Features of some provenances in an international provenance experiment of Gmelina arborea

International efforts to explore genetic resources of Gmelina arborea Linn., Roxb. (gmelina) were formulated during the period 1969–1974 by the FAO Panel of Experts on Forest Genetic Resources. As a first step in the work in 1975, the Danish/FAO Forest Tree Seed Centre (later Danida Forest Seed Centre) initiated, together with a number of public and private organizations in more than 20 countries, an international provenance experiment. The experiment included 36 provenances of natural populations in India and Thailand together with 24 landraces from 20 countries. The provenances were included in 60 provenance trials, which were established in the mid-1970s by more than 20 host countries. The following paper gives a summary of the performance of provenances from different regions of India, Thailand, and from exotic plantations in various countries. The results show (1) that plants originating from exotic plantations grow well and yield good products as compared to plants originating from natural forests, so it is feasible to continue basing new plantations on existing ones, and (2) that introduction of new material from some natural forests may increase the possibilities for further improvement in yield and wood properties. Palabras clave: Fuentes de semilla, Gmelina arborea, Procedencias, Razas locales, Recursos genéticos Resumen.Durante el período de 1969–1974, un grupo de expertos en Recursos Genéticos Forestales de la FAO, organizó esfuerzos al nivel internacional para explorar los recursos genéticos de la Gmelina arborea, Linn., Roxb. (gmelina). Como un primer paso hacia este esfuerzo, en 1975 la FAO de Dinamarca Forest Tree Seed Centre (luego Danida Forest Seed Centre) inició, en conjunto con organizaciones del sector público y privado de más de 20 países, un experimento internacional de procedencias. El experimento incluyó 36 procedencias de poblaciones naturales en India y Tailandia junto con 24‘razas locales’ de 20 países. Las procedencias se incluyeron en 60 ensayos de procedencia, los cuales fueron establecidos a mediados de los 70, por más de 20 países anfitriones. En este artículo se presenta un resumen del desempeño de las procedencias de las diferentes regiones de la India, Tailandia, y de las plantaciones exóticas en varios países. Los resultados muestran (1) que las plantas originarias de plantaciones exóticas crecen bien y ofrecen buenos productos, comparadas con las plantas originarias de bosques naturales, por lo cual se puede concluir que es posible continuar desarrollando nuevas plantaciones de plantaciones existentes, y (2) que la introducción de material nuevo procedente de algunos bosques naturales, puede aumentar las posibilidades para mejorar aún más el rendimiento y las propiedades de la madera.     

World view of Gmelina arborea: opportunities and challenges

Gmelina arborea Roxb. (gmelina) occurs naturally in 11 countries in tropical and subtropical regions of Asia. Approximately 700,000?ha of gmelina have now been established in plantations, small woodlots and agroforestry settings in west-central and eastern Africa, southeast Asia, the South Pacific, and northern Latin America. It is expected that planting areas will expand to 800,000?ha by 2020. The species has generated interest because of its fast growth and quick return on investment. Its wood can be used for a multitude of products that range from pulp to furniture parts. Gmelina also has great utility in agroforestry systems. Intensive breeding and improved clones will bring better growth, more uniform wood, better disease resistance, and products of higher quality to both local and international markets. Several factors might limit the degree of improvement and use of gmelina: (a) the species is susceptible to insect attacks and disease which might limit plantation expansion, (b) artificial pollinations are labor intensive and sometimes difficult to complete successfully, thus delaying breeding cycles and deployment of elite populations and clones and (c) the wood density of gmelina is approximately 410?kg/m³ at 8 years of age, which is lower than most commercial species of eucalypts and acacias. Low density affects pulp yields and product strength. These challenges can be met by: (a) development of clones resistant to insect and disease attacks as a cost effective means to maintain plantation stocking and productivity, (b) development of one-stop pollination techniques to increase pollination success rates and reduce the work loads in breeding programs, and (c) utilization of the great tree to tree variation in wood properties in gmelina to develop new races of trees that have both desirable growth rates and dense wood. Access to a broad genetic base of gmelina is central to meeting these challenges.

Palabras clave: Conservación, Mejoramiento, Plantaciones, Propiedades de madera, Silvicultura

Resumen. La Gmelina arborea Roxb. (gmelina) es nativa de 11 países, en regiones tropicales y subtropicales de Asia. Hasta el momento, aproximadamente 700,000 ha de gmelina han sido establecidas en plantaciones, lotes de árboles y en sitios agroforestales en el oeste central y el este de África, el sureste de Asia, el Pacifico Sur y el norte de América Latina. Se espera que para el año 2020, las áreas de plantación se hayan extendido a 800,000?ha. Esta especie ha generado interés debido a su rápido crecimiento y pronto retorno de inversión. Su madera puede ser utilizada en una multitud de productos, los cuales van desde pulpa de madera hasta partes para muebles. Además, la gmelina es de gran utilidad en programas agroforestales. El mejoramiento genético intensivo y clones mejorados darán como resultado un mejor crecimiento, madera más uniforme, mejor resistencia a las enfermedades y productos de mayor calidad tanto para los mercados locales como los internacionales.

Existen varios factores que pueden limitar el grado de mejoramiento y el uso de la gmelina: (a) la susceptibilidad de la especie al ataque de los insectos y las enfermedades, lo cual puede limitar la expansión de las plantaciones, (b) las polinizaciones artificiales requieren de mucha mano de obra y son dificiles de completar lo cual demora ciclos de mejoramiento y la utilización de las poblaciones élite y clones, y (c) la densidad de la madera de la gmelina a los 8 años de edad, de aproximadamente 410?kg/m³, es más baja que la densidad de la mayoría de las especies comerciales de eucalipto y acacias. La baja densidad afecta los rendimientos de pulpa y la fortaleza del producto. Estos retos pueden ser superados por medio de: (a) el desarrollo de clones resistentes al ataque de insectos y enfermedades como una forma económica y efectiva de mantener la densidad de plantaciones y su productividad, (b) el desarrollo de técnicas de polinización de un solo paso para aumentar las tasas de éxito de la polinización y reducir las cargas de trabajo en los programas de mejoramiento, y (c) el uso de la gran variabilidad de las propiedades de madera de la gmelina de árbol a árbol, para poder desarrollar nuevas razas de árboles las cuales tengan buenas tasas de crecimiento, y una densidad de madera deseada. El acceso a una amplia base genética es clave para poder alcanzar estos retos.

     

Growth potential of Gmelina arborea at 3 years of age in Colombia

New Forests - Smurfit Cartón de Colombia, a pulp and paper company based in Cali, established six genetic and growth and yield trials of Gmelina arborea (gmelina) in the North and Southwest...     

云南石梓的生物学特性与利用

对云南石梓的生态学、生物学特性作了报道 ,并从木材、天然色素和香料、药用方面论述了它的开发利用价值。云南石梓生长期为 4～ 1 0月 ,花期为 2～ 3月 ,果熟期为 5月。新鲜种子发芽率为 93% ;干燥器贮藏 2a ,发芽率为 98% ;低温贮藏 1a,发芽率为 77%。低温、干旱、台风、虫害影响云南石梓的生长。云南石梓在医药原料、天然香料和色素方面有较好的开发利用前景     

Three year performance of international provenance trials of Acacia auriculiformis

The performance of 25 provenances in international trials on seven sites in four countries was assessed for survival and growth at 3 years. Of these provenances, seven were from Queensland, 12 from Northern Territory, Australia, and six from Papua New Guinea. Significant growth differences were found: (a) among provenances at four sites, (b) among the sites, and (c) between provenance regions. The interaction between sites and provenances as well as between sites and provenance regions was also significant. The poorest growth was recorded in Kanchanaburi, Thailand, while the best growth was in Banjarbaru, Indonesia. Stability analyses of the provenance x site interaction revealed eight provenances with high vigour and good tree form that were relatively stable across sites. These included Archer River, South Coen, Coen River and Wenlock River provenances from Queensland; Noogoo Swamp and Mann River provenances from Northern Territory; and North Bensbach and Old Tonda Village provenances from Papua New Guinea.     

Diseases and insect pests of Gmelina arborea: real threats and real opportunities

Gmelina arborea Roxb. (gmelina) is a rapidly growing tree, which due to its drought tolerance and excellent wood properties, is emerging as an important plantation species. Perhaps the greatest threat to plantations of this tree is damage due to pests and diseases. Numerous insect pests and pathogens have been recorded in stands of gmelina in areas where the trees are native. Some fungal pathogens have been introduced into areas where the trees have been established as exotics. Among these, leaf spot caused by Pseudocercospora ranjita is most widespread although it has not caused any substantial damage. A serious vascular wilt disease caused by Ceratocystis fimbriata in Brazil has caused the most significant failure of G. arborea in plantations. In plantations within the natural range of the tree, insects have caused substantial damage. Among these, the defoliator Calopepla leayana (Chrysomelidae) appears to be most important. No serious insect pest problems have been recorded where G. arborea is grown as an exotic. All indications are that pathogens and insect pests will become much more serious impediments to the propagation of gmelina in the future. However, excellent opportunities exist to resolve such problems through biological control of insects and integrated disease and pest management. In addition, gmelina can be vegetatively propagated and thus, breeding and selection for insect and pathogen tolerance will facilitate the propagation of healthy trees. Palabras clave: Control biológico, Cuarentena, Especies exóticas, Implementación operacional de clones Resumen. La Gmelina arborea Roxb. (gmelina) es un árbol de rápido crecimiento, el cual debido a su tolerancia a las sequías y a sus excelentes propiedades de la madera se está convirtiendo en una especie de importancia para las plantaciones forestales. Tal vez, la amenaza más grande para las plantaciones de estos árboles es el daño causado por las plagas y las enfermedades. En las áreas en donde la especie es nativa, se han reportado gran cantidad de plagas de insectos y de patógenos. Algunos hongos patógenos se han introducido dentro de las áreas en donde los árboles han sido establecidos como especies exóticas. Entre estos, las manchas de las hojas ocasionadas por el hongo Pseudocercospora ranjita, es el más extendido aunque no ha causado ningún daño sustancial. Una seria enfermedad de marchitamiento vascular causada por el Ceratocystis fimbriata en el Brasil, ha causado la pérdida más seria en las plantaciones de G. arborea. En las plantaciones dentro del rango natural del árbol, los insectos han causado un daño considerable. Entre estos insectos, el defoliador más importante parece ser el Calopepla leayana (Chrysomelidae). En las áreas en donde la gmelina crece como una especie exótica no se han reportado problemas con las plagas de insectos. Todo parece indicar que en un futuro, los agentes patógenos y las plagas de insectos se convertirán en un impedimento más serio para la progagación de la gmelina. Sin embargo, a través del control biológico de insectos y del manejo integrado de las enfermedades y plagas, existen excelentes oportunidades para resolver este tipo de problemas. Además, la gmelina puede ser propagada vegetativamente y por lo tanto su mejoramiento y selección facilitará la propagación de árboles saludables por su resistenciacia contra los insectos y los patógenos.     

Cultivation and utilization of Gmelina arborea in South Yunnan,China

New Forests - Gmelina arborea (gmelina) naturally occurs in four prefectures in southern Yunnan, China. The conservation status of the species is threatened or endangered depending on the locality...     

Genetic diversity in natural populations of Gmelina arborea: implications for breeding and conservation

Gmelina arborea is a valuable plantation tree species that is native to South and Southeast Asia. In this study, 534 samples representing 19 natural populations in India, China, Thailand and Myanmar were analyzed with 10 polymorphic microsatellite markers. The genetic diversity analysis revealed highly polymorphic loci (N_a?=?16.4), a good level of genetic diversity (H_o?=?0.56; H_e?=?0.83) and the deficiency of heterozygotes in G. arborea populations evidenced by positive fixation index and deviation from Hardy?CWeinberg Equilibrium in all loci and most populations. The Analysis of Molecular Variance attributed 21, 10 and 69% of total genetic diversity to among-region, among-population (within region) and within-population variation. Unweighted Pair Group Method with Arithmetic Mean dendrogram and Principle Coordinate Analysis revealed three separate clusters composed of China, India and Thailand/Myanmar that were consistent with geographical distance and the presence of natural barriers to gene flow. Populations from within India grouped together genetically consistent with geographical locations, with the exception of the Nowgong population (eastern India), that might have originated from the Kasa area (western India) with which it has high genetic similarity. Understanding genetic diversity and structure of G. arborea populations serve as an important reference for tree breeding programs and conservation strategy. Breeding populations of G. arborea should include selections from each of the major geographic regions to maximize genetic diversity and heterosis. Vegetative propagated clones of elite trees can be used for plantation to address the issue of high level of segregation among seed derived plants.     

Biomass production and C-sequestration of Gmelina arborea in plantation and agroforestry system in India

Tree based land use systems make a valuable contribution to sequester carbon and improve productivity and nutrient cycling within the systems. This study was conducted to determine biomass production, C-sequestration and nitrogen allocation in Gmelina arborea planted as sole and agrisilviculture system on abandoned agricultural land. At 5 years, total stand biomass in agrisilviculture system was 14.1 Mg ha⁻¹. Plantations had 35% higher biomass than agrisilviculture system. At 5 years, leaves, stem, branches and roots contributed 4.1, 65.2, 10.0 and 20.7%, respectively to total standing biomass (17.9 Mg ha⁻¹). Over the 5 years of study, trees had 3.5 Mg ha⁻¹ more C and 36 kg ha⁻¹ more N in plantation than agrisilviculture system. Biomass and C storage followed differential allocation. Relatively more C was allocated in above ground components in plantations compared to agrisilviculture system. C:N ratios for tree components were higher in stem wood (135–142) followed by roots (134–139), branches (123–128) and leaves (20–21). In agrisilviculture system crops recommended are: soybean and cowpea in rainy season; wheat and mustard in winter season. After 5 years, soil organic C increased by 51.2 and 15.1% and N by 38.4 and 9.3% in plantation and agrisilviculture system, respectively. Total C storage in abandoned agricultural land before planting was 26.3 Mg ha⁻¹, which increased to 33.7 and 45.8 Mg ha⁻¹ after 5 years in plantation and agrisilviculture system, respectively. Net C storage (soil + tree) was 7.4 Mg ha⁻¹ in agrisilviculture system compared to 19.5 Mg ha⁻¹ in G. arborea monoculture stands. The studies suggest that competitive interactions played a significant role in agrisilviculture system. Plantations were more efficient in accreting C than agrisilviculture system on abandoned agricultural land.     

The effects of some extrinsic and intrinsic factors on the proportion of vessels in Gmelina arborea Roxb.

Summary Wood samples of Gmelina arborea were collected from four different localities (sites) in Nigeria. The proportion of vessels was determined by a modification of Ladell's (1959) randomized dot technique. The site and plot effects on vessel proportion were not significant. The tree effect was very highly significant with a variance component of up to 25.4 per cent. The tree mean values of vessel proportion ranged from 9 to 21.3 per cent. There was no close correlation between tree mean values of vessel proportion and tree growth parameters (tree height, diameter at breast height and crown diameter). The effect of stem height was not significant. The effects of radii (the variation around the stem's circumference) and age were very highly significant with variance components of up to 21 and 11.7 per cent respectively. The differences in the values of vessel proportion for earlywood and latewood were very highly significant; the variance component was 22.9 per cent. Earlywood had a lower proportion of vessels than latewood (12 and 16 per cent respectively). Vessel proportion was not correlated with ring width. The effects of factor interactions were not practically important.     

Estimation of genetic parameters using spatial analysis of Pinus elliottii Engelm. var. elliottii second-generation progeny trials in Argentina

Non-spatial and spatial analyses were carried out to estimate genetic parameters for growth and stem straightness traits between ages 4 and 7 in two series of eight progeny trials of Pinus elliottii Engelm. var. elliottii (PEE) established in 2004 and 2008, comprising 429 open-pollinated families from Instituto Nacional de Tecnología Agropecuaria (INTA) tree breeding population in Argentina. A first-order autoregressive spatial mixed model was found to significantly improve the fit of the model, compared with the standard non-spatial mixed model approach, due to substantial spatial heterogeneity within sites. The average individual-tree narrow-sense heritability estimates based on this spatial analysis were 0.49 for diameter at breast height, 0.36 for total height, and 0.48 for volume, with stem straightness being low to moderate (average?=?0.11). The additive genetic correlation estimates between growth traits were positive (0.51?≤?\(\hat{r}_{a}\)?≤?0.99) and statistically significant from zero. In contrast, the genetic correlations between growth traits and stem straightness although in general also positive were not significantly different from zero (??0.22?≤?\(\hat{r}_{a}\)?≤?0.59). Age-to-age genetic correlations were consistently higher for growth traits (\(\hat{r}_{a}\)?≥?0.81) than for stem straightness (\(\hat{r}_{a}\)?≥?0.33). The average additive genetic correlation estimated between sites within test series was high for all traits evaluated (average?>?0.72). In contrast, average additive genetic correlation estimated between sites across series was slightly lower (average?<?0.63). Implications of all these parameter estimates for genetic improvement of PEE in Argentina are discussed.

     

Effect of management treatment and growing regions on wood properties of Gmelina arborea in Costa Rica

Gmelina arborea (gmelina) was introduced into Costa Rica through reforestation programs with federal incentives. Two areas where gmelina planting were most abundant were the North Pacific and North regions of the country that are representative of dry tropical and humid tropical climatic zones, respectively. This distribution pattern has led to plantations with different management regimes, which still exist today, namely intensive, intermediate and no management treatment. This research looks at the type of wood being produced in both climatic regions and the effect of management intensity. Preliminary results indicate that gmelina wood from the dry region has a higher heartwood percentage, higher specific gravity, better mechanical properties and higher absorption of preservatives when pressure treated than does wood from the humid regions. With regards to management intensity, the results indicate that plantations with no management produced higher specific gravity wood with better mechanical properties than those with intensive or intermediate management. There were no differences between intermediate and intensive management regimes in relation to heartwood percent, decay resistance, and preservative absorption using the dip-diffusion system. Palabras clave: Clima, Duramen, Peso específico básico, Manejo, Propiedades de madera Resumen. La Gmelina arborea fue introducida en toda Costa Rica a través de los programas de reforestación con incentivos fiscales por parte del estado. Las dos áreas en particular, en donde se plantó gmelina ampliamente, fueron la Pacifico Norte y Norte de Costa Rica las cuales representan un clima tropical seco y un clima tropical húmedo respectivamente. Estos patrones de distribución en la reforestación, dieron como resultado diferentes grados de manejo, los cuales existen todavía, con áreas con manejo intensivo, intermedio y sin manejo alguno. Esta investigación examina los diferentes tipos de madera que se está produciendo en las dos regiones climáticas y el efecto que tiene la intensidad en el manejo de las mismas. Los resultados preliminares han indicado que la madera de gmelina proveniente del clima tropical seco presenta un mayor porcentaje de duramen, una mayor peso específico básico, mejores propiedades de resistencia y una mayor absorción de los preservantes, cuando se utiliza el método vacío-presión, que la madera proveniente de regiones húmedas. No se encontraron diferencias entre los regímenes de manejo intermedio y manejo intensivo, con relación al porcentaje del duramen, resistencia al ataque de los hongos, y la absorción de los preservantes cuando se utiliza el sistema de difusión (dip-diffusion system).     

Biomass production and root distribution of Gmelina arborea under an agrisilviculture system in subhumid tropics of Central India

A study of an agrisilviculture system comprising Gmelina arborea and soybean (Glycine max) was conducted in the subhumid region of Central India. Above- and below-ground biomass production and distribution of coarse and fine roots were studied in 4-year-old G. arborea, planted at a spacing of 2 × 2 m, 2 × 3 m, 2 × 4 m and 2 × 5 m. The total biomass varied from 10.89 Mg ha^–1 to 3.65 Mg ha^–1 depending on the tree density. Among the different tree components, stemwood contributed maximum biomass (54.3–79.4%), followed by branches and leaves. Root distribution pattern showed that most of the coarse roots were distributed in the top 40 cm of soil, whereas fine roots were concentrated in the top 20 cm. Coarse root biomass decreased with an increase in spacing. The spread of roots was asymmetrical in trees planted at 2 × 2 m and 2 × 3 m spacings, while it was symmetrical in trees planted at wide spacings. No significant difference was observed in the fine root biomass in different stands. The root:shoot ratio increased with an increase in spacing. Crop (soybean) growth and productivity varied significantly and it increased with a decrease in tree density. Soybean yield varied between 1.5 Mg ha^–1 to 2.1 Mg ha^–1. The role of root architecture of G. arborea trees on productivity of crops under agri-silviculture system is discussed.     

Root distribution of Acioa barteri,Alchornea cordifolia,Cassia siamea and Gmelina arborea in an acid Ultisol

A major constrait to alley cropping is the competition of tree or shrub roots with those of companion food crops for available water and nutrients in the topsoil. Root distribution patterns of Acioa barteri, Alchornea cordifolia, Cassia siamea and Gmelina arborea grown on an acid Ultisol at Onne in the humid forest zone of southeastern Nigeria were examined to a depth of 120 cm and laterally to 200 cm from the tree trunk to study the suitability of the species for alley cropping. The four woody species have roots throughout the soil profile examined but differ in the concentration of roots both laterally and vertically. Alchornea cordifolia, Cassia siamea and Gmelina arborea, in spite of higher underground biomass production, most of their fine roots (<2 mm diameter) were in the top 20 cm of the soil. This soil layer had 73%, 76%, and 74% of the total Alchornea cordifolia, Cassia siamea, and Gmelina arborea fine roots in the profile examined, respectively. Such root systems would compete with food crops for nutrients and moisture in the surface soil. Alchornea cordifolia and Gmelina arborea have many large woody roots in the surface soil which will make any tillage operation or seedbed preparation difficult. Acioa barteri in contrast, has the desirable rooting system with fewer fine roots in the surface soil (49%), and roots that are concentrated close to tree trunk and decrease markedly away from the tree base. In addition, Acioa barteri roots penetrate deeper soil horizons and can result in more efficient nutrient cycling from these layers, and reduced competition with shallow-rooted food crops. The rooting distribution patterns of Acioa barteri indicated that the species is a promising alley shrub in acid soils of the humid forest ecology. Therefore, consideration of rooting characteristics of potential tree/shrub species is recommended for the development of agroforestry systems such as alley cropping.IITA Journal Paper No: 91:/JA/24.     

Sustainable site productivity and nutrient management in a short rotation plantation of Gmelina arborea in East Kalimantan,Indonesia

New Forests - Sustainable Forest Management (SFM) requires information on plant growth and nutrient dynamics in forest ecosystems. To obtain fundamental information for SFM in short-rotation...     

Family variation and potential for genetic gain in frost resistance of Pinus radiata

Twenty-three Pinus radiata seed orchard clones of the New Zealand 850 series were each control-pollinated with a mix of 10 pollens to produce polycross families. The seed was sown in open nursery beds. Seedlings were potted up at six times of the year and subjected to white advective frosts in controlled-environment rooms, with up to seven frosting runs of variable severities at each time. There were significant differences (p< <0.001) between families in frost injury, such that, although there was statistically significant family × time interaction, some families were consistently more frost resistant (tolerant) than others. No association between frost resistance and growth rate was evident.Individual-tree heritability estimates for frost damage scores were around 0.3 at given times, and 0.20 over all times. Prospective gain in resistance from progeny testing over several seasons of the year, with 2:23 selection, is about 1°C. An additional gain of 0.4°C resistance appears obtainable from 1:90 selection of individuals within pair-crosses in a single frosting run. This additional (within-cross) gain might be increased to around 0.75°C, with the same culling rate but testing one ramet per seedling at each of four times of the year.     

Genetic parameters for grain angle in 28-year-old Norway spruce progeny trials and their parent seed orchard

? Sawn wood which acquires twist during drying is a substantial problem for the sawmill industry and is to a large extent caused by spiralled grain in the tree.

? In this study, the feasibility of using spiral grain angles as a selection trait in Norway spruce (Picea abies (L.) Karst) tree breeding and the extent of grain angle and its breeding values were investigated. Grain angles under bark and diameter were measured at breast height in three 28-year-old Norway spruce progeny trials and in their parent seed orchard.

? The mean grain angle value was 1.76° in the progeny trials and 1.84° in the seed orchard. Estimated genetic standard deviations for grain angle were almost 1°. Progeny trial heritabilities (H ² > 0.3) were larger than the seed orchard heritability (H ² = 0.24). Genotype by environment interaction among the progeny trials was negligible for grain angle. Progeny trial grain angles exhibited genetic correlation with seed orchard grain angles in the range 0.66 to 0.84.

? Thus, mature wood grain angles are also under considerable genetic control, raising the opportunity to reduce the occurence of left-grained trees, which are prone to producing twisted wood.

     

Growth and mineral nutrition of Gmelina arborea Roxb. seedlings fertilized with four sources of nitrogen on a latosolic soil

The growth and mineral nutrition of Gmelina arborea Roxb. seedlings were investigated in response to four nitrogen-based fertilizers applied at 0, 2.5, 5.0 or 7.5 g N per plant. Nitrogen sources included NH(4)-N as ammonium sulfate, NO(3)-N as potassium nitrate, NH(4)NO(3)-N as calcium ammonium nitrate, and urea-N as urea. Seedlings fertilized with NH(4)NO(3)-N or urea-N had greater height, collar diameter, dry weight, net assimilation rate, and relative growth rate than seedlings fertilized with NH(4)-N or NO(3)-N. For all sources of nitrogen, increasing the amount of exogenously supplied N per plant promoted shoot growth more than root development, hence the root to shoot ratios of all fertilized seedlings were smaller than those of the unfertilized controls. Applications of NO(3)-N increased the nitrogen, potassium, and phosphorus concentrations of fertilized seedlings. Regardless of source, a nitrogen application of 2.5 g N per plant was apparently optimal for the growth of Gmelina seedlings on a latosolic soil.