Resprouting vigour of two mediterranean shrub species after experimental fire treatments

Experimental fire treatments were carried out by applying a propane torch flame to individual stumps ofArbutus unedo andErica arborea, two dominant ericaceous shrubs living in relatively moist maquis of the western Mediterranean Basin. No mortality was observed in either species. Individual plant size, measured as the individual stump area, was the most important factor determining both number and biomass of resprouts for all fire treatments. The number of resprouts at 3 months was less at the higher temperature, but no difference could not be detected at 18 months. Duration of flame application had no effect on resprouting success. This effect was not statistically significant 18 months after treatments were applied. Biomass of resprouts was not clearly affected by different fire treatments either 3 months or 18 months after the start of the resprouting process.     

How to tell a shrub from a tree: A life‐history perspective from a South African savanna

The ecological differences between ‘shrubs’ and ‘trees’ are surprisingly poorly understood and clear ecological definitions of these two constructs do not exist. It is not clear whether a shrub is simply a small tree or whether shrubs represent a distinct life‐history strategy. This question is of special interest in African savannas, where shrubs and trees often co‐dominate, but are often treated uniformly as ‘woody plants’ even though the tree to shrub ratio is an important determinant of ecosystem functioning. In this study we use data from a long‐term fire experiment, together with a trait‐based approach to test (i) if woody species usually classified as shrubs or trees in African savanna differ in key traits related to disturbance and resource use; and (ii) if these differences justify the interpretation of the two growth forms as distinct life‐history strategies. We measured for 22 of the most common woody plant species of a South African savanna 27 plant traits related to plant architecture, life‐history, leaf characteristics, photosynthesis and resprouting capacity. Furthermore we evaluated their performance during a long‐term fire experiment. We found that woody plants authors call (i) shrubs; (ii) shrubs sometimes small trees; and (3) trees responded differently to long‐term fire treatments. We additionally found significant differences in architecture, diameter‐height‐allometry, foliage density, resprouting vigour after fire, minimum fruiting height and foliar δ¹³C between these three woody plant types. We interpret these findings as evidence for at least two different life‐history‐strategies: an avoidance/adaptation strategy for shrubs (early reproduction + adaptation to minor disturbance) and an escape strategy for trees (promoted investment in height growth + delayed reproduction).     

Long-term post-fire resprouting dynamics and reproduction of woody species in a Brazilian savanna

Resprouting is an efficient life history strategy by which woody savanna species can recover their aboveground biomass after fire. However, resprouting dynamics after fire and the time it takes to start producing flowers and fruits are still poorly understood, especially for the Brazilian savanna (Cerrado biome), where fire is an important driver of vegetation structure and ecosystem functioning. We investigated the resprouting dynamics and production of flowers and fruits of 26 woody species (20 tree and 6 shrub species for a total of 485 individuals) that were burned and the production of flowers and fruits for a subset of 12 species (139 individuals) in an unburned area in a Brazilian savanna. We classified the species’ resprouting strategies as hypogeal (at the soil level, with main stem death), epigeal (on the main stem or crown), and hypogeal + epigeal. We used generalized linear mixed-effect models to identify the post-fire recovery patterns for five years. Individuals with basal resprouts (hypogeal and hypogeal + epigeal resprouting) produced an average of 6 basal resprouts, but only 33% of resprouts survived after five years. Individuals in burned areas produced fewer flowers and fruits than individuals in unburned areas. At least a subset of individuals in all the resprouting strategies started to produce flowers and fruits in the first-year post-fire. About 68% of the species with hypogeal resprouts produced flowers and fruits in the first-year post-fire, but the intensity of flowering and fruiting was lower compared to individuals with other resprouting strategies over time. Although woody species have invested in post-fire growth and sexual reproduction in all resprouting strategies, the long time needed to recover these processes can make these species more vulnerable to frequent fires.     

Resprouting of Erica multiflora after experimental fire treatments

Abstract. The effect of fire intensity - both temperature and duration - on the resprouting pattern of the evergreen Mediterranean shrub Erica multiflora in relation to plant size, was experimentally investigated by subjecting plants to the flame of a propane torch, and observing mortality and resprouting after 5 and 20 months. Pre-treatment plant size was not important in determining post-fire plant survival, but it did influence the resprouting vigour, increasingly so with time. High temperatures induced higher mortality rates within populations, but duration of fire did not effect mortality. Biomass of resprouts was lower following more intense fire treatments, but this effect progressively disappeared over time, except in plants subjected to the most intense fire treatment. This is probably because of the increasing importance of the below-ground organs for the regeneration of the above-ground biomass. Some of the plants which were clipped but not exposed to fire also died 20 months after treatment. The effect of clipping onmortality andresprout-ing response, estimated as biomass of resprouts, was not significantly different from the effect induced by either low or medium temperature treatments, but was significantly different when compared with the effect of high-temperature treatments. Field observations show that the establishment of seedlings of E. multiflora is rare both after fire and between fires. Thus, our data support the idea that both a single fire or clipping can diminish the population size of a resprouting species. We conclude that fire may have a stochastic effect on E. multiflora populations, due to the variation in fire intensity existing within a single burning stand.     

Effects of habitat and growing season fires on resprouting of shrubs in longleaf pine savannas

The effects of habitat and timing of growing season fires on resprouting of shrubs were studied in second-growth longleaf pine savannas of the west Gulf coastal plain in the southeastern United States. Within the headwaters of three different drainages of the Calcasieu River in the Kisatchie National Forest in western Louisiana, replicated permanent transects were established that extended from xeric upland longleaf pine savannas into downslope hydric seepage savannas. All shrubs were mapped and tagged, and numbers of stems were counted prior to any fires. Replicated prescribed fires were set early (June) and late (August) during the 1990 growing season; maximum fire temperatures were measured within both upland and seepage habitats within each transect. Shrubs were relocated; stems were recensused two and twelve months after the fires. At least some shrubs of all species resprouted from underground organs; none regenerated solely from seed banks in the soil. There was no reduction in total numbers of stems one year after fires compared to before fires, either in the upland or in seepage savannas. In addition, there was no reduction in total numbers of stems one year after early or late growing season fires. Fire-related mortality was restricted to small shrubs (< 18 stems) and was not associated with high fire temperatures. The rate of resprouting varied among species and between habitats. Resprouting occurred more rapidly in seepage than upland savannas, but more resprouts were produced in upland than seepage savannas one year after fires. In contrast to other upland species, Vaccinium arboreum and V. elliottii delayed resprouting more than two months following fire. Stems of Rhus copallina and Pyrus arbutifolia, species with long rhizomes, increased more after fires in June than fires in August. We suggest that growing season fires may block further recruitment of shrubs into longleaf pine savannas, but reduction in numbers of large shrubs may require additional management.     

Uprooting and Burial of Invasive Alien Plants: A New Tool in Coastal Restoration?

Invasive alien plants are a problem for conservation management, and control of these species can be combined with habitat restoration. Subsoil burial of uprooted plants is a new method of mechanical control, which might be suitable in disturbed habitats. The method was tested in Rosa rugosa (Japanese Rose), an invasive shrub in north‐western Europe with negative effects on coastal biodiversity. Two months after uprooting and burial in dunes of north‐eastern Denmark, 89% of the 58 shrubs resprouted from roots and rhizomes; on average 41 resprouts per shrub. Resprout density was twice as high at former shrub margins compared with the center; resprouts were taller and originated from more superficial soil layers at the margin than in the center. Resprouting was negatively correlated with fragment depth, and no resprouts were observed from greater than 15 cm depth. The number of resprouts increased with fragment dry mass (0.5–168.5 g). After 18 months with harrowing the species was still resprouting, flowering, and fruiting, albeit with no difference between shrub margin and center. Resprouts were taller (26 cm) and coverage was higher (0–4%) after two compared with three times harrowing, whereas no difference was found in cover of native dune species (1–5%). The results show that even small fragments of R. rugosa resprout, and that resprouting persists despite repeated harrowing. Thus, careful subsoil burial of all fragments is necessary, special attention should be paid to the shrub margin, and follow‐up treatments are needed. The effectiveness of the burial method is discussed for restoration of coastal dunes.     

Winners and losers: tropical forest tree seedling survival across a West African forest–savanna transition

Forest encroachment into savanna is occurring at an unprecedented rate across tropical Africa, leading to a loss of valuable savanna habitat. One of the first stages of forest encroachment is the establishment of tree seedlings at the forest–savanna transition. This study examines the demographic bottleneck in the seedlings of five species of tropical forest pioneer trees in a forest–savanna transition zone in West Africa. Five species of tropical pioneer forest tree seedlings were planted in savanna, mixed/transition, and forest vegetation types and grown for 12 months, during which time fire occurred in the area. We examined seedling survival rates, height, and stem diameter before and after fire; and seedling biomass and starch allocation patterns after fire. Seedling survival rates were significantly affected by fire, drought, and vegetation type. Seedlings that preferentially allocated more resources to increasing root and leaf starch (starch storage helps recovery from fire) survived better in savanna environments (frequently burnt), while seedlings that allocated more resources to growth and resource‐capture traits (height, the number of leaves, stem diameter, specific leaf area, specific root length, root‐to‐shoot ratio) survived better in mixed/transition and forest environments. Larger (taller with a greater stem diameter) seedlings survived burning better than smaller seedlings. However, larger seedlings survived better than smaller ones even in the absence of fire. Bombax buonopozense was the forest species that survived best in the savanna environment, likely as a result of increased access to light allowing greater investment in belowground starch storage capacity and therefore a greater ability to cope with fire. Synthesis: Forest pioneer tree species survived best through fire and drought in the savanna compared to the other two vegetation types. This was likely a result of the open‐canopied savanna providing greater access to light, thereby releasing seedlings from light limitation and enabling them to make and store more starch. Fire can be used as a management tool for controlling forest encroachment into savanna as it significantly affects seedling survival. However, if rainfall increases as a result of global change factors, encroachment may be more difficult to control as seedling survival ostensibly increases when the pressure of drought is lifted. We propose B. buonopozense as an indicator species for forest encroachment into savanna in West African forest–savanna transitions.     

Using consecutive prescribed fires to reduce shrub encroachment in grassland by increasing shrub mortality

Woody plant encroachment into open grasslands occurs worldwide and causes multiple ecological and management impacts. Prescribed fire could be used to conserve grassland habitat but often has limited efficacy because many woody plants resprout after fire and rapidly reestablish abundance. If fire‐induced mortality could be increased, prescribed fire would be a more effective management tool. In California's central coast, shrub encroachment, especially of Baccharis pilularis (coyote brush), is converting coastal prairie into shrub‐dominated communities, with a consequent loss of native herbaceous species and open grassland habitat. B. pilularis has not been successfully controlled with single prescribed fire events because the shrub resprouts and reestablishes cover within a few years. We investigated whether two consecutive annual burns would control B. pilularis by killing resprouting shrubs, without reducing native herbaceous species or encouraging invasive plants. As expected, resprouting did occur; however, 2 years after the second burn, B. pilularis cover on burned plots was only 41% of the cover on unburned plots. Mortality of B. pilularis more than doubled following the second burn, likely maintaining a reduction in B. pilularis cover for longer than a single burn would have. Three native coastal prairie perennial grasses did not appear to be adversely affected by the two burns, nor did the burns result in increased cover of invasive species. Managers wanting to restore coastal prairie following B. pilularis encroachment should consider two consecutive annual burns, especially if moderate fire intensity is achievable.     

Effects of inter‐fire intervals on the reproductive output of resprouters and obligate seeders in the Proteaceae

Abstract Fire is often used as a management tool in fire‐prone communities to reduce fuel loads with the intention of reducing the severity and extent of unplanned fires, often resulting in the increased occurrence of fire in the dry sclerophyll vegetation of Australia. This study examined the effects of fire frequency (length of the inter‐fire interval) on the reproductive output of seven plant species in the Proteaceae, including obligate seeding shrubs (Hakea teretifolia, Petrophile pulchella), resprouting shrubs (Banksia spinulosa, Isopogon anemonifolius, Lambertia formosa) and resprouting trees (Banksia serrata, Xylomelum pyriforme). Reproductive output (measured as either number of confructescences or follicles) and relative size were estimated for 100 individuals at each of five sample sites, covering a range of past fire frequencies over 26 years including repeated short inter‐fire intervals. Patterns in reproductive output (after standardizing for size) were related to the life‐history attributes of the species. In areas that had experienced short inter‐fire intervals, obligate seeders had greater reproductive output compared with longer intervals, and the reproductive output of resprouting shrubs was less. Fire frequency did not affect reproductive output of the resprouting trees. The decreased reproductive output of the resprouting shrubs could be due to the allocation of resources to regrowth following fire rather than to reproduction. It is less clear what process resulted in the increased reproductive output of obligate seeders in high fire frequency areas, but it could be due to the most recent fires being more patchy in the areas experiencing shorter inter‐fire intervals, or it may have resulted from the selection for early reproduction in the high fire frequency areas. These results highlight the need to take into account past fire frequency at a site, in addition to time since the last fire, when planning prescribed fires.     

Post‐fire recovery occurs overwhelmingly by resprouting in the Chaco Serrano forest of Central Argentina

In fire‐prone landscapes, differences in post‐fire regeneration by resprouting between species or sites could be far more important in explaining vegetation physiognomy and composition than seed regeneration. This is the first study exploring the relative contribution of tree resprouts and seeds to post‐fire crown volume in the Chaco Serrano forest of South America. Additionally, we compare the resprouting response among species and quantify post‐fire changes in tree composition among sites. We established 290 permanent plots distributed in three sites affected by wildfires in 2005. For all tree species in all plots we recorded survival of every individual 1 year after the fire; at the plot level, we recorded the above‐ground tree volume before and 3 years after the fire. Resprouting from the base was the main resprouting type. Survival varied between species from 73% to 100% for native species and from 7% to 100% for non‐natives. Before the fire, crown volume was similar in the three sites, and was completely lost after the fire in 92% of the plots. Three years after the fire, between 8% and 58% of crown volume was recovered. The ratio of crown recovery because of resprouts and seedlings was 1562:1. Tree composition exhibited few changes because of the high post‐fire survival of most native species. We conclude that in the semiarid Chaco Serrano ecosystem tree species regenerate mainly by resprouting. This regeneration mode should be taken into account to better understand post‐fire successional pathways of these forests, their management and the restoration of burnt forest areas.     

Fire intensity and herbivory effects on postfire resprouting of Adenostoma fasciculatum in southern California chaparral

Summary Resprouting is the main regeneration mechanism after fire in Mediterranean-type ecosystems. Herbivores play an important role in controlling postfire seedling establishment, but their influence on regeneration by resprouting is less well known. To study the effects of fire intensity on resprouting of Adenostoma fasciculatum in southern California chaparral, and its interaction with herbivory, we conducted an experimental burn at three levels of fire intensity. We found that increasing fire intensity increased plant mortality, reduced the number of resprouts per plant, and delayed the time of resprouting. Herbivory increased with fire intensity, and was related to the time of resprouting. Plants resprouting later in the season and out of synchrony with the main flush were attacked more readily by herbivores. Post-resprouting mortality also increased with fire intensity and was significantly associated with herbivory in the higher fire intensity plots. Fire intensity effects on chaparral regeneration by resprouting may be farreaching through effects on the population structure, resprout production, and growth of Adenostoma fasciculatum.     

Fire-tolerance mechanisms of common woody plant species in a semiarid savanna in south-western Zimbabwe

The frequency of fire has increased in savannas yet few studies have assessed how plants persist when subjected to long‐term disturbance by fire. We investigated the contributions of bark thickness and resprouting to the persistence of woody plants in two fire trials that were started in 1948 and 1949. The number of resprouts per individual, bark thickness, basal diameter and height of woody plants were measured in unburnt plots and those burnt annually, triennially and quinquennially during the late dry season. Changes in tree density, number of resprouts and individuals in different height classes between 1963 and 2002 were assessed. Bark thickness varied among species and also increased with increases in basal diameter. Generally, plants with thick bark survived fire more than those with thin bark. Resprouting was the major fire survival strategy for most species. The number of resprouts produced per plant ranged from 4 ± 3 (Acacia rehmanniana) to 14 ± 9 (Pseudolachnostylis maprouneifolia). Fire reduced species richness in plots burnt annually and triennially by 47% and 6% respectively. Species richness increased in unburnt plots (5%) and those burnt quinquennially (16%). Most woody species survived fire through a combination of traits.     

Resprouting responses of trees in a fire‐prone tropical savanna following severe tornado damage

Fire and windstorms can cause severe disturbance, but their consequences for trees may differ. Resprouting enables persistence through frequent and severe disturbance. To explore responses to an abnormal disturbance and evolutionary hypotheses about resprouting as an adaptation, we analysed patterns of resprouting in four taxa following a tornado in a tropical savanna (Kakadu National Park, northern Australia) that is frequently burnt but is rarely subject to severe windthrow. Resprouting (i.e. survival) rates varied markedly among taxa and damage types, from 35% in uprooted Acacia spp. (Mimosaceae) to over 90% in eucalypts (Myrtaceae) and Erythrophleum chlorostachys (Caesalpiniaceae) with persistent tertiary branches. Most resprouting was from the epicormic strand‐bank on the stem or branches. Across all taxa, greater architectural damage reduced resprouting rates. Damage was magnified by proximity to the centre of the tornado path, suggesting an additional effect of internal damage. Smaller trees, trees whose trunks were snapped below 2 m, and those closer to the tornado path were more likely to resprout basally or from the roots rather than epicormically, although in Acacia spp. these resprouting modes were positively correlated. We hypothesize that trees of fire‐prone savannas have evolved to grow rapidly out of the flame zone; this was supported by more detailed analyses of Eucalyptus tetrodonta suggesting that resprouts emerging nearer the ground grow faster. Resprouting at ground level may be a bet‐hedging strategy to spread the risk of mortality among multiple stems when elevated sprouting was not possible. We conclude that the adaptation of eucalypts to frequent fire does not jeopardize their survival (by comparison with the more generalist Acacia spp.) following severe windthrow, providing an example of ‘exaptation’ rather than trade‐off in fitness under contrasting stressors.     

Fire and the demography of camelthorn (Acacia erioloba Meyer) in the southern Kalahari – evidence for a bonfire effect?

Fires in arid environments are rare, so are not deemed as important as in mesic savannas. We investigated mortality and resprouting amongst camelthorn (Acacia erioloba) after two fires (at Vaalbos National Park and Susanna farm) in semi‐arid savanna near Kimberley, South Africa. Resprouting response 18 months after a fire was the greatest amongst <6.5 m high trees; extent of foliage damage by fire and bark thickness were the next best predictors of resprouting vigour amongst that size class. The largest size class (8–12 m height) of A. erioloba suffered the greatest mortality rates (40% and 83% at Vaalbos and Susanna respectively), with damage either severe or minor. We hypothesize that large tree mortality rates are partly attributable to well‐developed assemblages of flammable subcanopy plants producing a bonfire beneath trees. These mortality rates indicate that fire reduces both tree abundance and relative representation of large trees, and although able to resprout, A. erioloba is fire‐sensitive, which may explain its restriction to Kalahari sands where rainfall is less than 900 mm year^?1. Therefore, although relatively infrequent, fires shape Kalahari woodland structure, particularly as A. erioloba is long lived and slow growing. Large trees have been shown to be important to biodiversity in the southern Kalahari, so frequent fires could impact biodiversity.     

Resprouting of saplings following a tropical rainforest fire in north‐east Queensland,Australia

Abstract In 2002, fire burnt areas of Mesophyll‐ and Notophyll Vine Forest in the Smithfield Conservation Park near Cairns, Australia. We assessed the ability of rainforest plant species to persist through fire via resprouting. Natural rates of mortality and resprouting in unburnt areas were assessed for all saplings (stems < 2 m) via 13, 2 × 50 m belt transects, and compared to estimates of mortality and resprouting in 26 transects in burnt areas. We also tested the resprouting ability per‐individual stem of each species against all other stems with which it co‐occurred. Totals of 1242 stems (138 species) were sampled in burnt transects and 503 stems (95 species) in unburnt transects (total number of unique species = 169). There was no difference in the number of stems existing prior to the fire in burnt and unburnt areas when expressed on a per‐sample area basis. Resprouting from basal shoots and root suckers was significantly greater in burnt than in unburnt areas, but rates of stem sprouting were not different. In burnt areas 72 species were tested for resprouting ability and most (65/72) resprouted at similar rates. All species analysed contained individuals that resprouted. The resprouting response of five species was significantly lower, and in two species was significantly higher. For these species especially, fire may act as a mechanism altering relative abundances. The fire coincided with an extreme El Niño event. Current predictions indicate El Niño conditions may become increasingly common, suggesting fire events within rainforest could become more frequent. Resprouting as a general phenomenon of rainforest species, and differential resprouting ability between species should therefore be an important consideration in assessing the potential path of vegetation change in rainforests after fire.     

Depletion of regenerative bud resources during cyclic drought: What are the implications for fire management?

Summary   Resprouting is a common regenerative strategy in plant taxa that occurs in fire and drought-prone environments. When plants are forced to use bud resources in quick succession as a result of repeated disturbances, recovery vigour may be diminished. The loss of bud resources through the combined effect of successive fire and drought is likely to be more damaging for plant survival and persistence than one or other disturbance on its own. In this study, we examine the resprouting response of seven trees and two shrubs after fire and drought in woodland communities in the New England and Bioregion of New South Wales. We also investigate whether there is a cumulative impact on plant vitality as a result of the combined disturbances of fire followed by drought. Preliminary results suggest that resprouting after drought occurs from buds located on the same morphological parts of tree and shrub species as after fire, although the response reflects the intensity of impact. Mortality in nine species affected by drought was similar to that in plants affected by both fire and drought. Since a drought between successive fires has the potential to deplete bud resources and debilitate plants, drought should be taken into account when determining fire regimes, and a severe drought between two fires should be considered in a similar way to an unplanned burn. Failure to do so may lead to reduced vigour and excessive mortality in resprouting species after planned fire.     

Early post-fire vegetation regeneration in <Emphasis Type="Italic">Larix kaempferi</Emphasis> artificial forests with an undergrowth of <Emphasis Type="Italic">Sasa senanensis</Emphasis>

Post-fire vegetation regeneration was studied for a 6-year period in a 13-year-old-artificial forest consisting of Larix kaempferi with a dense undergrowth of Sasa senanensis. The study site was classified into three fire severity categories according to the degree of Sasa senanensis scorching, that is, a high-severity category, a mid-severity category, and a low-severity category. Study plots were established in areas which fitted the criteria for each category, and in nearby unburned sites. A total of 41 woody species were newly emerged during the 6-year study period in the burned and unburned plots. Only a few seedlings and resprouts emerged in the unburned plots, while many seedlings emerged in the high-severity plots from the first year after fire onward. A high-severity fire that burns the rhizomes of Sasa is necessary for the vegetation recovery by germination of seed. Whereas the establishment of seedlings was restricted to a few years after fire, the regeneration through resprouting continued into the last year of observation. The survival time of resprouts was longer than that of seedlings, and the survival time of shade-tolerant species was longer than that of shade-intolerant species. In contrast, shade-intolerant species grew more rapidly than shade-tolerant species. The plants ability to exceed the maximum height of the Sasa before the bamboo recovers can be critical to the survival of shade-intolerant species. Because resprouts have a stronger resistance to the shade of Sasa than seedlings, the resprouts of shade-tolerant species play a major role in the re-establishment of woody species after fire in sites with considerable Sasa ground-cover.     

Post-fire regeneration strategies of Californian coastal sage shrubs

Summary Regeneration methods for coastal sage srub vegetation after fire were studied in the coastal Santa Monica Mountains of southern California. Six sites were sampled two years after a large fire of fall, 1978. The intensity of fire varied. Foliar cover and flowering incidence were recorded for individuals regenerating by resprouting or from seed. Resprouting plants contributed most to post-fire recovery, comprising 95% of the relative foliar shrub cover; 84% of resprout and 47% of seedling cover had flowered. An ANOVA of reproductive mode and fire intensity indicates that resprout total cover and individual size are significantly greater than those of seedlings, regardless of fire intensity. Among sites the average foliar cover of resprouts exceeded that of seedlings by factors ranging from 9 to 63. All coastal sage species examined resprout, although the potential vigor of resprouting appears to vary widely within genera (e.g. Encelia, Eriogonum, and Salvia) and even within species. In the second growing season following fire seedling density increased due to seeds shed by resprouted shrubs. Most of the cover on these stands of coastal sage scrub is destined to be either crown-sprouted individuals or their progeny.     

Development of Brachystegia‐Julbernardia woodland after clear‐felling in central Zambia: Evidence for high resilience

Question: Does the development of Brachystegia‐Julbernardia (miombo) woodland after felling, and under a variable fire regime, occur via a serai stage of fire‐tolerant species? Location: Four sites in central Zambia, Africa. Methods: Trees in replicate plots were clear‐cut and stumps and resprouts enumerated. Species recruited into the tree layer (> 2.0 m tall) were monitored for 11 years (1991–2001) and fire occurrence and herbaceous biomass assessed annually to determine fuel loads. Results: Fire frequency was variable at the study sites and fuel loads were generally too low to suppress woodland regeneration after felling. However, at one site a change from low to high fire frequency arrested woodland development and triggered a regression towards a ‘fire‐trap’ vegetation type in which a few fire‐tolerant species survived. There was no evidence to support the hypothesis that miombo woodland regeneration is facilitated by a sere of fire‐tolerant species. All regrowth after felling was from resprouting plants present before felling. Trees with a previous history of felling sprouted more vigorously than trees that had not been felled before. Species richness in the tree layer increased with time since felling because resprout species had different height growth rates. Conclusion: The resilience of miombo trees after clear‐felling is largely due to their capacity to regenerate vegetatively from resprouts and stumps after release from frequent fires. Coppicing is therefore recommended as a suitable management technique for miombo woodland in central southern Africa.     

POST-FIRE REGENERATION OF SOUTHERN CALIFORNIA CHAPARRAL

Succession of chaparral shrubs was studied for the first 4 years after fire on the four major slope faces at three elevations in southern California. Although total cover fluctuated from year to year, shrub cover increased annually through the third year. There was little or no increase in shrub cover between the third and fourth years. Four years after fire the shrubs covered 55% ground surface at the highest elevation site but only 28% at the lowest elevation site. Shrub cover was similar between slope faces with one exception; at the lowest elevation site shrub cover was twice as great on the north and east-facing slopes as on the south and west-facing slopes. Post-fire recovery of shrubs was by seedlings and/or resprouts. Yucca whipplei was an exception in that it did not resprout once the aboveground parts were killed nor did seedlings establish after fire, however the aboveground parts of many Y. whipplei survived the fire. Species which reproduced entirely by seed did so in the first post-fire year from soil-stored seed with the exception of Ceanothus greggii at the highest elevation site. This species was entirely absent the first year after fire but abundant in the second year. Species producing both resprouts and seedlings varied from site to site in the proportion of resprouts:seedlings. Between 83–100% of the post-fire populations of Cercocarpus betuloides, Arctostaphylos glandulosa, and Xylococcus bicolor were resprouts whereas 12–13% of Ceanothus tomentosus were resprouts. For Adenostoma fasciculatum, resprouts constituted 27–54% of the population at the lowest elevation and 65–94% at the highest elevation; whereas, the Quercus dumosa population was 100% resprouts at the lowest elevation and 31–67% resprouts at the highest elevation. Data are presented on the height of resprouts and seedlings for all species at the end of the first post-fire year.