Comparative spatial distribution, size, biomass and growth rate of two varieties of bracken fern (Pteridium aquilinum L. Kuhn) in a neotropical montane habitat (original) (raw)
Related papers
Growth of Tropical Bracken (Pteridium arachnoideum): Response to Weather Variations and Burning
Invasive Plant Science and Management, 2010
The ecology of tropical bracken, which occurs in tropical regions, is not well known. We studied its response to weather variations and burning in the south Ecuadorian Andes, where this weed had already overgrown 40% of the pastureland. In field observations, a constant 1 : 1 ratio of emerging and dying leaves suggested limitation of frond density by nutrient shortage. Short-term deviations from that ratio could be related to weather variations. Spells of dry weather temporarily increased mortality but stimulated emergence of new fronds. Lifespan of the fronds produced immediately after a fire was longer than of those produced during unaffected bracken growth. A burst of frond development during the initial 2 to 3 mo was observed after a fire followed by self-thinning to a stable level. To analyze the effect of fire on bracken, rhizomes were treated with heat pulses. Rhizomes were heat tolerant up to 70 C, and frond production from short shoots was enhanced by elevated temperature. ...
The bracken fern (Pteridium arachnoideum (Kaulf.) Maxon) dilemma in the Andes of Southern Ecuador
Ecotropica, 2003
Bracken fern (Pteridium aquilinum (L.) Kuhn) is one of the world's most powerful weeds, especially in agricultural areas. Its vigor and resistance to any kind of non-polluting pest control result from its extensive rhizome system. Growth of this rhizome system is strongly promoted by fire. As elsewhere in the tropics, farmers in the Andes of southern Ecuador make extensive use of fire to convert primary forest into arable land and to maintain their pastures. This communication addresses, from a phytosociological viewpoint, the ecological problems arising from the use of fire as an agricultural tool in the presence of the extremely aggressive and fire-tolerant bracken fern Pteridium arachnoideum. Repeated burning of the pastureland weakens the competitive strength of the most important pasture grass Setaria sphacelata, while the competitive strength of bracken increases. Pastures are finally abandoned when Pteridium has become completely predominant. Wind-dispersed seeds of several weedy Asteraceae and Melastomataceae species germinate under the canopy of the bracken leaves and, due to the steepness of the slopes, the seedlings receive sufficient light for further growth. The majority of these species are bushes that finally overtop the bracken leaves and can successfully compete with the shade intolerant fern. A vegetation composed of dense patches of Pteridium interspersed with individual bushes develops, which, because of the immense seed production of the bushes and the vigor of the bracken, is very stable and appears to be a longlasting and even at times the final successional stage. Since natural regeneration of the indigenous forest is very unlikely in these areas, reforestation may be the only way out of the dilemma caused by the extensive use of fire and the fire-tolerance of bracken.
The Bracken fern (Pteridium arachnoideum Kaulf.) dilemma in the Andes of Southern Ecuador
Ecotropica
Bracken fern (Pteridium aquilinum (L.) Kuhn) is one of the world's most powerful weeds, especially in agricultural areas. Its vigor and resistance to any kind of non-polluting pest control result from its extensive rhizome system. Growth of this rhizome system is strongly promoted by fire. As elsewhere in the tropics, farmers in the Andes of southern Ecuador make extensive use of fire to convert primary forest into arable land and to maintain their pastures. This communication addresses, from a phytosociological viewpoint, the ecological problems arising from the use of fire as an agricultural tool in the presence of the extremely aggressive and fire-tolerant bracken fern Pteridium arachnoideum. Repeated burning of the pastureland weakens the competitive strength of the most important pasture grass Setaria sphacelata, while the competitive strength of bracken increases. Pastures are finally abandoned when Pteridium has become completely predominant. Wind-dispersed seeds of several weedy Asteraceae and Melastomataceae species germinate under the canopy of the bracken leaves and, due to the steepness of the slopes, the seedlings receive sufficient light for further growth. The majority of these species are bushes that finally overtop the bracken leaves and can successfully compete with the shade intolerant fern. A vegetation composed of dense patches of Pteridium interspersed with individual bushes develops, which, because of the immense seed production of the bushes and the vigor of the bracken, is very stable and appears to be a longlasting and even at times the final successional stage. Since natural regeneration of the indigenous forest is very unlikely in these areas, reforestation may be the only way out of the dilemma caused by the extensive use of fire and the fire-tolerance of bracken.
Journal of Applied Ecology, 2013
1. Large areas of agricultural land around the world are degraded as a consequence of dominance by bracken fern (Pteridium spp.). Tropical production systems based on shifting cultivation and cattle breeding are particularly vulnerable to invasion of this species. In spite of this, effective methods for tropical bracken control are limited. 2. Fast-growing tree species have been used successfully to out-compete aggressively colonizing heliophytes and trigger natural succession. Drawing on a traditional Mayan management technique, we evaluate the potential of the pioneer tree balsa (Ochroma pyramidale) to control Pteridium caudatum in Chiapas, Mexico. We tested different bracken cutting frequencies and balsa propagation methods in a factorial randomized block experiment. Eighteen months later, we quantified bracken biomass under the young balsa canopy. 3. Living bracken rhizome biomass correlated significantly with balsa basal area, leaf litter biomass and understorey light intensity. While bracken rhizomes persisted in control plots, it was completely eradicated in plots with a minimum balsa basal area of 11 m 2 ha À1 . This threshold value was reached in less than 18 months with any of the tested propagation methods (seed broadcasting, direct sowing or nursery seedlings), on the condition of at least monthly bracken cutting during the first six months. 4. The ability of fast-growing broad-leaved pioneer trees like balsa to quickly out-compete bracken fern offers opportunities for large-scale application in tropical rural areas where economic and technical resources are scarce. 5. Synthesis and applications. Mayan subsistence farmers traditionally use balsa to outcompete invasive weeds, including bracken fern. Here, we highlight the usefulness of this method for quick and effective bracken control in southern Mexico. This approach, in combination with balsa's short rotation cycle, creates opportunities to rapidly convert bracken land into forest stands with commercial potential, thus providing local income and increasing the likelihood of adoption by rural people. We encourage further research to test the potential of balsa and other fast-growing pioneer trees species for controlling bracken and similar weeds.
Plant Ecology, 2011
We examined the effect of fire frequency and intensity on a Protea caffra tree population in the temperate montane grasslands of north-western KwaZulu-Natal, South Africa. We assessed the effect of fire by comparing the population structure of the resprouter P. caffra in discrete bracken (Pteridium aquilinum) patches with that in the surrounding grassland matrix. Fuel biomass did not differ between grassland and bracken, but bracken fuel was significantly drier than grass. Above-ground fire temperatures and fireline intensity, measured by P. caffra char height, were significantly higher in the bracken habitat. Forty-two percent of the P. caffra population in grassland and in bracken persisted by coppice resprouts, having lost their original stem to fire damage. Exposure to higher intensity bracken fire suppressed P. caffra regeneration and caused greater adult mortality compared with trees in grassland. Consequently, the P. caffra population in bracken was skewed towards old age with most trees severely fire damaged. The high incidence of small trees in grassland indicates that a regular fire interval of 2-3 years does not negatively affect regeneration of P. caffra. However, in bracken patches regular high intensity fires cause high mortality among all P. caffra size classes and will ultimately result in local extinction. Bracken thus has the potential to significantly alter tree-grass interactions in these montane grasslands.
Bracken fern facilitates tree seedling recruitment in tropical fire-degraded habitats
Forest Ecology and Management, 2015
Tropical forest regeneration is hindered by human-induced fires. After deforestation by fires, Pteridium spp. (bracken fern) often colonizes and dominates the vegetation for long time periods, presumably inhibiting the succession. Tree species from mature forests are rare in the degraded areas, potentially due to the lack of seed dispersal and unfavourable abiotic conditions. Here, we experimentally assess the effect of bracken presence, in terms of litter and shade, on seedling recruitment of three native, shade-tolerant tree species in the tropical mountains of Bolivia. In a spatially blocked design at eight sites, we compared seedling recruitment, survival and growth three months and one year after sowing between experimental litter and vegetation treatments and among habitat types (forest interior, degraded habitats close and far from the edge) and species (Clusia sphaerocarpa, Clusia lechleri and Clusia trochiformis). We found that species differed in their recruitment success and habitat preferences, but responded similarly to experimental treatments. Litter removal increased temperature and reduced humidity on the ground and vegetation removal increased canopy openness. Seedling recruitment was consistently reduced by litter and vegetation removal, and their interaction had a deleterious negative effect. Seedling survival and growth were also reduced by litter removal. Our results highlight the overlooked facilitative effects of bracken by ameliorating harsh abiotic conditions and increasing the probability of Clusia seedling recruitment and potentially other shade-tolerant tree species in degraded habitats. To enhance forest regeneration in fire-degraded areas, we recommend spreading seeds of shade-tolerant tree species into the bracken vegetation. This method is less costly and might be more efficient than previous methods that involved repeated bracken removal. Recruitment of late-successional species in the bracken vegetation is likely to promote the restoration of tropical forest; however, longterm studies are needed to test the success of such efforts.
Invasive Plant Science and Management, 2014
Neotropical bracken fern invades disturbed forests and burned and abandoned pastures in Latin America, inhibiting the growth of associated vegetation and altering community structure. Cutting of all aboveground vegetation every 6 to 12 mo has proven to be inefficient as a control method. We studied the impact of selective cutting of bracken every 2 mo, shading, and a combination of cutting + shading during 14 mo in a bracken-dominated, abandoned pasture in Veracruz, Mexico. At the end of the experiment, cutting with or without shading drastically reduced bracken cover from >90% to less than 1%, decreased leaf number from 18 to fewer than two leaves per m2, and depleted bracken leaf biomass. The significant reduction of bracken was correlated with a significant 3.9- to 5.7-fold increase in richness of other plant species. Cutting without shading was the only treatment that significantly reduced rhizome biomass to less than 62% of control plots, whereas cutting + shading was the on...
The Ecology of Bracken: Its Role in Succession and Implications for Control
Annals of Botany
Bracken (Pteridium) holds a pivotal role in succession, usually occurring in sequence between plagio-climax communities such as heathland and woodland. It is at this interface that bracken causes problems for man, as the subseral communities are more valuable for agricultural use and most have a greater conservation value than brackendominated ones (there are a few exceptions). This paper examines the role of bracken in a series of successional trajectories on lowland heaths; there is evidence that bracken occurs in a trajectory towards birch woodland in Dorset. Whether the bracken stage is an intermediate stage towards woodland or acts as a 'mini-climax' in itself remains to be demonstrated. Thereafter, the impact of bracken control on vegetation development is examined from two successional viewpoints, succession reversal towards the early successional communities, and successional accelerations towards woodland. A range of examples is provided from: (1) lowland heaths in England; (2) moorlands in upland Britain where bracken has been treated with asulam; and (3) in North Wales where attempts have been made to restock woodlands.
Changes in the rhizome system of bracken subjected to long-term experimental treatment
Journal of Applied Ecology, 2003
1. Bracken Pteridium aquilinum is a serious weed of upland and marginal land. Its extensive rhizome system and large carbohydrate reserves make control difficult. This paper reports the results of seven long-term experiments, established in four diverse UK locations, to test control and vegetation restoration treatments. 2. Samples were obtained from 580 rhizome pits between 1998 and 2000. Total dry mass per unit area (M , a measure of performance) and ratio of frond-bearing to total rhizome dry mass (R , a relative measure of investment in frond production) were measured. 3. The range of means for M in untreated bracken was 1•8-5•1 kg m − 2 , greater than that reported by others (1•2-3•0 kg m − 2). Measured values for R were 0•24-0•42, again differing from other reports (0•10-0•38), probably due to our policy of avoiding advancing bracken fronts. 4. Randomization tests were used to check for non-independence of sampling units. They confirmed the general adequacy of the results; there was little detectable interference between plots. Two regions contained matching pairs of experiments, thus variation within region was tested and differences were found in one region. 5. Five bracken control treatments (cutting, herbicide application and combinations) were employed at all but one experiment. Cutting once or twice per year generally gave the best results, reducing M by c. 60% after ≤ 5 years. Some subtreatments designed mainly for vegetation restoration, notably surface disturbance, also affected M. 6. R was reduced by herbicide treatment, for example from 0•30 to 0•16. Such low values of R are typical of invading bracken and are thought to represent rejuvenated and invasive rhizomes. Follow-up treatments are needed in such situations. Despite large differences between untreated M at matching experiments on Cannock Chase (Staffordshire), treatment effects were similar at both sites (cutting twice per year or cutting together with herbicide application were best). At Sourhope (Cheviot Hills) a different pattern of response was obtained, with cutting alone giving better results than treatments involving herbicide. 7. The ratio of rhizome to frond dry mass per unit area was 10 : 1 in good conditions for growth, but the proportionate size of rhizomes could be reduced in poor growing conditions such as wet summers. 8. Synthesis and applications. In order to develop a national control strategy the following must be considered: rhizome mass differs between sites and in response to control treatments; cutting twice per year is generally most effective; where cutting is impossible, herbicide treatment should be applied. Weather may affect rhizome mass, with wet years being detrimental. This raises the possibility that bracken may increase under the drier conditions that may occur with global warming.