Wood density at breast height as estimate of the whole tree density in Grevillea robusta

To validate the relationship between whole-tree average density and wood density at breast height, 60 Grevillea robusta trees were sampled from north-eastern Argentina plantations. Wood basic density was measured at five height levels in each tree. A weighted average density was calculated for each tree and a linear regression was calculated using whole-tree density as the independent variable and wood density at breast height as the regressor. The coefficient of determination (R²), standard error and mean percentage error were 81%, 12.7 kg m^–3 and 10.2% respectively, showing a close association between variables. Wood density at breast height is useful for estimating wood density of the whole tree in G. robusta.     

THE PROPORTIONS OF STAND MERCHANTABLE VOLUME BY LOG SIZE CLASSES IN PINUS RADIATA (D. Don)

Warren has developed a relationship for even aged stands of P. radiata in plantations in New Zealand whereby from the stand mean diameter over bark at breast height there can be derived the percentage of stand volume (up to a diameter limit of 4 or 6 in.) within various classes of log diameter (small end under bark).

The author discusses, for certain even aged plantation stands of P. radiata in Australia, the development and application of a similar relationship for thinned stands and thinnings, provided the distribution of the trees by diameter over bark at breast height approximates a normal distribution.     

Growth and form of provenances of Eucalyptus saligna at Wondo Genet,southern Ethiopia

A trial testing 10 provenances from across the natural range of Eucalyptus saligna and a local land race was established at Wondo Genet, southern Ethiopia. Eight years after planting, survival, tree height, diameter at breast height over bark, stem form, number of forks, height to the first fork, number of branches, branch diameter and branch angle were assessed. Volume per hectare was also calculated. Survival ranged between 36% (a provenance from 87 km north of Windsor, NSW) and 79% (Consuelo Tableland, Queensland), and differences were significant (P < 0.05). Among morphological characteristics, only the number of branches showed significant variation (P < 0.05), with the greatest number (12.4) being recorded for the Bulahdelah, NSW, provenance and the least (8.5) for the Clyde River, NSW, provenance. Major growth and morphological parameters (tree height, diameter, volume and stem form) did not differ significantly. The overall volume production (mean annual increment 26.4 m³ ha^?1) was well above the minimum acceptable growth observed on good sites elsewhere. Differences between provenances were small and mostly not significant, and no pattern of geographic variation was detected. Given the acceptable mean annual increment, those provenances represented by an adequate number of parent trees could be maintained for further selection and breeding, and to maintain genetic diversity of the species in Ethiopia.     

Stem biomass estimation based on stem reconstruction from terrestrial laser scanning point clouds

Forest biomass is often difficult to quantify because field measurements are time consuming and require destructive sampling. This study explores the retrieval of stem biomass of individual trees by terrestrial laser scanning (TLS). Destructive sampling was done to collect biomass data from sample trees and used as a dependent variable in a regression analysis. Two biomass estimation models were investigated: one based on diameter at breast height (DBH) and another based on the sum of the stem section volume. Both the DBH and the stem section volume were determined from automatic reconstruction of the stem curves. Two tree species (Scots pine and Norway spruce) were considered together. The quality of the performance of the models was evaluated via a leave-one-out cross-validation strategy using accurate field measurements for 30 trees. The correlation coefficient (r) and root mean square errors (RMSEs) between the predicted and measured stem biomass were used as measures of goodness of model fitting. The model with DBH as the predictor produced an r-value of 0.93 and an RMSE of 21.5%. For the model using the reconstructed stem and correspondingly derived stem volume as the predictor, an r-value of 0.98 and an RMSE of 12.5% were achieved. The results indicated that TLS measurements are capable of assessing stem biomass with high automation and accuracy by reconstructing the stem from TLS point clouds.     

A refined method for estimating capsule crops in individual jarrah (Eucalyptus marginata) crowns

An accurate measure of the number of capsules in the crowns of jarrah (Eucalyptus marginata) trees is needed to assess the potential for seedling regeneration prior to silvicultural treatment in jarrah forests. The current method of estimating capsule crops on jarrah trees uses stem diameter and estimates of capsule density in the crown, but has not been fully validated. In this study, we sought to develop an accurate and practical method of assessing capsule crops in the crowns of individual jarrah trees. We did this by measuring a number of tree characteristics prior to felling them. A total of 24 trees were selected, spanning a range of sizes and crown conditions, and the total number of capsules was counted for each tree. Multiple linear regression was used to model capsule number against various combinations of eight different tree/crown variables, with model fit compared using an adjusted coefficient of determination (adjR²). The final model recommended for field use included three easily measured variables (stem diameter, subjective assessment of capsule density, and subjective assessment of capsule clump distribution in the crown) and had a high degree of predictability (adjR² = 0.83), which was the same as that of the full model. This method substantially improved estimates of crown capsule numbers compared with the method currently used (adjR² increased from 0.29 to 0.83), which tended to underestimate canopy capsule numbers.     

Improving stem volume estimation of regrowth Eucalyptus fastigata with a lower stem form quotient

Stem volume equations were developed and validated using data from 877 sample trees. Initially, three commonly used models were compared. The least biased and most precise estimates of underbark stem volume was obtained using equations based on the combined variable model. A lower stem form quotient, calculated as the ratio of diameter at 4.5m above ground to diameter at breast height, was subsequently included resulting in a substantial improvement in precision.     

Converting diameter measurements of Pinus radiata taken at different breast heights

Two compatible conversion factors for converting diameter measurements taken at different breast heights were derived for Pinus radiata using taper data from more than 3000 trees. The two breast heights used for conversion were 1.3 and 1.4 m above ground, as defined in Australia and New Zealand, two major radiata-growing countries in the world. The conversion factors were estimated through three alternative statistical methods including simple least squares regression, seemingly unrelated regression and errors-in-variables models. The three sets of estimates were almost identical and had similar conversion accuracy, although the second method was slightly better. The conversion factors were more accurate than overbark taper equations used for the same purpose. The factor was 0.9916 for converting diameter measured at 1.3 to that at 1.4 m above ground, and the inverse of this value, 1.0084, was for the vice versa. When calculating tree and stand volume and biomass using equations with diameter at a different breast height as a predictor to that of the input data, the bias, either over or under estimation, could be between 1.67% and 2.00% without conversion. These conversion factors will facilitate the sharing of data among radiata growing countries with different definitions of breast height, but more importantly it will help correct the bias in stand volume and biomass estimation caused by the seemingly negligible difference in breast height when software for forest resource management and decision support developed in one country is applied in another. Such bias when accumulated over a large management area may not be financially insignificant for an astute forest management agency.     

Using tree hollow data to define large tree size for use in habitat assessment

Habitat assessments often require observers to estimate tree hollows in situ, which can be costly, destructive and prone to bias. An alternative is to count the number of trees above a specific size. The size at which a tree develops hollows differs substantially among tree species. To assist with setting standards for habitat assessment we defined a large tree as the size at which a species has a 50% probability of supporting a 2-cm diameter hollow. We estimated this size for 68 species using a meta-analysis based on 18 data sources. We found that large tree size ranged from 21 to 106 cm diameter at breast height (DBH). Each species was attributed to vegetation types (formations and classes) to explore variation in large tree sizes. Despite considerable variation within vegetation classes and formations, our results suggest that a large tree size of approximately 50 cm DBH may be appropriate for most vegetation types, with lower estimates in semi-arid vegetation (~30 cm) and higher estimates in wet sclerophyll forests (~80 cm). Our estimates provide empirical support for defining large trees at species vegetation class and formation levels within New South Wales, and highlights the need for more empirical data.     

Estimating diameter at breast height using personal laser scanning data based on stem surface nodes in polar coordinates

ABSTRACT

Personal laser scanning (PLS) has shown great potential in diameter of breast height (DBH) estimation. Compared with the current laser scanning technique, PLS is hardly restricted by occlusion and trafficability, and produces omnidirectional point cloud data. However, the DBH estimation accuracy using PLS data was not higher in the previous research. One of the leading sources of bias is overlapping and inaccurately co-registered point cloud fragments. Points of these fragments can be far from the stem surface, which leads to a large bias in DBH estimation. In this letter, a novel DBH estimation method using PLS data, the stem surface node method (SSN) is proposed. To reduce the impacts of the inaccurately co-registered points far from the surface, SSN attempts to use a number of stem surface nodes in polar coordinates instead of the whole stem point cloud to estimate DBH. Six plots with 247 stems under three different working conditions were selected to evaluate the method. Compared with the DBH estimation method using direct circle fitting, SSN achieved a total error reduction of 62.64% and 38.35% for bias and root mean squared error, respectively. These findings confirm that SSN is generally reliable and adaptive for different kinds of working conditions.     

Variation in oil content and tree size between six geographically separate Santalum spicatum families,established near Narrogin,Western Australia

Six geographically separate sandalwood (Santalum spicatum) tree families were established together in a trial near Narrogin, Western Australia to compare oil content and tree size variation at ages 10 and 18 years. The trial site contained a total of 300 sandalwood trees with 41–55 trees from each family. All 300 sandalwood trees were measured for tree size: height, stem diameter and bole length. Wood core samples (heartwood + sapwood) were also taken at 300 mm above the ground from 71 to 72 separate trees, at ages 10 and 18 years. Each wood core sample was ground separately and then a sub-sample was analysed for oil concentration, and α- and β-santalol concentration within the oil.

The mean extractable oil concentrations within the sandalwood stems at 300 mm above the ground were significantly greater from the Borden and Dumbleyung families (1.1–1.6%) than the Ravensthorpe family (0.5–0.8%), at both ages 10 and 18 years. However, the oil quality (mean concentration of α- and β-santalol) was not significantly different between the six families at ages 10 or 18 years. Instead, oil quality was highly variable within each family.

Between sandalwood ages 10 and 18 years, the overall mean extractable oil concentration from the six different families increased significantly from 0.8 to 1.3%. During the same time period, mean α-santalol concentration increased significantly from 8.6 to 13.8%, and mean β-santalol concentration also increased significantly from 3.3 to 4.5%.

Mean tree height, stem diameter and bole length varied significantly between the six families at age 18 years. The Borden family appeared to be more tree-like in form, with a significantly longer bole length, than some of the other families which were more shrub-like in appearance.     

Estimation of forest stand diameter class using airborne lidar and field data

In this study, a method for estimating the stand diameter at breast height (DBH) classes in a South Korea forest using airborne lidar and field data was proposed. First, a digital surface model (DSM) and digital terrain model (DTM) were generated from the lidar data that have a point density of 4.3 points/m², then a tree canopy model (TCM) was created by subtracting the DTM from the DSM. The tree height and crown diameter were estimated from the rasterized TCM using local maximum points, minimum points and a circle fitting algorithm. Individual tree heights and crown diameters were converted into DBH using the allometric equations obtained from the field survey data. We calculated the proportion of the total number of individual trees belonging to each DBH class in each stand to determine the stand DBH class according to the standard guidelines. More than 60% of the stand DBH classes were correctly estimated by the proposed method, and their area occupied over 80% of the total forest area. The proposed method generated more accurate results compared to the digital forest type map provided by the government.     

Integrating multi-source data for a tropical forest inventory—a case study in the Kon Tum region,Vietnam

This article presents a processing chain for forest volume mapping based on multi-source forest inventory methodology and the existing inventory data collected from the Kon Tum region, Vietnam. The modelling framework for imputing tally tree heights was built based on a mixed-effects height generalisation model. Mapping of the stem volume was based on nearest neighbour techniques (k-NN) and Landsat TM data after relative calibration with MODIS image material as underlying reference. The use of optical image materials, together with the demanding conditions set by a tropical forest structure, resulted in a moderate root mean square error value (76.6%) for the stem volume. The resulting volume maps, which were based on an objective estimation procedure, create the appropriate model dataset needed for testing the optimal large-scale inventory designs of forthcoming forest inventories that will be carried out in Vietnam.     

Estimating the volume of Australian hardwoods using centroid sampling

Centroid sampling was tested on 18 sample trees of Flindersia brayleyana and 124 sample trees of five species of Eucalyptus all of which were measured in detail. Volumes of the main bole of each tree and of logs (length approx. 6 m) derived from each bole were estimated using both Huber's formula and centroid sampling. These estimates were compared with ‘true’ volume obtained by summing the volumes derived using Smalian's formula of all the measured short sections comprising the main bole and each log respectively.

The mean error of the centroid estimate of volume of the main bole was not significant for Eucalyptus sieberi and E. diversicolor and was less than that derived from Huber's formula for all species except E. regnans. When all species were combined, the centroid estimate was clearly more accurate, its mean error (-2%) being just significant (p=0.046). Centroid sampling also gave more accurate estimates of the volume of the component logs.

Results of this study and earlier work suggest that centroid sampling is applicable to tree species of both excurrent and deliquescent growth habit.     

Authors and fields of research

Growth and morphological differences between 12 provenances of Grevillea robusta (from New South Wales and Queensland, Australia) grown at two locations on the tropical Atherton Tablelands of northern Australia were investigated at age 40 months. The following measurements were taken: tree survival; height; diameter at breast height (DBH); number of branches and forks per tree; branch diameter and angle; crown diameter and tree form.

Significant differences between the provenances were found in most of the characteristics measured. Only DBH showed a site x provenance interaction. Two provenances (Duck Creek and Tyalgum) performed best. Provenance similarities in their morphological responses were examined using hierarchical cluster analysis.     

Estimating plot-level tree structure in a deciduous forest by combining allometric equations,spatial wavelet analysis and airborne LiDAR

Object-oriented classification methods are increasingly used to derive plant-level structural information from high-resolution remotely sensed data from plant canopies. However, many automated, object-based classification approaches perform poorly in deciduous forests compared with coniferous forests. Here, we test the performance of the automated spatial wavelet analysis (SWA) algorithm for estimating plot-level canopy structure characteristics from a light detection and ranging (LiDAR) data set obtained from a northern mixed deciduous forest. Plot-level SWA-derived and co-located ground-based measurements of tree diameter at breast height (DBH) were linearly correlated when canopy cover was low (correlation coefficient (r)?=?0.80) or moderate (r?=?0.68), but were statistically unrelated when canopy cover was high. SWA-estimated crown diameters were not significantly correlated with allometrically based estimates of crown diameter. Our results show that, when combined with allometric equations, SWA can be useful for estimating deciduous forest structure information from LiDAR in forests with low to moderate (<175% projected canopy area/ground area) levels of canopy cover.     

Growth of Eucalyptus pellita and E. urophylla and effects on pasture production on the coastal lowlands of tropical northern Australia

Eucalyptus pellita F. Muell. and E. urophylla S. T. Blake are important timber species which have potential for wood production in plantation and agroforestry systems in humid northern Queensland. This study was established to examine two provenances of each species on a coastal lowland site, using randomised complete block design. Survival, height, diameter at breast height (DBH), bole length and tree form were measured at ages 12, 24 and 39 months. The height and biomass of the pasture underneath each provenance plot were also measured at 39 months. Significant differences occurred in most of the tree characteristics at 39 months. Differences in pasture growth, on the other hand, were not significant. Compared with the two E. pellita provenances, the provenances of E. urophylla had superior height and DBH growth but had worse form. Overall, however, both species had high survival, fast growth, satisfactory form, and minimal effects on pasture growth. Although all four taxa appear to be suitable for silvopastoral systems, further trials involving more provenances on a wider range of sites are recommended to establish the environmental and economic limits for the use of these species.     

Biomass and nutrient distribution in relation Pine in relation to previous land use I. Biomass

Above-ground biomass data are compared for 21-year-old radiata pine stands on three sites which had different types of land use prior to plantation establishment. The three sites, previously under native forest, grazed pasture and a pasture site subsequently used for crop production (cultivated) formed a continuous section of plantation in the 1968 age class. Biomass equations were developed for each tree component in relation to stem diameter for each site. There were no significant differences between sites in the coefficients for stemwood and bark, but different coefficients were required to relate stem diameter to the biomass of branches in the dead crown and foliage in the lower live crown. Stands on previously cultivated pasture (pasture followed by crops) accumulated 362,745 kg ha^?1 in the above-ground biomass; 40% and 13% more than the ex-native forest (259,183 kg ha^?1) and ex-pasture (320,055 kg ha^?1) sites, respectively. Trees on the previously cultivated pasture allocated a larger proportion of the total biomass to branches (17.4%) compared with the ex-native forest and ex-pasture trees (11.1%). This is attributed to reduced stocking and enriched soil resulting from different previous land use practices. The high frequency of multi-leadered trees in the ex-cultivated pasture increased the non-merchantable components to 26.7% of the total biomass.     

Quantitative estimation of errors in the indicator dilution measurement of extravascular lung water

Objective: To assess the accuracy of the diffusible indicators heavy water and thermal indicator in the measurement of extravascular lung water (EVLW). Design: Cardiac output (CO), mean transit time and EVLW for the two diffusible indicators were measured. CO for indocyanine green, gravimetric EVLW and the calculated mean transit time for a diffusible indicator were used as independent reference variables. CO, mean transit time and EVLW for the two diffusible indicators were compared to the reference variables and the percentage error for each measured variable was calculated for each bolus injection. Setting: 6 sheep with healthy lungs and 6 with pulmonary oedema in a research laboratory. Interventions: CO was altered with positive end-expiratory pressure and dobutamine. Measurements: All indicators were given together in a bolus through a central venous line. Indicators were detected simultaneously in the aorta, and CO, mean transit time and EVLW were measured. EVLW was measured gravimetrically (EVLW_grav) postmortem. Results: In the combination of a low CO and a large distribution volume, heavy water and thermal indicator produced a large number of slow wash-out curves. These curves were abolished from further analysis. The mean errors in CO and mean transit time for heavy water were close to zero and independent of the distribution volume; the product EVLW was close to EVLW_grav . The mean error in thermodilution CO measured in the aorta was close to zero but dependent on the distribution volume. The mean error in mean transit time for the thermal indicator was 36 % and dependent on the distribution volume. Their product EVLW overestimated EVLW_grav by 70 %. Conclusions: The results obtained for heavy water confirmed the theoretical basis of the indicator dilution method. The mean transit time for the thermal indicator was not proportionate to its distribution volume. The magnitude of this error prevents the calculation of an anatomically defined EVLW using a catheter-mounted thermistor in the aorta. Received: 18 December 1995 Accepted: 2 January 1997     

Effects of wind sway on stem form and crown development of Scots pine (Pinus sylvestris L.)

The distribution of growth was examined in 45-year-old Scots pine (Pinus sylvestris L.) trees stayed with wires attached at 30% and at 30% and 60% of the tree height, and in trees with a metal sail attached in the top of the crown. The treatments commenced in 1983 and 16 trees per treatment, including the control, were sampled in 1988. Increments of stem diameter, height, and volume in treated and control trees were estimated from stem and branch mensuration. Staying the trees promoted radial growth by about 10% above the point of attachment. Increasing the wind sway with sails promoted radial growth below the crown. Changes in the distribution of growth within the crown were not as obvious as the changes along the stem below the crown.