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Characterization of the complete chloroplast genome of the sibu olive tree, Canarium odontophyllum (Burseraceae)

Xin Tian Sim, Peishan Zou, Bui Manh Hung, Aik Teng Heng, Shiamala Devi Ramaiya And Shiou Yih Lee

Canarium odontophyllum, commonly known as ‘Dabai’, is a fruitbearing plant native to the Borneo island and valued for its unique flavor and potential nutritional and therapeutic benefits. Despite numerous studies on its phytochemical and pharmacological properties, genetic studies on this species remain scarce, hindering efforts to understand its evolutionary relationships, genetic diversity, and potential for molecular breeding. To address this gap, the complete chloroplast genome of C. odontophyllum was sequenced using nextgeneration sequencing technology, assembled, and annotated in this study. The genome spans 159,433 base pairs (bp) and comprises two inverted repeat (IR) regions (26,652 bp each), separated by a large single-copy (LSC) region (87,717 bp) and a small single-copy (SSC) region (18,412 bp). A total of 132 genes were identified, including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes, with an overall GC content of 37.7%. Phylogenetic analysis using both the maximum likelihood (ML) and Bayesian inference (BI) methods, based on 79 unique protein-coding sequences (CDS), confirmed the monophyly of Burseraceae. The analysis revealed that Canarium diverged after Commiphora, with C. odontophyllum closely related to C. album. These findings contribute valuable genomic data, enhancing the understanding of the evolutionary relationships within Canarium and the broader Burseraceae. This genomic information is expected to aid in future research focused on molecular breeding, genetic conservation, and evolutionary studies of C. odontophyllum.

Applying GIS and remote sensing to determine potential distribution areas of turtle in Nam Dong natural reserve, Thanh Hoa province

Ho Thu Phuong, Tran Quang Bao, Luca Luiselli, Bui Manh Hung*

The study of Nam Dong Natural Reserve in Thanh Hoa province utilized remote sensing and GIS to assess potential turtle distribution across its 646.95 ha area, comprising lowland subtropical, lowland tropical, and rocky mountain forests. The reserve, rich in biodiversity, hosts species listed on both the Vietnam and IUCN Red Lists. Vegetation was classified into five types, with medium forest covering 74.34%, and elevation into five bands, with 50.02% in the 250-500m range. The study identified 31 turtles from four species, predominantly found in medium forest (65.52%) and the 82-250m elevation band (51.72%). Platysternon megacephalum favored stream habitats, while Cuora galbinifrons was less water-dependent. The habitat suitability map categorized the reserve into four levels: very suitable (57.48%), suitable (30.74%), less suitable (9.41%), and not suitable (2.37%). Cuora galbinifrons had the largest very suitable area (447.95 ha), while Platysternon megacephalum had the largest not suitable area (348.77 ha). Overall, the reserve provides favorable conditions for freshwater turtles, with substantial forest coverage and a dense river network.

Population structure and spatial patterns of trees in successional stages of tropical forest in Gia Lai, Vietnam

Nguyen Minh Canh, Bui Manh Hung*, Bernard Dell, Le Van Cuong, Nguyen Thi Bich Phuong, Nguyen Quoc Luan, Sven Wagner

Regeneration will determine the success of forest restoration and affect the sustainability of future forest ecosystems. Research has been conducted to evaluate the characteristics of the regeneration storey and their spatial distribution on the ground. The study has established 10 plots (100 m x 100 m) for secondary forests, 10 plots for old-growth forests. Sub-plots (2 m x 2 m) were set up systemically to investigate the regeneration. The results showed that 148 species in secondary forest and 130 species in old-growth forest were found. The number of families in the secondary forest was lower than in the old-growth forest by 3 families. The Simpson index of both forest states was high (0.9769 and 0.9799 respectively). Canonical coresspondence analysis exposed that species composition of both species and families between the two types of stages was significant dissimilar. There were clear groups of species and families appeared together with similar frequency in plots proved by hierarchical classification. In both stages, the height frequency distribution was inverse-J shape forms. And these distributions were different in studied types. The good regeneration in two studies states of forests were 67.9% and 55.7%. Regeneration quality was significant associated with height and light classes. The number of regenerating trees generated in each 1-hectare plot of the secondary forest was almost twice that of the old-growth forest. In the secondary forest, most plots illustrated that the spatial pattern was random at all scales. Contrary, in the old-growth forest, the patterns were much more complicated.

Carbon mineralization potential and nutrient dynamics in soils under vegetation types and soil depths at Luot mountain

Nguyen Thi Bich Phuong, Nguyen Thi Bich Hoa, Tran Thi Hang, Bui Manh Hung, Pervez Khan

Soil mineralization is a crucial soil process that improves soil physical properties, enhances carbon sequestration, and provides essential minerals and available nutrients for plant growth. This study was conducted at five vegetation types and soil depths at Luot mountain area, located in VNUF campus, Hanoi city. Samples were incubated in the dark at 25°C and measured at intervals of 1, 2, 5, 10, 15, 25, 35, and 40 days in the laboratory to determine C-CO2 respiration from soils. The study showed that CO2 emissions were highest in topsoils and decreased with deeper soil depths. Mineralized C-CO2 decreased from Shrubs > Acacia + Native species (NS) > Pinus + NS > Native species > Control. CO2 emissions peaked early in the incubation period and then stabilized in the 40-day incubation period. Larger aggregates (≥ 5mm) decreased significantly under most vegetation types, except for Shrubs, where the reduction was minimal. Aggregate size ≥3mm increased post-incubation, notably under Pinus + NS and Native species, with smaller aggregates also increasing slightly. Organic matter content was highest in the topsoil but decreased post-incubation due to microbial C mineralization. There was an increase in soil organic matter at 10-20 cm and 20-40 cm layers after incubation, especially under Shrubs. Available nitrogen slightly increased in soils post-incubation for most vegetation types. Phosphorus content increased post-incubation, peaking under Shrubs, while potassium levels were generally poor but increased during incubation. The study found that C-CO2 mineralization was strongly associated with soil porosity and pH, suggesting that higher porosity and optimal pH enhance mineralization, with organic matter content being crucial for available nutrient cycles in soils.

Khả năng sinh trưởng của keo lai tam bội trong khảo nghiệm dòng vô tính tại Bắc Giang và Quảng Trị

Trần Hoàng Gia, Nguyễn Đức Kiên, Bùi Mạnh Hưng, Dương Hồng Quân, Nguyễn Hữu Sỹ, Đỗ Thanh Tùng

Việc mở rộng nhanh chóng về quy mô trồng rừng sản xuất trong nước những năm gần đây dẫn đến việc rừng trồng keo ở nước ta đang phải đối mặt với nguy cơ cao về dịch bệnh, đặc biệt là bệnh chết héo (Ceratocystis sp.) và bệnh phấn hồng (Corticium salmonicolor). Do đó, đòi hỏi công tác chọn tạo giống keo cần tiếp tục được thực hiện nhằm tạo ra những giống tốt, có khả năng hạn chế những rủi ro cho rừng trồng keo sau này. Mục tiêu của nghiên cứu nhằm chọn lọc được các dòng keo lai tam bội sinh trưởng nhanh, hình dạng thân đẹp phục vụ trồng rừng. Nghiên cứu được tiến hành trên 2 khảo nghiệm dòng vô tính tại Yên Thế, Bắc Giang và Cam Lộ, Quảng Trị, bao gồm các dòng keo lai tam bội mới chọn lọc và đối chứng là các giống keo lai đã được công nhận. Đánh giá sinh trưởng đã được thực hiện trên 2 khảo nghiệm dòng vô tính tại Yên Thế ở thời điểm 62 tháng tuổi và tại Cam Lộ ở thời điểm 57 tháng tuổi. Tại Yên Thế: có sự sai khác rõ rệt giữa các dòng về các chỉ tiêu sinh trưởng cũng như các chỉ tiêu chất lượng thân cây nhưng không có sự khác biệt về tỷ lệ sống; D1,3 trung bình là 12,27 cm, Hvn và V tương ứng là 14,17 m và 113,20 dm3/cây; về năng suất, dòng X201, X205, X102, X101 và X801 có năng suất từ 21,60 - 28,38 m3/ha/năm, vượt trội hơn so với các dòng khác tham gia khảo nghiệm. Mặt khác, năng suất của các dòng này cũng lớn hơn hoặc tương đương so với các giống được công nhận như BV10 và BV16, đồng thời có các chỉ tiêu chất lượng tốt nhất. Tại Cam Lộ: tỷ lệ sống trung bình đạt 69,60%; D1,3 trung bình đạt 9,63 cm; Hvn và V trung bình tương ứng đạt 12,24 m và 53,50 dm3/cây; có sự sai khác rõ rệt về các chỉ tiêu sinh trưởng và chất lượng thân cây; các dòng X201, X801, X102, X1117, X1141 có năng suất từ 24,62 - 31,83 m3/ha/năm, cao nhất trong khảo nghiệm. Những kết quả của nghiên cứu chọn giống tam bội là hết sức cần thiết, góp phần nâng cao hiệu quả kinh tế và phát triển tài nguyên rừng bền vững trong tương lai.

Assessing the biomass and carbon productivity of pure Pinus willachiana forest in Kumrat valley, Pakistan

Pervez Khan, Kaleem Ullah, Bui Manh Hung*, Adnan Ahmad, Shiou Yih Lee, Le Dinh Hai, Sohail Ahmad, Faisal Khan, Rehan Ullah, Sajjad Ullah, Rajpar Nawaz Muhammad

Forests are both a source and a carbon sink, which helps to reduce the amount of CO2 in the atmosphere. In addition to acting as carbon sinks, forests release carbon when there is land use for other purposes. This release of stored carbon occurs when biomass is removed from the forest. This study estimated the biomass and carbon stocks in pure Pinus wallichiana forest in the valley of Kumrat Dir Kohistan, Pakistan. The study area was divided into three different homogeneous strata. In each stratum 10 square shaped sample plots with plot size 0.1 hectare with fixed dimensions of (33×33 m) with a total of 30 sample plots were taken by following stratified random sampling method. To check the relationship of biomass and carbon stock with different parameter, regression models were developed. The results showed that in pure Pinus wallichiana forest, the biomass of upper storey vegetation have stored 465 t C ha-1, 1.1 t C.ha-1  in under storey vegetation, deadwood, litter, cone have 10.92 t C ha-1 and soil have stored 63.23 t C ha-1, with overall 540.25 t ha-1 of carbon. Ecological services in the region are provided by these natural coniferous forests, while maintaining carbon dioxide levels in the form of biomass. Results from this study will enhance to evaluate the role of these forests in regional and global C cycles, Reducing Emissions from Deforestation and forest Degradation (REDD+), sustainable forest management and policy matters on climate change.

A BIBLIOMETRIC ANALYSIS OF AGARWOOD RESEARCH AND THE IMPACT OF CITES LISTING

J-R. Chen, M. S. Hishamuddin*, B. M. Hung, R. Mohamed and S. Y. Lee*

Agarwood is a renowned fragrant non-timber wood product primarily originating from the Indo-Malesia region. It also

plays a pivotal role in the global industry due to its economic and cultural significance. As a response to illegal harvesting and trade activities leading to declining populations, all agarwood-producing species have progressively been incorporated into CITES Appendix II. We conducted an in-depth investigation into the temporal dynamics of the scientific literature pertaining to agarwood in this study. The evolving trends in agarwood research and the influence of CITES listing on publication numbers were elucidated by utilizing a bibliometric approach. The quantity of research activity was leveraged as an indicator of the engagement of a country, and the status of agarwood research before and after the CITES listing was analyzed. A rigorous selection process yielded 704 articles from the Web of Science (WoS) core database and 1,054 articles from Scopus, using four specific keywords: "agarwood," "Aquilaria," "Gyrinops," and "gaharu," spanning the years 1995–2022. A notable upswing in the number of scientific publications following the implementation of the CITES listing was identified, while China has been the leading country in most publications and research work since 2009 and 2008 based on WoS and Scopus, respectively. The journal "Molecules" has received the most related articles over the years, and the most popular keyword used is "agarwood." China is also, so far, the country with the most related patents filed. The trending research topics based on the keywords from 2021 to 2022 would be studies related to pharmacological effects, understanding the mechanism of agarwood formation, exploring alternative agarwood-producing species from Gyrinops, and promoting sustainability in agarwood production. Furthermore, the discussion also covered potential research initiatives that could address the existing knowledge gaps in agarwood research up to the present moment.

SOIL ORGANIC CARBON STOCKS IN NATURAL FORESTS OF DONGNAI CULTURE AND NATURE RESERVE, SOUTHEASTERN VIETNAM

CHAU, M. H. – QUY, N. V. – CUONG, L. V. – HIEU, N. T. – NGOAN, T. T. – HUNG, D. V. – HUNG, B. M. – PHU, N. V.

Even minor fluctuations in the carbon content in forest soil can significantly impact atmospheric carbon concentrations and future global climate patterns. Therefore, investigating the variation characteristics of soil organic carbon (SOC) in tropical forests is essential for comprehending the carbon sequestration potential of forest soil. This study delves into SOC dynamics within the natural forest types of Dongnai Culture and Nature Reserve in southeastern Vietnam. Nine 1000 m2 plots were sampled across rich, medium, and poor forests. Soil samples were collected from depths ranging from 0 to 60 cm. The findings revealed increased SOC content from poor to rich forests, with a decrease in depth. The total carbon (C) stocks ranged from 92.20 Mg C ha-1 in poor forests to 124.30 Mg C ha-1 in rich forests within the top 60 cm. Over 81% of soil C was concentrated in the upper 40 cm. Factors such as soil water content and slope gradient emerged as crucial determinants affecting SOC distribution. These results underscore the potential of forest management practices to augment SOC levels, thereby offering valuable insights for estimating carbon stocks in the forest ecosystems of southeastern Vietnam.

Traditional knowledge, attitude and behaviour of indigenous people towards endangered wildlife conservation in Kon Plong District, Vietnam

Nguyen Thi Thien Huong, Bui Manh Hung*, Andrzej Nienartowicz, Dong Thanh Hai, Nguyen Quoc Dung, A Siu, Tran Huu Vy, Lynn Smith

Indigenous knowledge, attitudes, and perceptions of local people are very important concepts for wildlife conservation. Endangered wildlife species that live in Kon Plong forests have been under pressure from the communities living around them, including wildlife hunting, trapping, capturing, illegal logging, and encroachment for residential and production land. This study aims to understand the knowledge, attitude, and behaviour of indigenous people towards endangered wildlife in order to protect these species. Some participatory rural appraisal tools were used to discuss the situation and collect information in nine villages of four communes in Kon Plong District from December 2019 to March 2020. The results showed that the levels of knowledge about endangered wildlife among indigenous people in communes were statistically different. People’s knowledge of the law influenced their behaviour. Gender had the greatest influence on the level of knowledge. Most indigenous people had a positive attitude and wanted to protect endangered animals. “Commune” and “culture” were the two factors affecting people’s attitudes. “Commune”, “culture”, and the level of understanding affected the hunting behaviour of people. Negative human impacts have seriously influenced endangered wildlife species. Therefore, it is necessary to develop a long-term conservation strategy and plan, including the establishment of Kon Plong Special-Use Forests, supporting livelihoods for local people, communicating, and raising awareness among local people, and increasing the participation of community organisations.

Variations in Soil Phosphorus Levels in Acacia Hybrid Plantations Across Different Ages in Southern Vietnam

Cuong, L.V., Karam D.S., Hung, B.M., Chau, M.H., and Quy, N.V.*

Phosphorus (P) plays a significant role in influencing nutrient cycles in terrestrial ecosystems. However, we must enhance our understanding of the changes and factors regulating soil P in Acacia hybrid plantations in southern Vietnam. This study aims to assess alterations in soil total phosphorus (TP) and available phosphorus (AP) levels and storage, as well as to identify the factors influencing soil TP and AP concentrations based on soil and forest stand characteristics across five different ages (2, 4, 6, 8, and 10 years old) of Acacia hybrid plantations within the Langa Forestry Company in southern Vietnam. Soil samples were collected to a depth of 0-100 cm for analysis. The results revealed that soil TP and AP concentrations in the five stands increased with stand age, showing a significant decrease with soil depth. Soil TP and AP stocks increased from 4.78-5.35 Mg ha−1 and from 0.12-0.50 Mg ha−1, respectively, as the stand developed. Additionally, soil TP and AP stocks displayed noticeable aggregation in the topsoil, with over 40% of TP storage and over 50% of AP storage occurring within 0-40 cm depth. The structural equation model (SEM) suggested that both soil parameters (i.e., soil bulk density and pH) and forest stand characteristics (i.e., plant biomass) significantly influenced soil TP and AP concentrations. Mainly, soil properties parameters had a more substantial impact on soil P concentrations than forest stand features parameters. Our findings offer new insights into soil phosphorus dynamics, with significant implications for Acacia hybrid forests' protection and sustainable management.

The Relative Importance of Stand and Soil Properties Parameters on Soil Organic Matter Content of Acacia Hybrid Forests in the South Central Coast Region of Vietnam

Cuong, L.V., Quy, N.V., Hung, B.M., Chau, M.H., and Doan, P.V.T.D. 

Soil organic matter (SOM) represents a crucial C reservoir for climate regulation and a necessary constituent for forest soil functions. Unfortunately, less attention was accorded to the alters in SOM under various stand ages and the relative significance of biotic (i.e., stand properties) and abiotic (i.e., soil physico-chemical features) parameters in the adjustment of SOM in forests. In the study, we investigated the SOM in soil layers of Acacia hybrid plantations over different age classes (young stand of 3 years, middle-aged stand of 6 years, and near-mature stand of 9 years) in the South Central Coast region of Vietnam. Characterizing forest stand features and other soil physico-chemical characteristics were also measured. The effects of the primary influence variables on SOM were explored. The results demonstrated that with the increase in stand age, the concentrations of SOM tended to increase. SOM content declined substantially with the increase in soil depth, showing a topsoil enrichment phenomenon. Stand structural and soil physico-chemical features significantly differed between the three plantation stand ages. The combined effect of stand and soil parameters explained 93% of alterations in SOM. Regarding the pure impacts, soil factors explained the most portion of shifts in SOM (41.10%). These findings illustrate the critical role of biotic and abiotic parameters in assessing the SOM concentration in A. hybrid forests across different stand ages. The results of the current study provide a deeper insight into the response of SOM to stand age and finally offer a reliable scientific basis for designing optimal organic matter management practices for the sustainable development of A. hybrid forests.

Species and tree quality spatial distribution patterns

and associations in Tuyen Quang, Vietnam

Khoa PV, Hung BM*, Dell B, Vinh NK & Chau MH

Spatial distribution patterns of trees are important keys to understanding forest structure and for proposing forest management solutions. Management of rainforests in Vietnam is constrained by a shortage of spatial forest data. Therefore, research was conducted in an upland secondary forest in Tuyen Quang, Vietnam to assess spatial distributions of species and quality levels, and associations between them. Tree diameter, height, coordinates and quality (Good, Medium and Bad) were recorded in three one-hectare plots. Tree density ranged from 920 - 1050 trees ha -1, and there were 61 - 69 species ha -1. The highest percentages of Good and Bad trees were 25.1% and 42.9%, respectively. The habitat was determined as heterogeneous to homogeneous. The spatial distribution of all species and ecological important species was mostly random and clustered. Associations among ecological important species was mainly independent. Tree qualities were randomly distributed, but Bad trees were more abundant in the understorey. Associations between tree qualities were mostly independent. The results on spatial distribution patterns and associations between species and qualities will be useful in helping to eliminate competition of trees in clusters, assist regeneration in gaps and determine options for reducing the frequency of Bad trees in the future. 

Monitoring forest cover in riparian zones along the rivers of Mari El Republic using satellite data

L.V. Tarasova, E.A. Kurbanov, O.N. Vorobiev, H. Bui, S.A. Lezhnin, D.M. Dergunov 

Landsat satellite data is widely used for monitoring forest cover. The use of the Google Earth Engine (GEE) cloud platform allows for the analysis of these data using various methods. The aim of this study is to investigate the dynamics and disturbance of forest cover in riparian zones from 1984 to 2022 based on Landsat time-series imagery. The study focuses on forested areas located within a 200-meter buffer zone along the 23 largest rivers in the Republic of Mari El. The classification of Landsat time-series data into four land cover classes using the Random Forest (RF) algorithm in GEE was carried out. At the first stage, 85 Landsat time-series images were classified, and the structure and dynamics of the classes were analyzed, resulting in a map of land cover changes. At the second stage, the LandTrendr algorithm was applied to detect areas of disturbance in the forest cover over the study period. The analysis of Landsat data revealed that overall, from 1984 to 2022, there has been an increase in forest cover area due to the replacement of non-forest areas and coniferous forests with deciduous forests. The greatest changes in disturbance indices were observed during the periods of 1985–1992 and 2010–2011, which can be attributed to the consequences of flooding in riparian forests and major wildfires in 2010. The application of cloud technologies and methodological approaches for change detection allows for the assessment of dynamics and disturbance based on multi-temporal satellite imagery at a regional scale.

Sách: Xác định thể tích cây từ đường kính gốc

PGS.TS. Bùi Mạnh Hưng (Chủ biên), PGS.TS. Đồng Thanh Hải (Đồng chủ biên), ThS. Phạm Tuấn Tùng, ThS. Lê Minh Tuyên.

     Cuốn sách trình bày tổng quan về phương pháp pháp xác định thể tích từ đường kính gốc cây, trong đó bao gồm tổng quan cả các phương pháp chặt hạ và không chặt hạ. Tuy nhiên, kết quả và bảng tra chỉ tập trung vào các phương pháp không chặt hạ cây. Bởi hiện nay, việc chặt hạ cây cần theo những quy trình nghiêm ngặt của nhà nước, số lượng chặt hạ rất hạn chế. Cuốn sách bao gồm 5 chương: Tổng quan về xác định thể tích thân cây từ đường kính gốc, Phương pháp điều tra số liệu và xác định thể tích, Bảng tra thể tích cây từ đường kính gốc, Tra tự động thể tích cây và Kết luận và Tồn tại.

      Cuốn sách được thực hiện nhằm đưa kiến thức và sản phẩm của nghiên cứu vào thực tiễn, phục vụ cho các đối tượng như học sinh, sinh viên, cán bộ Lâm nghiệp, cán bộ Kiểm lâm tại các đơn vị, cán bộ kỹ thật, cán bộ quản lý tại các cơ quan nghiên cứu, cơ quan nhà nước và các đối tượng khác có quan tâm. Cuốn sách này là tài liệu cần thiết, có thể được sử dụng để phục vụ việc học tập lý thuyết và thực hành các môn học như Điều tra rừng, Sản lượng rừng và các môn học khác ở bậc đại học và cao học trong lĩnh vực Lâm nghiệp. 

Nhà xuất bản Khoa học và Kỹ thuật.

ISBN: 978-604-67-2922-8

Key factors influencing tree planting decision of farmers on farm land: A case study in Malakand, Pakistan

Pervez Khan, Bui Manh Hung*, Le Dinh Hai, Sohail Ahmad, Faisal Khan, Sajjad Ullah, Adnan Ahmad, Shiou Yih Lee

In order to cope with forest degradation and deforestation, farm forestry is a new tool for plantation purposes that combat these issues. Planting trees on farmlands is the most practical and viable approach given in the current situation in Pakistan for recovering the degraded forest lands, ensuring the sustainable use of marginal areas, and satisfying the rural requirements for the benefits of trees, both economically and non-economically. Therefore a socio-economic study of farmers in relation to tree planting is very important, to understand farmers perception about farm trees growing. In this study a total of 120 households were surveyed and interviewed in district Malakand for factor affecting farm tree planting decision. The result of step wise binary logistics regression analysis indicated that the factors including: Education level, Attitude of tree planting and silviculture knowledge were significantly influenced on tree planting decision of household in the study area. The total household income for planter was significantly higher than non-planter. The study result may provide the basis for proposing solution for future to strengthen trees planting decision for plantation, with the intention of promoting household engagement and attract farmers towards plantation activities in the study area.

Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam

MAIHAI CHAU, NGUYENVAN QUY, XIAONIU XU, BUIMANH HUNG, LE VAN CUONG, TRANTHI NGOAN, THANHMINH NGUYEN 

Soil Carbon (C), Nitrogen (N), and Phosphorus (P) contents are the three most critical soil nutrient elements required for plant growth and development, and their ecological stoichiometric ratios are significant indicators for understanding soil nutrient balance and cycling. This study was conducted to probe variations in the soil organic C (SC), total N (SN), and total P (SP) contents and stoichiometry at five soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in Acacia hybrid plantations of five different ages (2-, 4-, 6-, 8-, and 10-year-old plantations) in Langa-Dongnai Forestry Company, Southern Vietnam. The results showed that forest age and soil depth substantially impacted soil nutrient contents and their stoichiometric characteristics. The concentrations of SC, SN, and SP as well as C/N, C/P, and N/P ratios increased as the forest stand age increased. The contents of SC, SN, and SP reduced with soil depth, indicating an obvious soil “surface-aggregation” phenomenon. The nutrient restriction varied based on forest stand development, shifting from restricted nitrogen in the earlier growth periods of trees to restricted phosphorus in the later growth periods. The findings demonstrate that to resolve the issue of restricted availability of these nutrient indexes, additional nitrogen should be supplied during earlier growth periods and additional phosphorus during later growth periods. The results further emphasize the importance of understanding SC, SN, and SP interactions and nutritional limitations and provide relevant theoretical support for sustainable Acacia hybrid plantation management in the Southern region.

Multivariate Spatial Structure of Secondary Forests in Tuyen Quang Province, Vietnam

Phung Van Khoa, Bui Manh Hung*, Bernard Dell, Nguyen Khac Vinh, Eldar Kurbanov, Le Van Cuong & Nguyen Thi Bich Phuong 

Forest management relies on forest spatial structure, but studies on the spatial structure of Vietnamese forests are limited. Therefore, two one–hectare plots were established in tropical rainforest in Tuyen Quang province to evaluate the characteristics and spatial structures of plant communities. Descriptive statistics and species importance value indices were calculated for each plot. Then, to assess differences between plots, detrended correspondence analysis was applied. Species mingling, uniform angle, diameter dominance and carbon stock dominance indices were also computed to analyze forest spatial structures. The results indicated that 65–70% of trees occurred in areas with high diversity, and 55–58% of trees were randomly distributed. The number of dominant and non–dominant individuals, in terms of diameter and carbon stock, was similar at the stand level. In all estimated patterns, units with high species mixtures predominated. As biodiversity increased, the distribution of forest trees became more random. The quadrivariate distribution illustrated considerable differences between plots, the study area and other regions. Findings from multivariate distributions provide accurate information in each group of spatial indices and these can be used to select appropriate silvicultural measures for stand management.

CARBON STOCK CHANGES IN MANGROVE OVER PERIODS

IN QUANG YEN TOWN, QUANG NINH PROVINCE

Le Thao Van, Bui Manh Hung*, Ha Tri Son, Nguyen Hai Hoa

Mangrove forests are often distributed in estuaries and tropical and subtropical coastal areas, where the tides come in and out every day. Mangroves play a significant role in human life in these areas. The study used PlanetScope images in 2017, 2020 and 2023 combined with NDVI index to build mangrove maps and determine biomass and carbon stocks for Quang Yen town. Results showed that the area of mangrove forests in Quang Yen town was 3470.026. 3358.81 and 3418.10 hectares for 2017, 2020, and 2023, respectively. The accuracy of the mangrove forest map between years was 88%, 88% and 88%, respectively. The total AGB reserves were 18,302,976 tons, 94,104,161 tons and 145,035,226 tons. The total AGC was 8,693,913 tons, 44,699,477 tons and 68,891,730 tons for 2017, 2020 and 2023. The use of remote sensing technology to build carbon strock maps for mangrove forests in Quang Yen town can be applied to other provinces especially for different periods. These findings are essential for sustainable mangrove management in the study area. At the same time, finding suitable solutions. Blue Carbon and Payment for Ecosystem Services are effective solutions that can be applied here to minimize risks and enhance the effectiveness of mangrove forests in the future.

SOIL NITROGEN STORAGE AND ASSOCIATED REGULATION FACTORS IN AN ACACIA HYBRID PLANTATION CHRONOSEQUENCE IN SOUTHERN VIETNAM

CHAU, M. H. – QUY, N. V. – HUNG, B. M. - XU, X. N. – CUONG, L. V.* – NGOAN, T. T. – DAI, Y. Z.

The study was designed to quantify the soil total nitrogen (STN) storage (SNS) and its controlling factors in Acacia hybrid (Acacia auriculiformis × A. mangium) plantations in five different ages (2-, 4-, 6-, 8-, and 10-years-old) in Langa - Dongnai Forestry Company, Southern Vietnam. A total of 75 soil samples were taken at five different soil depths from 0–100 cm. The STN concentration, SNS, soil properties, and plant biomass features (i.e., understorey vegetation biomass and litter biomass) were estimated. The STN concentration significantly increased with increasing forest stand age, whereas significantly decreased with increasing soil depth in all stand ages. The SNS in the uppermost 1 m soil layer in 2-, 4-, 6-, 8, and 10-yearold stands was 6.83, 9.50, 12.30, 17.15, and 19.41 Mg. ha-1, respectively. The SNS was focused mainly on the topsoil layers (0–40 cm). The SNS in the upper 0–40 cm soil layer accounted for over 50% of the total soil N stocks and the accumulation revealed decreasing tendencies with an increase of soil depth in all five stands. The soil organic carbon concentration and soil particle size fractions (i.e., soil silt concentration) were detected as the leading environmental parameters modulating the SNS variance. Our findings illustrate that considerations of N sequestration potential in Acacia hybrid plantations must take stand age into account and offer significant information for a better comprehension of the key environmental parameters driving SNS in Southern Vietnam.

Acacia canopy structure and carbon stock in Ba Vi, Vietnam

Bui Manh Hung*, Nguyen Thi Bich Phuong, Nguyen Van Quy, Nguyen Van Hop, Le Van Cuong, Yusif Habib

Forest structure is a key component of its management and assessment in every forest ecosystem. In the study, 23 plots were established to obtain data on the acacia forest community based on tree size. Results from the study indicated that the acacia community could be broadly divided into two groups based on tree-size variables. The diameter and height frequency distributions of group 1 were right-skewed, while those of group 2 were more complicated. In both groups, there were positive correlations between tree-size variables, nonetheless relationship between the diameter at breast height and total height was best described using the Cubic equation. Further, the Weibull and SHASH best simulated the diameter and height frequency distribution. High-quality trees were found in a large diameter (> 30 cm) and height groups (> 22 m). In contrast, low-quality plants often concentrated on the smallest. Therefore, trees with a diameter of 2-10 cm and a height of fewer than 8 m should receive attention to tend. Carbon stock in the two groups was 61.48 and 64.21 Mg/ha, respectively. Tending solutions and measurements should be carried out regularly to promptly propose silvicultural measures and improve forest quality in the future.

Tree-Size Variable Frequency Distribution Modeling for Tropical Forests in Ba Be, Vietnam

Bui Manh Hung*

Tree-size variable frequency distributions are essential for sustainable forest ecosystem management. In Vietnam, a few theoretical distributions have been found to simulate tree-size quantities. Therefore, this study was carried out to understand characteristics of the quantities, select and compare the best distributions for their frequency distributions in Ba Be, Vietnam. The study established 10 plots for three forest types (rich, medium and poor) and measured tree-size quantities. The study tested 64 theoretical distributions for all variables in three forest types. The results indicated that for the diameter quantity: Weibull (3P) (P means parameter), Pearson 6 (4P) and Wakeby were the best. For the height quantity, Pearson 6 (4P), Dagum (4P) and Gen. Extreme Value is the best fit. For the commercial height variable, the best functions were Burr and Burr (4P), while Burr, Pearson 6 (4P) and Gumbel Max were the best distributions for the crown width quantity. All best distributions were significant at p-value < 0.001. Therefore, these best models can be used to propose silvicultural measures and make contributions to sustainable forest management and planning in the study area and regions with similar conditions.

Allometric relationships among tree-size variables under tropical forest stages in Gia Lai, Vietnam

Bui Manh Hung*, Phung Van Khoa, Nguyen Thi Bich Phuong, Nguyen Van Quy, Bernard Dell

Allometric models play an undeniable role for estimating hard-to-measure quantities such as volume, biomass and carbon stock in forests. However, so far there has been limited model development for native forests in Vietnam. Therefore, this study was conducted to build and analyze the effectiveness of nonlinear and mixed models for secondary and old-growth forests in Gia Lai, Vietnam. The study measured diameter at breast height, total height, commercial height and crown width of forest trees in 20 plots (10 plots for each forest stage). The results showed that diameter had the strongest relationship with height. In the secondary forest, the Power, Korf and Ratskowky models were the best for pairs of variables, while Prodan, Weibull and Power models were the best fit in the old-growth forest. The nonlinear mixed-effect models were better than classic nonlinear models in both forest stages. Fixed and mixed models developed in this study are very valuable for estimating difficult-to-measure quantities and contribute to effective forest management in the study region.

Differences in Overstorey Structure and Biodiversity between Forest Stages in Gia Lai, Vietnam

Bui Manh Hung*, Lynn Smith, Nguyen Thi Bich Phuong, Sven Wagner

Forest structure is an essential key to successful and sustainable poor forest restoration. The study was conducted in Kon Ka Kinh National Park, Gia Lai, Vietnam. Ten plots were made in secondary and also ten plots in old-growth forests. Research results have shown that the secondary forest had a greater density, but the tree sizes are smaller than that of old-growth forests. The Beta fits best to the diameter frequency distribution in the secondary forests, while the Johnson fits best in the old-growth forests. The results for the height frequency distribution were the opposite. The Quadratic model was the best function to describe the relationship between diameter and height in the secondary forests. In old-growth forests, the Ratskowky model was the best model. The spatial distribution of trees was random in secondary forests, but regular in old-growth forests. Richness of secondary forests was bigger, while other indices were lower than those of old-growth forests. Tree quality classes had strong association with species. Findings of the study are good bases for poor secondary forest restoration in the Park.