Growth variations and heritabilities of teak CSO-derived families and provenances planted in two humid tropical sites

Sixteen families derived from a clonal seed orchard (CSO) and 10 “provenances” (Prov) of teak (Tectona grandis) were tested in two different sites to be compared with respect to their growth performances. Both sites were located in Sabah, East Malaysia, under 2,500 mm of annual rainfall and no distinct dry season. The land in Taliwas was flat but prone to waterlogging. In Luasong, the soil was more hilly, acidic, and less fertile, though deeper. Nearly 9 years after planting, the two classes of genetic entries showed significant differences for height (P?=?0.0002) and diameter at breast height (DBH) and volume (P?<?0.0001) for the two sites combined. The superiority of the CSO families compared with the Prov class was more obvious in Luasong with averages of 18.0 vs 15.2 m (+18.6 %) for height, 18.1 vs 15.1 cm (+20.2 %) for DBH, and 0.179 vs 0.107 m³ for individual tree volume (+67.9 %), as against 17.4 vs 15.7 m (+11.2 %), 19.1 vs 16.8 cm (+13.5 %), and 0.176 vs 0.126 m³ (+40.3 %), respectively, in Taliwas. The CSO families were also more prone to site interaction for height (P?=?0.004) and, to a lesser extent, for volume (P?=?0.017) than the “Prov” (P?=?0.030 and P?=?0.057, respectively). Narrow-sense heritabilities estimated for the 16 CSO families across the two sites were lower for DBH (0.17) and volume (0.23) than for height (0.38). Type B genetic correlations suggested also higher site × families interactions for height (r _B?=?0.28).     

Bayesian estimation of genetic parameters for growth,stem straightness,and survival in Eucalyptus globulus on an Andean Foothill site

Knowledge of the genetic variation of key economic traits in Eucalyptus globulus under cold conditions is crucial to the genetic improvement of environmental tolerances and other economic traits. A Bayesian analysis of genetic parameters for quantitative traits was carried out in 37 E. globulus open-pollinated families under cold conditions in southern Chile. The trial is located in the Andean foothills, in the Province of Bío-Bío. The Bayesian approach was performed using Gibbs sampling algorithm. Multi-trait linear and threshold models were fitted to phenotypic data (growth traits, survival, and stem straightness). Fifteen years after planting, height, diameter at breast height, and stem volume were found to be weakly to moderately heritable with Bayesian credible intervals (probability of 90 %): $ {\widehat{h}}^2 $ ?=?0.009–0.102, $ {\widehat{h}}^2 $ ?=?0.031–0.185, and $ {\widehat{h}}^2 $ ?=?0.045–0.205, respectively. Stem straightness was found to be weakly to moderately heritable ranging from 0.032 to 0.208 (Bayesian 90 % credible interval); posterior mode $ {\widehat{h}}^2 $ ?=?0.091. Tree survival at age of 15 years was high in the trial (84.8 %) with such heritability values ranging from 0.072 to 0.157. Survival was non-significantly genetically correlated to growth and stem straightness. Stem volume had the highest predicted genetic gains ranging from 17.9 to 23.7 % (selection rate of 15.8 and 8.3 %, respectively). The results of this study confirm the potential for selective breeding of this eucalypt in areas of southern Chile where cold is a significant constraint.     

红锥家系遗传变异与优良家系选择

为选择红锥(Castanopsis hystrix)优良家系,对2–11年生红锥家系的生长性状和遗传参数进行了研究分析。结果表明,家系间在树高、胸径和单株材积上的差异达显著或极显著水平,家系的树高、胸径和单株材积受中等或中等以上遗传控制,具有很强的家系和家系内单株选择潜力;家系的单株材积变异幅度较大,胸径居中,树高的较小,显示出红锥家系间存在着丰富的变异;家系和单株遗传力随林龄的增大逐渐变小,到7–9年生时逐渐稳定。年度生长性状的相关分析表明,树高、胸径和单株材积的遗传相关系数随林龄逐渐增大,到7年生时最大,分别达到0.9602、0.9340和0.9849,之后趋于稳定,因此,7年生可作为早期选择的适合年龄。结合早期选择及形质指标,11年生时最终选择出优良家系10个,其平均树高、胸径和单株材积分别为13.95 m、14.34 cm和0.1229 m3,平均遗传增益分别为12.24%、18.69%和51.59%,其通直度、圆满度、分枝角度、最大分枝、冠幅、枝下高等形质指标也提高7.71%~12.94%。     

樟子松人工林树冠表面积及体积预估模型的研究

基于樟子松(Pinus sylvestris var. mongolica)人工林6块固定标准地30株枝解析数据,在分析树冠表面积和树冠体积与林分变量和林木变量的基础上,利用幂函数建立了树冠表面积（CSA）和树冠体积(CV)的预估模型,同时还对林木材积生长量与CSA和CV进行了相关分析。研究结果表明：樟子松人工林树冠表面积和树冠体积随着林木胸径、树高和冠长的增大而增大,林木材积生长量与树冠表面积和树冠体积均明显呈线性关系。不同林分条件的樟子松人工林CSA和CV随林分年龄和胸径的增大而增大,CSA随林分密度的增大而减小,而CV与林分密度相关不紧密。林分树冠表面积和树冠体积预估模型的检验结果表明,两个模型的平均相对误差都在±8%之内,预估精度均大于91%,说明所建模型可以很好地预估樟子松人工林不同林分条件下的林木树冠表面积和树冠体积。     

Testing a method for reconstructing structural development of even-aged Abies sachalinensis stands

Accuracy of a stand reconstruction technique was examined by comparing the estimated values of the aboveground biomass, total stem volume, stem volume growth, and stand density of Abies sachalinensis stands to those observed between 1980 and 1998 in Hokkaido, northern Japan. Census data from two stands established in 1973, one fertilized and the other unfertilized, were used for the examination. The stand statistics in the past were estimated from the DBH and height of individual trees measured in 1998, data on the aboveground biomass and stem volume with bark for nine living trees of various sizes harvested in each plot in 1998 or in 1999, and data from the stem analysis of the same harvested trees. We showed that the reconstructed patterns of the frequency distribution in aboveground biomass and in stem volume were generally the same as those observed in both plots and in any year in the past (except for 1982 and/or 1980), and that the reproduced patterns of stand development over time were similar to those observed directly in the past. Accuracy in predicting stand statistics was generally in the order of ±10% relative error. We consider that the present method of stand reconstruction could be used to estimate aboveground biomass, total stem volume, and stem volume growth of a stand in the past. Interpretation of results for the early years (1982 and 1980) and for the stand density requires caution.     

Provenance tests for survival and growth of 50-year-old Japanese larch (Larix kaempferi) trees related to climatic conditions in central Japan

Survival and growth of Japanese larch (Larix kaempferi) from 25 provenances in the natural distributional range were examined at three test sites in central Japan. Climatic conditions of the sites and provenances indicated a contrast between northwest and southeast locations across the distributional range. Density, height, diameter, and crookedness of stems and width and length of branches were measured for 50-year-old trees, and per-area cross-sectional area and volume of stems were calculated. Variance components among the provenances were large in the stem area and volume (27–33 %) and the branch width (26 %); those among the sites were large in the stem height, diameter, and density (70–81 %); and those of interaction between sites and provenances were small (0–12 %) in all the variables. Principal component analyses showed that eastern provenances exhibited large size of stems and branches at most sites. Growth rate and maximum size at each site were estimated from fitting the stem volume at three ages (12, 31 or 32, and 50 years) to growth curves in logistic functions. Eastern provenances, where seasonal variation is least in temperature and most in precipitation, showed the highest performance of stem and branch growth. The findings from our long-term survey of the L. kaempferi provenance tests suggest climatic effects on survival and growth traits and potential provenances from which to select new breeding materials.     

The effectiveness of cloning for the genetic improvement of Mexican white cypress Cupressus lusitanica (Mill.)

Two trials on Mexican cypress Cupressus lusitanica Miller in the North Island of New Zealand were assessed for diameter at breast height and at one site, subjective scores for branch size and stem canker (caused by Seiridium spp.) at age 6 from planting. The trials comprised 15 open-pollinated families, represented by both cloned and seedling progeny. Linear mixed model methodology, using a spatial model for the residuals, was applied to estimate genetic parameters. Estimated narrow-sense heritabilities were moderate to high for diameter at breast height (range from 0.46 to 0.62), stem canker (≈0.30) and branch size (range from 0.23 to 0.45) and did not appear to differ significantly between propagule types for all traits. Clonally replicated progeny led to an increase in accuracy of selection for additive genetic merit when compared with seedling testing, with the improvement being greater for traits with lower narrow-sense heritabilities. Estimated additive genetic correlations between cloned and seedling progeny were moderate to high (≥0.65) for diameter and branch size, indicating that selection decisions would not be substantially changed using either propagule type for progeny testing. All estimates of non-additive genetic variation based on the cloned progeny were non-significant. The use of spatial analysis was effective for diameter and branch size, but not for stem canker. No significant genotype by environment interaction was detected for diameter. Implications of the results for breeding and deployment of C. lusitanica are discussed.     

Genetic variation in the susceptibility of Eucalyptus globulus to drought damage

Genetic variation in drought damage in Eucalyptus globulus was studied in a sublined trial series across four neighbouring sites in Western Australia linked by ten common families. The trials included approximately 400 open-pollinated families, encompassing 51 native stand collection localities and 19 subraces from throughout the geographic range of the species. Data were analysed using mixed models, with spatial analysis used to better identify genetic effects. Significant subrace differences in drought damage were detected, with both broad-scale, regional and localised clines evident. The quantitative genetic differentiation between subraces as measured by Q _ST (0.39?±?0.091) was significantly greater than the F _ST for neutral marker expectations and consistent with diversifying selection shaping the patterns of subrace divergence in drought susceptibility. This conclusion is supported by the significant association of subrace drought susceptibility with bioclimatic parameters, particularly those associated with temperature seasonality. Less drought damage was observed in subraces originating from areas with more temperature seasonality, but also less radiation and rainfall seasonality, less winter rainfall, higher radiation and higher temperatures in the warmest month. Significant additive genetic variation in drought damage was detected within subraces, with narrow-sense heritabilities ranging from 0.14 to 0.20. We argue that spatial genetic variation in drought susceptibility of E. globulus has been shaped by natural selection acting at multiple scales and discuss opportunities for exploiting this genetic variation in breeding and deployment programs.     

Sapwood to heartwood ratio affects whole-tree water use in dry forest legume and non-legume trees

We investigated vegetation structure, seasonal water use and leaf deciduousness in a seasonally dry forest of Dzibilchaltún, Mexico. Legumes, species which tend to dominate these forests, have an array of water-saving traits. We explored whether legume species had reduced water use under similar growth conditions as other non-legume species of this seasonally dry forest. Sap flux and conductive sapwood area were measured for eight legume and 12 non-legume species. Species abundance, diameter at breast height (DBH), wood density and seasonal leaf cover were characterized in 16, 10 × 10 m² plots. Seasonal stand water use was calculated using the sap flux and ecological data. As predicted, legumes presented lower whole-tree water use compared with sympatric non-legume species. This difference, however, was related to a higher allocation to non-conductive heartwood in legumes and not to differences in sap flux density. Differences in allocation were higher in wider stems (>10 cm DBH); legumes above 25 cm DBH presented nearly half the daily water use of non-legumes of similar size. Wet (July) and dry (March) season stand water use was 629,000 and 156,000 kg ha^?1 month^?1, respectively. During the wet season three non-legume species with high basal area dominated the stand water use, but due to early leaf fall in these species, dry season stand water use was dominated by the legumes.     

9年生枫香的遗传变异和优良家系单株选择

为选育枫香(Liquidambar formosana)优良家系,对其24个种源310个家系的遗传变异进行分析,采用多目标决策法选育用材林优良家系及单株。结果表明,9年生枫香胸径、树高、材积、第一枝下高、冠幅和树干通直度等性状在种源和家系间存在显著差异(P0.01),以云南富宁、广西凭祥和江西湖城3个种源的材积生长表现最佳。各性状的家系遗传力属于中等遗传控制,为0.24~0.44,单株遗传力为0.20~0.50。共选出优良家系26个和单株41株,优良家系的平均胸径、树高、材积、冠幅、树干通直度分别大于总体均值的19.63%、18.56%、52.16%、5.11%和4.03%;遗传增益分别为6.67%、8.24%、20.28%、1.82%和1.75%,优良单株平均材积大于总体均值的150.25%。这为枫香育种策略制定和生产应用等提供理论依据。     

A comparison of genetic information from open-pollinated and control-pollinated progeny tests in two eucalypt species

Genetic-parameter estimates and parental breeding-value predictions were compared from open-pollinated and control-pollinated progeny populations of Eucalyptus globulus and two populations of E. nitens. For E. globulus there were two types of open-pollinated populations (native stand open-pollinated and seed orchard open-pollinated) and two types of control-pollinated populations (intra-provenance and interprovenance full-sib families). For E. nitens there were two populations, a seed orchard open-pollinated population and intra-provenance full-sib families. Progeny tests were established across multiple sites and 2-year height and diameter were measured and volume calculated. Genetic parameters from native stand open-pollinated E. globulus were unlike the parameters from the other three E. globulus populations; heritability estimates were severely inflated, presumably due to high levels, and possibly differential levels, of inbreeding depression relative to the other populations. Estimates of dominance variance in the E. globulus full-sib populations were high, but were zero in the E. nitens population. Correlations among parental breeding values, predicted using data from the different populations, were generally low and non-significant, with two exceptions: predictions from the two E. globulus full-sib populations were significantly correlated (r=0.54, P = 0.001), as were predictions from the E. nitens seed orchard OP and full-sib population (r = 0.61, P = 0.08). There was some indication that superior parents of E. globulus native stand open-pollinated families also tended to have above-average breeding values based on the performance of intra-provenance full-sib offspring. The consequences of these results for exploitation of base-population collections from native stands are discussed.     

Genotypic variation in wood properties and growth traits of triploid hybrid clones of Populus tomentosa at three clonal trials

To better understand the genetic control of growth traits (tree height, dbh, and stem volume) and wood properties (basic wood density and fiber length) in triploid hybrid clones of Populus tomentosa, genetic relationships among selected wood properties with growth traits were examined in 5-year-old clonal field trials located in Yanzhou, Gaotang, and Xiangfen, northern China. In total, 180 trees from 10 clones were sampled from the three sites. The site had a moderate effect on basic wood density (BWD), stem wood dry weight (DWT), and tree growth and had a highly significant effect on fiber length (FL) (P?<?0.001). Clonal effects were also significant (P?<?0.05) for all studied traits (except for diameter at breast height (DBH) and stem volume (SV)). Clone × site interaction was significant for all the studied traits except for FL. The estimated repeatability of clonal means for FL (0.91) was higher than for BWD (0.71), DWT (0.62), tree height (0.62), DBH (0.61), and SV (0.55). Intersite genetic correlation estimates indicated that wood properties were more stable than growth traits. Phenotypic correlation estimates between SV and BWD ranged from ?0.29 to ?0.10.     

Costs of height gain in rainforest saplings: main-stem scaling, functional traits and strategy variation across 75 species

Background and Aims

Height gain plays an important role in plant life-history strategies and species coexistence. Here main-stem costs of height gain of saplings across species within a rainforest community are compared.

Methods

Scaling relationships of height to diameter at the sapling stage were compared among 75 woody rainforest plant species in subtropical eastern Australia using standardized major axis regression. Main-stem costs of height gain were then related to other functional traits that reflect aspects of species ecological strategies.

Key Results

Slopes (β) for the height–diameter (H–D) scaling relationship were close to 1·3, in line with previous reports and with theory. Main-stem volume to achieve 5 m in height varied substantially between species, including between species within groups based on adult height and successional status. The variation was largely independent of other species traits, being uncorrelated with mature plant height (H_max) and with leaf size, and weakly negatively correlated with wood density and seed size. The relationship between volume to reach 5 m and wood density was too weak to be regarded as a trade-off. Estimated main-stem dry mass to achieve 5 m height varied almost three-fold across species, with wood density and stem volume contributing roughly equally to the variation.

Conclusion

The wide range in economy of sapling height gain reported here is presumed to be associated with a trade-off between faster growth and higher mortality rates. It is suggested that wide diameters would have a stronger effect in preventing main-stem breakage in the short term, while high wood density would have a stronger effect in sustaining stem strength over time.     

Genetic stability of wood density and diameter in <Emphasis Type="Italic">Pinus radiata</Emphasis> D. Don plantation estate across Australia

Genetic variation for wood quality traits and diameter growth for radiata pine (Pinus radiata D. Don) at age 20/21 years was estimated from eight trials in Australia. The traits studied were wood density, acoustic time-of-flight (an indirect measure of stiffness) and diameter at breast height (DBH). Wood density and DBH exhibited significant additive genetic variation whereas non-additive effects were not significantly different from zero. Time of flight was also not significantly different from zero for both additive and non-additive effects, respectively. Average single-site heritability estimates (±SE) for wood density and DBH were 0.38 ± 0.10 and 0.16 ± 0.08, respectively. Pooled-site heritability estimates for wood density and DBH were 0.38 ± 0.10 and 0.08 ± 0.10, respectively. For density, there was little evidence of genotype-by-environment interaction (GEI) across the eight trials at the additive level (type B additive genetic correlation; r _BADD = 0.73 ± 0.08) and type B genetic correlation for full-sib families (r _BFS = 0.64 ± 0.08). In contrast, the type B additive genetic correlation for DBH was lower, (r _BADD = 0.51 ± 0.14), suggesting evidence of GEI. However, type B genetic correlation for full-sib families was moderate (0.63 ± 0.11) for DBH, suggesting that there may be some stable full-sib families. On the basis of the results of this study, GEI should be considered in order to optimise deployment of improved germplasm in Australia.     

Assessing the invasive potential of Eucalyptus globulus in Australia: quantification of wildling establishment from plantations

Eucalyptus globulus is one of the most widely planted temperate hardwood species in the world, and in Australia there are 538,000 hectares growing in plantations. Although it has been reported as invasive, quantification of E. globulus invasion is rare. We conducted surveys at two geographic scales to assess the level of, and factors influencing, wildling establishment from industrial E. globulus plantations in Australian. We surveyed 290 km of plantation boundary, both within (22 %) and outside (78 %) the species native range. In areas of relatively high establishment, a density triggered paired plot approach (plots with and without wildlings) was used to assess fine-scale factors influencing establishment. We recorded 4,939 wildlings (17/km), 98 % of which occurred within 10 m of the plantation edge (maximum 175 m). Establishment varied between regions, ranging from 1.2 to 39.6 wildlings/km. Generalized linear models showed that the probability of a wildling being present increased with plantation age, that wildling abundance was higher along burnt transects, as well as sites that received regular, relatively high rainfall and had lower mean annual temperatures. The only fine-scale/local factor influencing wildling presence was the reproductive output of the plantation. The current level of E. globulus establishment in Australia is low in comparison to other invasive forestry trees. However, given the relatively young age of the Australian estate, local and regional variation in establishment, and potential future changes in plantation management, monitoring is warranted. Implications for assessing the general invasiveness of Eucalyptus and possibilities for E. globulus wildling control are discussed.     

基于年轮分析的不同恢复途径下森林乔木层生物量和蓄积量的动态变化

基于树木年轮学与标准地调查法, 研究了川西亚高山林区3种恢复森林类型生物量、蓄积量及生产力动态变化特征, 旨在尝试年轮学在森林生长过程反演中的运用, 并探索不同恢复模式下森林生物量和蓄积量的动态变化。结果表明, 不同恢复类型发育至20年以后, 均进入生长加速期, 平均胸径间差异逐渐显著, 人工云杉(Picea asperata)林胸径增长最快, 明显高于天然恢复的次生桦木(Betula spp.)林和次生针阔混交林。在恢复过程中, 次生针阔混交林一直保持最高的林分平均地上生物量与林分蓄积量, 其地上平均生物量一直显著高于人工云杉林(p < 0.05), 在20年以后显著高于次生桦木林(p < 0.05)。与人工云杉林相比, 次生桦木林在25年前具有相对较高的生物量, 而在25年之后则低于人工云杉林。在0-20年桦木林林分蓄积量略高于云杉林, 而20年以后, 云杉林蓄积量则超过桦木林。不同恢复类型的生产力大小对比显示, 30年之前, 次生针阔混交林>次生桦木林>人工云杉林, 30年之后, 针阔混交林生产力仍然最高, 而人工云杉林则超过次生桦木林。川西林区次生针阔混交林恢复模式在生物量和蓄积量积累方面均具有显著优势。     

Soil Organic Carbon is Increased in Mixed-Species Plantations of Eucalyptus and Nitrogen-Fixing Acacia

Soil organic carbon (soil C) sequestration in forests is often higher under nitrogen (N₂)-fixing than under non-N₂-fixing tree species. Here, we examined whether soil C could be increased using mixed-species plantations compared to monocultures, which are less productive aboveground than mixtures. In addition, we compared soil C sequestration under N₂-fixing trees with non-N₂-fixing trees that received N fertilizer. Monocultures of Eucalyptus globulus (E) and the N₂-fixing Acacia mearnsii (A) and mixtures of these species were planted in a replacement series: 100%E, 75%E + 25%A, 50%E + 50%A, 25%E + 75%A and 100%A. Soil samples were also collected from fertilized monoculture treatments (100%EFer) of E. globulus (250 kg N ha^?1). Total organic C, N and phosphorus were determined at age 8 years at two soil depths (0–10 cm and 10–30 cm) and three density fractions of soil organic matter (SOM) were quantified for 0–5 cm depth. Soil C was highest in the 50%E + 50%A mixed stand and was highly correlated with aboveground biomass, not to the percentage of A. mearnsii in mixtures. This was largely due to soil C at 10–30 cm because there were no treatment effects on soil C at 0–10 cm. All density fractions of SOM at 0–5 cm increased with the percentage of A. mearnsii. In E. globulus monocultures, N fertilization did not increase soil C when compared with unfertilized stands. These results indicate that the inclusion of N₂-fixing trees into eucalypt plantations may increase soil C stocks through increased productivity.     

马尾松半同胞子代苗期与幼林生长变异分析及家系选择

为探讨马尾松改良种子园半同胞家系子代的生长变异情况,测定分析了26个家系1 年生苗高、地径和0.5年生、1.5 年生及2.5 年生幼林的树高、地径、胸径、材积和冠幅等生长指标。结果表明,各性状在家系间均存在极显著差异,参试群体的树高、胸径、材积和冠幅的家系遗传力大于0.8,且前三个性状的单株遗传力大于0.4,说明上述性状是遗传力较高的性状。2.5年生材积生长量显著高于普通生产种的优良家系有19个,入选率为73%,树高、胸径和材积的遗传增益分别为2.76%、3.60%和8.49%,与初级种子园混合种和普通生产种相比,其材积分别提高55.28%和218.28%。     

Partitioning of genetic variance and selection efficiency for alternative vegetative deployment strategies for white spruce in Eastern Canada

Genetic variances and selection efficiencies for growth traits of white spruce (Picea glauca (Moench) Voss) were estimated from clonally replicated full-sib progeny tests established both in nursery and field environments in New Brunswick, Canada. The available data included heights at 4, 5, and 6 years in the nursery test; height at 9 years, height, DBH, and volume at 14 years in the field test. Estimated variance components were interpreted according to an additive-dominance-epistasis model. For heights in the nursery test, while both non-additive and additive variances were important sources of genetic variation, the former decreased but the latter increased with age; among the non-additive genetic variance, the epistatic variance was much more important than the dominance variance. Different from the nursery traits, for traits in the field test, additive variance accounted for an average of 81% of the total genetic variance, whereas dominance variance explained most of the remaining genetic variance. Genetic parameters and selection efficiencies for three vegetative deployment strategies: deploying half-sib families (VD_FAM_HS), full-sib families (VD_FAM_FS), and multi-varietal forestry (MVF), were compared. Heritability estimates were moderate for VD_FAM_HS and VD_FAM_FS (0.61–0.72), high for MVF (>0.82) for the nursery heights, and high (>0.79) for the field traits for all strategies. Genetic correlations of volume at age 14 in the field test, the target trait for improvement, were strong (>0.85) with other field traits. Genetic correlations of VOL14 with the nursery heights were also strong (>0.71) at the half-sib and full-sib family levels, but were only moderate (>0.59) for MVF. Overall, practicing MVF is the most effective deployment strategy, yielding the highest genetic gains, followed by VD_FAM_FS and VD_FAM_HS, regardless of traits and selection methods. Furthermore, early selections for HT9 or for HT4–HT6 were very encouraging, resulting in higher gain in volume at age 14 on a per year basis.     

Nutrient limitation in rainforests and cloud forests along a 3,000-m elevation gradient in the Peruvian Andes

We report results from a large-scale nutrient fertilization experiment along a “megadiverse” (154 unique species were included in the study) 3,000-m elevation transect in the Peruvian Andes and adjacent lowland Amazonia. Our objectives were to test if nitrogen (N) and phosphorus (P) limitation shift along this elevation gradient, and to determine how an alleviation of nutrient limitation would manifest in ecosystem changes. Tree height decreased with increasing elevation, but leaf area index (LAI) and diameter at breast height (DBH) did not vary with elevation. Leaf N:P decreased with increasing elevation (from 24 at 200 m to 11 at 3,000 m), suggesting increased N limitation and decreased P limitation with increasing elevation. After 4 years of fertilization (N, P, N + P), plots at the lowland site (200 m) fertilized with N + P showed greater relative growth rates in DBH than did the control plots; no significant differences were evident at the 1,000 m site, and plots fertilized with N at the highest elevation sites (1,500, 3,000 m) showed greater relative growth rates in DBH than did the control plots, again suggesting increased N constraint with elevation. Across elevations in general N fertilization led to an increase in microbial respiration, while P and N + P addition led to an increase in root respiration and corresponding decrease in hyphal respiration. There was no significant canopy response (LAI, leaf nutrients) to fertilization, suggesting that photosynthetic capacity was not N or P limited in these ecosystems. In sum, our study significantly advances ecological understanding of nutrient cycling and ecosystem response in a region where our collective knowledge and data are sparse: we demonstrate N limitation in high elevation tropical montane forests, N and P co-limitation in lowland Amazonia, and a nutrient limitation response manifested not in canopy changes, but rather in stem and belowground changes.