Aboveground Tree Components Research Articles

Variation in the Basic Density of the Tree Components of Gray Alder and Common Alder

Species-specific basic density (BD) data are necessary to improve the indirect methods of biomass determination. The density of tree components (e.g., bark, branches, roots) is studied much less than that of stem wood. Nevertheless, ignoring the specific BD values of these components in biomass calculations can lead to errors. The study aims to investigate BD variation of aboveground and belowground tree components by studying a total of 162 gray alder (Alnus incana (L.) Moench) and common alder (Alnus glutinosa (L.) Gaertn.) trees. From them, 55 stumps were excavated to determine the BD of the belowground components. Our findings reveal that the volume-weighted BD of the stem (wood and bark) and the branch density of common alder are higher compared to gray alder. Both species have similar bark density, while the BD of belowground components is higher for gray alder. The stem wood density of both species increases upward from the stump to the top. Compared to gray alders, the stems of common alders have more distinct radial within-stem density variation. According to our results, the application of default Alnus spp. wood density values recommended in the IPCC guidelines for the calculation of total biomass and carbon stock is likely causing overestimation. The BD values obtained in our study on alders’ biomass components will allow for more accurate appraisals of total biomass and carbon stock for gray and common alder forests.

Aboveground carbon and nutrient distributions are hardly associated with canopy position for trees in temperate forests on poor and acidified sandy soils

High demands on forest for carbon storage and provision of timber and biofuel require precise and reliable estimates of the biomass, carbon and nutrient stocks in different tree compartments. Whether the fraction of biomass distributed in aboveground tree compartments and the carbon and nutrient concentrations varies systematically across trees in different canopy positions remains unclear despite its importance for understanding forest ecology. Here, we compared the distribution of biomass, carbon and nutrients from underlying carbon and nutrient concentrations between different aboveground tree compartments for 15 mature trees of European beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii) and Scots pine (Pinus sylvestris) with dominant, intermediate and suppressed canopy position.We show that carbon concentrations were relatively constant across tree compartments while nutrient concentrations increased from stem, bark, branches towards needles. Canopy position had only minor effects on carbon and nutrient concentrations and on the distribution of biomass, carbon and nutrients between aboveground tree components. Nutrient concentrations and stochiometric results confirm that the forests were affected by high N deposition and low availability of P and base cations.Our results imply that predictions from allometric scaling theory better apply to aboveground tree components than from functional equilibrium theory. Models aiming for estimating tree and forest biomass and carbon and nutrient stocks can apply equal biomass, carbon and nutrient stocks for trees independent of canopy position as a valid assumption but testing this assumption for a broader range of species and site conditions remains recommended.

Potential effectiveness of low-density plantings of manuka (Leptospermum scoparium) as an erosion mitigation strategy in steeplands, northern Hawke’s Bay, New Zealand

Background: Government-funded schemes introduced to encourage new afforestation (exotic and indigenous) include the establishment of low-density plantings (less than 1100 stems ha–1) of manuka (Leptospermum scoparium Forster et Forster f.) on steeplands with severe erosion susceptibility and considered marginal for pastoral production. There is, however, little quantitative data to establish when (i.e., how many years after planting) these plantings likely afford effective mitigation against the initiation of shallow landslides.Methods: Permanent sample plots [PSPs] were established within manuka plantings established in northern Hawke’s Bay, New Zealand, where above-ground growth metrics were recorded for plantings on three landform units including interfluve ridges, colluvial slopes, and slopes affected by landslides. The root systems of a small sub-set of manuka were hand-excavated and whole plants destructively sampled for analysis of differences in allometric relationships by year, between landforms, and for comparison of the above-ground components of trees within PSPs.Results: Six years after planting, interfluves and colluvial slopes were understocked by between 10 and 25%, and by up to 45% on sites previously affected by landslides. Root collar diameter (RCD) explained between 92 and 99% of the variation in manuka biomass. The overall above- and below-ground metrics for manuka excavated from interfluves were significantly greater (P<0.05) than those excavated from landslides. Irrespective of landform type, the greatest proportion of the mean total root length and biomass was found in the top 0–0.5 m of the soil profile, within a 0.5-m radius of the stump, and importantly, no roots were found below 1 m depth. The timing (years after planting) to attain canopy closure and root occupancy, if stands of m?nuka were to remain fully stocked, varies between landforms and would likely occur between 6.5 and 9 years after planting. However, variable rates in planting density, and of plant mortality, resulting in under-stocking would significantly delay this timing, particularly on landslide-affected slopes.Conclusions: Manuka planted at densities below 1100 stems ha–1 are unlikely to provide effective erosion mitigation on steep land until significant root mass develops below the depth of the shear plane at which most landslides occur. Increasing the planting density, reducing early seedling mortality by better management of weed competition, and/or their replacement (blanking) would probably improve the erosion mitigation effectiveness of future low-density manuka plantings.

Biomass estimation of aboveground tree components for Turkey oak (Quercus cerris L.) in south-eastern Turkey.

Biomass equations were developed for different components of oak trees (Quercus cerris L.), which have been managed in coppices at different development stages-small-diameter forest (SDF) and medium-diameter forest (MDF). In this context, four biomass regression models-two based on diameter at breast height (DBH) alone and two based on DBH and total tree height (H)-were developed for each of the crown, stem, and total aboveground biomass components. Akaike's information criterion (AIC), root mean square error percentage (RMSE (%)), mean absolute error percentage (MAE (%)), adjusted coefficient of determination (Adj.R2), and bias values were used to evaluate and compare the suitability of a total of 12 regression models developed for biomass components. As a result, in the estimation of crown biomass, only DBH-based models provided higher estimation accuracy than DBH-H-based models. For the most suitable model, estimated values were Adj.R2 = 0.60, bias = - 0.009, RMSE = 66%, and MAE = 41%. In models developed to estimate stem biomass, the estimation accuracy of DBH-H-based models was higher. In the goodness-of-fit statistics calculated for the most suitable model, Adj.R2, bias, RMSE, and MAE were 0.89, 0.010, 38%, and 23%, respectively. The models developed to estimate the total aboveground biomass were all close in terms of estimation accuracy. The biomass components (crown andstem) in the total aboveground biomass were proportionally as follows: crown at 38% and stem at 62% in the SDF stage, and crown at 35% and stem at 65% in the MDF stage, indicating lower crown and higher stem partitioning as the development stage increased.

Надземна фітомаса стовбурів Pinus Sylvestris L. у деревостанах північного степу України

Нормативно-довідникові дані є основним інформаційним базисом під час оцінювання біологічної продуктивності лісотвірних порід, зокрема сосни звичайної, у насадженнях різних лісорослинних зон України. Наведено результати моделювання надземної фітомаси компонентів стовбура дерев сосни звичайної у штучних деревостанах Північного Степу України. Математичному моделюванню підлягали такі компоненти надземної фітомаси стовбурів дерев сосни звичайної, як: об'єм деревини стовбура, об'єм кори стовбура та об'єм стовбура в корі. Представлено результати кореляційного аналізу та основні статистики об'ємів деревини, кори та стовбура в корі з основними таксаційними показниками досліджуваної породи – віком, висотою та діаметром на висоті 1,3 м дерева. Розроблено дво- і трифакторні регресійні алометричні моделі, які показують залежність об'єму компонентів надземної фітомаси дерев сосни звичайної від зазначених таксаційних характеристик. на підстаі отриманих моделей побудовано нормативно-довідникові таблиці для оцінювання компонентів надземної фітомаси стовбура дерев сосни звичайної у свіжозрубаному та абсолютно сухому станах. Показано, що надземна фітомаса деревини та стовбура в корі сосни звичайної збільшується із висотою та діаметром дерева. Водночас фітомаса компонента кори стовбура має тенденцію до зниження із висотою за сталої величини діаметра стовбура.

Structure, Diversity, and Carbon Stocks of the Tree Community of Kumasi, Ghana

Urban forestry has the potential to address many urban environmental and sustainability challenges. Yet in Africa, urban forest characterization and its potential to contribute to human wellbeing are often neglected or restrained. This paper describes the structure, diversity, and composition of an urban forest and its potential to store carbon as a means of climate change mitigation and adaptation in Kumasi. The vegetation inventory included a survey of 470,100-m2 plots based on a stratified random sampling technique and six streets ranging from 50 m to 1 km. A total of 3757 trees, comprising 176 species and 46 families, were enumerated. Tree abundance and species richness were left skewed and unimodally distributed based on diameter at breast height (DBH). Trees in the diameter classes >60 cm together had the lowest species richness (17%) and abundance (9%), yet contributed more than 50% of the total carbon stored in trees within the city. Overall, about 1.2 million tonnes of carbon is captured in aboveground components of trees in Kumasi, with a mean of 228 t C ha−1. Tree density, DBH, height, basal area, aboveground carbon storage, and species richness were significantly different among green spaces (p < 0.05). The diversity was also significantly different among urban zones (p < 0.0005). The DBH distribution of trees followed a modified reverse J-shaped model. The urban forest structure and composition is quite unique. The practice of urban forestry has the potential to conserve biological diversity and combat climate change. The introduction of policies and actions to support the expansion of urban forest cover and diversity is widely encouraged.

Quantifying aboveground components of Picea sitchensis for allometric comparisons among tall conifers in North American rainforests

Tree biomass is one of the most important variables for studying and managing forest ecosystems. With emphasis shifting from young forests grown for timber production to forests with old-growth characteristics, the need to quantify various components of individual trees in natural settings is increasing. Destructive methods are inherently limited by what is feasible to cut down, dissect, and measure. In contrast, crown mapping is a minimally invasive technique for quantifying aboveground tree components such as wood, cambium, bark, and leaves. Despite being applied mostly to large trees, it is generalizable to any woody plant and can be adapted to answer diverse questions about biology, ecology, and ecosystem functions. We present a generalized approach for non-destructively quantifying the three-dimensional structure and aboveground components of whole trees along with a new programmatic tool for error-checking, visualizing, and interacting with tree-level data. Crown-mapping data from 60 lowland rainforest Picea sitchensis trees are presented to demonstrate the utility of this method for deriving allometric equations of tree components based on ground measurements. The 60 trees range from 14 to 495 cm trunk diameter at breast height, 10 to 94 m tall, and include simple to structurally complex individuals in dominant to suppressed positions within forests varying widely in density. Final allometric equations explain > 90% of the variability in volumes and masses of bark, wood, and leaves; are applicable to P. sitchensis throughout much of its geographic range; and are conservative relative to equations based on smaller dissected trees. Dendrochronology and allometric equations demonstrate that Picea sitchensis radically out-paces both Pseudotsuga menziesii and Sequoia sempervirens in accumulation of aboveground biomass and leaves, becoming heavier (155 ± 9 Mg) than any living P. menziesii and almost half as heavy as any living S. sempervirens in <500 years.

Generalized biomass equations for Stone pine (Pinus pinea L.) across the Mediterranean basin

Accurate estimates of tree biomass are strongly required for forest carbon budget estimates and to understand ecosystem dynamics for a sustainable management. Existing biomass equations for Mediterranean species are scarce, stand- and site-specific and therefore are not suitable for large scale application.In this study, biomass allometric equations were developed for stone pine (Pinus pinea L.), a Mediterranean tree species with relevant ecologic and economic interest. A dataset of 283 harvested trees was compiled with above- and belowground biomass from 16 sites in three countries (Italy, Spain, Portugal) representative of the species’ geographical Mediterranean distribution. A preliminary approach comparing the ordinary least squares method and the mixed model approach was performed in order to evaluate the most appropriate method for nested data in the absence of calibration data. To quantify the sources of error associated with applying biomass equations beyond the geographical range of the data used to develop them, a residual analysis was conducted.The allometric analysis showed low intra-specific variability in aboveground biomass relationships, which was relatively insensitive to the stand and site conditions. Significant differences were found for the crown components (needles and branches), which may be attributed to local geographical adaptation, site conditions and stand management. The root biomass was highly correlated with diameter at breast height irrespective of the geographical origin. Biased estimates were found when using site-specific equations outside the geographical range from where they were developed.The new biomass equations improved the accuracy of biomass estimates, particularly for the aboveground components of higher dimension trees and for the root component, being highly suitable for use in regional and national biomass forest calculations. It is, up to the present, the most complete database of harvested stone pine trees worldwide.

Nutritional, carbon and energy evaluation of Eucalyptus nitens short rotation bioenergy plantations in northwestern Spain

Abstract: This study provides essential information related to the nutrient and carbon levels and the energy potential of Eucalytpus nitens (Deane & Maiden) Maiden bionenergy plantations located in northwestern Spain. Nutritional analysis showed that leaves and bark had the highest concentrations of N, P, K and Mg. Carbon concentration was constant for all above-ground tree components. Nutrients and carbon were analyzed at stand level according to plantation productivity. Stemwood, the main tree component at the end of the rotation, had the highest nutrient content, except for N and Ca, which were highest in leaves and bark respectively. Based on this study, the nutrient content per ha of above-ground biomass was 243-706 kg N, 44-122 kg P, 131-375 kg K, 121-329 kg Ca and 25-67 kg Mg at the end of the bioenergy rotation (6-12 years, depending on site quality) and 19-56 Mg C ha-1. Energy analysis showed a fairly constant Net Calorific Value for wood, 18.32 ± 0.19 MJ kg-1. The results obtained are valuable for selecting the most appropriate forest management system in these bioenergy plantations, and thereby promote the sustainable use of woody crops.

Ecosystem carbon pools of coppice-originated oak forests at different development stages

The carbon (C) pools of aboveground tree components (leaf, stem, branch, and stem bark), ground cover, organic, and mineral soil were examined and compared with three stand development stages based on the mean tree diameters [diameter at breast height (dbh) in which small-diameter forests (SDF) = 0–8 cm, medium-diameter forests (MDF) = 8–20 cm, and large-diameter forests (LDF) = 20–36 cm] in pure coppice-originated oak stands located in the northwestern Turkey. In tree components, only the stem C concentration differed significantly among the development stages. The total C pools of the total tree biomass changed between 13 and 89 Mg ha−1 from SDF to LDF. The C content of tree biomass was strongly correlated with dbh (R 2 = 0.83). The C contents of the ground cover differed significantly while the C contents in both organic soil layers were also markedly different and increased from SDF to LDF. The amount of C stored in the soil pedon was 84, 123, and 103 Mg ha−1, and the total ecosystem (without belowground tree parts) C pools were 97, 177, and 192 Mg ha−1, for the SDF, MDF, and LDF, respectively. Total ecosystem C content was significantly correlated (R 2 = 0.46) with dbh despite soil pedon C showed very weak correlation. The ratio between the C pool of the total aboveground tree components and total ecosystem C was 13 % in the SDF, 30 % in the MDF, and 46 % in the LDF. These results show that the soil was the main pool of C in the forests for all of the development stages.

Improving the robustness of biomass functions: from empirical to functional approaches

We developed precise, consistent, generic, and robust biomass equations for seven aboveground tree components of sessile and pedunculate oaks. These equations can be used to accurately estimate carbon stocks and fluxes in and out of the forest. Large uncertainties still persist when using existing biomass equations for larger scale applications. The objective of this study was to test two contrasting modeling approaches to obtain biomass estimates of various components (stem, stem wood, stem bark, crown, and three branch categories) for Quercus petraea and Quercus robur and to compare them in terms of predictive capacity, genericity, consistency, and robustness. All models were calibrated on a total of 117 oak trees sampled over a wide range of sites and stands and further tested on an independent data set of 33 trees. The “empirical” approach consisted in declining a common allometric equation based on two variables (diameter at breast height and total height) into all its possible forms and selecting the final model on purely statistical performances; the “structural” method was based on the fitting of a priori dedicated model forms for each component to allow a clear interpretation of the model parameters. For the stem components, both approaches resulted in similar statistical performances despite difference in model forms and number of parameters. Although equally performant on the validation data set for the total crown, only the structural model gave satisfactory results when applied to the independent data set. Both approaches failed to accurately predict the branch fractions on the validation data set. Using physically based model forms increased the robustness of the biomass equations.

Modelling biomass of young and dense Scots pine (&lt;i&gt;Pinus sylvestris&lt;/i&gt; L.) dominated mixed forests in northern Sweden

Biomass models for the biomass of above-ground tree components of Scots pine ( L.), Norway spruce ( [L.] Karst.) and birch ( Roth and Ehrh.) in young dense Scots pine dominated forest stands in northern Sweden were constructed. Destructive above-ground biomass sampling was conducted in naturally generated young, dense, Scots pine dominated mixed stands. Three sampling campaigns were undertaken, the first in 1997 and 1998. The second was six years later (2003), and the last 13 years after the first (2010). In total, 280 trees (126 Scots pine, 68 Norway spruce and 86 birches) were sampled from six different stands in northern Sweden. The sampled trees’ diameter at breast height (dbh) was in the range 1–22 cm (Scots pine), 1–21 cm (Norway spruce) and 1–11 cm (birch). Biomass predictions were tested using our models and the widely used biomass models originally constructed for managed stands. The results showed that the biomass allocation to tree components is different in unmanaged and managed young stands; higher foliage biomass and lower stem and branch biomass were detected in the unmanaged stands. The overall conclusion is that the biomass models for managed stands did not produce satisfactory biomass estimates in unthinned, dense, young stands.Pinus sylvestrisPicea abiesBetula pendulaBetula pubescens

Extending a Model System to Predict Biomass in Mixed-Species Southern Appalachian Hardwood Forests

Functions for estimating foliage, branches and nonmerchantable stem tops, merchantable stem, and total aboveground biomass for Appalachian hardwood trees were assembled and incorporated into an existing growth-and-yield simulator for mixed-species Appalachian hardwood forests. With these functions and user-defined stand table and stand characteristics, current estimates of biomass in the different aboveground tree components can be obtained by species and diameter class for a thinned or unthinned stand. In addition, future biomass estimates for a thinned stand can be obtained for a projection period of 1 to 10 years. These estimates can be used to assess forest ecosystem services of carbon sequestration and provide information that can be used to evaluate effects of different harvesting strategies on forest carbon and other nutrient pools. A comparison of these estimates to those obtained by the forest inventory and analysis (FIA) procedure, using data from eight FIA sample plots in the southern Appalachian region, indicated that estimating biomass directly from locally developed biomass equations may give biomass estimates for the tree bole and for tops and branches, that are different from those obtained by the FIA procedure.

Eucalyptus and Acacia tree growth over entire rotation in single- and mixed-species plantations across five sites in Brazil and Congo

The association of N2-fixing species (NFS) could be an attractive option for achieving a sustainable increase of Eucalyptus plantations (EP) productivity through a positive balance between facilitative effects and competition between species. A randomised block design was replicated at four sites (Cenibra, USP, Suzano and IP) in Southern Brazil and at one site in Congo. The development of mono-specific stands of Acacia mangium (100A) and Eucalyptus grandis or urophylla×grandis (100E), was compared with N fertilisation treatment (100E+N) and with mixed-species plantations in a 1:1 ratio (50A:50E), and in an additive series with varying densities of acacia for the same density of eucalypt (25A:100E, 50A:100E, 100A:100E). The objectives were to assess the effect of mixtures on tree growth and stand production, and the behaviour of the two species in contrasting soil and climatic conditions. Tree growth was monitored over stand rotation and the biomass of aboveground tree components estimated at mid-rotation and at harvesting age. Eucalyptus height was 13% higher in Brazil than in Congo. Favourable ecological conditions in Congo and Cenibra led to 50% higher Acacia tree height than at the other sites. A depressive effect of Eucalyptus neighbour trees on Acacia height and circumference growth, lower in Congo than in Brazil, was observed in the mixtures from age 1–2years onwards. Depressive effects of acacia on eucalypt height and circumference growth were low in USP, Suzano and IP, high in Cenibra, and not observed in Congo, in 50A:50E and 25A:100E. A positive though insignificant response to N fertilisation was only found in USP and Congo. Complementarity for light and soil resource capture between Eucalyptus and Acacia trees resulted in mean annual increments in total stand stemwood biomass (MAI) that were 7–15%, 6–12%, and 40% higher in the additive series than for 100E in Cenibra, USP and Congo, respectively at mid-rotation. Whilst lasting complementarity and facilitation in Congo led to 17–34% higher MAI in mixtures than for 100E at harvesting age, MAIs were not significantly higher in mixtures than for 100E in Brazil. Mixed-species plantations of Eucalyptus and A. mangium might enhance aboveground stand production on poor nutrient soils in warm and humid tropical climates with low water limitations.

Relationship between above-ground biomass allocation and stand density index in Populus x euramericana stands

The relationships between above-ground stem, branch, leaf masses and stand density index (SDI) were analysed in Populus×euramericana (Dode) Guinier stands in Jiangsu Province, China. The allometric equations developed in this study accurately estimated masses of above-ground and specific above-ground tree components in stands with different SDIs. The relationship between the mean above-ground mass w and the ratio of stem to the above-ground (wS/w) was examined. With increasing w, the stem mass ratio wS/w increased. Mean masses of above-ground and tree components decreased significantly with increasing SDI at age 9 years, indicating the presence of competition-induced limitations to growth. The mean above-ground mass‐SDI and mean component mass‐SDI were strongly correlated with above-ground mass-SDI and tree component mass‐SDI, respectively. An equation describing the relationship between the mean leaf area u and SDI was developed, which fitted well for the u-SDI data. Stem mass increment exponentially increased with increasing leaf area index.

Pattern of carbon allocation across three different stages of stand development of a Chinese pine (Pinus tabulaeformis) forest

AbstractThe pattern of carbon (C) allocation across different stages of stand development of Chinese pine (Pinus tabulaeformis) forests is poorly documented. In order to understand the effects of stand age on the C pool of the Chinese pine forest ecosystem, we have examined the above‐ and belowground C pools in three differently aged stands of Chinese pine in the northern mountains of Beijing, China, by plot‐level inventories and destructive sampling. Our results suggest that tree branch and foliage biomass should be estimated by age‐specific equations. Reasonably accurate estimates of tree stem, tree root, aboveground, and total tree biomass in a Chinese pine forest at different development stages were obtained using age‐independent allometric equations from tree diameter only. The ratio of belowground to aboveground tree biomass was relatively constant with stand aging, remaining around 21 %. The contribution of aboveground tree biomass C increased from 21 % of the total ecosystem C in a 25‐year‐old stand to 44 % in a 65‐year‐old stand, subsequently falling to 41 % in a 105‐year‐old stand, while the contribution of mineral soil C decreased from 64 % of the total ecosystem C in 25‐year‐old stand to 38 % in a 65‐year‐old stand, subsequently increasing to 41 % in a 105‐year‐old stand. The C stock of the total ecosystem and its aboveground tree, tree root, forest floor, and mineral soil components continuously increased with stand ageing, whereas the C stock of the understory showed a declining trend and contributed little to the total site C pool.

Carbon accumulation in the biomass and soil of different aged secondary forests in the humid tropics of Costa Rica

Efforts are needed in order to increase confidence for carbon accounts in the land use sector, especially in tropical forest ecosystems that often need to turn to default values given the lack of precise and reliable site specific data to quantify their carbon sequestration and storage capacity. The aim of this study was then to estimate biomass and carbon accumulation in young secondary forests, from 4 and up to 20 years of age, as well as its distribution among the different pools (tree including roots, herbaceous understory, dead wood, litter and soil), in humid tropical forests of Costa Rica. Carbon fraction for the different pools and tree components (stem, branches, leaves and roots) was estimated and varies between 37.3% (±3.3) and 50.3% (±2.9). Average carbon content in the soil was 4.1% (±2.1). Average forest plant biomass was 82.2 (±47.9) Mg ha −1 and the mean annual increment for carbon in the biomass was 4.2 Mg ha −1 yr −1. Approximately 65.2% of total biomass was found in the aboveground tree components, while 14.2% was found in structural roots and the rest in the herbaceous vegetation and necromass. Carbon in the soil increased by 1.1 Mg ha −1 yr −1. Total stored carbon in the forest was 180.4 Mg ha −1 at the age of 20 years. In these forests, most of the carbon (51–83%) was stored in the soil. Models selected to estimate biomass and carbon in trees as predicted by basal area had R 2 adjustments above 95%. Results from this study were then compared with those obtained for a variety of secondary and primary forests in different Latin-American tropical ecosystems and in tree plantations in the same study area.

Carbon accumulation in aboveground and belowground biomass and soil of different age native forest plantations in the humid tropical lowlands of Costa Rica

Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates. The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil) of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between 38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments of 7.1 and 5.3 Mg ha -1 year -1 for forest plantations of V. guatemal- ensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6% (±20.9) was found in structural roots. The soil (0-30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha -1 year -1 in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R 2 aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates and providing a more reliable account of the mitigation potential of forestry activities on climate change.

Aboveground biomass and nutrient allocation in an age-sequence of Larix olgensis plantations

Biomass and nutrient (N, P, K, Ca, Mg) stock in various aboveground tree components (stemwood, stembark, branches and leaves) were quantified in an age sequence of pure Larix olgensis plantations (20, 35, 53 and 69 years old) in Northeast China. The results show that the aboveground biomass allocation in various tree components was in the order of stemwood (62%–83%), branches (9%–21%), stembark (7%–11%) and leaves (1%–6%) for all stands. The proportion of stemwood biomass to total aboveground biomass increased whereas that of other tree components decreased consistently with stand age from 20 to 53 years old, but kept relatively constant with stand age from 53 and 69 years old. The nutrient allocation in various tree components generally followed the same pattern as the biomass allocation (i.e. stemwood > branches > stembark > leaves). The proportion of nutrient stock in leaves to total aboveground nutrient stock decreased consistently with increasing stand age, while that in stemwood increased with stand age from 20 to 53 years old but then decreased from 53 to 69 years old. The rate of nutrient removal for stands was estimated at different stand ages under different logging schemes, showing that the rate of nutrient removal would be unchanged when the rotation length was shortened to 20 years by the harvest of stem only, but greatly increased by the harvest of total aboveground biomass. The rate of nutrient removal would be a considerable reduction for all elements by debarking, especially for Ca.

Component respiration, ecosystem respiration and net primary production of a mature black spruce forest in northern Quebec

We measured respiratory fluxes of carbon dioxide by aboveground tree components and soil respiration with chambers in 2005 and scaled up these measurements over space and time to estimate annual ecosystem respiration (R(e)) at a mature black spruce (Picea mariana (Mill.) B.S.P.) ecosystem in Quebec, Canada. We estimated periodic annual net primary production (NPP) for this ecosystem also. R(e) was estimated at 10.32 Mg C ha(-)(1) year(-)(1); heterotrophic respiration (R(h)) accounted for 52% of R(e) and autotrophic respiration (R(a)) accounted for the remainder. We estimated NPP at 3.02 Mg C ha(-1) year(-1), including production of bryophyte biomass but not including shrub NPP. We used these estimates of carbon fluxes to calculate a carbon use efficiency [CUE = NPP/(NPP + R(a))] of 0.38. This estimate of CUE is similar to those reported for other boreal forest ecosystems and it is lower than the value frequently used in global studies. Based on the estimate of R(h) being greater than the estimate of NPP, the ecosystem was determined to emit approximately 2.38 Mg C ha(-1) year(-1) to the atmosphere in 2005. Estimates of gross primary production (GPP = NPP + R(a)) and R(e) differed substantially from estimates of these fluxes derived from eddy covariance measurements during 2005 at this site. The ecological estimates of GPP and R(e) were substantially greater than those estimated for eddy covariance measurements. Applying a correction for lack of energy balance closure to eddy covariance estimates reduces differences with ecological estimates. We reviewed possible sources of systematic error in ecological estimates and discuss other possible explanations for these discrepancies.