Mechanisms Of Natural Regeneration Research Articles

Neighborhood Competition and Understory-Associated Vegetation Are Important Factors Influencing the Natural Regeneration of Subtropical Mountain Forests

Natural regeneration is deemed essential for maintaining biodiversity and ecosystem stability. Previous studies, however, have primarily concentrated on regions exhibiting limited environmental and climatic variability, overlooking the classification of natural regeneration based on age and source. Research conducted at the mesoscale, characterized by increased environmental variability and the incorporation of neighborhood competition and understory-associated vegetation, enhances our comprehension of the multifaceted influences on natural regeneration. To comprehend this issue, this study implemented 60 plots, each measuring 20 m × 20 m, across five distinct areas of Chongqing, China. Twenty explanatory variables were chosen from five diverse categories: understory vegetation, neighborhood competition, stand structure, climatic factors, and environmental factors. And the naturally regenerated species were classified into seedlings and saplings, as well as endogenous and exogenous species, based on their age and origin. We examined the response of the different categories of natural regeneration to various factors and constructed a structural equation model (SEM) for significant factors to investigate their direct and indirect effects on natural regeneration. A total of 61 regenerated tree species belonging to 29 families and 42 genera were found in the study area, and the naturally regenerating species with high importance values were Quercus fabri, Robinia pseudoacacia, Alangium chinense, Cunninghamia lanceolata, and Ligustrum lucidum. It was found that neighborhood competition and understory-associated vegetation explained the largest proportion (more than 50%) of the variation in the different categories of natural regeneration, and forests with clumped distribution (W), a high mingling index (M) and strong competition (H) had a reduced natural regeneration capacity. Understory-associated herbs significantly reduced natural regeneration and the crowdedness index (C) significantly inhibited the understory-associated herbs, thus indirectly promoting natural regeneration. The shrub cover is significantly and positively correlated with the number of naturally regenerated plants and can be used as an indicator of a forest community’s regeneration potential. Understanding the differences in the importance of various factors at the mesoscale, as well as their direct and indirect impacts, can help us further comprehend the mechanisms of natural regeneration and provide a foundation for the sustainable development of forests.

SMART Materials for Biomedical Applications: Advancements and Challenges

The advancement of SMART (Self-Healing, Multifunctional, Adaptive, Responsive, and Tunable) materials has had a significant impact on the domain of biomedical applications. These materials possess distinct characteristics that exhibit responsiveness to alterations in their surroundings, rendering them exceedingly appealing for a wide range of therapeutic applications. This study aims to examine the progress and obstacles related to SMART materials within the field of biomedicine. In recent decades, notable advancements have been achieved in the development, synthesis, and analysis of intelligent materials specifically designed for biomedical purposes. Self-healing materials have been employed in the development of implants, wound healing scaffolds, and drug delivery systems, drawing inspiration from natural regeneration mechanisms. The ongoing advancements in SMART materials have significant opportunities for transforming biological applications. The progression of nanotechnology, biomaterials, and bioengineering is expected to play a significant role in the advancement of materials that possess enhanced qualities and capabilities. The integration of SMART materials with emerging technologies such as 3D printing, gene editing, and microfluidics has the potential to create novel opportunities in the field of precision medicine and personalised healthcare. The effective translation of SMART materials from the laboratory to the clinic will need concerted efforts by researchers, physicians, regulatory agencies, and industry partners to address the present difficulties.

Ecogenesis and primary soil formation on the East European Plain. A review

Abstract Numerous published studies have shown that soil formation, including primary pedogenesis, is closely connected functionally, energetically and operationally with ecogenesis as a key biogenic exploration mechanism of the Earth’s surface by living organisms. The ontogenetic stage of soil evolution, especially in the initial phases, is determined by geogenic conditions and the intensity and trends of biogenic-accumulative processes in the developing ecosystem. Primary soils are considered critical in the rapid development of the initial ancient biosphere, supporting multiple environmental possibilities for ecosystems in that stage of their formation. Currently, similar models of correlated soil formation and ecogenesis are actualised when new substrates appear suitable for biogenic-abiogenic interactions, which occur in both natural and anthropogenic landscapes. Biotic factors during primary pedogenesis have accumulative and transformative effects on the edaphic component complex. At this stage, the initial pedon is a key functional stage in the evolution of terrestrial ecosystems (biogeocenosis). When restoration of natural ecosystems occurs during the independent growth of exposed substrates, the natural regeneration mechanisms normally occur. These processes are based on the biogenic development of the substrate through the accumulation and transformation of organic matter.

Effects of biotic/abiotic factors on the seedling regeneration of Dacrydium pectinatum formations in tropical montane forests on Hainan Island, China

Exploring natural regeneration facilitates a better understanding of the mechanisms of community assembly and biodiversity formation. However, convincing data on tree regeneration in threatened tropical plant communities are lacking. Dacrydium pectinatum is a constructive and endangered species in tropical montane forests of Hainan Island. This study aims to identify the seedling regeneration patterns of D. pectinatum formation and their key drivers. A total of 204 seedling plots were investigated in the northwest (Bawangling, 90 plots), southwest (Jianfengling, 90 plots) and southeast (Diaoluoshan, 24 plots) of Hainan Island. We examined the variations in the seedling/adult composition, density and richness along local scales and elevation gradients and analyzed the relationships between biotic/abiotic variables and seedling regeneration. The seedling distribution pattern changed with environmental gradients, and the seedling density and richness decreased from low to high latitudes and from low to high elevations. Additionally, the adult density and total base area also showed consistent trends. At the community and species levels, the biotic neighborhood variables had a primary impact on the seedling density and richness. Multiple environmental factors (such as the canopy density, elevation, slope, soil organic matter, and soil total nitrogen) also showed significant correlations with the seedling density and richness. Our study supports conspecific negative density dependence and niche filtering as the general mechanisms of natural regeneration of D. pectinatum formations. Both biotic and abiotic factors might affect the survival and growth of seedlings, and their relative importance varies with environmental gradients and species. We conclude that enclosing forests with moderate stand densities in low-elevation areas to reduce human interference will help optimize the community structure. However, for high-elevation areas and high-density forests, appropriate thinning, manual regeneration and open gaps are needed to improve the light environment and soil nutrients, thereby promoting the natural regeneration of D. pectinatum formations.

Spatial Patterns and Interspecific Associations During Natural Regeneration in Three Types of Secondary Forest in the Central Part of the Greater Khingan Mountains, Heilongjiang Province, China

Seedling and sapling spatial patterns are important in community regeneration, and understanding the natural regeneration mechanisms of tree species in relation to spatial patterns will help improve forest management and community restoration efficiency. Based on data from three fixed plots established in birch forests (BF), coniferous and broadleaved mixed forests (CBMF) and coniferous mixed forests (CMF) in the central Greater Khingan Mountains in Heilongjiang Province, China, in 2017, we used the univariate and bivariate O-ring functions of the point pattern analysis method to evaluate the spatial patterns and associations of the main tree species in these three forest types at different development stages and identified the community successional stages according to the interspecific associations between dominant tree species and other tree species. The results showed that Betula platyphylla and Larix gmelinii in BF exhibited identical spatial distribution patterns and had a tendency to transition from an aggregated to a random distribution from saplings to adult trees, whereas every tree type in CBMF generally showed a random distribution. Adult trees of the main tree species in CMF, i.e., L. gmelinii and Picea koraiensis, mainly showed a random distribution, but P. koraiensis at other size classes generally showed an aggregated distribution. The intraspecific associations of the main tree species in BF and CMF at different development stages were constrained by the spatial scale within a given scope, while those in CBMF at different development stages were not significantly constrained by spatial scale. The results also show that the density of the three forest types was affected by the distance between the individuals of the various tree classes and adult trees, with different levels of influence. We analyzed the interspecific associations between dominant tree species and other tree species and then assessed community succession progress and found that the BF and CMF exhibited medium-term community succession, while the CBMF was in the primary stage. Our results further show that the spatial distribution patterns of the tree species in the small-diameter classes were jointly affected by adjacent habitats and diffusional limitations and that scale dependence existed in the intraspecific and interspecific associations. The analysis of the natural regeneration of spatial distribution and interspecific associations represents an efficient way to explore the stability of forest communities and dynamic changes in interspecific relationships during succession. The study results thus provide a theoretical basis for developing rational forest management measures.

INFLUENCE OF ACICULAS DEPOSITION ON NATURAL REGENERATION IN SUB-WOODS OF Pinus taeda L. FOREST STAND

This study was conducted in a commercial forest stand of Pinus taeda L. located in Curitibanos, in the State of Santa Catarina, Brazil. The objective of this study was to evaluate the influence of the physical barrier caused by the deposition of aciculas, on natural regeneration mechanisms of native species in sub-woods of P. taeda L. forest stand. Three plots (10 x 10 m) were installed in the sub-woods of the forest stand, and the natural regeneration was evaluated in the control (presence of aciculas) and clean (absence of aciculas) subplots, in addition to the seeds rain and soil seeds bank. The density and frequency parameters (absolute and relative) and the Shannon-Weaver Index (H’) were calculated, and the total density values of the seeds rain and seeds bank were subjected to ANOVA (p<0.05), while the density of regenerative seedlings was subjected to Student’s t Test (p<0.05), using the Software R Studio ®. The density of regenerative seedlings (ind.m-2) was higher in clean subplots, statistically. No significant statistical difference was observed for the density parameter (ind.m-2) among the subplots for the soil seeds bank, but only for the seeds rain. Shannon Diversity Index was higher in the plots closer to the fragment in all evaluated mechanisms. The obtained results indicate that the litter layer acts as a physical barrier to the breeding of the seeds bank and prevents the arrival of the seeds rain propagules directly to the soil, hindering the establishment of native plants and, consequently, the natural regeneration in the sub-woods.

CHUVA DE SEMENTES E ESTABELECIMENTO DE PLÂNTULAS EM FLORESTA TROPICAL NA REGIÃO NORDESTE DO BRASIL

Mecanismos de regeneração natural são fundamentais para o restabelecimento das funções ecológicas de fragmentos florestais e de áreas degradadas. O presente trabalho teve como objetivo avaliar a chuva de sementes e o estabelecimento de plântulas de espécies arbóreas em Floresta Atlântica, localizada na região Nordeste do Brasil. Para amostragem da chuva de sementes foram alocados 60 coletores (área de 0,196 m²), ficando equidistantes, aproximadamente, de 50 m. As coletas foram realizadas com intervalo de 30 dias por um período de 12 meses. Para avaliar o estabelecimento de plântulas foram alocadas subparcelas ao lado dos coletores, totalizando 60 subparcelas de 0,25 m² cada. Os indivíduos arbóreos identificados pelos diásporos coletados na chuva de sementes e pelas plântulas estabelecidas no fragmento foram contados e classificados quanto à síndrome de dispersão e grupo sucessional. A chuva de sementes foi representada por 60 morfoespécies e 20 famílias botânicas. O grupo ecológico e a síndrome de dispersão predominante foram de espécies secundárias iniciais e zoocórica, respectivamente. Em relação às plântulas estabelecidas foram contadas 122 plântulas, sendo Tapirira guianensis L. com maior número de plântulas. A chuva de sementes apresenta potencial para manutenção da dinâmica florestal por apresentar alta riqueza de espécies que compõe a atual vegetação, sendo composta, predominantemente, por espécies que produzem frutos abundantes com dispersão zoocórica que servem de alimento para fauna. Enquanto poucas sementes germinam para formar o banco de plântulas, a maioria está contribuindo para formação do banco de sementes.

Pérdida de semillas en fase de pre-dispersión en dos especies de Prosopis (Fabacea: Mimosoidea) del Desierto del Monte, Argentina

Pre-dispersal flters imposed on the seed stage can alter the likelihood of seed dispersal. We evaluate pre-dispersal seed loss due to predation by insects and abortion in Prosopis flexuosa and P. chilensis . This study was conducted in two protected areas in the Monte Desert. We collected P. flexuosa and P. chilensis fruits from different trees, from two plots and two years. Samples were maintained for 50 days in translucent PVC boles stored in a laboratory under stable temperature (25 °C) and natural photoperiod, awaiting the emergence of insects. Then we opened the fruits and individually examined all seeds to determine their condition. We found that total pre-dispersal seed loss was 32% in P. flexuosa and 21% in P. chilensis . Seed predation by insects was the major source of pre dispersal seed loss (19% in P. flexuosa and 14% in P. chilensis ). The main seed predator was the apionid weevil (Brentidae: Apioninae) in P. flexuosa , and bruchid beetles (Chrysomelidae: Bruchinae) in P. chilensis . Some bruchid beetles prey upon seeds, completing their life cycle, whereas others remain inside seeds (41% in P. flexuosa and 49% in P. chilensis , of total seed damaged by bruchid beetles). Seed abortion was another important source of seed loss, especially for P. flexuosa , but its cause still remains unknown. We show and discuss the extent of a proposed methodology to account for pre-dispersal seed predation that includes the immature stages of non-emergent bruchid. Pre-dispersal seed loss by insects and abortion represent an ecological flter that limits the amount of seeds available for dispersal and establishment of these species. Understanding seed loss process may contribute to know and predict Prosopis population dynamics, revealing the natural regeneration mechanisms to forest recovery. https://doi.org/10.25260/EA.18.28.2.0.576

Mecanismos de regeneração natural em remanescente de Floresta Ombrófila Mista, RS, Brasil

Neste estudo, objetivou-se caracterizar os mecanismos de regeneração natural em um remanescente de Floresta Ombrófila Mista. O trabalho foi realizado na Floresta Nacional de São Francisco de Paula, RS, Brasil, utilizando seis conglomerados de 1 ha, com 16 parcelas (20×20 m) cada, desconsiderando 10 m de bordadura. A amostragem da chuva de sementes (CS) foi realizada em 96 coletores circulares (1 m²), distribuídos no centro de cada parcela. O banco de sementes do solo (BS) foi amostrado de forma aleatória, a 3 m de cada coletor da CS, e o banco de plântulas (BP) foi amostrado em subparcelas de 2×2 m, alocadas a 4 m dos coletores, contabilizando o número de indivíduos (altura > 30 cm e diâmetro à altura do peito (DAP) < 1 cm) para cada espécie. Os mecanismos de regeneração foram avaliados quanto à composição florística e estrutura horizontal. Na CS, foram amostradas 81 espécies, 46 gêneros e 28 famílias, no BS, 103, 65 e 41 e no BP, 88, 57 e 36, respectivamente. A riqueza encontrada e abundante frutificação de espécies com dispersão zoocórica indicam a importância da chuva de sementes como mecanismo estratégico para o equilíbrio da fauna e flora no ecossistema. O banco de sementes do solo demonstra potencial para colonização imediata e restabelecimento da vegetação após perturbações e o banco de plântulas consiste na principal estratégia de regeneração de muitas espécies arbóreas que compõe a atual estrutura da floresta.

Natural regeneration of Spanish black pine [Pinus nigra Arn. ssp. salzmannii (Dunal) Franco] at contrasting altitudes in a Mediterranean mountain area

AbstractInformation on plant seed dispersal, natural loss dynamics of seeds and germination are critical for understanding natural regeneration mechanisms. The aim of this study was to assess the effect of different forest stand densities on seedfall, seed predation, and seedling germination of two populations of the endangered Spanish black Pine forests located at lower (Central population) and higher elevation near the limit of the species’ range (peripheral population) in the Cuenca Mountains of Central Spain. The seed predation and germination experiment also included a nested site preparation treatment. Seed fall varied significantly between 2006 and 2005 or 2007 in both populations. During the only mast year of 2006, higher seedfall was observed at lower elevation and in higher density stands. Predation rates were influenced by the seed crop since predators consumed more than 75 % of seeds in years with lower production and less than 15 % in a mast year. Seed germination is influenced by forest habitat, stand density and soil scalping. For common habitat types, and in a high seed production year, better seed germination rates were observed in medium and dense stands (25–30 and 35–40 m2 ha−1, respectively, in terms of basal area). No statistical difference in seed germination rate was found for Spanish black pine forest at its ecological distribution limit between lower and higher densities (15–20 and 35–40 m2 ha−1, in terms of basal area). In both sites, closed stands with soil scalping exhibited higher germination rates.

Mecanismos de regeneração natural em remanescente de Floresta Estacional Decidual

Diante da perda da biodiversidade e do habitat natural decorrentes da fragmentação das florestas, surge a necessidade de alternativas que possibilitem a recuperação desses ambientes. Assim, este estudo objetivou obter informações sobre o potencial dos mecanismos de regeneração natural (chuva de sementes, banco de sementes do solo, banco de plântulas e regeneração natural estabelecida) em um remanescente de Floresta Estacional Decidual, visando à conservação e recuperação destes ecossistemas. O estudo foi realizado de forma sistemática, a partir da demarcação de 14 unidades amostrais de 2.000 m², dentro das quais foram selecionadas, aleatoriamente, 70 subparcelas onde foram avaliados os mecanismos de regeneração. A chuva de sementes foi avaliada durante um ano, com base no material obtido mensalmente a partir de coletores. Para o estudo do banco de sementes foram tomadas amostras de solo, com uso de um gabarito de ferro com 25x25x5 cm de dimensões, monitoradas durante 7 meses mediante germinação das sementes. A regeneração natural foi avaliada em duas classes: banco de plântulas e regeneração natural estabelecida, onde foram identificados e medidos indivíduos com h≥30 cm e DAP<5 cm. A chuva de sementes apresentou densidade média de 1350 sementes.m-² na área, dentre as quais se observou 73 espécies, predominantemente, arbóreas. No banco de sementes do solo, foram observadas 108 espécies, sendo 74% herbáceas. No banco de plântulas foram encontradas 48 espécies, sendo estas esciófilas e heliófilas, já na regeneração estabelecida foram encontradas 37 espécies, em sua maioria esciófilas. Concluiu-se que as espécies com maior potencial para perpetuar na área estudada foram Gymnanthes concolor, Sorocea bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans e Dasyphyllum spinescens, sendo as mesmas indicadas para enriquecimento. Já as espécies Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica e Syagrus rommanzoffian apresentam certa restrição, dependendo de tratamentos silviculturais na floresta para garantir sua perpetuação na área.

Mecanismos de regeneração natural em diferentes ambientes de remanescente de Floresta Ombrófila Mista, São Francisco de Paula, RS

O objetivo deste trabalho foi avaliar os mecanismos de regeneração natural em três agrupamentos florísticos em remanescente de Floresta Ombrófila Mista, localizado em São Francisco de Paula, RS. A coleta dos dados foi realizada em seis conglomerados de um hectare, subdivididos em 16 parcelas cada, nas quais foram coletadas amostras da chuva de sementes, do banco de sementes no solo e do banco de plântulas. Os grupos florísticos apresentaram diferenças significativas para a densidade de indivíduos na chuva de sementes e no banco de plântulas. Para o banco de sementes no solo, o grupo G1 diferiu dos grupos G2 e G3. A riqueza de espécies observada no banco de plântulas sugere que este pode ser o mecanismo principal de manutenção da diversidade no remanescente. A chuva de sementes foi abundante e representou uma fonte expressiva de propágulos para abastecer o banco de sementes e banco de plântulas local e das áreas circunvizinhas. O banco de sementes do solo não apresentou potencial florístico para representar a riqueza de espécies presentes na vegetação arbórea, corroborando o estágio sucessional avançado desta floresta, uma vez que o banco de sementes é formado principalmente de espécies pioneiras.

Forest Regeneration from Pasture in the Dry Tropics of Panama: Effects of Cattle, Exotic Grass, and Forested Riparia

Abstract We currently have the opportunity to restore one of the most threatened tropical ecosystems on the Pacific coast of Panama as a consequence of land use change. Factors that influence succession must be understood in order to capitalize on natural regeneration mechanisms. In this study, we determined the effects of exotic grass removal, cattle removal, proximity to forested riparian zones, and topography (upslope vs. downslope) on the initial stages of forest regeneration from pasture in a dry tropical region. After 3 years, basal area, stem density, and species richness of plants (trees, shrubs, vines, and herbs) were significantly and positively affected by exclusion of cattle, presence of exotic grass (no herbicide application), and presence of adjacent forested riparian zones (p < 0.01). Interactions between factors were not significant. Cattle foraged and stomped on vegetation, whereas herbicide application, although effectively removing grass, also killed tree and shrub sprouts, the major source of regrowth. Proximity to forested riparian zones had the greatest effect on species diversity. Shannon’s index for diversity (H) equaled 3.23 in plots adjacent to forested riparian zones as compared to 2.78 in plots not associated with these areas. Our recommendations during the early stages of forest succession are to (1) exclude cattle, (2) make site‐specific decisions about herbicide application based on the presence or absence of forested riparia and prevalence of coppicing, and (3) actively conserve and protect riparian zones, which function as a critical source of diverse propagules.

Potential lateral expansion of Polylepis forest fragments in central Ecuador

High-Andean forests formed by Polylepis are among the most endangered forest types in South America and effective strategies are urgently required to facilitate their conservation. The remaining forest stands are presently distributed in discontinuous patches which usually form abrupt boundaries with the adjacent grassland vegetation. Mechanisms of natural regeneration in this transition zone between forest and grass paramo are still poorly understood. The present study investigates the establishment of seedlings, saplings and vegetative shoots along edges of Polylepis incana and P. pauta forests in the Páramo de Papallacta, central Ecuador. For each species, we analysed 18 transects of 20 m in length, which traversed the edge zone, and sampled 10 subplots of 2 m × 2 m each. Differences between subplot positions were analysed using a repeated measures ANOVA. In addition, we determined correlations of altitude and grazing parameters of the P. incana transects with regeneration data. Seedling numbers of both species were significantly higher in the forest interior than in the exterior, presumably due to less extreme climatic conditions and a more continuous seed rain. Sapling and ramet numbers, however, showed a clear maximum at the forest boundary, which indicates that favourable light conditions are required for sapling and ramet establishment. The importance of vegetative reproduction increased towards P. incana stands at higher altitudes, because the overall number of seedlings and saplings decreased significantly with increasing altitude. Sexual regeneration is limited at the upper distribution limit of the species, which we ascribe to extreme climatic conditions. In P. pauta stands, in contrast, there was no effect of altitude. Grazing by ungulates did not affect the recruitment of saplings or vegetative shoots in the investigated Polylepis stands, but trampling resulted in a significant increase in the abundance of P. incana seedlings. Our results show that boundaries of Polylepis stands are zones of high natural recruitment. Fire is expected to be the most relevant factor for the formation of edges at lower altitudes, as the use of fire strongly affects the reproductive boundary zone of the remaining Polylepis forests, whereas grazing at moderate animal loads does not lead to any severe consequences for these forest communities. We conclude that stands below the upper treeline would expand continuously towards the exterior if human impact ceased, and that the present patchy distribution of Polylepis is as a result of anthropogenic influence and not of natural site conditions.

Seed rain, soil seed bank, seed loss and regeneration of Castanopsis fargesii (Fagaceae) in a subtropical evergreen broad-leaved forest

Understanding the seed rain and seed loss dynamics in the natural condition has important significance for revealing the natural regeneration mechanisms. We conducted a 3-year field observation on seed rain, seed loss and natural regeneration of Castanopsis fargesii Franch., a dominant tree species in evergreen broad-leaved forests in Dujiangyan, southwestern China. The results showed that: (1) there were marked differences in (mature) seed production between mast (733,700 seeds in 2001) and regular (51,200 and 195,600 seeds in 2002 and 2003, respectively) years for C. fargesii. (2) Most seeds were dispersed in leaf litter, humus and 0–2 cm depth soil in seed bank. (3) Frequency distributions of both DBH and height indicated that C. fargesii had a relatively stable population. (4) Seed rain, seed ground density, seed loss, and leaf fall were highly dynamic and certain quantity of seeds were preserved on the ground for a prolonged time due to predator satiation in both the mast and regular years so that the continuous presence of seed bank and seedling recruitments in situ became possible. Both longer time observations and manipulative experiments should be carried out to better understand the roles of seed dispersal and regeneration process in the ecosystem performance.