INTRODUCTION
Canopy openings resulting from mortality, windfall, and the removal of one or multiple mature trees are vital sources of spatial heterogeneity in tropical rainforests, influencing the establishment, growth, and survival of tree species (Denslow, 1987; Clinton, 2003) These gaps are crucial phases in the forest restoration cycle and play a significant role in shaping forest structural dynamics, species richness, and composition (Richards, 1952; Brokaw, 1985; Denslow, 1987; Li et al., 2005) Studies have shown that germination, growth, survival, and mortality rates of seedlings and saplings within gaps vary among species, depending on biotic and abiotic factors as well as specific characteristics of the canopy openings (Lawes et al., 2007; Denslow, 1987; Osunkjoya et al., 1992; Gray and Spies, 1996; Taylor et al., 2006; Sapkota et al., 2009).
Canopy gaps play a crucial role in forest regeneration by initiating new growth cycles for canopy tree species, with small gaps favoring shade-tolerant species and large gaps promoting pioneer or light-demanding species These gaps facilitate the germination and establishment of different tree species based on their light requirements, with small gaps supporting shade-tolerant trees and large gaps enabling opportunist species to thrive by utilizing increased light availability The dynamic competition among tree species for resources like light, water, and nutrients influences forest composition and regeneration processes, making gap formation a key factor in maintaining forest diversity and health.
Moreover, the previous studies on canopy gaps also stated that gaps are normally heterogeneous in size and vary consistently within and between forest types (Brokaw,
Gap formation in forests is influenced by different tree species with varying numbers, sizes, and foliage structures, which create diverse gap environments These variations in gap sizes lead to differences in light intensity, temperature, and soil moisture within the forest, affecting ecological processes Consequently, the richness, composition, and diversity of tree species that colonize and fill these gaps can vary significantly both within and between forest types Additionally, the rates of seedling and sapling mortality and recruitment are impacted by these environmental differences, influencing overall forest dynamics and regeneration patterns (1985b; Osunkjoya et al., 1992; Clinton, 2003; Sapkota et al.).
Regeneration patterns in tropical evergreen forests are complex and difficult to predict, influenced by heterogeneous microclimatic conditions following gap formation (Clinton, 2003) Variations in microclimate, driven by differences in gap sizes, play a crucial role in forest succession by promoting pioneer seedlings while suppressing established and re-grown saplings (Drobyshev and Nihlgard, 2000; Sapkota et al., 2009) This heterogeneity in microclimate is also an important mechanism that facilitates species coexistence and maintains high tree species diversity within tropical rainforest communities (Kneeshaw and Bergeron, 1998; Orians, 1982; Connell, 1978).
In tropical regions, deforestation, habitat fragmentation, and rainforest degradation significantly influence the regeneration patterns of woody tree species in canopy gaps Understanding these complex patterns enhances knowledge of species richness, growth, composition, and diversity across different forest stand categories This insight enables researchers to predict how tree species composition may change within canopy gaps compared to regeneration beneath the forest canopy While the critical role of canopy gaps in forest regeneration and community dynamics has been widely recognized, most studies on forest regeneration in Vietnam have predominantly focused on other aspects, highlighting a gap in research on canopy gap ecology in the region.
Research on gap regeneration beneath the canopies of natural forests and artificial plantations remains limited, with studies by Phuong (1970), Hue (1975), Tam (1987), Kha (2009), Hoang Thi Tuyet (2010), and Nguyen Thi Thiet (2012) being scattered Clarifying the characteristics of this regeneration pattern is essential for effective forest management and restoration efforts This study in Ba Vi National Park aims to deepen understanding of gap regeneration, providing valuable insights and silvicultural recommendations to enhance forest gap restoration processes in the area.
OVERVIEW OF THE RESEARCH AREA
A study was conducted at Ba Vi National Park, located in Ba Vi District, Ha Noi City, in northern Vietnam The park is situated within the Ba Vi mountain range, approximately 48 km northwest of Hanoi, with geographic coordinates spanning from 21°01' to 21°07' N latitude and 105°18' to 105°25' E longitude.
The park was established in 1991 with total area of 7,377 ha The total natural area of Ba
Vi National Park spans 10,782.7 hectares, with 8,192.5 hectares of forest land, accounting for 75.98% of its total area The park features 4,200.5 hectares of natural forest, making up 51.27% of the forest land, and 3,992 hectares of planted forests, representing 48.73% Its high mountain terrain and extensive forests give the Ba Vi region a cool climate, especially during summer from April to October, while winter cloud cover creates a visually stunning landscape The park is located along a mountain range extending northeast to southwest, with notable peaks including Vua Peak at 1,296 meters, Tan Vien Peak at 1,226 meters, and Ngoc Hoa Peak at 1,120 meters.
Figure 2.1: Map of Forest Statuses in Ba Vi National Park
The park's tourism potential is highlighted by its stunning natural beauty and unique geographic and climate features, which contribute to a diverse and vibrant ecosystem As one of the four renowned mountainous ecological tourism centers alongside Da Lat, Sapa, and Tam Dao, it offers visitors a top destination for eco-tourism and nature exploration.
Ba Vi National Park is a biodiversity hotspot, hosting over 1,200 plant species, including 21 that are listed in Vietnam’s Red Book 2007, and currently recognized to contain 812 vascular plant species The park is home to 8 unique tree species such as Allomorphia baviensis, Begonia baviensis, and Pinanga baviensis, along with 15 rare and valuable plants like blue cypress, bamboo, and three-shot fern Its rich fauna includes 45 mammal species, 115 bird species, 27 amphibian species, and 61 reptiles, highlighting its crucial role in conserving Vietnam's diverse ecosystems.
Ba Vi National Park is home to 86 insect species, including 23 rare and valuable species such as coolies, horse bears, yellow pangolins, white pheasants, monkeys, leopards, bears, and flying squirrels, many of which are listed in Vietnam’s Red Book (2007) The park's diverse vegetation comprises three main types: low montane subtropical broadleaved evergreen moist forests, mixed forests of broadleaved and coniferous trees, and low montane tropical broadleaved evergreen rainforests, including bamboo forests and plantations This rich biodiversity highlights the ecological significance of Ba Vi National Park.
STUDY OBJECTIVES
Objectives of this study are:
(1) To identify and compare gap regeneration patterns among different forest categories
(2) To assess the relationship between gap-size classes and regeneration patterns
(3) To identify factors that may influence the abundances of dominant seedlings and saplings
(4) To recommend some silvicultural solutions to promote restoration process of forest gaps at the study area
STUDY METHODS
Data collection methods
4.1.1 Selection of the study areas
Based on forest classification maps available at Ba Vi National Park, the tropical evergreen moist forests are categorized into rich, medium, and poor forest types According to Circular No.34/2009/TT-BNNPTNT issued by the Ministry of Agriculture and Rural Development, the standing timber volume for these categories is defined as follows: rich forests contain 201 to 300 m³/hectare, medium forests have 101 to 200 m³/hectare, and poor forests range from 10 to 100 m³/hectare.
4.1.2 Gap sampling a Layout transect lines on maps
Before conducting the field survey, identify the survey lines of the research area on maps During the survey, a 25-meter-wide corridor centered on the designated line was established Within each study stand, transect belts with a width of 40 meters were systematically laid out, starting and ending 20 meters away from forest edges to avoid edge effects The forest edge was defined as the vertical projection of the surrounding edge onto the ground Additionally, selecting research gaps involved identifying specific areas within the study site that exhibited notable ecological or structural differences for targeted investigation.
Selected gaps must meet specific criteria: over 50% of each gap area should be located along the survey line, ensuring accurate data collection Each identified gap should have an estimated area of at least 25 square meters to ensure significance for analysis Additionally, a consistent number of gaps—15 per category—are selected to maintain representativeness across different areas These criteria help optimize survey efficiency and ensure reliable, meaningful results.
Based on field survey observations, the formation of each survey gap can be classified into three main categories: (i) gaps caused by dead trees, (ii) gaps resulting from broken branches, and (iii) gaps with unidentified causes This classification helps to understand the underlying processes contributing to gap formation in the forest.
The gap areas were identified using the triangle method, chosen for its reduced subjectivity and lower standard error compared to other techniques (Lima, 2005) This method involved marking all gap corners with wooden posts, connecting them with a plastic rope, and outlining the polygon border The border was then subdivided into triangles, with each triangle's area calculated using de Lima’s formula (2005) to ensure accurate measurement.
A 1 = [p (p-a) (p-b) (p-c)] 0.5 Where, A1 is area of the 1 st triangle; a, b, c are the triangle’s sides and p = (a+b+c)/2
The total area of a gap (A) was when obtained by summing up the area of all triangles which form the polygon (A = A 1 + A 2 +…+A n )
Figure 4.1: Gap area measurement and sample plot design Regeneration survey
During field study, each selected gap was divided into two concentric belts: the belt center and belt edge, to facilitate detailed surveys Each belt contained five 4 m² squares (2 m × 2 m), known as nested quadrats, used to assess regeneration For small gaps where the area was insufficient for a single main quadrat, three to four contiguous transect belts, each 2 m wide, were established across the gap center, extending to a total length of 12.5 m, ensuring comprehensive coverage of regeneration areas.
According to Al (2006), the maximum light intensity occurs at the center of forest gaps, influencing seedling establishment, growth, and species composition Consequently, seedlings and samples collected at the gap center may differ significantly from those at the edge, as highlighted by studies such as Phillip and Shure (1990), Mihók et al (2005b), and Holladay et al (2006) These variations underscore the importance of spatial position within gaps in understanding forest regeneration dynamics.
All tree saplings within the main quadrate, measuring at least 1.3 meters in height and with a diameter at breast height (DBH) less than 10 cm, along with seedlings within nested quadrates reaching heights between 0.3 meters and less than 1.3 meters, were identified Their heights were precisely measured to the nearest centimeter, and their root collar diameters were recorded to the nearest millimeter.
+ Name of regenerated trees was identified by expert experiences
+ Total height of regenerated trees was measured using Blumeleiss equipment
+ Quality of regenerated trees were identified and classified into 3 classes (A, B, C)
Where: A = good trees, no diseases, trunk is not twisted
B = less disease, deviation scattered, slightly twisted trunk
C = disease tree, a twisted tree, deviation scattered
The study identified and classified the gap-makers, or trees responsible for creating gaps, based on their modes of death or injury These included categories such as standing dead trees, trunks broken due to damage, and uprooted trees This classification helps understand the process of gap formation and the ecological roles of different tree types in shaping forest structure.
Shrubs and vegetation survey: In each square, survey conduct of shrub canopy The results were recorded in the following table:
ID Square-ID Major tree Height (m) Average cover (%) Note
Survey of under the forest canopy in around gap:
High trees located in edge gaps were identified as those with a DBH (Diameter at Breast Height) of 6 cm or more, based on expert assessment The DBH was precisely measured using a caliper, ensuring accurate data collection Crown height was recorded with a Blumeleiss tool, providing reliable height measurements, while canopy diameter was measured using a 30-meter tape to capture extensive spatial coverage These measurements support a comprehensive analysis of edge gap tree characteristics.
Data analysis methods
- Using mathematical statistics method in forestry and collected data were encoded to Microsoft Excel 2007 worksheets before exporting them to the SPSS 16.0 (SPSS_Inc.,
- In this study the percentage of gap area was calculated using the following equation:
PGA, representing the percentage of the gap area, is calculated using the areas of individual gaps (Ai) and the total gap area The formula considers the sum of all gap areas (sum of Ai for i = 1 to n), divided by the total length (L) and the width (W) of transect belts Specifically, PGA provides an essential metric for assessing gap distribution relative to the overall transect dimensions, where n denotes the total number of gaps, Ai is the area of each individual gap, L is the combined length of the transect, and W is the width of the belts, ensuring accurate ecological gap analysis and monitoring.
- Identify ratio of species composition:
K = (ni/ N)*10 Where: K: ratio of species composition ni: number of species
+ Evaluation the quality of regeneration trees Ratio of regeneration tree with each level was calculated using the following equation:
N% = (N i /N) × 100 Where: N%: number of tree percentage ratio of one quality level
Ni: number of regeneration tree of one quality level
- Identify regeneration origin is spring or seeding
- Effect of ecological factors to gap regeneration: using the following equation
BC = 2w/(A+B) Where: BC: coefficient of homologous
A: number of tree in high tree canopy
W: number of high tree is inherited by regeneration canopy
If index BC ≥ 0.75 is refer to regeneration tree close correlation with high tree canopy
If index BC ≤ 0.75 is refer to regeneration tree in research area locations, no inherit of high tree canopy
- Effect of shrubs and vegetation to gap regeneration were analyzed using Excel software
RESULTS AND DISCUSSIONS
Gap characteristics and size class distributions
Gaps in natural forests are typically created by either human activity or natural events At Ba Vi National Park, a protected area, the regeneration of woody tree species within these gaps occurs naturally without human intervention The study area’s characteristics and the formation history of these gaps are detailed in Table 5.1, providing insights into the natural processes shaping forest dynamics.
Table 5.1: Gap characteristics of the three forest categories Feature
Analysis of gap formation across different forest categories reveals that dead trees and broken branches are the two predominant indicators of tree death observed throughout the study area In the poor forest category, 46.67% of gaps resulted from dead trees, 33.33% from broken branches, and 20% remain unidentified regarding their formation history Medium forests show that 53.33% of gaps are caused by dead trees, 40% by broken branches, and 6.67% are unknown In the rich forest category, dead trees and broken branches continue to be the main factors contributing to gap formation, highlighting the key role of tree mortality in shaping forest structure.
13 formed by dead trees (40 %), seven gaps formed by branches broken (46.67 %) and two gaps were unidentified (13.33 %)
The average gap area is smallest in poor forests, measuring approximately 92 m², while rich forests have the largest average gap area at 173.17 m² In poor forest stands, gap sizes range from a minimum of 32 m² to a maximum of 162 m² Medium forests exhibit gap areas varying from 48 m² to 170 m², whereas rich forests show a broader range from 96 m² to 225 m² These variations indicate that gap sizes tend to increase with forest richness, highlighting differences in forest structure across the three categories.
Regarding the size class distributions of the canopy gaps, the results of this study showed in Figure 5.1:
Figure 5.1: The size class distributions of canopy gap
In the poor forest categories, the majority of identified gaps (40% or 6 out of 15) fall within the second gap size class, measuring between 50 and 100 m² The distribution of these gaps exhibits a sharp positive skewness, indicating that smaller gaps are more frequent while larger gaps are less common In medium forest conditions, 33.33% (5 gaps) and 46.67% of the gaps are observed, highlighting variations in gap size distribution across different forest categories.
(07 gaps) belong to the second and third size class In the rich forest, 46.67% (07 gaps) in
Poor forest Medium forest Rich forest Relative frequency (%)
Most canopy gaps observed in the study fall within the 50-200 m² size class, indicating that this is the predominant gap size in the area Larger gaps, measuring 200 m² or more, are relatively rare, with only four such gaps identified, all located within rich forest stands These larger gaps constitute approximately 26.66% of the total 15 gaps studied, highlighting their infrequency in the overall forest landscape.
Characteristics of regeneration in the gaps
5.2.1 Growth characteristics of canopy tree surrounding studied gaps
Discarded tree gaps are limited by surrounding canopy trees, which play a crucial role in maintaining forest structure From a silvicultural perspective, these mature trees are vital for seed dispersal and future forest regeneration Additionally, they serve as primary factors that influence the size of canopy gaps, indirectly affecting species composition and the density of regenerated trees within these gaps.
Table 5.2: Characteristics of surrounding canopy trees in the gaps
Categories Poor forest Medium forest Rich forest
According to Table 5.2, there are no significant differences in the number of canopy trees surrounding the studied gap across the three research categories In poor forest conditions, canopy gaps are limited by an average of 2.5 trees, whereas in medium and rich forests, the gaps are associated with approximately 4 trees.
In rich forests, surrounding trees exhibit greater DBH, total height, and crown diameter compared to those in the other categories Specifically, the highest values are observed in the rich forest, with an average DBH of 13.06 cm, an average height of 16.53 meters, and a crown diameter of 9.52 meters Conversely, the poorest forests show significantly lower measurements, with an average DBH of 11.65 cm, height of 9.6 meters, and crown diameter of 5.18 meters This indicates that forest quality directly influences tree size and structural characteristics.
Larger gap sizes in the landscape allow surrounding trees more space to grow and develop, resulting in their increased size compared to trees in smaller gaps This promotes healthier growth and development of trees in areas with wider openings, leading to a more diverse and robust forest structure.
5.2.2 Density and tree species composition in the gaps
Regeneration density, indicating the initial density of future forests, is a key metric reflecting forest health and vigor Species composition, representing the variety and proportion of different species, is vital for assessing biodiversity, ecosystem stability, and sustainability If regenerated trees encounter suitable ecological conditions, their current composition will shape the canopy layer of the future stand, ensuring a resilient and diverse forest ecosystem.
Table 5.3: Species compositions of regeneration tree in the gaps
2.94 Am + 1.17 Md + 0.88 Mb + 0.88 So + 0.88 Cp + 0.58 Mdm + 0.58 Lb + 0.58 Cp + 1.45 Others
1.53 Am + 0.96 Md + 0.77 Lb + 0.77 Ff + 0.77 Cp + 0.58 Mf + 0.58 Cp + 0.58 Mdm + 0.58 Gp + 0.58 Mb + 2.28 Others
Ej + 0.68 Ap + 0.68 Cb + 0.68 Ft + 3.16 Others
Edge gap 28 0.70 Ci + 0.53 C + 0.53 Cc + 0.53 Cc + 0.53
Center gap 31 0.86 Ab + 0.52 Wa + 0.52 Cc + 0.52 Ai +
0.68 Cc + 0.51 Ab + 0.51 Ci + 0.51 Wa + 0.51 Ag +0.51 Go + 0.51 A + 0.51 Cb + 0.51
Table 5.3 highlights the diversity of regeneration species across different study categories, with the highest number of tree species observed in poor forests Species composition at both the center and edge gaps is highly complex across all categories, with 5 to 10 species contributing to the composition formula and a relatively balanced regeneration ratio among species Notably, species composition varies between locations, particularly in medium and rich categories, indicating spatial differences in regeneration patterns.
The species composition of regenerated trees in the poorly managed forest includes Adinadra millettii, Macaranga denticulate, Magnolia baviensis, Schefflera octophylla, Cinnadenia paniculata, and Litsea baviensis Species distribution varies across different locations, with the central gap primarily dominated by light-demanding, fast-growing species like Adinadra millettii and Macaranga denticulate In contrast, the edge gaps feature a mix of light-demanding and shade-tolerant species such as Litsea baviensis and Ficus fulva, reflecting variations in ecological conditions This diversity highlights the influence of microhabitats on regeneration patterns in degraded forest areas.
In the medium forest, the regeneration of tree species primarily consists of Ichnocarpus polyanthus, Claoxylon indicum, Michelia balansae, and Cinnamomum camphora, with these species being light-demanding In the central gaps, dominant species include Ichnocarpus polyanthus and Claoxylon indicum, highlighting their preference for open, illuminated conditions Conversely, at the forest edges, the dominant species comprise both light-demanding and shade-tolerant species such as Claoxylon indicum, Cinnamomum camphora, and Camellia, reflecting greater biodiversity and adaptability to varying light levels.
The rich forest is dominated by key species such as Archidendropsis basaltica, Wightia annamensis, and Cinnamomum camphora, which play a vital role in its overall composition In the central gaps of this forest, dominant species include Archidendropsis basaltica, Wightia annamensis, and Adinandra, indicating their adaptability to open spaces Similar to poor and medium forest categories, these species are primarily light-demanding, thriving in areas with ample sunlight and minimal canopy cover.
Species composition varies significantly across different gap locations, with the center gap supporting many light-demanding species like Adinadra millettii, Macaranga denticulate, Archidendropsis basaltica, and Wightia annamensis due to high light intensity Conversely, shade-tolerant species such as Litsea baviensis, Ficus fulva, Cinnamomum camphora, and Camellia thrive in areas with lower light availability, highlighting the influence of light conditions on plant distribution Understanding these differences is essential for effective forest management and conservation strategies.
Archidendropsis basaltica, Cinnamomum camphora can be found in edge gap where light intensity is lower than in center gaps
5.2.3 Height distribution of regenerated trees
In canopy gaps, distribution in number of tree communities according to their height and location in gaps at the study area showed in Table 5.4:
Table 5.4: Distribution of regenerated trees according their height
Poor forest Medium forest Rich forest
Center gap Edge gap Center gap Edge gap Center gap Edge gap
Figure 5.2: Distribution of regenerated trees in poor forest
Figure 5.3: Distribution of regenerated trees in medium forest
Center gap Edge gap Number of tree
Figure 5.4: Distribution of regenerated trees in rich forest
The height distribution of regeneration trees in forest gaps, as shown in Table 5.4 and Figures 5.2 to 5.4, exhibits a sharply positive skewness, with most trees falling within the 0.5 to 1.5-meter height range, indicating favorable environmental conditions for seed dispersal and germination Observations across all three gap categories reveal a decline in the number of regenerated trees as height increases, with a significant decrease in trees taller than 1.5 meters Ecologically, this trend is attributed to increased competition for nutrients as trees grow taller and older Understanding these height distribution patterns is crucial for developing effective silvicultural strategies in natural forest gaps, balancing conservation goals and sustainable forest management.
Center gap Edge gap Number of tree
5.2.4 Density and quality of regenerated trees a Density of regenerated trees
As mentioned in study methods, regenerated trees can be classified into seedling or sapling based on their size and their densities were aggregated and mentioned in Table 5.5:
Table 5.5: Density of seedlings and saplings in studied areas
Table 5.5 reveals significant variations in regenerated tree densities across different forest categories In poor forests, saplings dominate the regeneration, comprising 82.36% at center gaps and 63.46% at edge gaps, indicating a reliance on younger stages for forest recovery Conversely, in medium and rich forests, seedlings are the primary regenerated form, accounting for 63.16% to 70.04% in medium forests and 51.72% to 55.93% in rich forests, demonstrating more advanced regeneration stages Notably, sapling densities in rich forests differ markedly, representing only 44.07% to 48.28% of total regenerated trees, which suggests a more mature regeneration process in these categories.
The quality of forest regeneration is determined by a combination of ecosystem factors that interact reciprocally Key parameters such as regeneration density, seedling quality, origin, regeneration ratio prospects, and seed vitality are essential indicators used to assess regeneration success These factors collectively influence the overall health and sustainability of forest recovery, making them critical for evaluating regeneration quality.
Forest regeneration ability indicates the level of environmental conditions favorable for seed dispersal and germination Overall forest quality and regeneration status serve as key indicators of the site's suitability for supporting healthy forest growth Based on collection and treatment data, the regeneration quality was assessed and summarized in Table 5.6, highlighting the relationship between site conditions and forest recovery potential.
Table 5.6: Distribution of regenerated tree according the quality
Figure 5.5: Quality of regeneration tree in poor forest
Good Medium Bad Regeneration ratio (%)
Figure 5.6: Quality of regeneration tree in medium forest
Figure 5.7: Quality of regeneration tree in rich forest
In both research categories—center and edge of gaps—higher proportions of good and medium quality are observed compared to poor quality Specifically, the regeneration ratio of good quality ranges from 61.4% to 78%, while medium quality constitutes between 17% and 29.4% Conversely, the proportion of bad quality is relatively low, occupying only 3.4% to 10.5%, indicating overall favorable regeneration outcomes in these areas.
Good Medium Bad Regeneration ratio (%)
Good Medium Bad Regeneration ratio (%)
Effect of factors to gap regeneration
5.3.1 Effect of under the forest canopy in around gap to gap regeneration
The relationship between the mother plant composition and regeneration composition serves as an important indicator of the inheritance of storey regeneration and the characteristics of the mother plant This relationship reflects the degree of mother plant sowing and its influence on forest development The extent of species composition inheritance in regeneration trees largely depends on factors such as the seed production capacity of the mother plant, germination conditions, ecological traits, and competitive abilities of each species Dominant species levels across the three research categories are summarized in Table 5.7, highlighting the significance of parent plant influence on forest regeneration dynamics.
Table 5.7: Relations between the high tree composition and regeneration tree
Number of species Number of regeneration tree inherited from the high tree
The analysis of Table 5.7 indicates that the ratio of high trees with regeneration trees inherited is relatively high, ranging from 50% to 100%, with the highest inheritance ratio observed in rich forests However, the Sorensen index results reveal that the BC index fluctuates between 0.88 and 1.02 in poor and rich forests, both exceeding 0.75, which suggests random regeneration with little inheritance from high trees across these areas Notably, only in medium forests within the central gap does the BC index fall below 0.75, indicating a closer relationship between regeneration tree composition and high tree presence, highlighting the influence of forest category on inheritance patterns.
5.3.2 Effect of shrubs and vegetation to gap regeneration
Shrubs and vegetation significantly influence the growth and development of regenerating trees, primarily through nutrient competition and light availability beneath the forest canopy Research indicates that a decrease in canopy cover leads to an increase in shrubs and understory vegetation, which benefits shade-tolerant, younger regeneration trees but may interfere with seedling growth as they mature Overall, shrubs and understory vegetation are key factors affecting the number of regeneration prospects in forests, playing a crucial role in forest regeneration dynamics.
The density of regenerated trees beneath the shrubs and vegetation canopy is very high; however, their overall ratio remains low due to the rapid growth and development of the surrounding shrubs, which increasingly compete with young trees The presence of dense shrubs and vegetation also influences seed germination rates, as seeds that fall directly onto the forest floor and encounter favorable soil conditions are more likely to germinate and establish Conversely, when seeds fall onto thick shrub or vegetation canopies, they do not contact the soil and thus have reduced chances of germination and successful growth.
Table 5.8: Effect of shrubs and vegetation to regeneration
In the three research categories, shrubs and vegetation cover—including species such as Microsorum pteropus, Callisia fragrans, and Gnetum montanum—show an average height of 0.8 to 1.12 meters and cover between 20% to 50% Regeneration density varies from 3,507 to 7,207 trees per hectare, with an observed trend: as average cover increases from 20% to 50%, regeneration density decreases from approximately 3,507 to 4,826 trees per hectare This indicates that dense shrub and vegetation growth significantly impact regeneration density by competing for nutrients and light, thus reducing regeneration success and quality Overall, soil regeneration is more consistent and favorable when the vegetation canopy cover is low across the three research categories.
Regeneration prospects was regeneration height higher than or equal to the average height of the shrubs, vegetation and above quality medium
The average cover of shrubs and vegetation directly influences regeneration density and its prospects When shrub and vegetation cover is low, regeneration density and future growth prospects are high, as there is less competition for nutrients Conversely, high shrub and vegetation cover reduces regeneration density due to increased competition for resources with regeneration trees To enhance regeneration success, it is necessary to manage shrub and vegetation cover by regulating their canopy, such as by removing excess shrubs, which decreases cover, reduces competition, and promotes better growth and development of regeneration trees, thereby increasing regeneration density and future potential.
Recommend some silvicultural solutions to promote restoration process of forest
Based on the study results, silvicultural strategies should be tailored to three forest categories—poor, medium, and rich forests—in Ba Vi National Park These strategies include delineating protected areas, implementing forest maintenance practices, promoting natural regeneration, and combining plantation efforts to enhance ecological protection Such approaches aim to preserve rare genetic resources, maintain biodiversity, and ensure the long-term sustainability and resilience of the natural forest ecosystem.
Based on recent research, it is recommended to employ technical solutions such as selecting high-quality seeds with a strong ability to adapt to the environmental conditions of Ba Vi National Park Prioritizing the planting of species with high economic and landscape value, such as Calocedrus macrolepis and Cinnamomum, will help create a sustainable and environmentally friendly forest ecosystem Incorporating dominant tree species native to Ba Vi ensures ecological compatibility, promotes biodiversity, and enhances the park’s overall biodiversity and aesthetic appeal.
27 parthenosylon, Madhuca pasquieri, Magnolia baviensis… to restoration vacant land and bring a high economic value
The average cover and height of shrubs and mid-level vegetation significantly impact the regeneration of the tree layer To promote successful seed sowing, scattering, germination, and growth of young trees, it is essential to reduce competition between shrubs, vegetation, and regenerating trees This can be achieved by cutting lianas and decreasing the overall cover of shrubs and undergrowth, especially in densely vegetated areas Proper cleaning, management, and density regulation are crucial for creating a favorable environment with sufficient space and nutrients for young tree development, both under the forest canopy and in gaps.
Large forest gaps exhibit high regeneration density but require regulation to reduce density and create optimal conditions for healthy tree growth As gap size increases, regeneration count also rises; however, excessively large gaps may lead to insufficient regeneration density In such cases, supplementary planting is necessary to maintain balanced forest regeneration and ensure proper forest development.
Effective forest regeneration depends on necessary conditions and appropriate application of silvicultural solutions, which must consider local economic and social factors Successful implementation requires assessing local capacity for capital investment, available manpower, and the community’s knowledge of silvicultural practices and traditional farming techniques Additionally, incorporating local knowledge and access to advanced technologies are crucial for ensuring that farming techniques positively impact forest development.
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
Dead trees and broken branches are the primary causes of gap formation across all forest categories In rich forests, the average gap area is the largest at 173.17 m², followed by medium forests with an average of 108 m², while poor forests have the smallest average gap area of 92 m² The variation in gap sizes among the three forest categories is relatively limited, indicating similar fluctuation ranges in gap areas.
The species composition of regeneration trees across research categories demonstrated moderate diversity and abundance, with the number of species ranging from 5 to 10, reflecting a dynamic species composition The ratio of regeneration among different species was generally equitable, indicating balanced regeneration processes Additionally, species composition varied across different locations, highlighting the influence of site-specific environmental factors on regeneration patterns.
Light source and space conditions significantly influence regeneration species composition in gaps The central area of gaps, which receives abundant light and has ample space, favors light-demanding, fast-growing regeneration species such as Adinandra millettii, Macaranga denticulate, Archidendropsis basaltica, Wightia annamensis, Ichnocarpus polyanthus, and Claoxylon indicum Conversely, shade-tolerant species like Litsea baviensis, Ficus fulva, Cinnamomum camphora, and Camellia are more common in areas with limited light Understanding these dynamics is crucial for forest regeneration and management strategies.
Regenerated composition across two locations in all three research categories demonstrates significant diversity and abundance, with regeneration tree counts fluctuating between 34 and 59 Overall regeneration density in these categories remains at a medium level, varying from 3,507 to [value missing], indicating a consistent recovery rate These findings highlight the importance of understanding spatial variations in regeneration patterns to support effective forest management and conservation strategies.
7207 tree/ha Regeneration density prospects from 2165 to 3479 tree/ha
Regeneration distribution varies according to height across the two locations and three research categories, with a general decreasing trend observed However, the extent of decrease differs between locations and among different height levels, indicating that both geographical and vertical factors influence regeneration patterns.
The regeneration quality across the three research categories shows that the highest regeneration ratio pertains to good-quality outcomes, while the lowest is observed in bad-quality results Specifically, the center gap exhibits superior regeneration quality compared to the edge gap, highlighting the importance of location in regeneration effectiveness These findings emphasize the significance of focusing on high-quality regeneration processes and optimizing conditions in the center gap for optimal results.
The regeneration of trees is significantly influenced by area gap and the number of regeneration trees, with a close relationship between these factors Larger area gaps tend to correspond with an increased number of regeneration trees, promoting effective forest recovery Additionally, shrubs and surrounding vegetation have a moderate impact on tree regeneration, contributing to the overall regeneration process.
Recommendations
Ongoing monitoring of regeneration characteristics in the study area is essential for assessing the dynamics of forest plant community regeneration over time This information provides a vital basis for developing sustainable forest management models in nearby production forest areas Continuous evaluation ensures that forest regeneration trends are accurately understood, supporting long-term conservation and sustainable utilization efforts.
This study investigates the relationship between primary factors such as light, temperature, humidity, and soil characteristics in forest understories and gaps It examines how these environmental conditions influence the composition and diversity of forest plant communities within the research area Understanding these interactions is essential for assessing forest ecosystem dynamics and informing conservation efforts The findings highlight the critical role of microclimatic variables and soil properties in shaping understory vegetation and overall forest health.
- The research the effect of fruitful cycle, source of seed to regeneration characteristics
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Brokaw, N.V.L., (1987) “Gap-Phase Regeneration of Three Pioneer Tree Species in a Tropical Forest”, Journal of Ecology 75, 9-19
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The study by Clebsch and Busing (1989) explores secondary succession, gap dynamics, and community structure in Southern Appalachian cove forests, highlighting how disturbances create opportunities for forest regeneration and influence species composition Clinton (2003) examines how factors such as light, temperature, and soil moisture vary with elevation, evergreen understory presence, and small canopy gaps in the southern Appalachians, revealing their significant impact on forest microclimates and plant growth Together, these studies provide valuable insights into the ecological processes shaping forest dynamics and the importance of gap and microclimate variability in forest management and conservation efforts.
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This study by Mihók, B., Gálhidy, L., Kelemen, K., and Standovár, T (2005b) investigates gap-phase regeneration in a managed beech forest, highlighting the crucial role of light availability, substrate characteristics, and ground vegetation cover in promoting tree regeneration The research emphasizes how forest management practices influence the regeneration processes and underscores the importance of habitat conditions such as soil features and ground vegetation for successful forest renewal These findings provide valuable insights for sustainable forest management and conservation strategies aimed at enhancing regeneration in beech forests.
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Research by Sapkota and Odén (2009) highlights that gap characteristics significantly influence the regeneration, dominance, and early growth of woody species, emphasizing the importance of understanding gap dynamics for forest management Similarly, Schupp et al (1989) demonstrate that the arrival and survival of tropical tree seedlings in treefall gaps are affected by gap size and environmental conditions, which are crucial factors for successful forest regeneration and biodiversity conservation These studies collectively underscore the vital role of gap ecology in maintaining healthy forest ecosystems and promoting species diversity.
Taylor, A.H., Shi Wei, J., Lian Jun, Z., Chun Ping, L., Chang Jin, M., Jinyan, H., (2006) Regeneration patterns and tree species coexistence in old-growth Abies-Picea forests in southwestern China Forest Ecology and Management 223, 303-317
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Inventory and Planning Institute Hanoi In Vietnamese
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Nguyen Thi Kha (2009), research gap regeneration characteristics and under canopy forest situation IIIA1 in Mai Son Forestry Company, Luc Nam district, Bac Giang province, master thesis forest Science
Nguyen Thi Thiet (2012), research gap regeneration characteristics at forest situation IIIA2 in Thuong Tien Nature Reserve, Kim Boi district, Hoa Binh province, master thesis forest Science
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Tran Ngu Phuong (1970), Initial research in northern Vietnam forest, publisher of scientific and technical, Hanoi
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Appendix 01: Symbol name some plants used in the research
ID Vietnamese name Latin name Abbreviation
1 Chè sim Adinadra millettii Am
2 Lá nến Macaranga denticulate Md
3 Mỡ Ba vì Maglolia baviensis Mb
6 Bời lời Ba vì Litsea baviensis Lb
7 Re hương Cinnamomum parthenoxylon Cp
8 Ngõa lông Ficus fulva Ff
9 Ba soi Macaranga denticulata Muell Mdm
10 Mần tray Ba vì Ichnocarpus polyanthus Ip
11 Lộc mại Claoxylon indicum Ci
14 Súm mật Eurya japonica Ej
15 Gội xanh Aglaia perviridis Ap
16 Mỏ chim Cleidio brevipetiolatum Cb
17 Dâu tằm Ficus tristylis Ft
19 Long não Cinnamomum camphora Cc
20 Giẻ gai Bắc bộ Castanopsis chinensis Cc
22 Phân mã Archidendropsis basaltica Ab
ID Vietnamese name Latin name Abbreviation
23 Long mức Trung bộ Wightia annamensis Wa
24 Chè đuôi lươn Adinandra integerrima Ai
25 Vỏ sạn Osmanthus pedulculatus gagnep
26 Bứa lá dài Garcinia oblongitolia Go
27 Re bầu Cinnamomum bejolghota Cb
28 Gội trắng Aphanaminix grandiflora Bl Ag
30 Thôi ba Alangium sinesis As
31 Bồ đề Styrax tonkinensis St
32 Mé cò ke Grewia paniculata Gp
33 Ba bét Mallotus floribundus Mf
34 Hu đay Trema angustifolia Ta
35 Màng tang Litsea cubeba Lc
37 Mỡ ba vì Maglolia baviensis Mb
38 Chẹo thui lá to Helicia grandifolia Hg
39 Cây óc chó Ficus hirta Fh
40 Côm phờ lơ ri Elaeocarpus griffithii Eg
43 Máu chó bắc bộ Knema tonkinensis Kt
44 Su bắc bắc bộ Alseodaphne tonkinensis At
45 Dâu gia xoan Allospondias lakheonsis Al