their successful establishment at a site.

Modelling the persistence of an apparently immortal Banksia species after fire and land clearing

A stage-based model was developed for the population dynamics of Banksia goodii, a rare long-lived shrub in Western Australia. While few seeds are produced, death of adults due to senescence or fire has yet to be observed. A sensitivity analysis showed that population growth is close to zero as long as post-fire mortality and recruitment are within their usual low bounds. To remain viable, the size of a population remnant should exceed about 80 individuals. If fires occur at random intervals, an average of one fire in 10–15 years is optimal. Regular fires should have inter-fire periods of 15–20 years. Loss of adult plants due to human activities, such as land clearing, will increase mortality beyond its natural bounds and cannot be compensated for, due to the low fecundity of this species. Hand sowing after a fire may raise establishment by orders of magnitude and achieve a permanent population increase within the first year. Conservation authorities should target the sensitive factors through active management at the recruitment stage and by ensuring that no further loss of mature plants takes place through land clearance. ©

Fire-Stick Forestry: A Matrix Model in Support of Skilful Fire Management of Callitris intratropica R. T. Baker by North Australian Aborigenes

The response of a monospecific stand of Callitris intratropica R. T. Baker & H. G. Smith to a range of fire intensities and inter-fire periods were simulated using a stage based matrix model. The model used published values for life history parameters and incorporated linear density dependence in fecundity and growth. Mild fires (i.e. those that killed to mature trees) with mean period between 2 to 8 years maintained a healthy stand structure. More frequent or more intense fires resulted in damage or extinction of the stand, whereas decreasing frequency or intensity yielded stands which were heavily stocked with saplings, few of which were recruited into the larger size classes. These results were largely insensitive to modification of life history parameters. We conclude that stands of C. intratropica on sites without topographic fire-protection must have been maintained by Aboriginal fire management. Observed damage and decline of C. intratropica stands is consistent with a reversion to uncontrolled fire regimes in the recent past.

Germination ecology of six shrubs in fire-prone Cape fynbos

To explain the recruitment and coexistence of species which establish after fire, this study predicted that each species would have different germination cues as a component of different regeneration niches. Furthermore, for species subject to natural fire frequencies of 10–20 years, fire-related cues, seed dormancy, extended longevity and fire-related germination cues might be predicted. However, results indicated broadly similar germination requirements. Seeds subjected to two heat treatments and a charcoal extract failed to show significantly enhanced germination. Instead, highest germination successes were achieved under alternating diurnal temperatures which implied an indirect fire cue, viz. the removal of insulating vegetation. Leachate solution inhibited germination in two species suggesting allelopathic effects during inter-fire periods. Only two species showed dormancy and three species did not have extended longevity but showed declining germinability after three years. Finally, in order to determine the potential germination from a soil-stored seed bank, data analysis simulated a seed bank comprising three years' accumulation of seeds. In each species the proportion of germinable seeds varied each year over the three years. Also, the germinability in response to ageing varied for each year's seed production. This would explain the variation in densities of the six species after different fire events, and hence offers a better explanation for species' coexistence.

Postfire Flowering Patterns in Blandfordia nobilis (Liliaceae)

Blandfordia nobilis Smith (Liliaceae) is a small herbaceous monocotyledon that resprouts from a rhizomatous corm after fire. The complex pattern of flowering shown in the five years following a fire in January 1987 was investigated for five populations near Sydney. This pattern was then related to concurrent changes in soil chemistry. Most (60%) plants flowered in the first post-fire flowering season (November-January), but this dropped to fewer than 20% of the plants flowering by the third or fourth season. Most plants flowered only once, but almost all plants did flower. Consequently, 35% of the flowering events were by plants that flowered only within the first year. Flowering in the first season produced more flowers per plant in that season, and was also correlated with increased chance that a plant would flower again. Repeat flowering produced fewer flowers per plant in the subsequent seasons, but multiple flowering did increase the total number of flowers produced per plant. This form of pulse flowering and short secondary juvenile period after fire seems to be typical of resprouting monocotyledons in Australia, but is much less common among resprouting dicotyledons. The pulse of flowering appears to be closely associated with changes in the soil chemistry during the post-fire period. Many of the soil attributes measured show either a characteristic decrease or increase during the 3-4 years following the fire, with a subsequent reversal in the trend. The plants thus flower prolifically during these changing soil conditions, but almost cease flowering when these changes are reversed, thereby taking advantage of soil conditions that are not available throughout most of the inter-fire period.

Vegetative morphology and interfire survival strategies in the Cape Fynbos grasses

It is shown that there is a wide range of structural variation in the habit of the Arundineae and Ehrharteae of the fynbos of the Cape Floristic Region (Cape Province, South Africa). Structural differences in the bases of the fynbos grasses have been classified into four groups: swollen, knotty tillering, weak and annual. Variation in the position of the innovation buds occurs with one group having basal perennating buds, implying that all the culm material is annual, while the second group has cauline innovation buds, leading to the development of a divaricate perennial herb. The recognition of caducous, mesic (orthophyllous) and sclerophyllous leaf blades is also possible, based on leaf morphology and anatomy. These variations in growth forms allow the classification of the Cape grasses into five guilds adapted for survival in the dense fynbos vegetation that develops between the well-spaced fires in these heathlands. The following guilds have been recognized: competition avoiders that grow on rock ledges and outcrops where competition from shrubby vegetation is reduced; reseeders, that survive the protracted interfire period as seed; geophytes, that survive this period as underground organs; coppicers, that survive as small plants; and competitors, that grow tall by means of cauline innovation buds, and so are able to compete with the shrubby heath vegetation.

Postfire Demography of Thermopsis macrophylla H. A. var. agnina J. T. Howell (Fabaceae), a Rare Perennial Herb in Chaparral

-Demography of the rare perennial herb Santa Ynez thermopsis (Thermopsis macrophylla var. agnina) was monitored at two sites for 9 yr after a controlled burn in the Santa Ynez Mountains near Santa Barbara, California. One of the burned sites was located in chaparral and the other in a fuelbreak, an area purposely cleared of chaparral to slow the advance of wildfire. Numerous individuals resprouted in the 1st yr after the fire and thousands of seedlings established from heat-stimulated germination of refractory seed. Vegetation before and after the fire was markedly different between the two sites. Despite this difference, however, seedling production was very similar on the two sites. Losses of recruits-seedlings that survived beyond the 1st yr-also were similar. Nine yr after the fire the density of recruits was equivalent on both sites. Recruits were significantly taller in the fuelbreak than in the chaparral but the average number of stems/individual was not different. Individuals that resprouted after the fire produced more than 106 seeds/900 m2 from 1980-1987. However, only 3.9% of the seed was present in the soil 8 yr after the fire. Seed production by recruits, in contrast, was very low and appeared to be declining. Thus, this species relies heavily on seed production by resprouts to maintain a sizable soil-seed bank. In addition to seed production by resprouts, the survival of recruits during the interfire period is a critical life history stage in the population biology of this species. Recruits that survive both the interfire period and the next fire show marked increases in stem production, seed output and survivorship.

Nutrient accumulation in and release from the litter layer of karri ( Eucalyptus diversicolor) forests of southwestern Australia

Dry weight and nutrient content of the litter layer of pole-stand karri forest growing in southwestern Australia were related to period of accumulation by the function X t =X SS (1 − e − kt )+ X 0e − kt where X t is the amount of dry weight or nutrients present in the forest floor at time t, X SS is the amount present under equilibrium conditions, X 0 is the amount present at t=0, and k is a constant. This relation explained 90% of the variation in litter dry weight and from 65% to 91% of the variation in amounts of nutrients accumulating in the forest floor. Rate of dry weight and nutrient accumulation was initially rapid, reaching 50% of the equilibrium values, X SS, in 2.4 to 5.5 years. Almost half of the litter dry weight and two-thirds of the N, P and S were stored in the fine (< 1-cm) fraction of litter 9 years after fire. Rates of release of dry weight and nutrients from the forest floor were estimated from annual inputs in litterfall and annual increments in the amounts stored in the forest floor. The mobile elements Na and K were released rapidly from the litter layer, Ca and Mg were released at approximately the same rate as litter dry-weight and N, P and S initially accumulated were then slowly released from the forest floor. The effects of periodic prescribed burning on cycling of nutrients in forest litter are discussed. Nitrogen and P are the elements most affected by current burning practices. More research is needed to quantify the effects of recurrent fires in karri forest on P nutrition. Budgets based on data currently available on rates of N accession in rainfall and through symbiotic and non-symbiotic N 2-fixation suggest that, with current burning frequencies, volatilization of N from the litter layer and understorey vegetation during fire may exceed cumulative accretion of N to the ecosystem during inter-fire periods. More precise estimates of N inputs and outputs are needed to confirm this.