INTRODUCTION
Canopy openings created by tree mortality, windfall, and the removal of mature trees are crucial for fostering spatial heterogeneity essential for the establishment, growth, and survival of tree species in tropical rainforests These openings are significant phases in the forest restoration cycle and play a vital role in forest structural dynamics, influencing species richness and composition Research indicates that the germination, growth, survival, and mortality rates of seedlings and saplings in these gaps differ among species, influenced by both biotic and abiotic factors as well as specific characteristics of the canopy gaps.
Canopy gaps in forests play a crucial role in initiating new regeneration cycles for tree species, as they influence competition for light, water, and nutrients Small gaps favor the germination and establishment of shade-tolerant species, while larger gaps support the growth of pioneer or light-demanding species These larger openings also allow suppressed saplings to thrive by accessing increased light, enabling them to mature effectively.
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,
Gaps in forests are created by various tree species that differ in number, size, and foliage structure, leading to a range of gap sizes This variation affects light intensity, temperature, and soil moisture levels within the gaps Consequently, the richness, composition, and diversity of tree species that colonize these gaps can vary significantly, influencing the mortality and recruitment rates of seedlings and saplings across different forest types.
Regeneration patterns in tropical evergreen forests are unpredictable due to heterogeneous changes in microclimatic conditions following gap formation These changes are crucial for promoting pioneer seedlings while suppressing established saplings Variations in gap sizes significantly influence forest succession and play a vital role in species coexistence, contributing to the high diversity of tree species in tropical rainforest communities.
In tropical regions, the loss, fragmentation, and degradation of rainforests significantly affect the regeneration patterns of woody tree species in canopy gaps Understanding these complex patterns enhances our limited knowledge of species richness, growth, composition, and diversity within different forest stands This insight allows researchers to predict the dynamics of tree species composition in canopy gaps compared to regeneration beneath the forest canopy While the importance of canopy gaps in regeneration processes and community dynamics has been emphasized, most studies on forest regeneration in Vietnam have primarily concentrated on other aspects.
Limited studies on gap regeneration in natural forests and artificial plantations have been conducted by researchers such as Phuong (1970), Hue (1975), Tam (1987), Kha (2009), Hoang Thi Tuyet (2010), and Nguyen Thi Thiet (2012), but these findings are scattered A clearer understanding of this regeneration pattern is essential for effective forest management This study in Ba Vi National Park aims to enhance knowledge of gap regeneration characteristics and to recommend silvicultural solutions that promote the restoration of forest gaps in the area.
OVERVIEW OF THE RESEARCH AREA
A study was conducted at Ba Vi National Park, situated in Ba Vi District, Ha Noi City, Vietnam The park is located at coordinates 21°01' to 21°07' N latitude and 105°18' to 105°25' E longitude, nestled within the Ba Vi mountain range and approximately 48 km northwest of Ha Noi.
The park was established in 1991 with total area of 7,377 ha The total natural area of Ba
Vi National Park spans an area of 10,782.7 hectares, with 8,192.5 hectares designated as forest land, making up 75.98% of the park's total area This includes 4,200.5 hectares of natural forests (51.27% of the forest land) and 3,992 hectares of planted forests (48.73%) The park's high mountain terrain and extensive forest cover contribute to its cool climate, particularly during the summer months from April to October, while winter brings a captivating landscape shrouded in clouds The park is located along a mountain range that runs northeast to southwest, featuring notable peaks such as 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 unique ecosystem, characterized by its stunning natural beauty and distinct geographic and climatic features, positions it as one of the four premier mountainous ecological tourism centers in Vietnam, alongside Da Lat, Sapa, and Tam Dao.
Ba Vi National Park boasts a rich biodiversity, featuring over 1,200 plant species, with 21 listed in Vietnam's Red Book 2007 Recent studies indicate the presence of 812 vascular plant species, including eight unique tree species such as Allomorphia baviensis and Begonia baviensis The park also shelters 15 rare and valuable plants, including blue cypress and silver leaf bassia In terms of wildlife, Ba Vi is home to 45 mammal species, 115 bird species, 27 amphibian species, and 61 reptile species, making it a vital ecological haven.
Ba Vi National Park is home to 86 insect species, including 23 precious and rare species listed in Vietnam's Red Book (2007), such as coolies, horse bears, yellow pangolins, white pheasants, monkeys, leopards, bears, and flying squirrels The park's vegetation comprises three main types: low montane subtropical broadleaved evergreen moist lower montane forests, mixed forests of broadleaved evergreen and coniferous subtropical trees, and low montane tropical broadleaved evergreen rainforests, including tropical woodlands, bamboo forests, and plantations.
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
Ba Vi National Park features three classifications of tropical evergreen moist forests: rich, medium, and poor According to Circular No 34/2009/TT-BNNPTNT from the Ministry of Agriculture and Rural Development, the timber volume of standing trees in these categories varies significantly The rich forest category boasts a timber volume of 201 to 300 m³ per hectare, the medium forest category ranges from 101 to 200 m³ per hectare, and the poor forest category has a timber volume of 10 to 100 m³ per hectare.
4.1.2 Gap sampling a Layout transect lines on maps
Before conducting a field survey, it is essential to identify survey lines of the research area on maps The survey width is centered at 25 meters, and within each study stand, arbitrary transect belts of 40 meters are established, starting and ending 20 meters away from any forest edges The gap edge is defined as the vertical projection of the surrounding edge onto the ground Additionally, the selection of research gaps is a crucial step in this process.
To ensure effective selection, gaps must meet specific criteria: (i) over 50% of the gap area should fall within the survey line, (ii) each gap must have a minimum estimated area of 25 m², and (iii) a total of 15 gaps should be selected per category.
The history of gap formation in surveyed areas can be categorized into three distinct groups: (i) gaps created by dead trees, (ii) those resulting from broken branches, and (iii) gaps with unidentified causes.
The area of each gap was determined using the triangle method, which is favored for its objectivity and low standard error compared to other techniques (Lima, 2005) To implement this method, wooden posts were used to mark all corners of the gaps, and consecutive corners were connected with plastic rope The polygon's border was outlined with plastic rope and subsequently divided into triangles The area of each triangle was calculated using de Lima’s formula (2005).
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
In the field study, each identified gap was categorized into two concentric belts: the belt center gap and the belt edge gap Within each belt, five squares, each measuring 4 m² (2m × 2m), were established to assess regeneration, known as nested quadrates For smaller gaps where a single main quadrate could not be accommodated, three to four contiguous transect belts, each 2 m wide, were placed across the center of the gap, extending to a total length of 12.5 m.
Research indicates that light intensity peaks at the center of gaps, leading to variations in seedling establishment, growth, and species composition between the gap center and edge (Phillip and Shure, 1990; Mihók et al., 2005b; Holladay et al., 2006).
All saplings of tree species within the main quadrate, measuring at least 1.3 meters in height and with a diameter at breast height (DBH) of less than 10 cm, were identified Additionally, seedlings within nested quadrates that reached a height between 0.3 meters and less than 1.3 meters were also recorded Heights were measured to the nearest centimeter, while root collar diameters were measured 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 identified gap-makers, which are the trees responsible for creating gaps, were classified based on their types of death or injury, such as standing dead, trunk broken, or uprooted.
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:
All high trees in edge gaps with a diameter at breast height (DBH) of 6 cm or more were marked, and their species were identified by experts The DBH was measured using a caliper, crown height was determined with a Blume-Leiss instrument, and canopy diameter was assessed using a 30-meter tape.
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:
The PGA, or percentage of the gap area, is calculated using the formula where Ai represents the area of the i-th gap, n denotes the total number of gaps, L signifies the total length of the transect belts, and W indicates their width.
- 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 human activities or natural events At Ba Vi National Park, a protected area, the regeneration of woody tree species in these gaps occurs naturally, without human intervention The characteristics and formation history of these gaps in the study area are detailed in Table 5.1.
Table 5.1: Gap characteristics of the three forest categories Feature
The study revealed that dead trees and broken branches are the predominant causes of gap formation in the observed area In the poor forest category, 46.67% of the gaps were created by dead trees, while 33.33% were due to broken branches, with 20% remaining unidentified In the medium forest category, dead trees accounted for 53.33% of the gaps, broken branches for 40%, and 6.67% were unidentified The rich forest category also exhibited a notable presence of gaps, though specific details were not provided.
13 formed by dead trees (40 %), seven gaps formed by branches broken (46.67 %) and two gaps were unidentified (13.33 %)
In terms of gap areas across three forest categories, poor forests exhibit the smallest average area of 92 m², while rich forests have the largest average area at 173.17 m² The gap sizes in poor forests range from a minimum of 32 m² to a maximum of 162 m² In contrast, medium forests show gap areas varying from 48 m² to 170 m², and rich forests have gaps ranging from 96 m² to 225 m².
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, 40% of the studied gaps, totaling six gaps, fall within the second size class of 50 to 100 m², indicating a sharply positive skew in the distribution In the medium forest, 33.33% of the gaps, equivalent to five gaps, and 46.67% were also observed, highlighting the variation in gap sizes 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 (%)
The majority of canopy gaps observed in the study fall within the size class of 50 to 200 m², while large gaps measuring 200 m² or more are rare, with only four such gaps identified in a rich forest stand, accounting for 26.66% of the total 15 gaps studied.
Characteristics of regeneration in the gaps
5.2.1 Growth characteristics of canopy tree surrounding studied gaps
Canopy gaps created by the loss of tall trees are constrained by neighboring canopy trees, which are vital for future seed regeneration These surrounding trees not only influence the size of the canopy gaps but also indirectly affect the species composition and density of regenerated trees within those gaps.
Table 5.2: Characteristics of surrounding canopy trees in the gaps
Categories Poor forest Medium forest Rich forest
Table 5.2 reveals that there are no significant differences in the number of canopy trees surrounding the studied gaps across the three research categories In the poor forest category, the canopy gaps were limited to an average of 2.5 trees, while medium and rich forests had an average of 4 trees.
In rich forests, trees exhibit greater dimensions compared to those in poorer forest categories, with an average diameter at breast height (DBH) of 13.06 cm, an average height of 16.53 m, and a crown diameter of 9.52 m In contrast, poor forests show lower measurements, averaging 11.65 cm in DBH, 9.6 m in height, and 5.18 m in crown diameter.
Larger gap sizes in forests allow surrounding trees ample space to grow and develop, resulting in their heights surpassing those of trees in smaller gaps.
5.2.2 Density and tree species composition in the gaps
Regeneration density serves as a key indicator of future forest health, reflecting the initial density of the overall forest Additionally, species composition is crucial, as it reveals the diversity and ratio of species present, indicating their contribution to ecosystem stability, sustainability, and biodiversity The current structure of regenerated trees will contribute to the future canopy layer if the trees are provided with suitable ecological conditions for growth and development.
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 illustrates the diverse regeneration species across study categories, with the highest number of tree species found in poor forests The species compositions at both center and edge gaps are notably complex, ranging from 5 to 10 species according to the species composition formula, with a relatively equitable regeneration ratio among them Additionally, species composition varies significantly between different locations, particularly in medium and rich categories.
The regenerated tree species in the poor forest include Adinadra millettii, Macaranga denticulate, Magnolia baviensis, Schefflera octophylla, Cinnadenia paniculata, and Litsea baviensis, with variations in species composition across different locations In the center gap, the dominant species are light-demanding and fast-growing, namely Adinadra millettii and Macaranga denticulate Conversely, the edge gap features a mix of both light-demanding and shade-tolerant species, including Adinadra millettii, Macaranga denticulate, Litsea baviensis, and Ficus fulva.
In the medium forest, the regeneration tree species composition features Ichnocarpus polyanthus, Claoxylon indicum, Michelia balansae, and Cinnamomum camphora, with Ichnocarpus polyanthus and Claoxylon indicum being dominant in the center gap, both of which are light-demanding species Conversely, the edge gap showcases a mix of light-demanding and shade-tolerant species, including Claoxylon indicum, Cinnamomum camphora, and Camellia.
The rich forest primarily features dominant species such as Archidendropsis basaltica, Wightia annamensis, and Cinnamomum camphora Within the central gap of this ecosystem, Archidendropsis basaltica, Wightia annamensis, and Adinandra are the prevalent species Similar to the poor and medium forest categories, these species are predominantly light-demanding, thriving in well-lit environments.
Species compositions vary significantly across different gap locations In the center gap, the high light intensity supports a variety of light-demanding species, including Adinandra millettii, Macaranga denticulate, Archidendropsis basaltica, Wightia annamensis, and Ichnocarpus polyanthus Conversely, shade-tolerant species such as Litsea baviensis, Ficus fulva, Cinnamomum camphora, and Camellia thrive in lower light conditions.
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 study findings, illustrated in Table 5.4 and Figures 5.2, 5.3, and 5.4, reveal a pronounced positive skewness in the height distributions of regeneration trees within gaps across various tree categories Most tree species are concentrated within the 0.5 to 1.5 height groups, indicating favorable environmental conditions for seed dispersal and germination Additionally, the data shows a decline in the number of regenerated trees as their height increases, particularly for those exceeding 1.5 meters This trend suggests that competition for nutritional space intensifies among individuals as they age Understanding the factors influencing height distribution is crucial for developing effective silvicultural strategies in natural forest gaps that align with both conservation efforts and business objectives.
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 indicates significant variations in the densities of regenerated trees across different forest categories In the poor forest category, saplings make up 82.36% of the total regenerated trees in center gaps and 63.46% in edge gaps Conversely, seedlings are predominant in the medium and rich forest categories, with densities ranging from 63.16% to 70.04% in medium forests and from 51.72% to 55.93% in rich forests Notably, in rich forests, sapling densities present a contrasting scenario, comprising 44.07% to 48.28% of the total regenerated trees.
The quality of forest regeneration is influenced by various ecosystem factors, resulting in aggregated outcomes Key parameters for quantifying regeneration quality include density, quality, origin, regeneration ratio, and the seed's regeneration ability.
The regeneration ability of forests indicates the environmental conditions that influence seed dispersal and germination The overall quality of a forest, particularly its regeneration, serves as a key indicator of the relationship between the site and the forest trees The findings regarding regeneration quality are detailed in Table 5.6.
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 locations, the quality of medium and good quality specimens surpasses that of bad quality The regeneration ratio for good quality ranges from 61.4% to 78%, while medium quality accounts for 17% to 29.4% In contrast, bad quality only represents 3.4% to 10.5%.
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 composition of mother plants and regeneration serves as an indicator of the inheritance patterns in forest regeneration This connection reflects the extent of mother plant sowing The species composition in regenerated trees is significantly influenced by the mother plant's seed production, germination conditions, ecological traits, and competitive abilities of each species The dominant levels of species composition across three research categories are summarized in Table 5.7.
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 presented in Table 5.7 indicates that the ratio of high trees with regeneration tree inheritance is notably high, ranging from 50% to 100% Among the three categories, the highest ratio of inheritance from high trees to regeneration trees is observed in rich forests However, the Sorensen index results reveal fluctuations in the BC index, which ranges from 0.88 to 1.02 in both poor and rich forests, indicating that the regeneration trees in the study area do not inherit traits from the high tree composition, as BC values exceed 0.75 Notably, in the medium forest category, the BC index falls below 0.75 in the center gap, suggesting a closer relationship between the regeneration tree composition and the high tree composition.
5.3.2 Effect of shrubs and vegetation to gap regeneration
Shrubs and vegetation significantly influence the growth and development of tree regeneration, primarily through competition for nutrients and light beneath the forest canopy Research indicates that a decrease in average cover leads to an increase in shrubs and vegetation, which benefits shade-tolerant young trees However, as these seedlings mature, the presence of shrubs and vegetation can hinder their growth Ultimately, shrubs and vegetation play a crucial role in determining the number of successful regeneration prospects within the forest ecosystem.
The density of regenerated trees beneath shrubs and vegetation canopies is high; however, their growth is limited due to the rapid development of surrounding shrubs, which create strong competition This competition gradually suppresses the regeneration of trees Additionally, the presence of dense shrubs and vegetation affects seed germination rates Seeds that fall onto the forest floor and come into contact with the soil under favorable conditions can germinate and thrive In contrast, seeds that land beneath thick shrub canopies often fail to reach the soil, resulting in poor germination.
Table 5.8: Effect of shrubs and vegetation to regeneration
The study of shrubs and vegetation canopy, including species such as Microsorum pteropus and Callisia fragrans, reveals an average height of 0.8 to 1.12 meters and cover ranging from 20% to 50% Regeneration density varies between 3,507 to 7,207 trees per hectare, as indicated in Table 5.8, where an increase in average cover correlates with a decrease in regeneration density—from 20% cover with 3,507 trees/ha to over 50% cover with 4,826 trees/ha This suggests that the dense growth of shrubs and vegetation significantly impacts regeneration density by competing for nutritional resources and light, ultimately leading to a decline in both regeneration density and quality Consequently, across the three research categories, regeneration is consistently low in relation to average canopy cover.
Regeneration prospects was regeneration height higher than or equal to the average height of the shrubs, vegetation and above quality medium
The average height and cover of shrubs significantly influence the density of tree regeneration When shrub cover is low, the prospects for tree regeneration density are high Conversely, high shrub cover leads to increased competition for nutrients, resulting in lower regeneration density and prospects To enhance tree regeneration, it is essential to manage shrub canopies by reducing their cover, which facilitates the growth and development of regeneration trees and improves their density prospects.
Recommend some silvicultural solutions to promote restoration process of forest
To enhance the ecological integrity of Ba Vi National Park, silvicultural solutions must be implemented across three research categories: poor, medium, and rich forests These solutions include delineating protected areas, maintaining existing forests, promoting natural regeneration, and integrating plantations that support ecological protection and preserve rare genetic resources and biodiversity.
Based on research findings, it is recommended to select a variety of high-quality seeds that demonstrate strong adaptability to the environmental conditions of Ba Vi National Park Prioritizing species with significant economic and aesthetic value will contribute to the establishment of an eco-friendly forest ecosystem Key species to consider for planting include Calocedrus macrolepis and Cinnamomum, which are well-suited to the region.
27 parthenosylon, Madhuca pasquieri, Magnolia baviensis… to restoration vacant land and bring a high economic value
To enhance the regeneration of the tree layer, it is essential to manage the average cover and height of shrubs and vegetation Reducing competition among shrubs and young trees will facilitate better conditions for seed sowing, germination, and growth This can be achieved by cutting back lianas and decreasing shrub cover, particularly in densely vegetated areas Additionally, cleaning and caring for the regeneration prospects while regulating their density will improve living conditions and nutritional availability for young trees beneath the forest canopy and in gaps.
To promote healthy tree growth in forest gaps, it is essential to regulate regeneration density Larger gaps tend to support more regeneration; however, if the gap is excessively large, the regeneration density may be insufficient In such cases, additional planting may be necessary to optimize forest space and ensure a thriving ecosystem.
To enhance forest regeneration and development, it is essential to implement silvicultural solutions that are accepted within the local economic and social conditions When applying these solutions, factors such as capital investment capacity, manpower availability, and the community's knowledge of silviculture and traditional farming techniques must be considered Additionally, the ability to adopt advanced techniques and leverage local knowledge plays a crucial role in the effective deployment of farming methods that positively impact forest health.
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
In forest ecosystems, dead trees and broken branches significantly contribute to gap formation, with 15 gaps identified across three forest categories: poor, medium, and rich The average gap area in rich forests is the largest at 173.17 m², followed by medium forests at 108 m², while poor forests exhibit the smallest average gap area of 92 m² Notably, the variation in gap area across these forest categories remains relatively consistent.
The regeneration tree species composition exhibited notable diversity and abundance, with the number of species ranging from 5 to 10 The ratio of regeneration among these species was relatively balanced, indicating equitable distribution Additionally, variations in species composition were observed across different locations.
The composition of regeneration species in gaps is significantly influenced by light availability and spatial conditions In central gaps, where light is abundant, a variety of light-demanding, fast-growing species thrive, including Adinadra millettii, Macaranga denticulate, Archidendropsis basaltica, Wightia annamensis, Ichnocarpus polyanthus, and Claoxylon indicum Conversely, shade-tolerant species such as Litsea baviensis, Ficus fulva, and Cinnamomum camphora are also present, indicating a diverse ecological response to varying light conditions.
The study revealed that the regeneration composition in two gap locations across three research categories showed a diversity and abundance of regeneration trees ranging from 34 to 59 Additionally, the regeneration density within these categories was assessed at a medium level, fluctuating between 3,507 and higher values.
7207 tree/ha Regeneration density prospects from 2165 to 3479 tree/ha
The distribution of regeneration varies with height across both locations, showing a decreasing trend in all three research categories However, the extent of this decrease differs between the locations and at various height levels.
The study reveals that the regeneration ratio of high-quality outcomes is significantly greater than that of low-quality results across all three research categories Additionally, it is noted that the center gap demonstrates superior quality compared to the edge gap.
The regeneration of trees is significantly influenced by the size of area gaps, with larger gaps correlating to a higher number of regenerating trees Additionally, the presence of shrubs and other vegetation impacts tree regeneration at a moderate level.
Recommendations
Ongoing monitoring of regeneration characteristics in the study area over the coming years is essential for assessing the dynamics of forest plant communities This evaluation will serve as a foundation for developing a sustainable forest model in nearby production forest areas.
This study examines how key environmental factors, such as light, temperature, humidity, and soil characteristics, influence forest understory and gap dynamics, specifically focusing on their impact on plant communities in the research area.
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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