Natural Regeneration Of Tropical Forest Research Articles

Natural forest regeneration over a fallow age chronosequence in central African moist forests

AbstractA better understanding of the natural regeneration in tropical forests could help develop more effective restoration strategies. This study examined relationships in structural and diversity attributes of natural regeneration in five forest fallow ages after slash‐and‐burn agriculture (6 months, 2 years, 5 years, 10 years, and 15 years) in the Republic of Congo. For each fallow age, all stems with a diameter ≥1 cm and below 5 cm (height ≥ 130 cm), corresponding to natural forest regeneration, were identified to the species level, and measured (diameter and height) in 12 plots (10 m × 10 m). Three structural attributes (stem density, maximum diameter, and maximum height) and five diversity indices (species richness, Shannon diversity, Simpson diversity, Fisher's alpha and Pielou's evenness) were estimated at the plot level. Our results revealed an increase in structural and diversity attributes with fallow ages, except stem density. The young fallow (6 months, 2 years and 5 years) had greater stem density (61 ± 48 stems), while the old fallow (10 years and 15 years) had higher maximum height (5.39 ± 2.36 m) and Shannon's index (0.94 ± 0.18). These results provided new insights into natural regeneration between young and old secondary forests.

Natural regeneration in tropical forests along a disturbance gradient in South-East Cameroon

The dynamics of tropical forests are highly dependent on the forest understorey. Understanding its diversity and composition is essential to ensure sustainable management of forest ecosystems. In this study, following a gradient of human disturbance, we analysed the density, diversity and floristic composition of the forest understorey in three land use types of south-eastern Cameroon: a protected area, a selective logging concession and community forests. Vegetation was inventoried in thirty-three permanent one-hectare plots. Woody individuals (tree, shrub, liana) were classified in four strata depending on their diameter: seedling (dbh < 1 cm), sapling (1–9.9 cm), small trees (10–29.9 cm), large tree (≥30 cm). A total of 4,159 individuals (dbh < 10 cm) belonging to 418 species and 232 genera were recorded. They mainly represent tree species (65%) and shade tolerant plants (77%), with diaspores disseminated by animals (74%). Life forms and modes of dissemination were significantly different between land use types. Abundance, species richness and diversity of juveniles varied significantly between strata and land use types: they were globally the highest in plots that have been logged less than five years before inventory. In terms of species composition, the different land use types were not clearly separated, indicating some resilience to disturbance. A low similarity between strata was observed. In all types, most canopy species are light demanding and cannot regenerate in the understorey. This indicates a natural evolution of the forest stands in the absence of silviculture. The presence of species that currently dominate the canopy of these forests will be gradually reduced without human intervention.

Diversity and Phytosociology of Natural Regeneration in a Sub-tropical Forest of Chittagong Hill Tracts, Bangladesh: Implications for Conservation

ABSTRACT Natural regeneration in tropical forests is considered an essential part of forest restoration efforts; however, it is often under-estimated where the main focus has traditionally been on tree planting. This study assessed natural regeneration and its potential for the conservation of native tree species in Sitapahar Forest Reserve, Bangladesh. We established 99 temporary plots (2 m × 2 m each) in three canopy classes, namely dense canopy (DC, 70–100% canopy coverage), moderate canopy (MC, 40–70%), and open canopy (OC, <40%). In each plot, regenerating tree species were counted, identified, and height (m), collar diameter (cm), and diameter at breast height (dbh, cm) were measured. We identified 79 regenerating tree species under 31 plant families of which 61 were found in DC areas followed by 56 and 36 in MC and OC areas, respectively. Most of the species in DC areas were late-successional, while the OC areas were dominated by early successional species. Diversity and density of regeneration were lowest in OC areas. Findings of this study suggest harnessing biodiversity conservation by promoting natural regeneration and identifying the areas with higher potential for assisted natural regeneration that will enable in situ conservation of rare and vulnerable species by protecting them from further erosion.

Small understorey trees have greater capacity than canopy trees to adjust hydraulic traits following prolonged experimental drought in a tropical forest.

Future climate change predictions for tropical forests highlight increased frequency and intensity of extreme drought events. However, it remains unclear whether large and small trees have differential strategies to tolerate drought due to the different niches they occupy. The future of tropical forests is ultimately dependent on the capacity of small trees (<10cm in diameter) to adjust their hydraulic system to tolerate drought. To address this question, we evaluated whether the drought tolerance of neotropical small trees can adjust to experimental water stress and was different from tall trees. We measured multiple drought resistance-related hydraulic traits across nine common neotropical genera at the world's longest-running tropical forest throughfall-exclusion experiment and compared their responses with surviving large canopy trees. Small understorey trees in both the control and the throughfall-exclusion treatment had lower minimum stomatal conductance and maximum hydraulic leaf-specific conductivity relative to large trees of the same genera, as well as a greater hydraulic safety margin (HSM), percentage loss of conductivity and embolism resistance, demonstrating that they occupy a distinct hydraulic niche. Surprisingly, in response to the drought treatment, small trees increased specific hydraulic conductivity by 56.3% and leaf:sapwood area ratio by 45.6%. The greater HSM of small understorey trees relative to large canopy trees likely enabled them to adjust other aspects of their hydraulic systems to increase hydraulic conductivity and take advantage of increases in light availability in the understorey resulting from the drought-induced mortality of canopy trees. Our results demonstrate that differences in hydraulic strategies between small understorey and large canopy trees drive hydraulic niche segregation. Small understorey trees can adjust their hydraulic systems in response to changes in water and light availability, indicating that natural regeneration of tropical forests following long-term drought may be possible.

Nutritional Efficiency of Forest Species in Natural Regeneration of Tropical Forest in Brazil

The knowledge of the nutritional aspects of native species, mainly in natural regeneration, may be important for understanding their establishment, particularly in areas with low nutrient availability soils, such as tropical soils. This study aimed to determine the biological utilization efficiency (BUE) of the nutrients N, P, K, Ca, and Mg of forest species of natural regeneration in a Lowlands Dense Ombrophilous forest fragment in Pernambuco, Brazil. A phytosociological study of the fragment was carried out and were defined the ten species with the highest absolute density (AD). Three individuals per species were selected. The N, P, K, Ca, and Mg contents were determined in the sample leaves of the species, and the foliar biomass was determined “in loco”. Nine individuals of each species were collected according to the following diameter intervals at the base (DBs): DBs&amp;lt;5 cm; 5≤DBs&amp;lt;10 cm and 10≤DBs&amp;lt;15 cm. The content, stock and BUE of nutrients were calculated per species. The BUE of nutrients by species varied according to the following decreasing order: P&amp;gt;Mg&amp;gt;K&amp;gt;Ca&amp;gt;N. The highest BUE of nutrients was of the species Protium heptaphyllum. In tropical soils of low natural fertility, the use of these species can be recommended in environmental reforestation projects. The difference in the nutritional demand of the forest species can indicate the planting of those with greater capacity of absorption and BUE of nutrients, being more efficient in areas of soils with low natural fertility like in the tropical forests.

Factors Affecting Natural Regeneration of Tropical Forests across a Precipitation Gradient in Myanmar

Natural regeneration is an essential component of forest dynamics and the recovery of ecosystem functions. Therefore, understanding regeneration status, and how abiotic and biotic factors affect it, is important for ecological studies. This study discovered different regeneration statuses of tropical forests in response to differences in rainfall in Myanmar, and the environmental and overstory factors that had the most influence on understory regeneration. Study sites were set up in regions with 625 to 2035 mm of annual rainfall, and ecological characteristics were measured. According to the results, natural regeneration increased with rainfall, showing a good regeneration status at all sites. Forests within a range of 1411–2035 mm of annual rainfall had a significantly higher density and species diversity at specific natural regeneration stages than those with 625–1029 mm. Not only abiotic but also overstory structure affected the natural regeneration of forests. However, not all factors influenced natural regeneration status. Overstory size distribution parameters did not show a significant influence on natural regeneration. Average annual rainfall (abiotic), as well as ecosystem complexity, density, species richness, and diversity (overstory), were found to be the most influential factors for the density and diversity of natural regeneration. The results of this study will support silviculture and the management of tropical forests.

Efecto de la luz y micorrizas en la germinación de semillas de árboles de selvas secas

La germinación es un proceso fundamental en la regeneración natural de las selvas tropicales. En las selvas secas la germinación es afectada por la pronunciada estacionalidad que causa una alta heterogeneidad de la cantidad de luz que llega al suelo y la interacción con las micorrizas. La germinación se estudió en tres especies características de selvas secas: Tecoma stans (L.) Juss. ex Kunth, Senna racemosa(Mill.) H.S. Irwin y Barneby, y Bauhinia forficata Link. subsp. pruinosa (Vogel) Fortunato &amp; Wunderlin. El proceso germinativo fue evaluado en un diseño factorial con tres tratamientos de germinación: testigo (suelo de la selva de origen + nutrimentos), micorriza (Glomus intrarradices) y testigo químico (Triple 17: Nitrógeno + Fósforo + Potasio); y cuatro niveles de luz (10%, 30%, 50% y 70%); se evaluó el proceso germinativo con nueve variables. Ambos factores influyeron de manera independiente en la respuesta de germinación y solo se encontraron efectos de interacción en la tasa promedio de germinación de T. stans y en la incertidumbre de la sincronía de la germinación de B. forficata. Los niveles bajos e intermedios de luz aumentaron la tasa promedio de germinación y valor máximo de germinación de T. stans. Además, los porcentajes de germinación de S. racemosa incrementaron en niveles intermedios y altos de luz. En B. forficata no se registró ningún efecto de la disponibilidad de luz sobre el proceso de germinación. La adición de micorriza afectó positivamente la tasa promedio de germinación en T. stans y los porcentajes de germinación en S. racemosa y B. forficata, aunque en estas dos últimas de forma asincrónica. El uso de niveles de luz adecuados y la adición de micorriza beneficiarían la germinación in situ de especies importantes en la regeneración de las selvas secas tropicales, aunque con ciertas restricciones.

Stimulating Natural Regeneration of Tropical Forest on Degraded Land: Approaches, Outcomes, and Information Gaps

AbstractExtensive land clearing in many parts of the global tropics is a major threat to biodiversity, and strategies are urgently needed to reinstate forest. Tree planting is a commonly used strategy to rapidly restore forest to degraded landscapes. However, tree planting is expensive, and in most cases financial constraints prevent its use at a scale needed to address the ongoing legacy of land clearing. Here, we conduct a quantitative review of literature from the global tropics and evaluate outcomes of less intensive interventions (i.e. non‐planting) aimed at stimulating natural regeneration of forest. We focus specifically on overcoming barriers to native plant regeneration that predominate in the earliest stages of succession. Common interventions include varied strategies to suppress herbaceous vegetation (e.g. cutting or herbicide treatment), and measures to bolster propagule supply (e.g. direct seeding and artificial bird perches). There was an apparent trend among pair‐wise comparisons of effect sizes to suggest that combined interventions to simultaneously suppress herbaceous vegetation and increase propagule supply resulted in the most consistent outcomes in terms of promoting progress toward restoring forest structure. Despite an obvious demand for lower cost interventions, a paucity of information means that it is still premature to generalize outcomes of specific interventions and their overall cost relative to active tree planting. Nevertheless, we report an increase in research effort in this area, and suggest promising directions to accelerate progress that will improve capacity to select optimal, cost effective strategies that achieve long‐term restoration objectives with a particular level of certainty.

FRUGIVORIA E DISPERSÃO DE SEMENTES POR PEIXES

Biotic or abiotic processes of seed dispersal are important for the maintenance of the diversity, and for the natural regeneration in tropical forests. Ichthyochory is one of the fundamental mechanisms for seed dispersal in flooded environments, as the “igapó” forests. A study on the ichthyochory of the igapós was conducted at Amanã Sustainable Development Reserve, in the middle Solimões river, from June 2002 to September 2004. Monthly samples of frugivorous fish were taken, with the main fishing gears used locally. Guts of 1,688 fish caught were examined. The main species were Myloplus rubripinnis (29.21%), Hemiodus immaculatus (18.96%),Colossoma macropom um (16.23%) and Mylossoma duriventre (16.05%). The diet was made of vegetables (fruits, leave and flowers), and animals (arthropods). 53.02% of all fish caught ingested fruits. The total number of intact seeds in the stomachs and intestines were 8,069 and 5,763 respectively. About 61.9% of the Brycon melanopterus (matrinchão), 46.34% of the Brycon amazonicus (mamuri) and 30.22% of M . rubripinnis (parum ) analysed had intact seeds in their guts. Seeds of Nectandra amazonum and Genipa spruceana ingested proved to be more viable than those non-ingested by fish. The high rates of frugivory, the presence of intact seeds in the guts of fish and the greater viability of ingested seeds all suggest that these animals are important seed dispersors in the “igapó” forests of Amanã Reserve.

Simulation model of natural tropical forest dynamics

Assessments of the long-term natural regeneration of tropical forests following selective logging are today mostly based on extrapolation of limited empirical observations. Mounting evidence suggests that current logging policies overestimate forest regrowth by a wide margin, and are therefore not sustainable. The need for more reliable assessment of natural forest growth dynamics has led to the development of a vertically and spatially structured dynamic simulation model of natural forest development. The model accounts explicitly for biomass and tree numbers in five distinct canopy layers (seedlings, saplings, poles, main canopy, emergents). Energy accounting of assimilation and dissimilation rates leads to biomass, diameter, and height growth in each layer. Leaf mass in each layer determines photoproduction, and light and photosynthesis conditions in lower layers. Transitions to higher layers, mortalities in each layer, and seed events are accounted for. The basic model simulates the development dynamics of a forest gap. Parallel computation of spatially distributed single gap models with stochastic mortalities and seed dispersal provides a simulation of the spatial dynamics of the tropical forest mosaic. Simulation results are provided with parameters corresponding to unlogged and logged Malaysian lowland dipterocarp forest.

Taxa de regeneração natural na floresta tropical úmida.

Apresenta um modelo matemático para expressar a taxa de regeneração natural em florestas tropicais, através dos valores de abundância. 0 modelo proposto e. o seguinte-.tr = { (A1/A0)- 1 }. 100, onde:tr = taxa de regeneração natural em percentagem;A = abundância absoluta = número de indivíduos por unidade de área;A1 = A0 + ne - ns = abundância absoluta final;ne = número de indivíduos que ingressaram no estudo, por germinação ou mudança de categoria de tamanho (in-put)) ;ns = número de indivíduos que saíram do estudo, por morte ou mudança de categoria de tamanho (out-put).-1 = constante que indica a mortalidade.Os resultados demonstram que a floresta está em equilíbrio dinâmico, uma vez que, apresentou um valor de + 0,10% para a taxa de regeneração natural, a qual pode ser utilizada para espécies, grupos de espécies ou para o total da floresta.