Thresholds and alternative states in a Neotropical dry forest in response to fire severity.

Neotropical xerophytic forest ecosystems evolved with fires that shaped their resilience to disturbance events. However, it is unknown whether forest resilience to fires persists under a new fire regime influenced by anthropogenic disturbance and climate change. We asked whether there was evidence for a fire severity threshold causing an abrupt transition from a forest to an alternative shrub thicket state in the presence of typical postfire management. We studied a heterogeneous wildfire event to assess medium-term effects (11 years) of varying fire severity in a xerophytic Caldén forest in central Argentina. We conducted vegetation surveys in patches that were exposed to low (LFS), medium (MFS), and high (HFS) fire severities but had similar prefire woody canopy cover. Satellite images were used to quantify fire severity using a delta Normalized Burning Ratio (dNBR) and to map prefire canopy cover. Postfire total woody canopy cover was higher in low and medium than high severity patches, but the understory woody component was highest in HFS patches. The density of woody plants was over three times higher under HFS than MFS and LFS due to the contribution of small woody plants to the total density. Unlike LFS and MFS patches, the small plants in HFS patches were persistent, multistem shrubs that resulted from the resprouting of top-killed Prosopis caldenia trees and, more importantly, from young shrubs that probably established after the wildfire. Our results suggest that the Caldén forest is resilient to fires of low to moderate severities but not to high-severity fires. Fire severities with dNBR values > ~600 triggered an abrupt transition to a shrub thicket state. Postfire grazing and controlled-fire treatments likely contributed to shrub dominance after high-severity wildfire. Forest to shrub thicket transitions enable recurring high-severity fire events. We propose that repeated fires combined with grazing can trap the system in a shrub thicket state. Further studies are needed to determine whether the relationships between fire and vegetation structure examined in this case study represent general mechanisms of irreversible state changes across the Caldenal forest region and whether analogous threshold relationships exist in other fire-prone woodland ecosystems.

High resilience of campos rupestres plants to the interaction of drought and fire.

The concurrent impacts of multiple disturbances have the potential to modify ecosystem functioning by diminishing recovery capacity and resilience. Nevertheless, it remains uncertain how plant species from tropical communities respond to the cumulative effects of drought and fire. In this study, we evaluated the responses of six plant species from campos rupestres subjected to a mild drought followed by fire and tested if plants subjected to simulated drought show reductions in carbon uptake and depletion of non-structural carbohydrate (NSC) reserves, thus constraining their resprouting. We monitored monthly variations in leaf gas exchange and aboveground biomass over 18 months. Subsequently, an accidental fire occurred in the study area, leading us to collect samples of belowground structures for NSC analyses on the day of the burn. There were no differences in the frequency of resprouting between the above two conditions. Additionally, gas exchange in most species either remained stable or increased after the fire. Drought had no adverse effects on NSC reserves in the belowground structures and may have contributed to species resprouting after fire. The impact of drought pre-conditions on post-fire aboveground biomass was generally minor for most species, except Vellozia nivea, which displayed roughly a 5% reduction in biomass following the drought. Our findings highlight the remarkable resilience of campos rupestres species, even after enduring 18 months of reduced water availability and an unintended fire event. These species demonstrated the capacity to maintain their physiological functions and resprouting capacities after a fire event, underscoring their strong recovery potential.

Why woody plant modularity through time and space must be integrated in fire research?

Different ecosystems evolved and are maintained by fire, with their vegetation hosting species with a wide diversity of persistence strategies allowing them to insulate their body and resprout new branches after fire disturbance. Changes in fire regime are predicted due to climate change, either by promoting more frequent and/or severe fires or by reducing the number of fire events due to the limitation of fuel load. Predicting the future of fire-driven ecosystems is a complex task as species' survival depends on many factors that vary in space and time. Since plants are constantly experiencing new environments as they grow through meristem development, woody plant modularity, modules morpho-physiological aspects and their integration should be considered when investigating species strategies in fire-prone ecosystems: according to their position and their tissue composition, plants' modules experience fire differently and will contribute differently to other modules and the whole plant survival, with consequences cascading over the overall vegetation structure. Growth modules may hold the key to understanding how fast plants can get protected from fire, ultimately helping us to predict which species will persist across changing fire regimes. We present an empirical example showing how different fire-return intervals translate into distinct pressures on the timing, protection and location of modules, and discuss how these can translate into modifications in the vegetation structure due to climate change.

Bark production of generalist and specialist species across savannas and forests in the Cerrado.

BACKGROUND AND AIMS: Bark allows species to survive fire, protecting their inner tissues and allowing new branches to resprout from aerial buds. Thus, bark production is likely to be selected with aerial bud protection in fire-prone ecosystems. By considering the coexistence of fire-prone and fire-free ecosystems, in addition to the different impacts of flames on different growth forms, in this study we tested whether: (1) species from areas with higher fire frequencies have a faster bark production; (2) bark growth rate differs between trees and shrubs; (3) generalists adjust their bark production according to their environment (fire-prone or fire-free ecosystems); and (4) fast bark production results in better aerial bud protection. METHODS: We sampled two different types of forests and savannas in the Cerrado and registered every woody individual with height between 1.5 and 3 m tall (directly exposed to the flames). For the 123 species registered, we sampled three different individuals in each vegetation type where the species occurred to assess their bark production and aerial bud protection. We then checked, for each species, their preferred habitat (savanna and forest specialists or generalists) and their predominant growth form. KEY RESULTS: A minimal threshold of 0.13 mm per growth unit of bark production differentiated woody communities from savannas and forests. Shrubs and trees did not differ in terms of bark growth rate, despite being exposed to the flames in a different manner. Generalist species in savannas were able to produce bark above the threshold. However, when these species were in forests they produced bark below the threshold. Finally, a higher bark growth rate accounted for a better aerial bud protection. CONCLUSIONS: Generalist species are likely to be capable of displaying plasticity in their bark production, which could be important for their success in contrasting ecosystems. The relationship between aerial bud protection and bark growth rate suggests that bark production plays an important role in protecting the dormant buds, in addition to being selected in fire-prone ecosystems.

Fire exclusion changes belowground bud bank and bud-bearing organ composition jeopardizing open savanna resilience.

Belowground bud bank regeneration is a successful strategy for plants in fire-prone communities. It depends on the number and location of dormant and viable buds stored on belowground organs. A highly diverse belowground bud-bearing organ system maintained by a frequent interval of fire events guarantees the supply of a bud bank that enables plants to persist and resprout after disturbance. We investigated how different fire exclusion and fire frequencies, affected the herbaceous layer in tropical savannas, by assessing belowground persistence and regeneration traits. Contrary to our hypothesis, we found that under a shorter fire exclusion period, the total bud bank increased at a lower fire frequency. But sites at longer fire exclusion and infrequent fire, the bud bank was smaller the longer the period since the last fire. However, the major shift was concerning organ diversity since fire exclusion was more related to loss of belowground diversity rather than decreasing of the belowground bud bank size. Furthermore, fire-associated bud-bearing structures like xylopodia disappeared in the fire suppressed areas, whereas clonal organs, such as rhizomes, developed in the bud bank. By quantifying belowground bud bank traits under different fire histories, we highlight the importance of the local fire regime on the composition of the belowground plant components, which can affect the tropical savanna aboveground plant community. Given that, loss of the belowground bud-bearing component of the plant community will have a direct effect on vegetation regeneration in post-fire environments, and consequently, on plant community resilience.

Regeneración de un bosque secundario afectado por el Huracán Otto en Costa Rica / Regeneration of a secondary forest affected by Hurricane Otto in Costa Rica

Resumen Introducción: Se han realizado múltiples estudios en bosques afectados por huracanes, pero la información obtenida para Costa Rica es escasa, o nula en el caso de impactos directos como lo fue Otto, por lo que es necesario ampliar el conocimiento que se tiene acerca de los efectos de estos fenómenos en bosques tropicales y los mecanismos de recuperación de estos biomas. Consecuentemente se vuelve necesario identificar la vulnerabilidad de los ecosistemas a largo plazo y cuantificar las pérdidas que se generan a diferentes escalas, producto de los intensos eventos pluviales y los fuertes vientos. Objetivo: Determinar el comportamiento y estado de la recuperación en un bosque secundario afectado directamente por el huracán Otto en Boca Tapada, Pital, San Carlos, Costa Rica. Métodos: Se establecieron 10 unidades de muestreo de 20 x 50 m distribuidas de forma sistemática dentro de un bosque secundario afectado por el huracán Otto en Boca Tapada de San Carlos. Se evaluó la condición actual del bosque, se identificaron las especies que más daño recibieron por consecuencia de los fuertes vientos, así como las que poseen capacidad de recuperarse a través de rebrotes. Se realizó un sobrevuelo con un vehículo no tripulado, y se construyó un ortomosaico que fue posteriormente digitalizado y clasificado de acuerdo con el estado de la cobertura forestal presente en tres tiempos evaluados, condición inicial, después del aprovechamiento forestal y la condición al momento de realizado el muestreo. Se comparó la densidad poblacional, diversidad y área basal con lo presentado para un bosque primario aledaño al sitio de estudio, que también fue afectado por el paso del huracán Otto. Resultados: Se obtuvo que un 69.5 % de los individuos con d ≥ 5 cm se encuentran en buen estado, un 20.3 % fue descopado y un 12.7 % inclinado sin exposición de raíces. La familia que más riqueza de especies aporta es Fabaceae, esta misma es la que más abundancia de individuos dañados posee y la que presentó mayor cantidad de especies con capacidad de rebrotar. La especie que más daños sufrió fue Couma macrocarpa (Euphorbiaceae). El área de cobertura boscosa inicial fue afectada en un 7,63 % por el aprovechamiento forestal, y en un 44.25 % por el paso del huracán Otto. Se determinó que existen diferencias significativas en la diversidad de especies (P = 0.0004; α = 0.05) y en la densidad de individuos (P = 0.0011; α = 0.05), el bosque secundario es quien posee la mayor media. No se presentaron diferencias significativas en los valores de área basal (P = 0.6951; α = 0.05). Conclusiones: Un 30,5 % de la masa forestal fue afectada por el paso del huracán Otto y la familia Fabaceae representa un papel importante en la recuperación del bosque. Además, el aprovechamiento forestal en un bosque puede aumentar el riesgo de afectación por el paso de huracanes y el bosque secundario posee mayor diversidad de especies y mayor densidad de individuos que el bosque primario.

Abstract Introduction: Multiple studies have been carried out in forests affected by hurricanes, but the information obtained for Costa Rica is scarce or null, in the case of direct impacts such as Otto, so it is necessary to expand the existing knowledge about the effects of these phenomena on tropical forests and the recovery mechanisms of these biomes. Consequently, it is necessary to identify the vulnerability of ecosystems in long term and quantify the losses that are generated at different scales, as a result of the intense events of rain and strong winds. Objective: Determining behavior and recovery status in a secondary forest directly affected by Hurricane Otto in Boca Tapada, Pital, San Carlos, Costa Rica. Methods: Ten 20 x 50 m sampling units were systematically distributed within a secondary forest affected by Hurricane Otto in Boca Tapada, San Carlos. The current condition of the forest was evaluated, the species that received the most damage due to high winds were identified, as well as those that have the capacity to recover through regrowths. An overflight was carried out with an unmanned aerial vehicle and an orthomosaic was constructed, subsequently digitized, and classified according to the state of the forest cover presented in three evaluated moments, initial condition, after logging and the condition at the time of sampling. Population density, diversity, and basal area, were compared to data obtained in an adjacent primary forest also affected by the passage of Hurricane Otto. Results: It was obtained that 69.5 % of individuals with d ≥ 5 cm are in good condition, 20.3 % were broken in the tree canopy and 12.7% inclined without exposure of the roots. The family that provided the greatest species richness is Fabaceae, which is the same with the greatest abundance of damaged individuals and the one with the highest number of species with the ability to resprouting. The species that suffered the most damage was Couma macrocarpa (Euphorbiaceae). The initial area of forest cover was reduced by 7.63 % due to logging and 44.25 % due to Hurricane Otto. It was determined that there are significant differences in species diversity (P = 0.0004; α = 0.05) and in the density of individuals (P = 0.0011; α = 0.05). The secondary forest has the highest average in both cases. There are no significant differences in the values of the basal area (P = 0.6951; α = 0.05). Conclusions: 30.5 % of the forest mass was affected by the passage of Hurricane Otto and the Fabaceae family plays an important role in forest recovery. In addition, forest harvesting in a forest can increase the risk of being affected by the passage of hurricanes and the secondary forest has a greater diversity of species and a higher density of individuals than the primary forest.

Growth and survival over ten years of Brazil-nut trees planted in three anthropogenic habitats in northern Amazonia / Crescimento e sobrevivência da castanheira do Brasil em três habitats antropogênicos após dez anos de plantação

We examined the growth and survival of Brazil-nut trees, Bertholletia excelsa (Lecythidaceae) under different environmental conditions and levels of canopy openness within experimental plantations in the Trombetas River valley, in northern Brazil. We planted 144 seedlings in three anthropogenic habitats with different levels of sunlight exposition: crop field (100% canopy opening), shrub fallow (20-80% canopy opening) and Brazil-nut forest ( 10% canopy opening). We measured plant height and diameter annually and recorded mortality and resprouting over ten years. The performance of B. excelsa differed significantly among habitats, with the highest growth rate observed at the highest level of canopy openness (crop field). Survival was highest in crop field (85%) and shrub fallow (63%) and lowest in Brazil-nut forest (17%). Resprouting capacity was higher in the crop field, as Brazil-nut plants recovered after fire episodes, with most plants resprouting more than one shoot. Some trees in the crop field began to produce flowers and fruits at 9-10 years. We showed that B. excelsa juveniles are light-demanding, with higher survival and growth under conditions of high light exposure. We suggest the use of Brazil-nut trees for reforestation, restoration of degraded lands and enrichment of secondary vegetation, as long as an adequate management is adopted (e.g., maintaining plants exposed to direct sunlight and control of competing pioneer species).(AU)

No presente estudo analisamos o crescimento e a sobrevivência da castanheira, Bertholletia excelsa (Lecythidaceae) em diferentes condições ambientais e níveis de abertura de dossel em plantações experimentais localizadas na bacia do Rio Trombetas, na Amazônia oriental brasileira. Plantamos 144 mudas em habitats antrópicos com diferentes intensidades de luz: roçados recentemente abandonados (100% de abertura de dossel), capoeira de 2-3 anos (20-80% de abertura de dossel) e castanhal maduro ( 10% de abertura de dossel). Anualmente, durante dez anos, medimos a altura e diâmetro das plantas, e registramos mortalidade e rebrotação. A performance de B. excelsa variou significativamente entre os habitats, tendo a taxa de crescimento mais alta sido observada no roçado. A sobrevivência foi mais alta no roçado (85%) e na capoeira (63%) e mais baixa no castanhal (17%). A capacidade de rebrotação das plantas de castanheira foi maior no roçado, onde as plantas de castanheira se recuperaram após episódios de fogo, a maioria com rebrotação de mais de um caule. Algumas plantas do roçado começaram a produzir flores e frutos aos 9-10 anos do plantio. Nós mostramos que plantas jovens de B. excelsa são heliófilas (com alta demanda de luz), com maior crescimento e sobrevivência em condições de alta luminosidade. Sugerimos a utilização da castanheira em programas de reflorestamento, restauração de áreas degradadas e enriquecimento de floresta secundária, sempre que se adotem medidas adequadas de manejo (e.g., manutenção das condições de exposição direta à luz solar e controle de espécies pioneiras competidoras).(AU)

Rebrote arbóreo en la regeneración del bosque tropical de Calakmul, Campeche, México / Arboreal resprouting in the Calakmul, Campeche, Mexico tropical forest regeneration

Resumen Los estudios detallados para comprender como los bosques neotropicales se reestablecen en el tiempo, a través de la sucesión secundaria aún resultan necesarios. Entre los mecanismos de regeneración que actúan en los bosques tropicales, el rebrote de árboles predomina en especies leñosas, con la ventaja de reiniciar el crecimiento de raíces establecidas, que permiten restituir el dosel forestal. El objetivo de este estudio fue identificar y cuantificar las especies arbóreas con capacidad de rebrote en distintas etapas de la sucesión secundaria (barbecho) después del sistema agrícola tradicional de milpa, comparadas con las comunidades del bosque tropical predominante en la Reserva de la Biósfera de Calakmul, y cómo influyen estas especies en la recuperación de la composición de este ecosistema. Se calculó el porcentaje de especies con y sin rebrote para cada etapa sucesional. Se registraron 13 972 individuos (32 % con rebrote y 68 % sin rebrote) y 168 especies (79 % con rebrote y 21 % sin rebrote), el porcentaje de individuos con rebrote va disminuyendo conforme avanza la edad de la sucesión. El número de individuos con rebrote y la composición de especies fueron significativamente diferentes entre etapas. Se puede concluir que la mayoría de especies arbóreas del bosque en Calakmul, presentan la capacidad de rebrotar, lo cual tiene influencia en el rápido proceso sucesional del bosque después de la roza-tumba y quema, restituyendo la cobertura y estructura forestal, así como la composición de las especies originales.(AU)

Abstract Detailed studies to understand recovering of Neotropical forests over time, through secondary succession, are still necessaries. Between acting mechanisms of regeneration in the tropical forests, the arboreal resprout predominates in woody species, with the advantage of restart the growth from still rooting plants, allowing the restoring of forest canopy. The study aim was to identify and quantify the tree species with resprouting capacity in different stages of secondary succession (tree-fallow) after the traditional milpa agricultural system, compared with tropical forest communities in the Calakmul Biosphere Reserve and, enlightening how these species influences the recovery of the composition of this ecosystem. Was calculated the proportions of species with or without resprouting by successional stage. There were 13 972 individuals (32 % resprouting and 68 % not resprouting) and 168 species (79 % resprouting and 21 % not resprouting), the percentage of individuals regrowing decreases as the successional stage progresses. The number of individuals resprouting and species composition were significantly different between successional stages. In conclusion, mostly arboreal species in the region of Calakmul, can regrow, which influences the successional development of the forest after slash-and-burn, helping to restore the coverage, structure, as well as species composition original.(AU)

Propagation studies in Smilax fluminensis Steud. (Smilacaceae) / Estudos de propagação em Smilax fluminensis Steud. (Smilacaceae)

Smilax L. species, popularly known in Brazil as salsaparrilha, have been used in folk medicine as tonic against rheumatism and as anti-syphilitic since the sixteenth century; however, until today, their roots have been explored in an extractive way. The aim of this study was to analyze the propagation of Smilax fluminensis aiming to meet the demand and to propose procedures for its sustainable management. It was analyzed the percentage of seed germination, rooting of aerial and subterranean stem cuttings and plant resprouting capacity after removal of the shoots. The monitoring lasted one year. Seeds were subjected to temperatures: 25°C, 30°C, 20-30°C and 20-35°C under a daily photoperiod of eight hours and in the absence of light. For rooting the stem cuttings, aerial and subterranean stems about 20cm long with two nodal regions were subjected to treatment with distilled water (control) and indolbutyric acid (IBA) at 100ppm. The best germination percentages obtained for S. fluminensis were 80 percent at 20-30°C under light and 85 percent at 30°C in the dark. Only subterranean stem cuttings showed significant difference concerning fresh and dry matter of roots with higher values in treatments with hormone compared to the control.

As espécies do gênero Smilax L., conhecidas popularmente como salsaparrilha, são empregadas na medicina popular como fortificante contra o reumatismo e antissifilítico desde o século XVI, porém até hoje as suas raízes são exploradas de maneira extrativista. O objetivo deste estudo foi analisar a propagação de Smilax fluminensis visando a auxiliar no atendimento da demanda e apontar propostas para o seu manejo sustentável. Foram analisados a porcentagem de germinação de sementes, o enraizamento de estacas de ramos aéreos e subterrâneos e o acompanhamento ao longo de um ano da capacidade de rebrotamento das plantas após a retirada dos ramos aéreos. As sementes foram submetidas às temperaturas: 25, 30, 20-30 e 20-35°C, sob fotoperíodo diário de oito horas e na ausência de luz. Para o enraizamento de estacas, foram utilizados ramos aéreos e subterrâneos com aproximadamente 20cm com duas regiões nodais submetidas ao tratamento com água destilada (controle) e com ácido indolbutírico (AIB) a 100ppm. As melhores porcentagens de germinação obtidas para S. fluminensis, 80 por cento em 20-30°C no claro e 85 por cento a 30°C no escuro. Apenas as estacas de ramos subterrâneos enraizaram, houve diferença significativa em relação à massa fresca e seca de raízes com valores maiores nos tratamentos com hormônio em relação ao controle.

Propagation studies in Smilax fluminensis Steud. (Smilacaceae)

Smilax L. species, popularly known in Brazil as salsaparrilha, have been used in folk medicine as tonic against rheumatism and as anti-syphilitic since the sixteenth century; however, until today, their roots have been explored in an extractive way. The aim of this study was to analyze the propagation of Smilax fluminensis aiming to meet the demand and to propose procedures for its sustainable management. It was analyzed the percentage of seed germination, rooting of aerial and subterranean stem cuttings and plant resprouting capacity after removal of the shoots. The monitoring lasted one year. Seeds were subjected to temperatures: 25°C, 30°C, 20-30°C and 20-35°C under a daily photoperiod of eight hours and in the absence of light. For rooting the stem cuttings, aerial and subterranean stems about 20cm long with two nodal regions were subjected to treatment with distilled water (control) and indolbutyric acid (IBA) at 100ppm. The best germination percentages obtained for S. fluminensis were 80% at 20-30°C under light and 85% at 30°C in the dark. Only subterranean stem cuttings showed significant difference concerning fresh and dry matter of roots with higher values in treatments with hormone compared to the control.

As espécies do gênero Smilax L., conhecidas popularmente como salsaparrilha, são empregadas na medicina popular como fortificante contra o reumatismo e antissifilítico desde o século XVI, porém até hoje as suas raízes são exploradas de maneira extrativista. O objetivo deste estudo foi analisar a propagação de Smilax fluminensis visando a auxiliar no atendimento da demanda e apontar propostas para o seu manejo sustentável. Foram analisados a porcentagem de germinação de sementes, o enraizamento de estacas de ramos aéreos e subterrâneos e o acompanhamento ao longo de um ano da capacidade de rebrotamento das plantas após a retirada dos ramos aéreos. As sementes foram submetidas às temperaturas: 25, 30, 20-30 e 20-35°C, sob fotoperíodo diário de oito horas e na ausência de luz. Para o enraizamento de estacas, foram utilizados ramos aéreos e subterrâneos com aproximadamente 20cm com duas regiões nodais submetidas ao tratamento com água destilada (controle) e com ácido indolbutírico (AIB) a 100ppm. As melhores porcentagens de germinação obtidas para S. fluminensis, 80% em 20-30°C no claro e 85% a 30°C no escuro. Apenas as estacas de ramos subterrâneos enraizaram, houve diferença significativa em relação à massa fresca e seca de raízes com valores maiores nos tratamentos com hormônio em relação ao controle.

Propagation studies in Smilax fluminensis Steud. (Smilacaceae)

Smilax L. species, popularly known in Brazil as salsaparrilha, have been used in folk medicine as tonic against rheumatism and as anti-syphilitic since the sixteenth century; however, until today, their roots have been explored in an extractive way. The aim of this study was to analyze the propagation of Smilax fluminensis aiming to meet the demand and to propose procedures for its sustainable management. It was analyzed the percentage of seed germination, rooting of aerial and subterranean stem cuttings and plant resprouting capacity after removal of the shoots. The monitoring lasted one year. Seeds were subjected to temperatures: 25°C, 30°C, 20-30°C and 20-35°C under a daily photoperiod of eight hours and in the absence of light. For rooting the stem cuttings, aerial and subterranean stems about 20cm long with two nodal regions were subjected to treatment with distilled water (control) and indolbutyric acid (IBA) at 100ppm. The best germination percentages obtained for S. fluminensis were 80% at 20-30°C under light and 85% at 30°C in the dark. Only subterranean stem cuttings showed significant difference concerning fresh and dry matter of roots with higher values in treatments with hormone compared to the control.

As espécies do gênero Smilax L., conhecidas popularmente como salsaparrilha, são empregadas na medicina popular como fortificante contra o reumatismo e antissifilítico desde o século XVI, porém até hoje as suas raízes são exploradas de maneira extrativista. O objetivo deste estudo foi analisar a propagação de Smilax fluminensis visando a auxiliar no atendimento da demanda e apontar propostas para o seu manejo sustentável. Foram analisados a porcentagem de germinação de sementes, o enraizamento de estacas de ramos aéreos e subterrâneos e o acompanhamento ao longo de um ano da capacidade de rebrotamento das plantas após a retirada dos ramos aéreos. As sementes foram submetidas às temperaturas: 25, 30, 20-30 e 20-35°C, sob fotoperíodo diário de oito horas e na ausência de luz. Para o enraizamento de estacas, foram utilizados ramos aéreos e subterrâneos com aproximadamente 20cm com duas regiões nodais submetidas ao tratamento com água destilada (controle) e com ácido indolbutírico (AIB) a 100ppm. As melhores porcentagens de germinação obtidas para S. fluminensis, 80% em 20-30°C no claro e 85% a 30°C no escuro. Apenas as estacas de ramos subterrâneos enraizaram, houve diferença significativa em relação à massa fresca e seca de raízes com valores maiores nos tratamentos com hormônio em relação ao controle.

Fire effects on the population structure of Zanthoxylum rhoifolium Lam (Rutaceae) in a Brazilian savanna / Efeitos do fogo na estrutura da população de Zanthoxylum rhoifolium Lam (Rutaceae) em uma savana brasileira

Since cerrado fires may impede the growth of seedlings into trees, they may shape the population of woody species. In this study, we assessed the effects of a severe fire on the population structure and spatial distribution of Zanthoxylum rhoifolium, a widespread cerrado tree. We were interested to know the importance of the resprouting and sexual reproduction in regenerating the population. The study area had been for about six years protected from fire, before a severe fire at the end of the dry season in 2006. We sampled and measured all individuals of Z. rhoifolium found in 80 plots of 25 m². We found 149 individuals before the fire and 112 after the fire, of which 77 were resprouts from burned seedlings and saplings. We did not find significant differences between the population structure before and after the fire. The spatial distribution of the population remained clumped after the fire. Thus, the Z. rhoifolium population was very resilient to a severe fire. We did not find any new seedlings. As a consequence, resprouting seems to be more important than sexual reproduction in promptly regenerating the Z. rhoifolium populations.

Uma vez que as queimadas no cerrado podem impedir o crescimento de plântulas, elas podem moldar a população de espécies arbóreas. Neste estudo, avaliamos os efeitos de uma queimada severa na estrutura e na distribuição espacial da população de Zanthoxylum rhoifolium, uma espécie de árvore comum no cerrado. O objetivo era saber a importância relativa do rebrotamento e da reprodução sexuada na regeneração da população. A área de estudo, há aproximadamente seis anos sem queimar, sofreu uma queimada severa no final da estação seca de 2006. Amostramos todos os indivíduos de Z. rhoifolium encontrados em 80 parcelas de 25 m². Encontramos 149 indivíduos antes do fogo e 112 depois dele, dos quais 77 eram rebrotas de plântulas e jovens queimados. Não encontramos diferenças significativas entre a estrutura da população antes e após o fogo. A distribuição espacial da população permaneceu agregada após a queimada. Portanto, a população de Z. rhoifolium foi resiliente ao fogo. Não foi encontrada nenhuma nova plântula. Consequentemente, o rebrotamento parece ser mais importante que a reprodução sexuada na regeneração imediata das populações de Z. rhoifolium.

Fire effects on the population structure of Zanthoxylum rhoifolium Lam (Rutaceae) in a Brazilian savanna

Since cerrado fires may impede the growth of seedlings into trees, they may shape the population of woody species. In this study, we assessed the effects of a severe fire on the population structure and spatial distribution of Zanthoxylum rhoifolium, a widespread cerrado tree. We were interested to know the importance of the resprouting and sexual reproduction in regenerating the population. The study area had been for about six years protected from fire, before a severe fire at the end of the dry season in 2006. We sampled and measured all individuals of Z. rhoifolium found in 80 plots of 25 m². We found 149 individuals before the fire and 112 after the fire, of which 77 were resprouts from burned seedlings and saplings. We did not find significant differences between the population structure before and after the fire. The spatial distribution of the population remained clumped after the fire. Thus, the Z. rhoifolium population was very resilient to a severe fire. We did not find any new seedlings. As a consequence, resprouting seems to be more important than sexual reproduction in promptly regenerating the Z. rhoifolium populations.

Uma vez que as queimadas no cerrado podem impedir o crescimento de plântulas, elas podem moldar a população de espécies arbóreas. Neste estudo, avaliamos os efeitos de uma queimada severa na estrutura e na distribuição espacial da população de Zanthoxylum rhoifolium, uma espécie de árvore comum no cerrado. O objetivo era saber a importância relativa do rebrotamento e da reprodução sexuada na regeneração da população. A área de estudo, há aproximadamente seis anos sem queimar, sofreu uma queimada severa no final da estação seca de 2006. Amostramos todos os indivíduos de Z. rhoifolium encontrados em 80 parcelas de 25 m². Encontramos 149 indivíduos antes do fogo e 112 depois dele, dos quais 77 eram rebrotas de plântulas e jovens queimados. Não encontramos diferenças significativas entre a estrutura da população antes e após o fogo. A distribuição espacial da população permaneceu agregada após a queimada. Portanto, a população de Z. rhoifolium foi resiliente ao fogo. Não foi encontrada nenhuma nova plântula. Consequentemente, o rebrotamento parece ser mais importante que a reprodução sexuada na regeneração imediata das populações de Z. rhoifolium.