Estimating biomass of individual pine trees using airborne lidar

Airborne lidar (Light Detection And Ranging) is a proven technology that can be used to accurately assess aboveground forest biomass and bio-energy feedstocks. The overall goal of this study was to develop a method for assessing aboveground biomass and component biomass for individual trees using airborne lidar data in forest settings typical for loblolly pine stands (Pinus taeda L.) in the southeastern United States. More specific objectives included: (1) assessing the accuracy of estimating diameter at breast height (dbh) for individual pine trees using lidar-derived individual tree measurements, such as tree height and crown diameter, and (2) investigating the use of lidar-derived individual tree measurements with linear and nonlinear regression to estimate per tree aboveground biomass. In addition, the study presents a method for estimating the biomass of individual tree components, such as foliage, coarse roots, stem bark, and stem wood, as derived quantities from the aboveground biomass prediction. A lidar software application, TreeVaW, was used to extract forest inventory parameters at individual tree level from a lidar-derived canopy height model. Lidar-measured parameters at individual tree level, such as height and crown diameter, were used with regression models to estimate dbh, aboveground tree biomass, and tree-component biomass. Field measurements were collected for 45 loblolly pine trees over 0.1- and 0.01-acre plots. Linear regression models were able to explain 93% of the variability associated with individual tree biomass, 90% for dbh, and 79–80% for components biomass.     

The use of forest-derived specific gravity for the conversion of volume to biomass for open-grown trees on agricultural land

Accounting for agroforestry contributions to carbon sequestration and cellulosic feedstock production requires biomass equations that accurately estimate biomass in open-grown trees. Since equations for open-grown trees are rare and developing these is expensive, existing forest-based equations are an attractive alternative for open-grown trees in carbon accounting and biomass modeling. How accurate this alternative is depends on how similar the key attributes, such as specific gravity, trunk shape, and crown architecture, are between open- and forest-grown trees. We evaluated the use of forest-derived specific gravity for conversion of volume to biomass for morphologically distinct open-grown species: green ash, ponderosa pine, and eastern redcedar. Trunk biomass was consistently and significantly underestimated from 6.3% to 16.6% depending on species, indicating open-grown trees have greater trunk specific gravity than forest-grown counterparts within the same geographic region; however a conclusive difference in branch specific gravity was not found between open- and forest-grown trees. Open-grown trees have greater trunk specific gravity, sharper trunk taper, and larger crown. When forest-based equations are used for trunk biomass of open-grown trees, the greater trunk specific gravity results in underestimation; however, the sharper trunk taper results in overestimation. Studies are needed to examine whether the underestimation could be offset by the overestimation and how the larger crown affects biomass estimation when forest-based equations are used for open-grown trees. Our results provide an essential understanding to interpret the biometric relationship of open- to forest-grown trees and to develop an efficient means how forest-based equations might be best modified for open-grown trees.     

Productivity, aboveground biomass, nutrient uptake and carbon content in fast-growing tree plantations of native and introduced species in the Southern Region of Costa Rica

Early growth performance of four native and two introduced tree species was studied during six years at 13 sites in the southern region of Costa Rica. Selected study sites represent a wide environmental gradient.The selected species were: Pinus caribaea Morelet var hondurensis (Barret y Golfari) and Gmelina arborea Roxb as the introduced species, and Terminalia amazonia (J.F. Gmelin) Exell, Vochysia ferruginea Mart., Vochysia guatemalensis Donn. Sm. and Hieronyma alchorneoides Fr. Allemao. A study about the distribution of aboveground biomass, nutrients and total carbon content of these young plantations by compartments (branches, stem, bark and leaves) was also conducted. Biomass equations for tree compartments were fitted simultaneously using the data corresponding to 24 trees felled. Total export quantities of nutrient from stem and bark biomass were estimated in order to conduct an evaluation of the potential effect of harvesting these species on soil nutrient reserves. The data presented in this study related to plantation growth, aboveground biomass and nutrient concentration and C content by tree compartment, aboveground biomass equations by tree compartment, soil nutrient reserves, stability indices can be used as a reference for: a) selection of tree species vs site characteristics, b) estimation of nutrient export by stem + bark harvesting, c) planning for a second rotation, c) maintenance of site productivity and d) generate better carbon sequestration estimations.     

Allometric equations for estimating above- and belowground biomass in Tea (Camellia sinensis (L.) O. Kuntze) agroforestry system of Barak Valley,Assam, northeast India

Tea (Camellia sinensis (L.) O. Kuntze) agroforestry has widespread implications for the earnings and food security for a large fraction of population in NorthEast India. It also has immense potentiality to act as a considerable reservoir of biomass carbon providing climate change mitigation options. In the present study an attempt was made to develop allometric equations for above- and belowground biomass estimation specific to Tea [C. sinensis (L.) O. Kuntze] in Barak Valley of northeast India. Relationships were developed through destructive sampling and regressing diameter alone and along height, wood density, crown area, branch count with biomass. Allometric power function equation and linear equivalents have been developed. Diameter singly could predict significantly aboveground biomass (AGB) root biomass (BGB) and total Tea biomass (TB) with over 95% accuracy. Whereas incorporation of height, crown area, wood density, branch count with diameter influenced the model in terms of modified coefficient of determination and minimized estimation errors. Branches, stem and leaves accounted 50, 21 and 6% of AGB respectively. Root biomass (BGB) contributed 23% of the total Tea bush biomass. The samples exhibited overall BGB/AGB ratio of 0.30 ± 0.08 and biomass expansion factor (BEF) by 4.23 ± 1.6. Biomass of different components significantly differs in varied diameter sizes.     

Above ground biomass production and nutrient distribution in growing bamboo (Bambusa bambos (L.) Voss)

Above ground biomass production and nutrient distribution in growing Bamboo (Bambusa bambos (L.) Voss) from two days old (0.12 m height) to maturity (28.5 m height) were studied over five months. The average daily increase in height was 30 cm and independent of rain. There was a linear increase in the total above ground biomass for all components with the percentage contribution of culm maximum followed by branches, and leaves. Culm recruitment was monsoon dependent. The percentage distribution of N, P, K, Ca and Mg between components varied. Biomass equations were derived to estimate the green weight of the whole bamboo culm, the weights of the branches, leaves, and rhizomes and the relationships between the oven dry weights of various tree components as dependent variables and diameter (D), height (H), diameter and height (DH), square of diameter and height (D²H), square of diameter (D²), basal area (B), basal area diameter and height (BH) were determined. Of these, diameter and height (DH) was found to be most closely correlated with total above ground biomass. This was therefore used for the prediction of total biomass.     

Aboveground tree additive biomass models in Ecuadorian highland agroforestry systems

Agroforestry land-use systems in the Andean region have great socioeconomical and biophysical relevance due to the abundance of products and services they provide. Biomass estimation in these systems constitutes a priority concern as it facilitates assessment of carbon sink potential and functionality for biomass production. In this paper, a set of equations were fitted to enable easy and reliable estimation of the total aboveground biomass of four frequently used species in Andean agroforestry systems: Acacia melanoxylon L., Alnus acuminata Kunth., Buddleja coriacea Remy. and Polylepis racemosa Ruiz&Pav. The best models for each biomass component (stem, thick branches, thin branches and leaves) per species were fitted simultaneously according to SUR methodology (seemingly unrelated regressions). All models showed high goodness of fit statistics and more than 70% of the observed variation in biomass components was explained by the independent variables. The inclusion of height as a predictive variable in the models improved their predictive reliability and expanded the application range. The models developed here are useful for assessing the sustainability of agroforestry systems and could support governmental or non-governmental forest conservation incentive programs and initiatives.     

Predictive models for dry weight estimation of above and below ground biomass components of Populus deltoides in India: Development and comparative diagnosis

This article concentrates on development of statistical models for prediction of biomass components (above and below ground) of standing trees of Populus deltoides. Twenty seven trees (three each from age one to nine years) were destructively harvested, separated, sorted, sub-sampled, dried to constant weight at 60 °C and weighted for biomass components (leaf, twig, branch, bole, stump root, lateral root, fine root). Harvesting in a similar manner, was continued annually up to nine years of tree age and thus in all 27 sampled trees were available for analysis and fitting of models. Diameter at breast height (dbh) alone was a very good predictor of dry weight and accordingly the height was not included in the model. Various functions viz (linear, allometric, logistic, gompertz and chapman-richards), were attempted for dry weight estimation. The linear model, though easiest to fit, suffered from the ‘negative estimation problem’, specifically for the lower range of explanatory variate. Of the remaining non-linear models, the allometric model outperformed the others on the basis of validation criterions. The value of R² ranged from 0.95 to 0.99, for the allometric models fitted on various biomass components. The proposed models can be used for prediction of component wise dry biomass of P. deltoides for a wide range of dbh values (1-50 cm) at one end and can also help farmers in the choice of economical harvest rather than the traditional physical rotation. In addition, they can be used in carbon sequestration studies, which needs complete biomass estimation.     

Evaluation of predictive models for Douglas-fir bark thickness at breast height following 12 biomass harvest treatments

Foresters often require an estimation of bark thickness from a reference height (typically breast height) to accurately estimate the bark or wood volume of a tree. Various models for estimating the bark thickness of interior Douglas-fir (Pseudotsuga menziesii var. glauca) from measured dbh (diameter at breast height) were evaluated. Sample trees were from northern Rocky Mountain mixed conifer stands that had been subjected to four levels of experimental woody biomass harvesting. Among simple linear, nonlinear, and segmented linear mixed effects models, the segmented linear model performed best. A join point (where the linear equations are linked) for the segmentation was statistically detected at approximately 19.0 cm dbh. The join point seems to indicate the size at which juvenile Douglas-fir trees boost the production of bark tissue, perhaps as those trees express dominance over competing understory vegetation. Woody biomass utilization level had no impact on bark thickness, indicating that the bark:dbh relationship does not depend on biomass utilization intensity. The study results enable accurate bark thickness estimation for interior Douglas-fir in this region, and suggest several silvicultural applications for juvenile Douglas-fir stand management.     

Silvicultural manipulation and site effect on above and belowground biomass equations for young Pinus radiata

There is little understanding of how silvicultural treatments, during the early stages of tree development, affect allometric relationships. We developed and compared stem, branch, foliage, coarse and fine root biomass, and leaf area estimation equations, for four-year-old genetically improved radiata pine trees grown on three contrasting soil-site conditions. At each site, selected trees were destructively sampled from a control (shovel planted, no weed control, fertilized with 2 g of boron), a shovel planted + weed control (2 first years) + complete fertilization (nitrogen + phosphorus + boron 2 first years + potassium 2nd year), and a soil tillage (subsoil at 60 cm) + weed control (first 2 years) + complete fertilization treatment. Tissues were separated into foliage, branch, stem, fine and coarse roots (>2 mm). Regression equations for each tree biomass tissue versus leaf area were fit for each site and compared among treatments and sites with the same genetic material. Our results indicated that individual tree biomasses for young plantations are affected by silvicultural treatment and site growing conditions. Higher variability in estimates was found for foliage and branches due to the ephemeral nature of these components. Stem biomass equations vary less, but differences in biomass equations were found among sites and treatments. Coarse root biomass estimates were variable but less than expected, considering the gradient among sites. Similar to stem biomass, a simple positive general linear relationship between root collar diameter, or diameter at breast height with coarse roots biomass was developed across sites and treatments.     

Use of harmonized equations to estimate above-ground woody biomass for two hybrid poplar clones in the Pacific Northwest

Equations were developed to estimate components of above-ground woody biomass, as a function of diameter, height, spacing and age for two hybrid poplar clones in western Washington. Independent and harmonized fitting techniques are compared. With the small sample sizes that are unavoidable in such experiments, harmonized equations provided more useful and consistent estimates of biomass increment than did independent equations by age and spacing. They were also better suited to interpolation and extrapolation of long-term trends of biomass increment than those based on the independent fits.     

Performance of 14 hybrid poplar clones grown in Beijing,China

Evaluating the performance of poplar clones to be used in short-rotation intensive culture (SRIC) and selecting superior clones are critical to increase wood production and ecological effects. This study described the growth and aboveground biomass production of 14 hybrid poplar clones after three growing seasons, evaluated the clones with cluster analysis on multiple basis. At the end of each growing season, total tree height, basal diameter and biomass were measured. Highest production was found for clone NE-353 and DN-70 with mean annual biomass production 22 Mg ha^?1 year^?1. Lowest performance was observed for clone 311-93 and 309-74 with biomass production 0.29 and 0.75 Mg ha^?1 year^?1. Cluster analysis was conducted with survival and tree volume index, all measured at the end of the third growing season. The clones were grouped into four classes. Clone R-247, DN-70 and Simplot had higher survival and highest tree volume index, appeared to well adapted to the region; clone 52-225, 58-280, NE-353, DN-34, PC-01 and OP-367 exhibited moderate survival and Growth; clone DN-14273, R-419 showed moderate survival and low growth; clone 195-529, 311-93 and 309-74 performed poorest with lowest survival and tree volume index and these clones may not suitable for biomass producers in this region.     

Some metals in aboveground biomass of Scots pine in Lithuania

The stocks of iron (Fe), manganese (Mn), zinc (Zn) and aluminium (Al) in different compartments of the aboveground tree biomass were estimated in Scots pine (Pinus sylvestris L.) stands in Lithuania. Simulated removals of metals due to the forest biomass extraction in a model Scots pine stands during a 100-year-long rotation period were compared with metals pools in sandy soil and the fluxes through atmospheric deposition. Applying whole tree harvesting, total removal comprised about 20 kg ha⁻¹ of each Al and Mn, and 5 times lower amount of each Zn and Fe. The metals were mainly removed with stemwood and living branches. However, metal export with aboveground biomass represented relatively small proportion of metals in mineral sandy soil. The annual inputs of Fe and Zn with atmospheric deposition were over 10 times higher than the mean annual removals with total aboveground biomass. The content of metals in forest biomass fuel ash was relatively small to compare with their total removals. The findings of this study have an important implications for future practice, i.e. the recommended maximum forest biomass fuel ash dose for the compensating fertilising could be increased with respect to balanced output – input in Lithuania.     

Suitability of published biomass equations for aspen in Central Europe—Results from a case study

Published biomass equations were applied to sample trees from an 18-year-old Populus tremula (L.)×P. tremuloides (Michx.) (Astria) stand in Germany and compared with the measured dry weights. Equations originally developed for quaking aspen did not perform better than equations derived from European aspen data. The complexity of equations also did not influence the mean percent deviation of calculated dry weights from measured dry weights. Equations derived from measurements in short-rotation coppice cultures grossly overestimated weights. The accuracy of the predictions of total tree biomass changed according to the gradient in height:diameter ratio of the sample trees of the original studies. Equations from trees with similar h/d ratio as the sample trees were more accurate than others. When equations from the literature are used to estimate biomass for given stands, equations that resulted from sample trees with similar height:diameter ratios should be preferred.     

Biomass equations and estimation for Gmelina arborea and Nauclea diderrichii stands in Akure forest reserve

Biomass estimation was carried out for even-aged stands of Gmelina arborea and Nauclea diderrichii in Akure forest reserve. Linear and allometric regression equations for biomass prediction were developed for trees of both species. The yield of each species and total above-ground biomass (TAGB) were estimated and compared. The various equations developed were assessed based on high coefficient of determination (R²), significant F-ratio, and small Furnival index (FI) to select appropriate equation for prediction. The t-test shows a significant difference when the total volume and total dry weight of both species were compared, Gmelina arborea having a greater value than Nauclea diderrichii in both cases. The total volume of Gmelina arborea per hectare was 721.40 m³ and 265.18 m³ for Nauclea diderrichii. The TAGB for Gmelina arborea was 264,762 kg/ha and 88,293 kg/ha for Nauclea diderrichii.     

A novel approach to simulate growth of multi-stem willow in bioenergy production systems with a simple process-based model (3PG)

An important requirement for commercialization of willow biomass production in short-rotation crop (SRC) plantations is the reliable and cost-efficient estimation of biomass yield. Predictions and simulations of willow stand biomass have been problematic due to issues with modeling the multi-stem growth form of willow. The aim of this paper was to develop a new approach for managing allometric measurements from multi-stemmed willow for stand growth simulations. The 3PG model (Physiological Principles in Predicting Growth) was parameterized for willow and was used for biomass yield simulation for an entire 22-yr cycle (seven 3-yr rotations) of willow in SRC plantations. The multi-stemmed growth form was transformed into a single-stem modeling form by deriving whole plant willow allometric relationships using detailed stem-level measurements of basal area, stem biomass and volume. 3PG model predictions for plant diameter, height, biomass, and stand biomass and volume were within the 95% confidence range of mean plot values. Model simulations showed that after seven 3-yr rotations only 20% of planted cuttings would survive (a decrease from 15,152 to 3022 plants ha⁻¹), but stand volume would increase continuously with each subsequent rotation. 3PG predictions for cumulative (for 22 yr) aboveground biomass was 272 Mg ha⁻¹ and mean annual yield was 12 Mg ha⁻¹ yr⁻¹, comparing favorably with other findings. To our knowledge, this work is the first where the 3PG model was calibrated and used for willow species. Once parameterized for a specific willow clone, 3PG can predict biomass accumulation for any agricultural land in North America using only available soil and climate data.     

Enhancement of bioenergy estimations within forests using airborne laser scanning and multispectral line scanner data

Forest biomass is a substantial source of renewable energy and is becoming increasingly important due to environmental and economic reasons. In Germany, several studies have assessed the bioenergy potential for large areas, e.g. for an entire Federal state. However, in most cases it was not possible to provide detailed maps showing the biomass and the sustainable energy potential for individual forest stands. Thus, the aim of this study was to develop a new and robust method that provides detailed information regarding the spatial distribution of biomass and forest residues as a potential energy resource using a combination of remotely sensed and in situ data. A case study was carried out in a mixed forest in Southern Germany. First, regression analyses were applied to identify relationships between field measurements with several remote sensing metrics to estimate timber volume, mean stem diameter and age. Cross-validation yielded relative root mean square errors (RMSEs) of 30.20% for volume, 27.92% for diameter and 28.81% for the estimation of the age. The absolute RMSEs were smaller than the standard deviation of the observed variables. Next, the regression equations were used to compute attributes for individual forest stands. Stand attributes were then used to model forest residues. To estimate the sustainable annual potential, the actual harvest volume, as defined by forest management planning, was included in the model. Different model parameters were analyzed and an average potential from 0.993 to 1.181 t ha⁻¹ a⁻¹ was computed. The results were compared to previous studies in Germany.     

Above-ground biomass functions for Scots pine in Lithuania

This study presents biomass functions applicable to Scots pine (Pinus sylvestris L.) on Arenosols in Lithuania, and exemplifies the potential biomass removal from Scots pine stands during thinnings. Scots pine is the most common tree species on Arenosols in Lithuania. Stands of ages 10, 20, 40, 50 and 65 years were chosen for the biomass study. We sampled 5 Scots pine trees per plot (in total 25 trees) that were stratified according to the basal area. The sampling was performed in April 2003, before the vegetative period. The following components of each tree were sampled for the above-ground biomass measurements: (1) 5 stem discs, (2) 1 branch with needles from each whorl and (3) 1 dead branch per tree.Observed biomasses of above-ground components were examined using a non-linear regression model, using stem diameter (D), tree height (H) and D²H as independent variables.For stemwood biomass, the best approximation was D²H. However, D²H was not the best parameter for crown biomass because it does not allow evaluation of the opposite effects of diameter and height on crown biomass. The calculations at stand level showed that crown biomass changed insignificantly with the increase in stand age. However, the total stand biomass increased with age due to the growth of the stem. The removal of all logging residues from the Scots pine stand over a 100-year rotation could increase extraction of forest fuel by 15–20% compared with conventional harvesting.     

Modeling stump biomass of stands using harvester measurements for adaptive energy wood procurement systems

The value and volumes of industrial stump fuel supply are increasing for energy production. Accurate estimates of aboveground and belowground biomass of trees are important when estimating the potential of stumps as a bioenergy source. In this study two stump biomass equations were adapted and tested using them as calibrated stump biomass models computed as the cumulative sum by a local stand. In addition, variables derived from stem measurements of the forest harvester data were examined to predict stump biomass of a stand by applying regression analysis. The true stump yield (dry weight) was used as the reference data in the study. Both biomass models performed well (adjusted R² ˜ 0.84) and no advance was found in using other stem dimensions as independent variables in the model. The stand-level model can be used in innovative stump biomass prediction tools for increasing efficiency of energy wood procurement planning to stands within a certain area. In practice, wood procurement managers would need to adapt developed system and decide whether the degree of accuracy/precision provided by the models is acceptable in their local stand harvesting conditions.     

A management tool for estimating bioenergy production and carbon sequestration in Eucalyptus globulus and Eucalyptus nitens grown as short rotation woody crops in north-west Spain

This study proposes stand level models for estimating biomass yield, total energy and carbon sequestration in Eucalyptus globulus and Eucalyptus nitens plantations, on the basis of measurements made in 131 plots established at the usual range of initial forest densities for southwestern Europe. The timber volume, total aboveground biomass, logging residue biomass, crown biomass, carbon in aboveground biomass and soil organic layer, energy in aboveground biomass, energy in logging residue biomass and usable cellulose yield were represented in the form of isolines (taking mortality into account) and plotted against dominant height. These variables were calculated and compared with previously published data on two silvicultural options for short rotation forestry, one destined for bioenergy production and the other consisting of the standard silviculture regime applied to both species in southern Europe, considering the average site index for each species. Yield levels were higher in E. nitens than in E. globulus for all variables because of faster diameter increment at similar densities. The total yield in terms of biomass was 13.9-14.6 Mg ha⁻¹ y⁻¹ for E. globulus and 20.4-21.5 Mg ha⁻¹ y⁻¹ for E. nitens. Energy in aboveground biomass ranged between 233 and 245 GJ ha⁻¹ y⁻¹ for E. globulus and 345 and 364 GJ ha⁻¹ y⁻¹ for E. nitens, carbon accumulation rate in aboveground biomass and soil organic layer was 6.9-7.2 Mg ha⁻¹ y⁻¹ for E. globulus and 12.7-13.5 Mg ha⁻¹ y⁻¹ for E. nitens, and usable cellulose was 5.7-5.9 Mg ha⁻¹ y⁻¹ for E. globulus and 9.0-10.1 Mg ha⁻¹ y⁻¹ for E. nitens. It was found that 50% increments in the initial density result in only marginal increments in biomass and usable cellulose yields.     

Aboveground and belowground biomass allocation in native Prosopis caldenia Burkart secondaries woodlands in the semi-arid Argentinean pampas

The woodlands in the south-west of the Argentinean pampas are dominated by Prosopis Caldenia Burkart (calden). The current deforestation rate of this woodlands is 0.82% per year. Different compensation initiatives have begun that recognize the role of forests as environmental service providers. The financial incentives they offer make it necessary to quantify the amount of carbon stored in the forest biomass. A model for estimating calden biomass was developed. Thirty-eight trees were selected, felled and divided into sections. An equation system was fitted using joint generalized regression to ensure the additivity property. A weighted regression was used to avoid heteroscedasticity. In these woodlands fire is the main disturbance and it can modify tree allometry, due this all models included the area of the base of the stem and tree height as independent variables since it indirectly collects this variability. Total biomass and the stem fraction had the highest R2_Adj. values (0.75), while branches with a diameter less than 7 cm had the lowest (0.58). Tree biomass was also analyzed by partitioning into the basic fractions of stem, crown, roots, and the root/shoot ratio. Biomass allocation was greatest in the crown fraction and the mean root/shoot ratio was 0.58. The carbon stock of the caldenales considering only calden tree biomass is 20.2 Mg ha⁻¹. While the overall carbon balance of the region is negative (deforestation and biomass burning, the remnant forested area has increased their calden density and in an indirect way his carbon sequestration capacity could also be increased.