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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 ...

Biotic and abiotic factors control aboveground biomass (AGB) and the structure of forest ecosystems. This study analyses the variation of AGB and stand structure of evergreen broadleaved forests among six ecoregions of Vietnam. A data set of 173 1-ha plots from 52 locations in undisturbed old-growth forests was developed. The results indicate that basal area and AGB are closely correlated with annual precipitation, but not with annual temperature, evaporation or hours of sunshine. Basal area and AGB are positively correlated with trees > 30 cm DBH. Most areas surveyed (52.6%) in these old-growth forests had AGB of 100–200 Mg ha−1; 5.2% had AGB of 400–500 Mg ha−1, and 0.6% had AGB of > 800 Mg ha−1. Seventy percent of the areas surveyed had stand densities of 300–600 ind. ha−1, and 64% had basal areas of 20–40 m2 ha−1. Precipitation is an important factor influencing the AGB of old-growth, evergreen broadleaved forests in Vietnam. Disturbances causing the loss of large-diameter trees (e.g., > 100 cm DBH) affects AGB but may not seriously affect stand density.

Forest plantation growers in Vietnam commonly burn residues after harvesting and often apply suboptimal amounts of nutrients during plantation establishment. We examined whether the retention of forest residue, and application of phosphorus fertiliser at higher rates, can increase rates of growth. A factorial combination of residue management (burning vs retention) and phosphorus fertiliser application at planting (15 vs 100 kg ha-1) treatments were applied at a steeply sloping site in northern Vietnam. Two adjacent experiments were established, one with Acacia mangium and the other with a Eucalyptus hybrid (Eucalyptus urophylla × Eucalyptus pellita). Standing volume and leaf area index in A. mangium were greater following burning; this was mostly attributable to the significantly higher survival rate of seedlings. Burning of residues was associated with increases in the number of large branches per tree, and a higher crown damage index (CDI). In the Eucalyptus hybrid, diameter and height responses to the higher rate of fertiliser were observed at age 6 and 12 months, but not beyond. High phosphorus application also led to higher CDI. Standard fertiliser treatment, applied in amounts equivalent to 17, 15 and 8 kg ha-1 of nitrogen, phosphorus and potassium, respectively, was adequate to meet the early growth requirement of eucalypt and acacia plantations at this site. The relatively low amounts of harvest residue and high fertility levels at the site may have masked more significant responses of trees to the silvicultural treatments applied in this study. On steep slopes, especially if soil is poorly fertile, harvest residue retention with adequate weed and termite control may be preferential to burning as it is closely correlated with reducing factors that negatively impact productivity, i.e. water run-off and soil erosion.

Most tropical forests outside protected areas have been or will be selectively logged because the timber industry is a main income-generating resource for many developing countries. Therefore, understanding the composition of commercial timber species and logging types is key for sustainable forest management in countries like Vietnam as they move toward fulfilling Reducing Emissions from Deforestation and Forest Degradation (REDD+) agreements. Seven 1-ha plots were surveyed in the Central Highland of Vietnam, and 18 commercial tree species from these plots, whose timber is widely used by local people for housing and furniture making and timber is easily sold at local markets for high prices, were analyzed. In total, 151 tree species with a diameter at breast height (DBH) of ≥ 10 cm were recorded. The 18 commercially valuable species assessed in this study accounted for 33.2% of all stems (total of 524 stems ha−1 for all species), 47.1% of basal area (total of 34.35 m2 ha−1 for all species), and 50.8% of aboveground biomass/AGB (total of 262.68 Mg ha−1 for all species). Practicing diameter-limit harvesting of all commercially valuable species with DBH of ≥ 40 cm, which is widely performed in Vietnam, will reduce the number of stems by 7%, basal area by 31.6%, and AGB by 38.2%. Because such harvesting practices cause severe ecological impacts on the remaining forest, logged forests may require > 40 years to recover the structure status of a pre-logged forest. In addition, the recovery of the 18 commercially valuable species may require a much longer time because they comprised 33.2% of stems. Permission for logging natural forests should be given in Vietnam to sustain lives of local communities, where logging has been prohibited. However, alternative harvesting systems, such as reduced-impact logging systems, should be considered. The systems selected must simultaneously generate economic returns for local people and respect the REDD+ agreements with regard to protecting biodiversity and reducing carbon emissions.

Forest plantation growers in Vietnam commonly burn residues after harvesting and often apply suboptimal amounts of nutrients during plantation establishment. We examined whether the retention of forest residue, and application of phosphorus fertiliser at higher rates, can increase rates of growth. A factorial combination of residue management (burning vs retention) and phosphorus fertiliser application at planting (15 vs 100 kg ha−1) treatments were applied at a steeply sloping site in northern Vietnam. Two adjacent experiments were established, one with Acacia mangium and the other with a Eucalyptus hybrid (Eucalyptus urophylla × Eucalyptus pellita). Standing volume and leaf area index in A. mangium were greater following burning; this was mostly attributable to the significantly higher survival rate of seedlings. Burning of residues was associated with increases in the number of large branches per tree, and a higher crown damage index (CDI). In the Eucalyptus hybrid, diameter and height responses to the higher rate of fertiliser were observed at age 6 and 12 months, but not beyond. High phosphorus application also led to higher CDI. Standard fertiliser treatment, applied in amounts equivalent to 17, 15 and 8 kg ha−1 of nitrogen, phosphorus and potassium, respectively, was adequate to meet the early growth requirement of eucalypt and acacia plantations at this site. The relatively low amounts of harvest residue and high fertility levels at the site may have masked more significant responses of trees to the silvicultural treatments applied in this study. On steep slopes, especially if soil is poorly fertile, harvest residue retention with adequate weed and termite control may be preferential to burning as it is closely correlated with reducing factors that negatively impact productivity, i.e. water run-off and soil erosion.Keywords: branch size, burning harvest residue, crown damage index, phosphorus application, slope position, tropical plantation

In this article we present the analysis of practical and economical use of the territory of Suoi Sap catchment basin, Son-La province, Vietnam. We used the data of a route survey, performed by the Vietnam National Forestry University, for the assessment. We analyzed the climatic conditions, soil and vegetation resources, and economical use of the territory. The research territory is located in the Northern, mountainous part of Vietnam. It was determined that the slopes of the length from 500 to 2000 m (87%) with steepness from 10 to 40 (90%) prevail in the catchment area. The amount of precipitation (rain) is more than 1750 mm, with most of them falling in summer-autumn (MaySeptember). This leads to the spread of erosion processes, an increase of polluted and degraded lands. In this regard, the organization of rational and efficient use of land should include the creation of optimal conditions for the reproduction and protection of soil fertility, increasing its role in agricultural production. The scientifically based analysis of the impact of natural and other factors on the state of land resources of the catchment area allows us to recommend the use of the most rational and correct criteria and methods of land use in the area. In general, the solution of this problem for similar territories of Vietnam requires the definition of criteria for the ecological and economic efficiency of land use, the analysis of land use, the development of a scientific and methodological approach to the qualitative assessment of land use control in the context of the development of an agrarian economy. WOCAT system has been used in the development of effective watershed land-use technologies.

SUMMARY This is the first study on carbon stock estimation in the tropical evergreen broadleaf forests in Central Highland, Vietnam. As result of selective logging and shifting cultivation, remaining forests are silviculturally classified to five categories by governmental standard basing on standing volume (V), including very poor forest (V ≤ 10 m3/ha), poor forest (10 300 m3/ha). Carbon stock of four pools including big trees (diameter at breast height/dbh ≥ 5 cm), short vegetation layer (dbh < 5 cm), necromass, and soil was measured by using 150 plots of 50 m × 50 m each. Soil carbon stock was assessed from soil samples taken to 30 cm depth. The results indicated total carbon stock increased from 75 tons C/ha in very poor forest to 199 tons C/ha in medium forest, and to 255 tons C/ha in very rich forest. Carbon stock in necromass was significant different (ANOVA; F(4,145) = 61.70, p < 0.001) amo...

What are the roles and responsibilities of different levels of government over forests and land use in Vietnam? Over the last two decades how have government priorities shifted? How has decentralisation been realised through changing land laws and forest protection and development programs? Which powers and responsibilities are centralized, and which are decentralized? What role do local people play?This report reviews the statutory distribution of powers and responsibilities across levels and sectors. It outlines the legal mandates held by national and lower level governments with regard to land and forest allocation, afforestation programs, rubber plantations, Payments for Forest Environmental Services (PFES), land use planning, and more. The review considers legal and policy changes in land use and forestry in Vietnam following the ‘doi moi’ reform in 1986 up to 2014.After a short introduction, the second section describes the decentralization process, including mechanisms for participation. The third section outlines sources of revenue available to different government levels from forest fees and payments for environmental services. The fourth section details the specific distribution of powers and arenas of responsibility related to multiple land use sectors across and within levels, and the fifth and final section concludes on the policy changes and processes in relation to observed forest cover change.The study was commissioned under CIFOR’s Global Comparative Study on REDD+, as part of a research project on multilevel governance and carbon management at the landscape scale. It is intended as a reference for researchers and policy makers working on land use issues in Vietnam.