The role of seed banks in vegetation dynamics and restoration of dry tropical ecosystems

Abstract. This paper reviews studies on seed banks in tropical dry vegetation and, for comparison, some wet tropical and dry subtropical vegetation. A first general conclusion is that tropical seed banks are smaller than those in temperate ecosystems. Many studies are devoted to only one species, among which are several Acacia species, both tropical and subtropical, some of which reach densities in the seed bank of up to 10000 seeds/m². The lesser importance of the seed bank strategy in tropical species may be related to higher risks of seed loss through higher mortality (fire, predation, pathogens etc.), or to intermittent germination occasions in relation to ephemeral favourable conditions (e.g. rains during the dry season). Regarding vegetation dynamics, the importance of seed banks and regeneration from seeds is most pronounced in larger forest gaps. Examples are discussed of rapid succession to forest of savannas after protection from fire, which is partly due to regeneration from the seed bank. The significance of seed banks in vegetation restoration projects is outlined and the need for additional sowing of seeds of important species underlined.     

Fire-mediated interactions between shrubs in a South American temperate savannah

We examined spatial patterns of fire-caused mortality and after-fire establishment of two dominant shrub species, Baccharis dracunculifolia and Eupatorium buniifolium in a humid temperate South American savannah. Our objective was to determine whether fires mediate in interactions between these two species. After a natural fire burned a large tract of savannah, we established two plots (respectively 550 and 500 m²) within which we mapped all surviving and dead shrubs as well as all individuals of shrub species that recruited in the following year. We used techniques of point-pattern analysis to test specific null hypotheses about spatial associations in the distribution, mortality, and establishment of shrubs. Results support the notions that fire mediates interactions between these two species. Fire-caused death of E. buniifolium tended to occur selectively in the vicinities of Baccharis individuals, and recruitment of B. dracunculifolia tended to be concentrated in the places of dead shrubs. These responses, however, were contingent on local abundances of shrubs which depend in part from the recent fire history. Anthropogenic perturbation of the natural fire regime would have therefore distorted the role of fire mediated interactions as drivers of the dynamics of the vegetation of this temperate savannah.     

Effects of fire history and N and P fertilization on seedling biomass,Specific Leaf Area,and root:shoot ratios in a South African savannah

Fire exerts clear direct effects on savannah vegetation dynamics, but the indirect effects of fire, for example via changes in soil fertility, are less clear. In fire-dominated nutrient-poor savannahs, there is little evidence that fire affects plant-available nutrients, but plant performance on soils with contrasting fire histories has not been investigated. A bioassay experiment was conducted in Kruger National Park, South Africa, to test for effects of long-term fire manipulation on the ability of soils to influence tree growth. Combretum hereroense, a common savannah species, was used as a phytometer species in an experiment that combined fire history with N and P fertilization treatments. The results suggested no effect of fire history on a number of seedling traits after seven months of growth. Root mass and shoot:root ratios responded to P addition, with seedlings exhibiting lower allocation to root tissue under elevated P, particularly in the presence of N, suggesting some N and P co-limitation. Overall, it is concluded that there is little evidence that fire degrades or alters soil chemistry in a way that is likely to influence vegetation structure and dynamics in nutrient-poor savannah ecosystems.     

Diversity of germination strategies and seed dormancy in herbaceous species of campo rupestre grasslands

The effects of fire on the vegetation vary across continents. However, in Neotropical fire‐prone grasslands, the relationship between fire and seed germination is still poorly understood, while their regeneration, especially after strong anthropogenic disturbance, is challenging for their conservation. In the present study, we assessed diversity of germination strategies in 15 dominant herbaceous species from Neotropical altitudinal grasslands (locally known as campos rupestres). We exposed seeds to several fire‐related treatments. We also compared germination between regularly and post‐fire fruiting species. Finally, we investigated the diversity of dormancy classes aiming at better understanding the biogeography and phylogeny of seed dormancy. Germination strategies varied among families. Velloziaceae and Xyridaceae produced non‐dormant, fast‐germinating seeds. Cyperaceae and Poaceae showed an extremely low or null germination due to a high proportion of unviable or embryo‐less seeds. The seeds of campo rupestre grasslands are fire resistant, but there is no evidence that fire triggers germination in this fire‐prone ecosystem. Although heat and charred wood did not promote germination, smoke enhanced germination in one grass species and decreased the mean germination time and improved synchrony in Xyridaceae and Velloziaceae. Fire had a positive effect on post‐fire regeneration by stimulating fruit set in some Cyperaceae and Poaceae species. These species produced faster germinating seeds with higher germination percentage and synchrony compared to regularly fruiting Cyperaceae and Poaceae species. This strategy of dispersion and regeneration seems to be an alternative to the production of seeds with germination triggered by fire. Physiological dormancy is reported for the first time in several clades of Neotropical plants. Our data help advance the knowledge on the role of fire in the regeneration of Neotropical grasslands.     

Spatial relationships between the standing vegetation and the soil seed bank in a fire-prone encroached dehesa in Central Spain

Postfire vegetation regeneration in many fire-prone ecosystems is soil seed bank dependent. Although vegetation and seed bank may be spatially structured, the role of prefire vegetation patterns and fire in determining postfire vegetation patterns is poorly known. Here, we investigated the spatial patterning of species abundance and richness in the vegetation and seed bank of a Mediterranean encroached dehesa in Central Spain. The seed bank was studied with and without a heat shock simulating a spatially homogeneous fire. Semivariograms and cross-semivariograms showed that species richness in the vegetation was aggregated in patches, mainly of herbs, with highest values corresponding to high herb cover and low tree cover. Species richness in the seed bank was also structured in patches, but the spatial pattern was weak. Seedling density of germinates in the seed bank also showed weak spatial pattern. Heating increased overall germination and species richness, and the intensity of the spatial pattern of species richness, particularly of herbaceous species. However, seed bank density patterns disappeared after heat shock because of increased germination of shrubs without spatial pattern. Our results document that the spatial structure of plant richness in the vegetation may persist after fire due to the spatial patterns of herbaceous species in the seed bank, and that postfire species richness patterns can arise independently of fire intensity patterns. However, the spatial structure of the vegetation after fire can be altered by the feedback between shrub encroachment and an eventual fire because of the ubiquitous germination of shrubs.     

Does Fire Trigger Seed Germination in the Neotropical Savannas? Experimental Tests with Six Cerrado Species

The Cerrado (Brazilian savanna) is a biodiversity hotspot with a history of fire that goes back as far as 10 million years. Fire has influenced the evolution of several aspects of the vegetation, including reproduction and life cycles. This study tested how fire by‐products such as heat and smoke affect the germination of six species common to two Cerrado open physiognomies: wet grasslands and the campo sujo (grassland with scattered shrubs and dwarf trees). We subjected seeds collected in northern Brazil to heat shock and smoke treatments, both separately and combined, using different temperatures, exposure times, and smoke concentrations in aqueous solutions. High temperatures and smoke did not break seed dormancy nor stimulate germination of the Cerrado study species. However, seeds were not killed by high temperatures, indicating that they are fire‐tolerant. Our findings differed from those of other fire‐prone ecosystems (mostly of Mediterranean vegetation), where fire stimulates germination. Moreover, we provide important information regarding germination strategies of non‐woody Cerrado plants, showing the importance of considering the tolerance of seeds to high temperatures when evaluating fire‐related traits in fire‐prone ecosystems.     

Effects of heat on the germination of sclerophyllous forest species in the highlands of Madagascar

The effects of fire on germination have been extensively studied in many ecosystems. Several studies have shown that plant species in ecosystems frequently exposed to fire can survive through two main mechanisms: vegetative regeneration (re‐sprouts) and recruitment of new individuals from a fire‐resistant seed bank. In Africa, an increase in temperature can break seed dormancy and stimulate germination of some herbaceous and woody species. In Madagascar, the once widespread highland ecosystems dominated by woody species are now highly fragmented and dominated by anthropic grasslands and fields, with a significantly reduced area occupied by sclerophyllous forests referred to as ‘tapia woodlands’. Six species of this endemic vegetation type were studied: Abrahamia ibityensis (Anacardiaceae), Aphloia theiformis (Aphloiaceae), Carissa edulis (Apocynaceae), Pentachlaena latifolia (Sarcolaenaceae), Uapaca bojeri (Phyllanthaceae) and Vaccinium secundiflorum (Ericaceae). Germination tests were conducted (i) by soaking seeds in water for 24 h (imbibition) or (ii) by exposing the seeds to dry heat. Four different temperatures (40, 60, 80 and 120°C) were applied, and seeds were exposed for 10, 30, 60 and 90 min. To simulate hotter faster‐burning fires, two higher temperatures (100 and 120°C) were also used by exposing seeds to dry heat for 5 min. The results did not reveal any significant effect of 24‐h water imbibition on germination. For most species, germination decreased with increasing temperature of treatment using dry heat. Uapaca bojeri did not germinate under any treatment. Further studies on the biological and ecological characteristics of tapia woodland species in response to fire are needed to help guide conservation, management and restoration activities focusing on this endemic vegetation type.     

Feeding patterns of elephants at the Atherstone Collaborative Nature Reserve

The African savannah elephant (Loxodonta africana Blumenbach) is a generalist herbivore that relies on widely distributed resources. Vegetation decline, aggravated by these elephants, can compromise local conservation efforts. Thus it imperative to understand the factors that drive them to consume specific plant species and plant parts. The objective of our study was to investigate the feeding patterns of African savannah elephants in the enclosed bushveld savannah at the Atherstone Collaborative Nature Reserve in South Africa. For 1 year, we examined elephant selection of woody versus herbaceous vegetation, and identified which plant species and parts were preferentially consumed. We accomplished this by directly observing feeding elephants, and by utilizing data collected on elephant footprints, dung piles, stripped bark and broken branches. We further conducted vegetation surveys to determine selection frequency relative to species abundance. Elephants showed a preference for different plant parts consumption in the feeding plots. In total, leaves, branches and bark contributed mostly to their diet. Seasonal selection patterns showed an increasing proportion of bark and branch consumption during the dry season.     

THE ROLE OF FIRE AND OTHER INFLUENCES ON THE SAVANNAH HABITAT, WITH SUGGESTIONS FOR FURTHER RESEARCH

The derivation and definitions of the word “savannah” are discussed. The roles of fire, grazing and shifting cultivation as limiting factors in the savannah habitat are briefly considered. The savannah regions of Africa are made up of communities of plants and animals which have been “deflected” from their normal course of ecological succession by the influences of cultivation, fire, grazing and browsing. Fire-sensitive plants are those which have not developed a resistance to burning. Many plants, for example “geophytes”, have become fire-tolerant. The ability of woody plants to survive underground and regenerate quickly in savannah regions when given respite from grass fires for a few years is one of the reasons why regrowth is so difficult to control in overgrazed country, tsetse control clearings and areas protected from fire. The savannah regions can be regarded as areas of natural or semi-natural vegetation which provide a habitat for wild and/or domestic ungulates. Therefore, it is from the rangeland aspect that the possibilities for further research in the savannah habitat should be considered. To succeed in future research projects, the disciplined co-operation of the local people is essential. A few suggestions for some of the more obvious lines of research are: 1. Prolonged investigations on the effects of fire, grazing and browsing on all types of savannah country. 2. More intensive investigations on root systems and soil moisture relationships of the plants concerned are necessary. 3. Studies of the nutritive value of different plants. 4. Closer investigation into the cultivation of land for subsistence agriculture when it might be put to better use as rangeland is necessary. 5. The possibilities of using all suitable parts of the savannah regions to the best advantage must be investigated in detail. 6. The conservation and use of wild life resources must be studied as an integral part of savannah research.     

Seed heat tolerance and germination of six legume species native to a fire-prone longleaf pine forest

Recognition of spatial heterogeneity of fire at fine scales is emerging, particularly in ecosystems characterized by frequent, low-intensity fire regimes. Differences in heat flux associated with variation in fuel and moisture conditions create microsites that affect survivorship and establishment of species. We studied the mechanisms by which fire affects seed germination using exposure of seeds to fire surrogates (moist and dry heat). Tolerance (survival) and germination responses of six perennial, herbaceous legume species common to the fire-prone longleaf pine–wiregrass ecosystem of the southeastern USA were examined the following heat treatments. Moist heat was more effective in stimulating germination than dry heat flux for most species examined. We also compared intrinsic seed properties (relative seed coat hardness, percent moisture, and seed mass) among species relative to their heat tolerance and heat-stimulated germination responses. Seed coat hardness was closely associated with the probability of dry and moist heat-stimulated germination. Variation among species in optimal germination conditions and degree of heat tolerance likely reflects selection for specific microsites among a potentially diverse suite of conditions associated with a low-intensity fire regime. Fire-stimulated germination, coupled with characteristics of seed dormancy and longevity in the soil, likely fosters favorable recruitment opportunities in restoration situations aimed at reintroducing a frequently prescribed burn regime to a relict longleaf pine site. In a restoration context in which externally available seed pool inputs are limited, this regenerative mechanism may provide a significant source of recruitment for vegetative recovery in a post-fire landscape.     

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.     

The role of soil seed banks in the restoration of dry acidic dune grassland after burning of Ulex europaeus scrub

Question: Can the seed bank play a significant role in the restoration of plant communities of dry acidic dune grassland where fire has destroyed Ulex europaeus scrub? Location: Northern French Atlantic coast. Methods: One year after the fire, the seed bank and vegetation were sampled in 1 m × 1 m plots along three transects from the oldest scrub vegetation towards the grassland. Differences in species richness, seed density and contribution of ecological groups in the seed bank and vegetation along the transects were analysed. Results: Seed density and species richness in the seed bank decreased significantly from the grassland towards the centre of the scrub vegetation; 50% of the seed bank consisted of core species of the target plant community, such as Carex arenaria, Aira praecox, Rumex acetosella and Agrostis capillaris. Seeds of these species were also found in the deeper soil layers beneath the oldest scrub vegetation, indicating that they can be considered to be long‐term persistent. Beneath the youngest scrub vegetation, seeds of rare satellite target species also occurred. However, no target species were established on the burned site after one year, resulting in a large discrepancy between seed bank and vegetation. Conclusions: Although the seeds present in the soil indicate that restoration of the acidic grassland based on the seed bank is possible, additional management actions such as mowing and soil disturbance may be necessary to restrict resprouting of Ulex and to stimulate the germination of seeds of target species in the deeper soil layers.     

Zoogeography of a South African Province: A framework for management

State‐level conservation in South Africa is structured around distinct political entities (i.e. municipalities). This is problematic because an ecological approach that considers species distribution is required to delineate meaningful management units. To do so, vegetation types can be used as management units—however, it is uncertain whether vertebrate communities are associated with vegetation types as defined by the national vegetation map. Here, we investigate mammal diversity patterns within and among biomes (savannah and grassland) and bioregions and test whether different mammal communities were associated with different vegetation types. We used an extensive database of species occurrences in the North West Province. We found that species richness was higher in the savannah than grassland biome. Beta diversity was higher within the savannah than grassland biome, due to greater environmental heterogeneity, though one grassland bioregion was similar to the savannah bioregions. Mammal communities were significantly different among bioregions, but not biomes, suggesting mammal communities are congruent with vegetation type at finer scales (i.e. bioregional), but not at coarser scales (biomes). It thus makes sense to use a bioregional framework to design mammal management strategies. The invasion of grasslands by savannah species should be monitored, specifically given the predicted changes in climate.     

Transcriptome analysis of germinating maize kernels exposed to smoke-water and the active compound KAR<Subscript>1</Subscript>

Background  

Smoke released from burning vegetation functions as an important environmental signal promoting the germination of many plant species following a fire. It not only promotes the germination of species from fire-prone habitats, but several species from non-fire-prone areas also respond, including some crops. The germination stimulatory activity can largely be attributed to the presence of a highly active butenolide compound, 3-methyl-2H-furo[2,3-c]pyran-2-one (referred to as karrikin 1 or KAR₁), that has previously been isolated from plant-derived smoke. Several hypotheses have arisen regarding the molecular background of smoke and KAR₁ action.     

The promotive effect of smoke derived from burnt native vegetation on seed germination of Western Australian plants

Exposure of dormant seed to cold smoke derived from burnt native vegetation had a positive influence on germination in one or more seed provenances in 45 out of 94 species of native Western Australian plants that are normally hard to germinate. When tested under controlled conditions some species showed earlier germination in smoke treatments than controls; in others smoke-treated seeds continued to germinate for several weeks after controls had achieved full germination. In the remainder, treated and control seeds germinated to similar time schedules. A group of 23 species which responded positively had previously been recorded as extremely difficult or impossible to germinate using conventional techniques. These included members of the genera Geleznowia (Rutaceae), Hibbertia (Dilleniaceae), Stirlingia (Proteaceae), Verticordia (Myrtaceae), Actinostrobus (Cupressaceae) and Pimelea (Thymelaeaceae). Both large- and small-seeded species were encountered amongst the positively responding taxa, which encompassed representatives of 15 families and 26 genera of dicotyledons, 5 families and 8 genera of monocotyledons and the gymnosperm Actinostrobus acuminatus. Sowing seeds on smoke-fumigated filter papers or watering with aqueous eluates of smoke elicited similar degrees of stimulation of germination, as did exposure to gaseous smoke in a readily germinating species Anigozanthos manglesii (Haemodoraceae) and the normally intractable species Lysinema ciliatum (Epacridaceae). Exposing recently burnt and unburnt natural bushland sites to smoke, smoked water or smoked dry sand elicited a significant germination response in 15 species. Over one third of the species sampled in the burnt site exhibited germination additional to that caused by the fire. Data are discussed in relation to previous germination studies on Australian and other taxa.     

Influence of multiple fire‐related germination cues on three Sydney Grevillea (Proteaceae) species

Abstract Many species found in fire‐prone habitats that possess a soil‐stored seedbank only recruit seedlings in large numbers following a fire. Fire‐related germination cues are presumably used by these seeds as signals that a fire has occurred, and would include the heating that occurs in the soil and the combustion products of burning vegetation, smoke and charcoal. Three Sydney species, Grevillea buxifolia (Sm.) R. Br., Grevillea sericea (Sm.) R. Br. and Grevillea speciosa (Knight) McGillivray, were studied for the interactive effects of these cues on their germination. The germination of all species was found to increase with both smoke and heat treatments. While smoke always had a greater influence than heat, the relationship between the two treatments varied with species. The presence of two fire‐related germination cues should allow these species to take better advantage of the recruitment opportunities of the post‐fire environment.     

Fire‐related cues and germination from the soil seed bank of senescent remnants of mallee vegetation on Eastern Kangaroo Island

Plant communities dominated by narrow‐leaved mallee (Eucalyptus cneorifolia) are almost entirely confined to north‐eastern Kangaroo Island, South Australia, an area which has been extensively cleared for agriculture. Consequently, surviving examples consist mostly of small remnants which are thought to be senescent due to the exclusion of fire. This senescence is associated with the loss of many native understory species. Prescribed burns have been suggested as a management tool to stimulate the restoration of native plants from the soil seed bank; however, no seed bank studies have previously been conducted on Kangaroo Island and the seed bank literature usually focuses on particular species rather than on plant communities. We conducted an experiment to investigate the effects of the fire‐related cues heat and smoke on the germination of plants from the seed bank in soil sampled from 10 long‐ungrazed narrow‐leaved mallee sites on Kangaroo Island. Eighty trays of soil were monitored in a controlled glasshouse for five months after being subjected to heat and/or smoke treatments. The overall number of native, but not exotic, plant species germinating from the soil seed bank was significantly increased by all three fire‐related treatments (heat, smoke and heat plus smoke) compared with the control (no fire‐related treatment). Different plant life forms exhibited varying responses to heat and smoke treatments. The results of this study illustrate that the application of fire‐related treatments to soil seed banks in controlled glasshouse conditions can stimulate the recruitment of native species, including several species of conservation concern. These findings also indicate the potential of using these treatments for the ex situ germination of fire dependent species for revegetation purposes and indicate aspects of prescribed burns that may be important for restoring different components of native vegetation.     

Influence of fire on critically endangered Swartland Shale Renosterveld in the Cape Floristic Region

Questions

The degree to which renosterveld shrublands are fire‐dependent is currently unclear. To address this issue, the following questions were asked: (1) does smoke stimulate germination of soil‐stored seeds in renosterveld; (2) does recently‐burned renosterveld display changed composition and higher diversity than unburned vegetation; and (3) how do the species compositions of renosterveld soil seed banks and standing vegetation compare?

Location

Swartland, Cape Floristic Region, South Africa.

Methods

Soil seed bank samples from a north‐ and south‐facing slope were smoke‐treated and germinated to test for smoke‐stimulated germination. Burned standing vegetation was surveyed 16 months post‐fire, as was unburned vegetation on the same slopes. Seed bank species richness and density were compared between smoke‐treated and untreated samples within and between slopes. Burned and unburned standing vegetation were compared within and between slopes in terms of species richness, abundance and aerial cover. Compositional similarity of the seed banks and standing vegetation was assessed.

Results

Seed banks were dominated by annuals and graminoids. Smoke treatment had no effect, except for driving significantly higher species richness and seedling density in south‐facing slope perennial shrubs. Species richness and seedling density were significantly higher in seed banks on the south‐facing slope compared to the north‐facing slope. Burned standing vegetation exhibited significantly higher diversity than unburned vegetation. Annuals and graminoids displayed significantly higher species richness and aerial cover in burned renosterveld. The north‐facing slope contained less than half the number of species/m² compared to the south‐facing slope. The seed banks and standing vegetation showed low to intermediate similarity (Sørensen = 31%–53%), but grouped close together on an NMDS plot, suggesting intermediate similarity overall.

Conclusions

Elevated germination of perennial shrubs in smoke‐treated seed bank samples and increased diversity of post‐fire standing vegetation suggest the renosterveld in this study shows elements of a fire‐driven system. Certain species only recruited in burned sites, suggesting fire‐stimulated germination. Aspect had a major influence on plant community composition, with the mesic south‐facing slope being more diverse than the xeric north‐facing slope. The similarity between the seed banks and standing vegetation was higher than previously shown for renosterveld, and appears to be higher than for fynbos.     

Effects of fire intensity on plant species composition of sandstone communities in the Sydney region

Abstract Fire intensity measures the heat output of a fire, and variation in fire intensity has been shown to have many effects on the demography of plant species, although the consequent effects on the floristic composition of communities have rarely been quantified. The effects of variation in fire intensity on the floristic composition of dry sclerophyll vegetation with different fire histories near Sydney was estimated. In particular, differences in species abundance of woodland and shrubland communities subjected to four fire‐intensity classes: unburnt, low intensity (<500 kW m^?1), medium intensity (500–2500 kW m^?1) and high intensity (>2500 kW m^?1) were examined. The samples had a standardized previous fire frequency and season, thus minimizing the effects of other aspects of the fire regime. There was a clear effect of fire intensity on the relative abundances of the vascular plant species, with increasing intensity of the fire producing vegetation that was increasingly different from the unburnt vegetation. This pattern was repeated in both the woodland and shrubland vegetation types, suggesting that it was not an artefact of the experimental conditions. However, the effects of fire intensity on floristic composition were no greater than were the differences between these two similar vegetation types, with variation in fire intensity accounting for only approximately 10% of the floristic variation. Nevertheless, the effects of fire intensity on the abundance of individual species were consistent across taxonomic groups, with the monocotyledon and Fabaceae species being more abundant at higher than lower intensities, the Proteaceae and Rutaceae more abundant at intermediate intensities, and the Epacridaceae more abundant at lower rather than higher intensities. The number of fire‐tolerant species increased with increasing fire intensity, and those fire‐tolerant species present were most abundant in the areas burnt with medium intensity. The number of fire‐sensitive species did not respond to fire intensity, and those species present were most abundant in the areas burnt with low intensity. This suggests that either fire‐sensitive species respond poorly to higher fire intensities or fire‐tolerant species respond poorly to lower fire intensities, perhaps because of differences in seed germination, seedling survival or competition among adults.