Stand Stem Biomass Research Articles

Production patterns of loblolly pine plantations along a geographic gradient in southern Brazil

Pinus taeda plantations depend directly on the supply of resources (light, water, and nutrients) available to the stand. However, studies quantifying edaphic and climatic factors in P. taeda stands are scarce. This study aimed to identify the main edaphic, climatic and stand factors that influence the productivity and growth pattern of P. taeda plantations in southern Brazil. A total of 24 stands, ranging between 8 and 10 years old were evaluated. Biometric variables such as height, diameter at breast height (DBH), stem analysis, growth rings, specific gravity, and soil chemical and physical variables were evaluated. Site index (SI), stem biomass, mean annual increment without bark (MAI) and correlations between variables were calculated. We observed that by nine years after planting, none of the plots had reached their maximum growth; and MAI, standing stem biomass and SI ranged from 15 to 35 m³ ha−1 year−1, 56–131 Mg ha−1, and 12–19 m, respectively, with higher values in Três Barras site. Stem biomass were positively related with SI (r = 0.89), and stem production was related with higher available water content (r = 0.41), warm temperatures (r = 0.61), and higher relative air humidity (r = 0.58). The study corroborates the role of nutrients, well-drained soils, mild climatic conditions, and low water deficit to explain the high yields of P. taeda in Brazil compared to other locations around the world. Based on these results, studies on fertilization, genetic material, and more frequent use of stem analysis, associated with X-ray densitometry, are recommended for P. taeda.

Tree Water Use, Water Use Efficiency, and Carbon Isotope Discrimination in Relation to Growth Potential in Populus deltoides and Hybrids under Field Conditions

We explored the relationship between tree growth, water use, and related hydraulic traits in Populus deltoides Bartr. ex Marsh.and hybrid clones, to examine potential trade-offs between growth and water use efficiency. Nine genotypes, six P. deltoides and three hybrid clones, that represented genotypes with high (Group H), intermediate (Group I), and low (Group L) growth performance were selected for study, based on year-two standing stem biomass in a replicated field trial. In year four, tree growth, transpiration (Et), canopy stomatal conductance (Gs), whole-tree hydraulic conductance (Gp), and carbon isotope discrimination (Δ13C) were measured. Tree sap flux was measured continuously using thermal dissipation probes. We hypothesized that Group H genotypes would have increased growth efficiency (GE), increased water use efficiency of production (WUEp, woody biomass growth/Et), lower Δ13C, and greater Gp than slower growing genotypes. Tree GE increased with relative growth rate (RGR), and mean GE in Group H was significantly greater than L, but not I. Tree WUEp ranged between 1.7 and 3.9 kg biomass m3 H2O−1, which increased with RGR. At similar levels of Et, WUEp was significantly greater in Group H (2.45 ± 0.20 kg m−3), compared to I (2.03 ± 0.18 kg m−3) or L (1.72 ± 0.23 kg m−3). Leaf and wood Δ13C scaled positively with stem biomass growth but was not correlated with WUEp. However, at a similar biomass increment, clones in Group H and I had significantly lower leaf Δ13C than Group L. Similarly, Group H clones had a significantly lower wood Δ13C than Group L, supporting our hypothesis of increased WUE in larger trees. Tree physiological and hydraulic traits partially explain differences in WUEp and Δ13C, and suggest that clone selection and management activities that increase tree biomass production will likely increase tree and stand WUE. However, more research is needed to discern the underlying hydraulic mechanisms responsible for the higher WUE exhibited by large trees and distinct clones.

Density management diagrams for sweet chestnut high-forest stands in Portugal

Abstract: This study aims to develop stand density management diagrams (SDMDs) for pure even-aged high-forest stands of sweet chestnut in Portugal, defining the appropriate upper and lower limits of growing stock while considering the biological, technological and economic objectives that are expected for these stands. The SDMDs were developed with data collected from high-forest stands in northern Portugal, which is the main representative area of these stands in the country. Data were collected from 23 pure even-aged permanent plots with re-measurement intervals of 4-10 years, 43 semi-permanent plots and 18 even-aged temporary plots; all plots were established in chestnut high-forest stands with a broad range of ages. SDMDs were constructed by simultaneously fitting four nonlinear equations relating stand variables using the full information likelihood technique. SDMDs for the estimation of stand total volume, stand stem biomass, stand total aboveground biomass, and carbon content in aboveground biomass are presented as bivariate graphs with dominant height on the x-axis and the number of trees per hectare on the y-axis (using logarithmic scale). A tool is made available to define an optimal range of stand density for a silviculture oriented to single-stem selection on a tree-by-tree basis, focusing management on the most valuable trees. This tool is aimed to support forest managers in the decision-making process, enabling them to schedule thinnings on the basis of the dominant height growth of the trees with the greatest potential (frame trees), maintaining an adequate growing stock and assessing the corresponding aboveground wood volume, biomass, carbon, and mean diameter breast height.

Modelling stand biomass fractions in Galician Eucalyptus globulus plantations by use of different LiDAR pulse densities

Aims of study: To evaluate the potential use of canopy height and intensity distributions, determined by airborne LiDAR, for the estimation of crown, stem and aboveground biomass fractions.To assess the effects of a reduction in LiDAR pulse densities on model precision.Area of study: The study area is located in Galicia, NW Spain. The forests are representative of Eucalyptus globules stands in NW Spain, characterized by low-intensity silvicultural treatments and by the presence of tall shrub.Material and methods: Linear, multiplicative power and exponential models were used to establish empirical relationships between field measurements and LiDAR metrics.A random selection of LiDAR returns and a comparison of the prediction errors by LiDAR pulse density factor were performed to study a possible loss of fit in these models.Main results: Models showed similar goodness-of-fit statistics to those reported in the international literature. R2 ranged from 0.52 to 0.75 for stand crown biomass, from 0.64 to 0.87 for stand stem biomass, and from 0.63 to 0.86 for stand aboveground biomass. The RMSE/MEAN · 100 of the set of fitted models ranged from 17.4% to 28.4%.Models precision was essentially maintained when 87.5% of the original point cloud was reduced, i.e. a reduction from 4 pulses m–2 to 0.5 pulses m–2.Research highlights: Considering the results of this study, the low-density LiDAR data that are released by the Spanish National Geographic Institute will be an excellent source of information for reducing the cost of forest inventories.Key words: Eucalypt plantations; airborne laser scanning; aboveground biomass; carbon stocks; remote sensing; forest inventory.

Regional-scale stand density management diagrams for Pyrenean oak (Quercus pyrenaica Willd.) stands in north-west Spain

Abstract: Stand Density Management Diagrams are useful tools for designing and evaluating alternative density management regimes without the need of implementing any silvicultural action, and allowing the future stand conditions to be predicted prior to implementing management schedules. In this study, stand density management diagrams were developed for Pyrenean oak (Quercus pyrenaica Willd.) stands in north-west Spain by including data on stand volume, stand aboveground biomass, stand stem biomass and carbon pools. Data were obtained from Third National Forest Inventory plots (n=1860). The large geographical area analyzed in this study was classified by provenance regions, which were compared in terms of biomass production in order to define areas with similar characteristics for use as management units. The comparisons identified 6 independent groups. Different stand-level models and the associated diagrams for the aforementioned stand variables were therefore developed for each group.

Modifying the G’DAY process-based model to simulate the spatial variability of Eucalyptus plantation growth on deep tropical soils

Large differences in productivity have been observed between neighboring Eucalyptus plantations in Brazil, that cannot be explained by climate and are unlikely to be due solely to altered management practices. Current ecophysiological models used by forestry companies to simulate stand development in large plantation zones rely on empirical site fertility indices (representing water and nutrient availability) to capture this spatial variability in growth rates. We propose a model that requires no empirical assessment of site fertility to simulate stand growth over entire rotations. We applied a modified version of the G’DAY model of carbon, nitrogen and water cycling at a daily time step to short-rotation plantations located in São Paulo State, including a simple mechanistic description of the effect of water availability on growth. The progressive and rapid root exploration of deep soil layers was modeled in a simple way, by considering that maximum plant available water increased with mean tree height. The model was parameterized using detailed measurements made over the entire rotation of an experimental stand of Eucalyptus grandis, and was subsequently applied to 16 clonal stands managed in a similar way by one company, but with different planting dates and contrasting productivity levels. Stem biomass simulations, driven by daily weather data (maximum and minimum air temperatures, global radiation and rainfall), were strongly correlated with company inventory estimates of stem biomass carried out at different ages. The temporal variation of leaf area index was also adequately simulated, as was shown by comparison with leaf area index derived from satellite data. The model was able to capture more than 95% of the variability of standing stem biomass and more than 85% of the variability of stem growth measured on these stands, provided spatial differences in soil water holding capacity were taken into account.

Estimation of stand variables in Pinus radiata D. Don plantations using different LiDAR pulse densities

This study aimed to verify the validity of linear, power function and exponential models to estimate stand variables in Galician Atlantic forests of Pinus radiata D. Don using Light Detection and Ranging (LiDAR). These forests differ in structure and species composition from boreal forests, in which this methodology is fully developed. The models tested use LiDAR-derived canopy height and intensity distribution metrics as explanatory variables to predict the following stand attributes: mean height, dominant height, stand basal area, stand volume, stand crown biomass, stand stem biomass and stand aboveground biomass. Exponential models performed best in most cases, with goodness-of-fit statistics similar to those reported in the international literature for boreal forests. The coefficient of determination ranged from 0.44 (for stand crown biomass) to 0.87 (for dominant height), and the root mean square error/mean·100 ranged from 8.2 per cent (for dominant height) to 31.6 per cent (for stand stem biomass). Model precision did not essentially vary after reducing 94 per cent of the original point cloud, i.e. when laser pulse density was reduced from 8 pulses m−2 to only 0.5 pulses m−2.

Allometric equations to predict the total aboveground biomass of tree species in a planted forest in Egypt

AbstractThe aim of this study is to estimate the total above‐ground biomass (TAGB), stem height (H), diameter at breast height (dbh) and basal area of five tree species (ages 7‐8 years) irrigated by municipal sewage water in the Egyptian‐Chinese friendship forest, Sadat City, Egypt. From the biomass data that obtained through destructive sampling, models for predicting aboveground biomass were developed. The highest values for stem density and height were estimated for Eucalyptus citriodora, while the lowest value for density was obtained for Dalbergia sissoo and stem height for Khaya senegalensis. The highest values for basal area and dbh were obtained for Casuarina spp., while the lowest values were recorded for Dalbergia sissoo. Eucalyptus camaldulensis had the highest stand stem biomass and TAGB (55.5, 83.9 t DW ha‐1, respectively). In addition, Casuarina spp. had the highest leafy branches biomass (32.5 t DW ha‐1) while Dalbergia sissoo had the lowest values for all tree components. All the generated allometric equations had high correlation coefficients at high probability levels. Moreover, the results revealed that not only the dbh data can be used as independent variable for biomass determination, but also stem height and size index are recommended for biomass estimation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Development of a stand density management diagram for radiata pine stands including assessment of stand stability

A stand density management diagram (SDMD) was constructed for Pinus radiata D. Don plantations in Galicia (north-western Spain) on the basis of four equations that were fitted simultaneously to data collected from 223 permanent plots. The relative spacing index was used to characterize the growing stock. The diagram provides information about quadratic mean diameter, stand merchantable volume, stand above-ground biomass, stand stem biomass and stand carbon pools. In addition, an estimation of the average slenderness coefficient for the whole stand and for each quarter of the stand diameter distribution was included. This information can be used to assess the stability of the whole stand and different crown classes, respectively. The SDMD outlined here allows foresters to make quick and easy comparisons among different thinning schedules in which both timber production and the risk of damage from wind or snow are considered. Two alternative density management systems, one that includes thinning operations and another that only includes the density-related mortality provided by a mortality function, are outlined in the diagram. © Institute of Chartered Foresters, 2009. All rights reserved.

An ecoregional model for estimating volume, biomass and carbon pools in maritime pine stands in Galicia (northwestern Spain)

Stand density management diagrams, including information about stand volume, stand aboveground biomass, stand stem biomass and carbon pools, were developed for maritime pine stands in Galicia, by applying biomass regression functions and carbon estimates to data from a network of 266 plots located throughout Galicia. The models were constructed on the basis of five equations that were fitted simultaneously using the full information maximum likelihood procedure. The first equation relates quadratic mean diameter to the number of stems per hectare and dominant height. The next three equations relate stand volume, stand aboveground biomass, and stand stem biomass to quadratic mean diameter, number of stems per hectare and dominant height. The last equation relates carbon pools in stand aboveground biomass to stand aboveground biomass. Evaluation of the equations used to develop the diagrams, by the non-linear extra sum of squares method and the Lakkis–Jones test, revealed differences for the two ecoregions defined for the species in Galicia. Different stand-level models and the associated diagrams for stand volume, stand aboveground biomass, stand stem biomass, and carbon pool estimation were therefore developed for each ecoregion.

Does disturbance prevent total basal area and biomass in indigenous forests from being at equilibrium with the local environment?

Understanding the determinants of the amount of biomass in various forests is presently a global imperative because forests may (e.g. Phillips et al. 2002) or may not be carbon sinks (Clark 2002). Presently, the assumption for modelling and empirical studies is that forest biomass and net primary production (NPP) are in equilibrium. For example, Beerling & Woodward (2001) modelled world-wide plant biomass on the basis of how net primary productivity (NPP) and annual transpiration rates affect tree size. They predicted that the largest stands of organic carbon are in the wet tropics. Similarly, in a recent textbook, Chapin et al. (2002) indicate that amongst forests, tropical forests have the greatest biomass and greatest NPP. In contrast, Midgley (2001) drew attention to the negative correlation between basal area and disturbance rates in some tropical forests. Also, Enquist & Niklas (2001) demonstrated that biomass is not correlated with latitude. Indeed, many indigenous forests with exceptionally large total basal areas and thus total standing stem biomass occur in the cool-temperate areas. For example, the Pacific Northwest redwood and Tasmanian mountain-ash forests have a total basal area of 300+ m2 ha−1, which exceeds the mean of many tropical forests (i.e. 35 m2 ha−1) (see Midgley 2001 and references therein).

Long-term growth and ecophysiological responses of a southeastern Oklahoma loblolly pine plantation to early rotation thinning

A thinning levels study was initiated in a 9-year-old loblolly pine ( Pinus taeda L.) plantation containing 26.6 m 2 ha −1 basal area during the spring of 1984 in southeastern Oklahoma. Thinning treatments consisted of (1) three control plots (BA100), (2) three plots thinned to approximately 50% of the original basal area (BA50) and (3) three plots that were thinned to 25% of the original basal area (BA25). In 1987 the BA50 and BA25 plots were both rethinned to a basal area of 12 m 2 ha −1. No other thinnings were done through age 24. The control plots have attained a basal area of 45.3 m 2 ha −1 and basal area is now starting to decline. The BA25 and BA50 plots have basal areas between 34 and 35 m 2 ha −1. Mortality has averaged about 90 trees ha −1 per year from age 10 to age 24 on the control plot, declining from 2078 trees ha −1 at age 10 to 827 trees ha −1 at age 24. Mortality losses in the BA25 and BA50 plots have been only 3.2–7.7 trees ha −1 per year over the entire study period. Cumulative stem biomass lost to mortality was 10.5, 16.0 and 61 Mg ha −1, respectively, for the BA25, BA50 and BA100 treatments. Cumulative standing live biomass at age 24 in the BA100 treatment is 132 Mg ha −1. Cumulative standing live biomass in the BA25 and BA50 treatments at age 24 is 86 and 79%, respectively, of that observed in the BA100 treatment. These results suggest wide ranges of residual stand densities left after an early thinning will produce a high percentage of the potential total maximum standing stem biomass. Diameter distributions at age 24 show only 33% of the trees in the BA100 treatments have the dimensions to be sawtimber (≥30 cm) but 92 and 95% of the trees in the BA25 and BA50, respectively, are sawtimber dimension or larger. Mean annual stem biomass production (MAI) of the BA100 treatment is 7.5 Mg ha −1 per year at age 24. MAI of the thinned treatments is about 5.1 Mg ha −1 per year and is converging to that of the BA100 treatment. The basis for this convergence is not that the live trees in the BA100 treatment are producing live biomass less rapidly than the thinned plots, but that mortality losses in the BA100 plot are much higher. Current annual stemwood production in all treatments is often limited by the severe summer droughts that occur in this region. The wide variations in weather experienced at this site also result in variations in earlywood:latewood ratio and ring specific gravity.

Production, allocation, and stemwood growth efficiency of Pinus taeda L. stands in response to 6 years of intensive management

Loblolly pine ( Pinus taeda L.) is a highly plastic species with respect to growth responses to forest management. Loblolly pine is the most planted species across the southern United States, a region with the most expansive and intensively managed forest plantations in the world. Management intensity, using tools such as site preparation and fertilization, is increasing greatly in scope over time. To better define to the productive potential of loblolly pine under intensive management, the influence of 6 years of management with weed control (W), weed control plus irrigation (WI), weed control plus irrigation and fertigation (irrigation with a fertilizer solution) (WIF), or weed control plus irrigation, fertigation, and pest control (WIFP) since plantation establishment on stand productivity in loblolly pine was examined. The site is located near Bainbridge, GA (30°48′N latitude and 84°39′W longitude) and is of medium quality (site index=18 m, base age 25). Increasing management intensity greatly accelerated stand development and biomass accumulation. At age 6 total production (above plus belowground) was nearly doubled from 50 to 93 Mg ha −1 in WIFP stands compared to W stands, and standing stem biomass increased from 24 Mg ha −1 in W stands to 48 Mg ha −1 in response to WIFP treatment. Stem current annual increment (CAI) peaked at age 5 in the WIF and WIFP stands at 17–18 Mg ha −1 per year at a basal area between 18 and 21 m 2 ha −1. Year to year variation in CAI was better explained by previous-year leaf area index (LAI) than current-year LAI. Maximum stemwood production in loblolly pine was achieved through large increases in LAI and small decreases in allocation to woody roots (tap+coarse roots) versus woody shoots (stem+branches) associated with intensive treatments.

Relationships between polarimetric SAR backscatter and forest canopy and sub-canopy biophysical properties

This paper highlights the potential of multiwaveband polarimetric SAR data for the estimation of both canopy (percentage canopy closure) and sub-canopy (stem biomass) biophysical variables of a Sitka spruce forest in upland Wales. Stand stem biomass was estimated using forest survey data on diameter at breast height (DBH) and tree height from 0.01 ha plots. Photographs of the forest canopy were taken using a camera fitted with a wide-angle fisheye lens from a number of locations within a stand. The photographs were later digitized and estimates of stand percentage canopy closure were derived using image processing software. It was found that C-band HV and VV, and L-band HV and VV polarization backscatter were significantly related to stem biomass. There was no sensitivity to percentage canopy closure using single polarization backscatter but highly significant relationships were obtained using ratios of single polarization backscatter and variables derived from the polarization signatures. The strong correlations between C-band backscatter and stem biomass indicated a relationship between the structure of the top crown layer and sub-canopy biomass.