Acacia Mangium Plantation Research Articles

Identification and pathogenicity of Ceratocystis manginecans causing wilt disease on Acacia mangium in Sabah, Malaysia

Abstract. Yunus NM, Maid M, Yong WTL, Anthony FE, Sudin M, Taylor PWJ. 2024. Identification and pathogenicity of Ceratocystis manginecans causing wilt disease on Acacia mangium in Sabah, Malaysia. Biodiversitas 25: 2170-2182. An alarming incidence of wilt disease has been reported in an Acacia mangium plantation in Ulu Kukut, Kota Belud District, Sabah, Malaysia. Infected trees exhibited symptoms such as severe wilting, sapwood discoloration or black lesion, and a fruity-sweet odor emanating from the fermentation exudate at the wound lesion. This is the first investigation of the causal wilt pathogen in a commercial A. mangium plantation in Ulu Kukut, located in the western region of Sabah. This study aimed to identify the causal fungal pathogen from infected A. mangium trees using morphological characterization and DNA sequence comparisons for the regions of Internal Transcribed Spacer (ITS), beta-tubulin 1 (bt1), transcription elongation factor-1 alpha (tef1), guanine nucleotide-binding protein subunit beta-like protein (ms204), and second largest subunits of RNA polymerase II (rpb2). The fungal isolates shared morphological characteristics with the wilt pathogen Ceratocystis sp., including a globose base with a long neck-ended tip with ostiolar hyphae. Sequence-based phylogenetic analysis confirmed the identity of Ceratocystis manginecans, distinguishing them from all other Ceratocystis species. Bioassays inoculating phyllodes and twigs of 1-year-old A. mangium trees confirmed that C. manginecans was the cause of wilt disease. Confirming the identity of the causal agent of the increasingly destructive and severe wilt disease aids in developing effective disease management strategies for Acacia-based plantations.

Paying for forest carbon: Cost‐effectiveness of the Verified Carbon Standard (VCS) remuneration scheme

AbstractForests play an essential role in climate change mitigation by absorbing carbon dioxide from the atmosphere and storing carbon in biomass. Carbon sequestration can be increased by the extension of rotation cycles in existing plantation forests. This study examines the cost‐effectiveness of the remuneration scheme employed by Verified Carbon Standard (VCS), a commonly used carbon accounting method based on the average amount of carbon stored in the forest. We compare the net present value of carbon remuneration under VCS with that of a scheme that remunerates actual carbon storage in each year which we call “current carbon accounting.” We use data for an Acacia mangium plantation in Indonesia where the forestry sector is expected to contribute more than half of the reductions of carbon emissions according to Indonesia's Nationally Determined Contribution (NDC) under the Paris Agreement. For our baseline scenario, we find, first, that the payments needed to incentivise additional carbon storage under VCS are considerably higher than under current carbon accounting. Second, the inefficiency is more pronounced at lower discount rates. Third, recent prices reported for VCS forest credits are not sufficient to incentivise forest managers to lengthen the forest rotation in Indonesian plantation forests.

Effects of species mixture on understory vegetation, soil properties and bacterial diversity of Acacia cincinnata, Eucalyptus robusta and Acacia mangium plantations in Southeastern China

The establishment of mixed forests is gaining increasing attention as a way to optimize forest production, improve ecological benefits, and serve as a safety net for impacts of future climate uncertainties. However, practical knowledge about which species and what proportion of them should be mixed is still lacking. Thus, this study was conducted to identify suitable species for a mixture with Acacia cincinnata. The mixtures tested in this study were A. cincinnata and Eucalyptus robusta (6:4), A. cincinnata and Acacia mangium (3:1), and monoculture plantation of A. cincinnata established in 2014. After seven years of growth, we analyzed the effects of species mixing on tree species growth, understory vegetation, and soil physicochemical properties as well as bacterial community structure and diversity. The results showed that species mixing had no significant effect on the diameter and individual volume of A. cincinnata. However, mixed planting increased the total stocking volume compared to monoculture plantation of A. cincinnata. The species diversity, biomass and nutrient stocks in the understory vegetation were significantly increased by stand mixing. The soil of mixed stand of A. cincinnata and A. mangium had the highest C and N contents, whereas the soil of monoculture A. cincinnata stands had the highest P content. The diversity of soil bacterial community was highest in the mixing stand of A. cincinnata and E. robusta, followed by monoculture A. cincinnata stand and mixed stand of A. cincinnata and A. mangium. The relative abundance of Proteobacteria and Actinobacteria was highest in mixed stand soil of A. cincinnata and E. robusta. Furthermore, the relative abundance of Firmicutes was high in the mixed stand soils of A. cincinnata and A. mangium while the relative abundance of Verrucomicrobia was high in the mixed stand of A. cincinnata and E. robusta stand. In general, the study revealed that the establishment of mixed-species forest enhances the diversity and composition of understory vegetation, soil physicochemical and soils bacterial community; thereby increasing biodiversity, nutrient cycling and carbon sequestration in the biomass and soil. From the viewpoints of forest productivity and ecological benefits, it is advisable to establish a mixed forest of A. cincinnata and A. mangium in southern China. Overall, our work revealed that the sustainability of mixed-species plantations relies on the interactions between soil attributes, vegetation, and bacterial community.

The Effect of Road Conditions on Acacia mangium Timber Hauling Performance

The quality of timber could be affected by timber hauling, primarily when it remained in the forest and became vulnerable to pests and fungi attacks. Additionally, road conditions could also influence the slickness of hauling. Therefore, this study aimed to identify the effect of road conditions on hauling performance, cost, and soil deterioration. This research analyzed four types of road conditions in Acacia mangium plantations in West Java and Banten, including dry, wet, uphill, and downhill roads. The results indicated that the average hauling performance of 6.604 m3km/hour on the uphill road was the least among all road types. The uphill soil road had the highest average hauling cost of 30,685 IDR/m3km and the deepest average rut of 17.503 cm compared to others. These results would provide better information on low-cost and environmentally friendly timber hauling productivity.

Utilizing Locally Available Bioresources for Powering Remote Indigenous Communities: A Framework and Case Study

We establish a framework to examine the feasibility of using local vegetation for bioenergy power systems in small-scale applications and remote settings. The framework has broad application, and we present a specific case here to demonstrate the process. Our case study is the Tiwi Islands in northern Australia, where a large Acacia mangium plantation is a potential source of biofuel feedstock. Two types of technology were considered: 1. Bio-oil from pyrolysis in diesel generators and 2. Direct combustion coupled with a steam turbine. The biomass was characterized and found to have adequate properties for an energy crop, with a lower heating value of about 18 MJ/kg and entire tree ash content of 2%. Measurements from trees that were damaged from wildfires had similar results, showing potential value recovery for a plantation after unplanned fire. In comparison to a petroleum diesel-based generator, the bio-oil system was 12% more expensive. The direct combustion system was found to be the most economical of those explored here, costing as low as 61% of the bio-oil system. Additional social and environmental benefits were identified, including local employment opportunities, improved energy security and reduced greenhouse gas emissions. Our findings of high techno-economic potential of bioenergy systems, especially through direct combustion, are widely applicable to on-demand renewable energy supply in remote communities.

Introducing N2-Fixing Tree Species into Eucalyptus Plantation in Subtropical China Alleviated Carbon and Nitrogen Constraints within Soil Aggregates

Soil extracellular enzymatic activity (EEA) and extracellular enzymatic stoichiometry (EES) within aggregates indicate variations in soil-nutrient effectiveness and the nutrient requirements of microorganisms. However, the responses of soil EEA and EES after introducing N2-fixing tree species into Eucalyptus plantations are poorly understood. Therefore, we examined soils from a 15-year-old pure Eucalyptus urophylla plantation (PP) and mixed E. urophylla and Acacia mangium plantation (MP) based on the theory of EEA and EES at the aggregate scale. Aggregates were separated into four fractions using a dry-sieving procedure: >2, 1–2, 0.25–1, and <0.25 mm. We measured the EEA of soil carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes, and examined potential factors (soil physicochemical properties, microbial biomass, and litterfall [LF]) that may influence EEA and EES. Significantly higher (p < 0.05) EEA levels in all aggregates were found in MP than in PP. The average natural logarithmic ratio of C-, N-, and P-acquiring enzyme activities in our study was 1.44:1.21:1, which deviated from the global mean ratio of 1:1:1 and implied that soil microbes were limited by C and N. Moreover, the enzyme C:N ratio (EC:N), C:P ratio (EC:P), and vector length (VL) were markedly lower (p < 0.05) in bulk soil and most aggregates in MP compared to PP, suggesting that C limitation was more serious in PP than in MP. Furthermore, while the vector angle (VA) of bulk soil and four aggregate sizes were all <45° in both the PP and the MP, they were markedly higher (p < 0.05) in bulk soil and >2 mm aggregate in MP than in PP. This indicated that mixing N2-fixing species with Eucalyptus alleviated but did not eliminate N limitation. Our study also found that nitrate nitrogen (NO3−-N), total nitrogen (TN), and microbial biomass C:P ratio (MBC:MBP) were the main factors driving changes in EEA, while LF was a key factor controlling EES (p < 0.05). Overall, introducing N2-fixing species into the Eucalyptus plantation alleviated but did not eliminate C and N limitation. The results provide specific recommendations for soil-nutrient management in Eucalyptus plantations in subtropical China.

LITTERFALL, LITTER DECOMPOSITION AND NUTRIENT RETURN OF REHABILITATED MINING AREAS AND NATURAL FOREST IN PHANGNGA FORESTRY RESEARCH STATION, SOUTHERN THAILAND

Litterfall and litter decomposition play important roles in the maintenance of nutrient cycling and rehabilitation of degraded lands. Litterfall, litter decomposition and nutrient return were investigated in a 27-year-old Acacia mangium plantation on sandy and clay sites, and in a mixed plantation at the Phangnga Forestry Research Station, Phangnga Province, Thailand. Additionally, secondary and primary forests were investigated and compared with the values obtained from the Acacia mangium and the mixed plantations. The results indicated that litter production in A. mangium plantation on sandy and clay sites, and in mixed plantations (15.47, 11.68 and 7.89 t/ha/yr, respectively) was higher than that in the secondary and primary forests (6.34 and 6.92 t/ha/yr, respectively). The rate of litter decomposition was the greatest in the secondary forest (3.01/yr) and the lowest occurred in the primary forest (1.15/yr). The decomposition rate of the mixed leaf litter between native trees and A. mangium in plantations was higher than that of only A mangium leaf, except in the mixed plantations. A high initial nitrogen concentration in A. mangium could accelerate litter decomposition and improve litter quality in the mixed litter. In addition, the nutrient return in plantations was higher than that in the secondary and primary forests, especially for N. Increased litter production, high decomposition rate and nutrient return from A. mangium plantation had important roles in nutrient cycling, suggesting that a mixed plantation consisting of A. mangium and native trees should be considered for the reclamation of mining land. Keywords: litter decomposition, litterfall, mining rehabilitation, nutrient return, tropical forest

Phyllode inoculation provides a rapid protocol for preliminary screening of Acacia species for tolerance to Ceratocystis wilt and canker disease

Ceratocystis wilt and canker disease has devastated Acacia mangium plantations in south-east Asia. Current screening methodologies to identify resistant or tolerant germplasm use potted plants in a greenhouse as a preliminary screening to select material for field trials, but these tests are time-consuming, motivating a search for rapid screening protocols. In this study, inoculation procedures were tested on three species of Acacia, viz. A. mangium, A. crassicarpa and a hybrid of A. auriculiformis and A. mangium, using three isolates of Ceratocystis manginecans. Mycelial plugs were compared with spore suspensions as inoculum to infect artificial wounds on the stems of A. mangium potted plants. The rapid screening protocols involved inoculation of stem segments with mycelial plugs and detached phyllodes with a spore suspension, with susceptibility measured by lesion length on the stems or necrosis length on the phyllodes. Both mycelial plugs and spore suspensions produced a similar level of disease incidence, so either inoculum form can be used for an assay. The stem segments were prone to contamination by other fungi and to desiccation, while results from the potted plant and phyllode protocols showed similar trends of susceptibility among the Acacia clones and species. The ease, rapidity, and reproducibility of the phyllode inoculation protocol makes it a potential replacement for inoculation of potted plants as a preliminary screening protocol to identify disease tolerant A. mangium germplasm prior to field screening.

Survey, Identification, and Pathogenicity of Ceratocystis fimbriata Complex Associated with Wilt Disease on Acacia mangium in Malaysia

Ceratocystis wilt disease surveys were conducted in three selected Malaysian Acacia mangium plantations. These completed surveys revealed the occurrence of the wilt disease, with the incidence of infection ranging from 7.5% to 13.6%. Signs of wood-boring insects, bark peeling due to squirrel activity, and pruning wounds were often associated with this disease. The fungus most frequently isolated from the diseased trees was the Ceratocystis fungus. The analysis on the morphological characteristics has identified the fungus as Ceratocystis fimbriata complex. Phylogenetic analysis based on the sequences of the ITS, and concatenated sequences of EF1α-βT regions grouped the isolates within the C. fimbriata sensu stricto, in comparison to other C. fimbriata isolates. Pathogenicity tests were conducted on six to nine-month-old healthy A. mangium seedlings by inoculating these seedlings with eight out of the 16 isolates. The results demonstrated that all the isolates were pathogenic, with mortality beginning as early as two weeks after inoculation. However, an ANOVA test indicated a significant difference between the pathogenicity levels among the fungal isolates. The results also showed that pathogen aggressiveness was not correlated with geographical origin. A host range test was also conducted by using C. fimbriata SSB3 and FRIM1162 isolates against several forest plantation species. The findings suggested that only A. mangium was susceptible to C. fimbriata. The other species remained healthy with no symptoms of infection even after seven weeks of treatment, as compared to the A. mangium species, where between 38 to 60% of the inoculated plants had died. This study provides new information on the status of Ceratocystis wilt disease, especially on the occurrence and effects on A. mangium plantation, by giving insights on how to control and manage this ferocious plant pathogen in the future.

Effect of Acacia mangium Canopy on Physicochemical Characteristics and Nutrient Concentrations of the Soil at Ayer Hitam Forest Reserve, Malaysia

The establishment of an Acacia mangium plantation often alters physicochemical characteristics and nutrient concentrations of soils. We aimed to evaluate the invasive potential of A. mangium forest on the soil in Ayer Hitam Forest Reserve, Peninsular, Malaysia. To achieve the mentioned target, four different regions, namely, the open ground region (OG), Acacia mangium region (AM), transition region (TZ), and native forest region (NF), were selected and each of the regions was divided into six plots. Composite samples were randomly taken from subplots at 0–15 cm depth (topsoil) and 15–30 cm depth (subsoil). Some physicochemical properties such as soil moisture and texture, textural classification, bulk density and particle density, pH, electric conductivity (EC), exchangeable bases (EB) (Ca, Mg and K), cation exchange capacity (CEC), organic matter (OM), total nitrogen (TN), and available phosphorous (Av. P) were analyzed. The results of our study showed that the soil of the AM region, which was clay loam, contained clay (51%), silt (32%), and sand (16%). The chemical analysis of topsoil showed significant differences in terms of OM%, exchangeable- Ca, Mg, K (molc kg−1), N (%), gravitational water content (GWC), and Avail. P between all four regions. Additionally, the highest pH and OM of topsoil were seen in the AM region with 4.5% and 4.33%, respectively. In the subsoil, there were significant differences (p ≤ 0.01) in terms of EC (ds/m), OM (%), Exchangeable- Ca, Mg and K (cmolc kg−1), GWC, available phosphorus, and N (%) between all four regions. The highest GWC, N (%), and Ca (cmolc kg−1) were observed in the AM region with 16.00, 0.14%, and 0.64 cmolc kg−1, respectively. These results showed that A. mangium changed some soil characteristics due to its invasion potential. In summary, A. mangium showed high adaptability on degraded forest land and high ability to accumulate the soil physicochemical properties to enhance its growth.

N2O emissions in Acacia mangium stands with different ages, in Sumatra, Indonesia

We compared nitrous oxide (N2O) emissions in different-aged (1, 3, and 5 years) Acacia mangium plantations and secondary forests for two and a half years at three areas in Sumatra, Indonesia. N2O emission was high from November to March (rainy season) and low from May to November (relatively drier season). In the first year, the average ± standard deviation of annual N2O emissions in 1-year-old sites was 8.92 ± 2.29 kg ha−1 of N, which was larger than those in 3-year-old (2.58 ± 2.28 kg ha−1 of N) and 5-year-old (2.16 ± 1.12 kg ha−1 of N) sites and secondary forests (1.38 ± 0.45 kg ha−1 of N) (p < 0.001). However, there is no significant difference in N2O flux among treatments after the second year. Although nitrogen mineralization and nitrification potential did not differ among tree ages, inorganic nitrogen and NH4/NO3 ratio in 1-year-old acacia site in the first year were significantly different from those in the other aged forests and secondary forests. Results of linear mixed model suggest that water-filled pore space and nitrogen availability are key factors for N2O emission in these sites. N2O emission within 1 year after planting contributed to 41% of total emission during the 7-year rotation period. Therefore, reduction in N2O emission within 1 year after planting is important for the total emission from acacia plantation.

Different mechanisms underlying the divergent responses of soil respiration components to an introduction of N2-fixer tree species into Eucalyptus plantations

Soil respiration (Rs), primarily rhizospheric (Rr) and heterotrophic respiration (Rh) is an important CO2 efflux from soil to the atmosphere. Previous studies demonstrated that introducing N2- fixing species into plantations could increase soil carbon stock and modify carbon chemical composition by altering microbial community and associated enzymes activities. However, their responses of Rs and its two components (Rr and Rh) remain poorly understood. This study investigated how Rs and its components responded to the introduction of N2-fixer tree species in a subtropical eucalyptus plantation and to further ascertain its underlying mechanisms. We measured Rs and its components (Rr and Rh) and used phospholipid fatty acids (PLFAs) as bioindicators to study soil microbial communities and activities of four extracellular enzymes as indicators of soil microbial functioning in an 8-year-old pure Eucalyptus urophylla plantation (PP) and an 8-year-old mixed E. urophylla and Acacia mangium (N2-fixer tree species) plantation (MP) in subtropical China. We found that Rs was significantly reduced by approximately 12.5%, with divergent responses of Rr and Rh in the MP. Compared with PP, the Rr decreased by 41.7% and Rh increased by 36.6% in plantation with N2-fixer species. The decreased Rr in the MP was largely associated with a reduction in fine root biomass. In contrast, the increased Rh in the MP was induced by an increase in total microbial biomass, changing the microbial community structure and enhancing the activities of β-1,4-glucosidase. The enzymatic changes were associated with an increase in N availability. Our results indicate that shifts in both biotic and abiotic factors resulting from the introduction of N2-fixer species shaped changes in Rs and its components.

Shifts on archaeal community structure in pure and mixed Eucalyptus grandis and Acacia mangium plantations

Archaeal community has important contributors to nutrient cycling in the forest ecosystems. However, how soil-litter attributes shift their community structure remains poorly understood. To date, the structure of the archaeal community has never been reported either in pure or in mixed eucalypt and acacia plantations, especially in tropical soils. Here, we analyzed the archaeal community and performed correlations with C, N and P attributes in soil-litter layers of pure Eucalyptus grandis without (E) and with N fertilization (E + N), a mixed system of E. grandis and Acacia mangium (E + A), and a pure A. mangium (A) plantation. We extracted DNA from soil (0–20 cm) and litter samples at 27 and 39 months after planting and sequenced the archaeal 16S rRNA gene. We also analyzed the abundance of 16S rRNA and amoA genes by quantitative PCR and assessed the correlations between molecular data with soil-litter attributes (i.e., microbial and enzyme activities, and C, N and P contents). The high-throughput sequencing of the archaeal 16S rRNA gene revealed that the treatments influenced the archaeal community structure. However, the litter layer showed more significant modifications, since archaeal richness, diversity, and the relative abundance of Thaumarchaeota increased in the litter of pure acacia and mixed treatments at both, 27 and 39 months after planting. There was no clear pattern regarding the abundance of functional genes in the soil, but archaeal structure responded to treatments in the litter layer, in which NH4+, total-N and the C/N ratio were the most important attributes for community group differentiation. Our study provides novel insights into the structure and function of archaea in pure and mixed forest systems, but highlights that young mixed plantations exert a low effect on soil community structure. Archaeal community may have an important role in nutrient cycling in the litter interface, especially related to the N cycle in the initial stages of tree development.

KEANEKARAGAMAN JENIS TUMBUHAN BAWAH TANAMAN AKASIA (Acacia mangium Willd) DI BUKIT PENGHIJAUAN MANDOR KABUPATEN LANDAK

Acacia mangium plantations in Bukit Penghijauan has grown by various species of understoreys. This study aims are to examine uderstoreys diversity and determine the amount of species and dominant of understoreys that’s growing under Acacia stands in Bukit Penghijauan Mandor Landak District. The study used a survey method with a systematic sampling of squares. Laying of plots was carried out by purposive sampling in area where are acacia plants. The size of plot is 10 m x 10 m, devided in to 25 sample plots of size 2 m x 2 m. Prymary data on taken involve species name, amount of individuals each species and herbarium specimens as identification device. The study result swowed that understoreys that be discovered under acacia stands in Bukit Penghijauan Mandor Landak District as much 21 species. The domination that species is paku resam (Gleichenia linearis Burm Clarke), rumput bede (Paspalum conjugatum Berg) and akar rambat (Psychotria sarmentosoides).Keywords : Bukit penghijauan, Species diversity, Understoreys.

Long-term structural and functional changes in Acacia mangium plantations in subtropical China

Subtropical China has a large area of Acacia mangium plantations; however, some key aspects of the structural and functional changes and the associated mechanisms after planting are still not well understood. We established a permanent plot in an A. mangium plantation and monitored the plant diversity (i.e., the number of species), biomass, soil physical and chemical properties and light transmittance from 1984 to 2018. Protocols for standard observation and measurement of Chinese Ecological Research Network were adopted. The total number of species in the plantation increased gradually from 3 to 38 during the 34-year period. The biomass in the tree layer initially increased rapidly from 1.60 to 185.01 t/ha within 7 years and then slowly increased to 188.69 t/ha during the following 27 years. The soil fertility of the A. mangium plantation improved continuously over the 34-year period. Vegetation restoration had positive effects on soil properties, such as soil moisture, soil bulk density, soil organic matter and soil total nitrogen and available phosphorus contents. The structure (i.e., plant diversity and light transmittance) and function (i.e., biomass and soil fertility) of the A. mangium plantation were not restored synchronously after 34 years of development. However, considering that the tree species richness in the natural forests in this region was 134, this plantation has slowly transformed from plantation to a natural forest. Artificial intercropping with native tree species can facilitate succession to a natural forest.

Biomass and carbon storage in an age-sequence of Acacia mangium plantation forests in Southeastern region, Vietnam

Aim of the study: The major objective of this study was to estimate the biomass increment and carbon (C) storage of the main ecosystem components in an age-sequence of three Acacia mangium plantation stands.Area of study: Chang Riec Historical - Cultural Forest, Southeastern region, Vietnam.Material and methods: In order to assess the biomass of different tree components, 36 trees with diameter at breast height ranging from 13.38 to 22.87 cm were harvested from the different aged stands. Biomasses of understory (shrubs and herbs), and litter were also determined. Carbon storage in the trees and understory biomass, litter, and mineral soil (0-50 cm) were determined by analyzing the C content of each compartment.Main results: The biomass in trees, understory vegetation, litter, and ecosystem increased with stand age. Soil C represented 61.99% of the total, aboveground tree biomass C made up 26.73%, belowground tree biomass C accounted for 7.01%, and litter comprised 2.96%, whereas only a small amount (1.30%) was associated with understory vegetation. The average C content of total tree (47.97%) was higher than those of understory and litter. Soil organic C stock in the top 50 cm depth in 4-, 7- and 11-year-old stands of A. mangium were 86.86, 126.88 and 140.94 Mg. C ha-1 respectively. Soil C concentration decreased continually with increasing soil depth. Total C storage of three planted forests ranged from 131.36 to 255.86 Mg. C ha-1, of which 56.09 - 67.61% of C storage was in the soil and 26.88 - 40.40% in the trees.Research highlights: These results suggest that A. mangium is a promising afforestation tree species with fast growing, high biomass accumulation and high C sequestration potential.Keywords: Acacia mangium plantations; Biomass; Ecosystem carbon storage; Age-sequence; Vietnam.

Soil Characterisation Assessment of the Acacia mangium Plantation at Dakoura, Linden

Research suggests that bauxite mining causes extensive damage to soils, alters microbial communities, and affects vegetative health. At the Dakoura mined-out site at Linden, Upper Demerara-Berbice (Region X), reclamation work by the Guyana Geology and Mines Commission aimed to re-establish ecological integrity at this disturbed area. Acacia mangium was selected for site reclamation due to its ability to restore soil fertility and cope in extreme conditions, such as highly acidic soils.

Phytophthora acaciivora sp. nov. associated with dying Acacia mangium in Vietnam.

Acacia mangium plantations account for more than 50 % of the exotic plantations in Vietnam. A new black butt symptom was discovered in 2012, followed by the wilting sign in Acacia seedlings in Tuyen Quang Province. Isolations recovered two Phytophthora species, the well-known Acacia pathogen P. cinnamomi, and an unknown species. The new species is described here as Phytophthora acaciivora sp. nov. Phylogenetically this species resides in clade 2d and is most closely related to P. frigida. Phytophthora acaciivora is a heterothallic species, oospores are aplerotic and antheridia are amphigynous. It produces predominantly elongated ovoid, semi papillate, persistent sporangia, no hyphal swellings and no chlamydospores. Optimum temperature for the growth is 25-30 °C and the maximum temperature is over 37.5 °C. Studies are underway to determine the impact of this new species on Acacia plantations in Vietnam.

Effect of harvest residue management on soil properties of Eucalyptus hybrid and Acacia mangium plantations planted on steep slopes in northern Vietnam

Burning harvest residues during site preparation can compromise the soil-nutrient stock in short-rotation plantations, but this practice remains common in northern Vietnam. This study compared the effect of two contrasting harvest-residue treatments (burning vs retention) on soil total carbon (TC), total nitrogen (TN), extractable P (ext-P), exchangeable K (exch-K) and bulk density (BD) of two adjacent randomised complete-block trials, one of Eucalyptus hybrid (Eucalyptus urophylla × E. pellita) and the other of Acacia mangium planted on steep slopes. Harvest-residue management had no effect on soil properties of either E. hybrid or A. mangium two years after planting. Soil pH in E. hybrid increased and exch-K in A. mangium decreased during the first year; ext-P decreased over time in both species though this was only significant in the residue-retention treatment in A. mangium. Slope significantly influenced pH and TC of E. hybrid and TC and TN of A. mangium. It appeared that slope position and correlative factors such as surface runoff and erosion had led to the observed distribution of some soil properties along the steep slope.

Implementing Occupational Safety and Health Management System in a Forest Management Unit (FMU) X: A Financial Analysis

Occupational safety and health (OSH) issues in the Indonesian forestry sector have not been addressed properly even though activities in this sector pose a high risk of OSH disorders. The standard instrument (applies on a national scale) to ensure OSH protection in each business units is the Sistem Manajemen K3 (SMK3, Government Regulation Numbered 50 Year 2012). At present, not many forest management units in Indonesia are willing to implement integrated SMK3, because of the assumption that SMK3 is a cost-centered activity. This study aims to present an overview of SMK3 implementation cost (for 64, 122, and 166 criteria) in a Forest Management Unit (FMU) X, as well as analyzing financial capacity of the FMU X to allocate sufficient funds for the SMK3 implementation. The results showed that the Acacia mangium plantation in the FMU X is a feasible business, indicated by the Net Present Value (NPV) of IDR377,690,545, Benefit-Cost Ratio (BCR) 3.96, and Internal Rate of Return (IRR) 25.02%. Further analysis shows that FMU X has good financial ability to support any cost required in implementating SMK3. It is the best for the FMU X to implement 166 criteria (advanced level) of SMK3 (at a cost of IDR704,598/ha/year, NPV of IDR376,393,262, BCR 3.92, and IRR 24.75%).