Comparative evaluation of natural regeneration assessment methods and their responses to environmental factors

Forests cover approximately 31% of the Earth’s land area. They serve as critical habitats for the majority of terrestrial organisms. Natural regeneration is the main method for renewing forests. This process not only drives forest development but also plays a crucial role in maintaining ecosystem productivity, stabilizing community structure and conserving biodiversity. Current studies indicate that the natural forest regeneration process is influenced by a multitude of environmental factors, including light availability, water resources, wind patterns, soil properties, geography features and groundcover. Light strongly influences processes such as photosynthetic efficiency, biomass allocation and photoinhibition in tree growth. Temperature plays an important role in forest regeneration by influencing seed germination, seedling development, and nutrient cycling in the soil. Water availability regulates the competition between trees and other vegetation. Wind plays a key role in seed dispersal, and with the recovery process following wind disturbances potentially extending for 30–50 years. Soil composition, both physical and chemical, as well as biological factors such as microorganisms, directly determine the trajectory and efficiency of forest ecosystem recovery. Geo-environmental factors such as altitude and topography further shape regeneration by modifying climatic conditions and hydrothermal conditions. In addition, the groundcover layer can promote seed germination while also posing challenges to regeneration through resource competition or by promoting the spread of pathogens and pests. Despite significant advances, several gaps remain in the research: (1) Research on the effects of wind speed on trees’ physiological properties, such as growth and root stability, is limited; (2) Most existing studies primarily focus on seed-based regeneration, with relatively little attention given to coppicing regeneration; (3) There is a scarcity predictive ecological models for coping with future climate change. Addressing these gaps requires more comprehensive studies on the impact of wind factors on the physiological and ecological characteristics of seedlings and young trees to break through the bottleneck associated with natural regeneration. Furthermore, in-depth studies are needed on emergent plants resilience and their adaptability under varying light, soil and climate conditions. A systematic comparison of coppicing regeneration with seed-dependent regeneration is suggested to understand the advantages and challenges associated with different regeneration methods.

Modeling the environmental response of leaf net photosynthesis in Pinus pinea L. natural regeneration

Beech is a very widespread species on the entire Eurasian continent. It grows and develops in different ecological and habitat conditions in a wide horizontal and vertical amplitude. It can be found at altitudes below 100 and above 2,000 m. Beech forests develop in different age stands from young to very old (old-growth forests). They can be pure or mixed with other species or they can be very different in origin (generative or vegetative). They develop as eaven-aged or uneaven-aged stands, and some of the beech forests have the characteristics of forests with high natural values and are very important for the conservation of biodiversity. Their natural regeneration process is of essential importance for the survival and sustainable development of beech forests. Restoration of beech forests can be achieved naturally or artificially. In modern forestry science and practice, natural forest regeneration is always preferred. The processes of natural regeneration have different development depending on whether they take place under the protection of the parent stand or take place in an open canopy in the forest or on uncultivated terrain. The density of the canopy has a great influence, so that with the increase of the canopy of the parent stand during the natural renewal, there is a decrease in the number of regeneration individuals(offsprings) in all developmental stages. During the natural regeneration in different conditions of the stand canopy and the size of the openings within the forest, the most abundant and best regeneration is observed in the openings up to 500 m², then for openings within 500 and 1,000 m², and least in openings between 1,000 and 1,500 m². This clearly indicates that large openings within the forest are not suitable for the natural regeneration of beech because the number of offsprings, which are very necessary in the younger developmental stages, is continuously decreasing. The natural renewal that develops in the conditions of circular openings within the size of up to 500 m² has the best quality structure of the offspring. In such openings, about 60% of the offspring is of good quality, about 25% is of medium quality and about 15% is of poor quality. In openings between 500 and 1,000 m2 , the number of good quality natural regeneration is reduced to 41%, the number of medium quality natural regeneration is increased to 38% and from poor quality to 21%. The quality structure of natural regeneration is further reduced in openings between 1,000 and 1,500 m² where only about 20% of the offsprings is of good quality, about 30% is of medium quality and about 50% is ofpoor quality. With openings larger than 500 m², weeds are very common. Beech stands in different habitats have large differences in their productivity, caused by the wide range of the beech forests in different habitat conditions and in different cultivation forms. Aboveground biomass in beech forests varies depending on the age of the forest, the way it is managed and used, as well as numerous environmental factors. High values of aboveground biomass in preserved oldgrowth beech forests above 750 t·ha-1 are known. Moderate values in commercial forests range between 200 and 400 t·ha-1 . In dominant trees, the largest biomass is found in tree crowns, while in subdominant and suppressed trees, the largest biomass is in the trunk, which is the result of a smaller crown due to the lack of solar radiation. Generally, 1/3 or slightly less of the aboveground biomass comes from the branches, the leaves cover about 1-2%, while the largest biomass (60- 70%) is concentrated in the tree. Dead biomass in beech forests consists of dead biomass accumulated in the forest floor, as well as in standing and lying dead biomass. Forest biomass varies in European beech forests: beech forests in the north show less biomass of 3-12 t·ha-1 , while high values (25-75 t·ha-1 ) are registered for the southeastern parts. Standing dead biomass in forests amounts to 1.2-6.0% of living aboveground biomass or 2-5 t·ha-1 . Lying dead biomass in European beech forests varies to a very large extent depending on the conservation of beech forests and their developmental stage. The European range is 32-310 m3 ∙ha-1 , and values above 130 m3 ∙ha-1 belong to the preserved beech forest reserves. When choosing methods of beech forest management, one should always take into account the biological characteristics of beech in relation to the ecological conditions in the area where beech develops. Today, various and professionally supported methods of forest management with the aim of their sustainable development demand great importance for beech 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.

Natural forest regeneration, i.e. self-renewal of forest stands, involves the replacement of old trees by the next generation and is influenced by environmental factors. The spatial structure of tree regeneration depends on and also influences the properties of the stands themselves. Few studies have investigated spatial patterns of naturally regenerated areas in Mexican pine–oak forests, which are considered one of the world’s top 34 biodiversity hotspots. In this study, we analyzed the spatial patterns, particularly the spatial structure, in clusters of naturally regenerated trees in seven 100 × 100 m plots in the Sierra Madre Occidental (northern Mexico), in relation to three factors: slope, geographical aspect and distance between each sapling to the edge of the nearest gap in the canopy. Three indices were used to describe spatial structure and the data were analyzed by bivariate Ripley’s K(t)-functions and three-parameter and six-parameter Weibull models. The results indicate that sapling regeneration was marginal in canopy gaps. Sapling density was ten times higher under the canopy cover, close to the edge than in the gaps. On average, the first maximum number of saplings was detected inside the canopy at about 81 cm from the gap edge, forming ring-type spatial patterns around the canopy gaps. These results contrast with the gap dynamics described in many other studies. We attribute these findings to the nurse effect of trees, which ameliorate abiotic effects, such as the extreme drought that occurred in 2011 and 2012 in the study region. In covered zones close to canopy edges, thece orientation. We recommend adapting or changing the current forest management system to improve continuous forest regeneration (including adaptive silviculture). We also strongly support i) research on the effects of cattle grazing on natural regeneration in the region and ii) reduction of livestock pressure, which is essential to support forest renewal. Complementary reforestation, in addition to maintenance of the few saplings growing within the gaps, may help enhance forest regeneration. Finally, the use of alternative regeneration methods, such as an irregular group shelterwood method (Expanding Gap Silviculture “Femelschlag”), should also be considered, in order to promote natural regeneration more purposefully.

Natural regeneration plays an important role in species diversity and evolution. Exploring the causes of variation in regeneration dynamics can provide key insights into the factors affecting regeneration. However, the relationship between the regeneration of Larix principis-rupprechtii and environmental factors in North China has remained unexplored. In this study, 14 plots were established based on the three extents of regenerated plant numbers in Shanxi Province. Redundancy analysis determined that environmental factors (topography, stand structure, soil property, and litter) affected natural regeneration. Structural equation modeling identified the most important direct and indirect factors that affected L. principis-rupprechtii natural regeneration. Litter thickness, canopy density, and adult tree diameter at breast height were positively correlated with natural regeneration. Aspect and total nitrogen volume were negatively associated with natural regeneration. Additionally, there was no significant correlation between natural regeneration and other environmental factors (altitude, slope, adult tree height, stand density, soil water content, SOC, total P, available N, available P, or soil enzyme). Further artificial intervention measures should be considered to promote plantation regeneration. These findings provide an effective basis for future forest restorations and sustainable management.

Based on target tree management, the effects of different thinning intensities and environmental factors on the natural regeneration of a Pinus massoniana and Quercus variabilis mixed forest were explored in order to provide a theoretical basis for the natural regeneration and sustainable forest management of P. massoniana and Quercus L. mixed forests. Taking the mixed forest after thinning as the research object, three average thinning intensities of WT (7.6%) for weak thinning, LT (15.3%) for light thinning, and MT (24.3%) for moderate thinning were carried out in 5 m×5 m quadrats with 7–10 replicates for each intensity level and 3 replicates for the control. Three years after the thinning, the amount of natural regeneration, growth height, regeneration density, diversity of regenerated tree species and their influencing factors at different thinning intensities were measured and analyzed. The results indicated four main features of the subsequent regeneration. (1) There were 32 species of vascular plants in the 28 quadrats 3 years after thinning, belonging to 22 families and 30 genera, and the dominant species for regeneration were arbor species. The number of regeneration species increased with increasing thinning intensity. (2) As thinning intensity increased, the number of natural regeneration plants between various height classes rose; so, the increased thinning intensity promoted the density of different height classes during regeneration. (3) As thinning intensity increased, so did species abundance S and species evenness. The degree and intrinsic diversity increased, while the Shannon-Weiner and Simpson indices showed no discernible trends. (4) Slope, aspect, and slope position, as well as thinning intensity, all had significant impacts on species richness, species evenness, and regeneration density. MT has the most appropriate promoting effect on natural regeneration and species diversity, so increased thinning intensity can promote natural regeneration and species diversity in the P. massoniana and Q. variabilis mixed forest. In addition, aspect and slope position can increase the species richness S and diversity of natural regeneration, whereas slope has a clear inhibitory effect on the species richness S and diversity during natural regeneration.

How environmental factors affect forest regeneration is relevant for systems that depend partially or fully on natural regeneration. P. pinaster post-disturbance regeneration and its relationship to environmental factors was studied in five P. pinaster forest populations of central Spain. We expected that: 1) different harvesting methods or wildfire would promote natural regeneration in all populations, but with local and regional variations,or 2) alternatively, different site-dependent stand factors would affect natural regeneration, although generalized climate effects would be seen. Analysis of variance and multivariate analysis were used to test differences, to classify ecological variations, and to search for the most important factors affecting regeneration. The results suggest that the recovery of P. pinaster forest in burnt stands, and stand replacement in harvested stands, can be achieved soon after disturbance if climatic conditions and other local-site factors (e.g., soil and overstory structure in harvested stands, cone bank in burnt stands) make the stand suitable for natural regeneration. Heterogeneous regeneration can be expected in all cases. The time of precipitation strongly influenced seedling density and successive regeneration development stages. Edaphic properties, combined with water availability from precipitation, can seriously limit the natural establishment of P. pinaster in xeric systems or during years of intense drought. Although many factors contribute to high variability, natural regeneration has been very effective (successful) in P. pinaster forests, which contributes to the generalization that natural regeneration is a viable forestry option in many forest types.

Evidence of environmental impact on the Cerrado is characterised by the presence of large homogeneous pastures and agricultural areas, with the presence of very fragmented and scattered forest fragments. When these areas are abandoned due to low productivity, natural regeneration begins, which is influenced by environmental factors. The goal of the present study was to evaluate the forest cover temporal dynamics in anthropogenic areas and the influence of climate on natural regeneration in the Cerrado. The study site was an anthropogenic area that has been protected against the entrance of domestic animals and agriculture since 2002. Environments were identified, and natural regeneration dynamics were analysed by the use of vegetation indices calculated from satellite images. Statistical analysis Non-parametric Mann-Kendall was used to check the trend of the rain and the Normalized Difference Vegetation Index, multivariate analysis to verify the correlations and groups between the years of occurrence of El Niño and La Niña and the values of Normalized Difference Index. Natural regeneration in the Cerrado increased over time and was positively correlated with rainfall incidence. The process of recovery of degraded areas by natural regeneration technique proved efficient in the Cerrado, however, natural regeneration is negatively influenced by the weather phenomenon El Niño.

Extensive tropical forest loss and degradation have stimulated increasing awareness at the international policy level of the need to undertake large‐scale forest landscape restoration (FLR). Natural regeneration offers a cost‐effective way to achieve large‐scale FLR, but is often overlooked in favor of tree plantations. The studies presented in this special issue show how natural regeneration can become an important part of FLR and highlight the ecological, environmental, and social factors that must be considered to effectively do so. They also identify major knowledge gaps and outline a research agenda to support the use of natural regeneration in FLR. Six central questions emerge from these studies: (1) What are the ecological, economic, and livelihood outcomes of active and passive restoration interventions?; (2) What are the tradeoffs and synergies among ecological, economic, and livelihood outcomes of natural regeneration, restoration and productive land uses, and how do they evolve in the face of market and climate shocks?; (3) What diagnostic tools are needed to identify and map target areas for natural regeneration?; (4) How should spatial prioritization frameworks incorporate natural regeneration into FLR?; (5) What legal frameworks and governance structures are best suited to encourage natural regeneration and how do they change across regions and landscapes?; (6) What financial mechanisms can foster low‐cost natural regeneration? Natural regeneration is not a panacea to solve tensions and conflicts over land use, but it can be advantageous under some circumstances. Identifying under what conditions this is the case is an important avenue for future research.

Abstract. Marod D, Sungkaew S, Thinkampaeng S, Wachrinrat C, Hermhuk S, Thongsawi J, Phumphuang W, Yarnvudhi A, Yatar C, Cheysawat S, Sawasmongkol C. 2024. Natural tree regeneration after selective cutting in a dry evergreen forest in Northeastern Thailand. Biodiversitas 25: 4074-4085. Forest degradation is a serious problem caused by anthropogenic disturbance, nevertheless, forest recovery rates vary among forest ecosystems. We investigated forest regeneration after selective cutting in a dry evergreen forest at the Wang Nam Khiao Forestry Research and Training Station (WFRS), Nakhon Ratchasima Province, Thailand. In 2002, a 1-ha permanent plot was established in the forest. All woody plant (sapling and trees) in the plot with Diameter at Breast Height (DBH) >2 cm were identified, and their DBHs and positions were recorded. Data on environmental and topographic factors and soil properties were collected to analyze their relationships with tree spatial distribution. Tree monitoring was conducted in 2004, 2018, and 2020 and forest dynamics were analyzed for the periods 2002-2004, 2004-2018, and 2018-2020. In 2020, we identified 3,669 trees of 91 species, 81 genera, and 36 families. Based on importance index values, the dominant tree species (all with DBH ?4.5 cm) were Walsura pinnata Hassk., Dialium cochinchinense Pierre, Hopea ferrea Laness., Hydnocarpus ilicifolius King and Vitex scabra Wall. ex Schauer. Based on the DBH class distribution, the natural regeneration of all woody plants tended toward a reverse J-shaped, indicating a good regeneration condition. The results of forest dynamics analysis showed that the net recruitment rate (2.75±1.70% year-1) was higher than the mortality rate (2.14±0.73% year-1) throughout the study period. Tree spatial distributions varied among species and across environmental factors which were strongly influenced by soil texture followed by topographic and can be divided into generalist and specialist species. This indicates that the forest is going toward a positive regeneration trajectory after the disturbances. Nonetheless, additional information based on forest monitoring is required. Additionally, an understanding of the relationships between species niches and environmental changes is important for tree regeneration research and forest restoration programs; it will allow better matching of tree species to their optimal environmental conditions, thereby increasing the likelihood of plant community success.

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.

En los andes del Ecuador existen plantaciones de Pinus radiata y Pinus patula, sembradas entre matorrales, páramos y áreas abiertas; y, se desconoce la sucesión vegetal, sus cambios y desarrollo. Se investigó una plantación de Pinus radiata en la hoya de Loja con el objetivo de caracterizar la composición florística y monitorear la regeneración natural considerando categorías de regeneración: plántulas, brinzales y latizales. Se establecieron 5 parcelas de 20 m x 20 m, se anidaron 5 subparcelas de 5 m x 5 m y 5 subparcelas de 1 m x 1 m. Se midió altura y diámetro basal. Se determinó la sobrevivencia y crecimiento en un periodo de 12 meses; se analizó la influencia de variables ambientales: luminosidad, pendiente, profundidad del suelo horizonte O, sobre la diversidad y abundancia de la regeneración natural. Se identificaron 24 especies, 21 géneros y 22 familias. La mayor diversidad presentan los latizales; las especies con mayor IVI en las tres categorías son: Piper barbatum, Viburnum triphyllum y Frangula granulosa. Los latizales presentan mayor sobrevivencia (99,37 %), seguida por brinzales (87,59 %) y plántulas (82,76 %). El incremento en altura y diámetro es mayor en Frangula granulosa, Clusia latipes, Critoniopsis pycnantha y Alnus acuminata. No existe influencia significativa de los factores ambientales sobre la diversidad y abundancia de la regeneración natural. La regeneración natural encontrada en las condiciones de hábitat de la plantación; demuestra que es factible la recuperación de la vegetación natural y la presencia de un bosque natural cuando desaparezca la plantación forestal.

To mitigate the loss of Colombia's Moist Forests—35% of their original extent by 2021—understanding successional dynamics is critical for effective restoration. This study synthesizes data from 34 peer‐reviewed articles to evaluate the efficacy of restoration methods (natural regeneration, native or exotic plantations, nucleation, remediation, agroforestry, or silvopastoral systems) in recovering vegetation structure, leaf litter, soil nutrients, and species richness. Using meta‐analyses and multivariate models, we compared active restoration methods with natural regeneration, evaluated their similarity to old‐growth native forests, and identified key drivers of recovery. Results showed that native plantations and silvopastoral systems accelerate vegetation structure recovery in early successions (<30 years), reaching metrics comparable to old‐growth native forests, whereas natural regeneration progresses slower. Exotic plantations underperformed in vegetation recovery, reinforcing the importance of using native species for restoration. Despite differences in structural recovery, species richness (plants, birds, and insects). Soil nutrients and leaf litter accumulation showed no significant variation across restoration methods, highlighting the cost‐effectiveness of natural regeneration in resilient landscapes. Environmental factors—particularly precipitation, elevation, and climatic seasonality—strongly influenced tree density, basal area, and bird richness. Succession time and prior land use activity further shaped recovery outcomes, with forest degradation exhibiting faster structural recovery. The large residual heterogeneity in the meta‐analyses reflects the variability in restoration contexts, emphasizing the need for site‐specific strategies: active restoration in highly degraded or fragmented landscapes and natural regeneration in well‐connected, resilient regions. These insights align with national and global restoration initiatives, integrating research with diverse outcomes in tropical forest restoration.

Environmental influences on post-harvest natural regeneration in Mexican pine–oak forests