Woody Biomass Production Research Articles

Early effects of two planting densities on growth dynamics and water-use efficiency in Robinia pseudoacacia (L.) and Populus deltoides (Bartr. ex Marsh.) × P. nigra (L.) short rotation plantations

Black locust is an interesting option for biomass production at sites prone to water shortage because the species combines water-use efficiency and a biomass yield largely superior to that of poplars under the conditions of the study. Black locust (Robinia pseudoacacia L.) is an interesting tree species for woody biomass production. However, its potential for this purpose has been much less studied and characterized than that for species from the Salicaceae family (i.e., poplar and willow). The objective of our study was to evaluate the potential of black locust for biomass production as compared to that of poplar. We estimated biomass production, growth habit, and efficiency of water use of two provenances of black locust (1) compared to those of poplar (Populus deltoides Bartr. ex Marsh. × P. nigra L.), (2) at two planting densities, and (3) 2 and 4 years after planting. Black locust had a very different growth habit, much higher biomass production, and larger water-use efficiency than poplar. These differences were exacerbated during the driest year of the experiment. However, black locust responded very badly to harvesting. Black locust was more productive and more efficient in terms of water use than poplar, especially during the driest year of the experiment.

Environmental Sustainability of Heat Produced by Poplar Short-Rotation Coppice (SRC) Woody Biomass

As demonstrated for some time, the reduction of greenhouse gases in the atmosphere can also take place using agroforestry biomass. Short-rotation coppice (SRC) is one of the sources of woody biomass production. In our work, the supply of woody biomass was considered by examining four different cutting shifts (2, 3, 4 and 5 years) and, for each, the Global Warming Potential (GWP) was evaluated according to the IPCC 2007 method. Regarding the rotation cycle, four biomass collection systems characterized by different levels of mechanization were analyzed and compared. In this study, it was assumed that the biomass produced by the SRC plantations was burned in a 350 kWt biomass power plant to heat a public building. The environmental impact generated by the production of 1 GJ of thermal energy was assessed for each of the forest plants examined, considering the entire life cycle, from the field phase to the energy production. The results were compared with those obtained to produce the same amount of thermal energy from a diesel boiler. Comparing the two systems analyzed, it was shown that the production and use of wood biomass to obtain thermal energy can lead to a reduction in the Global Warming Potential of over 70% compared to the use of fossil fuel.

A STELLA-Based Model to Simultaneously Predict Hydrological Processes, N Uptake and Biomass Production in a Eucalyptus Plantation

Eucalyptus is one of the fastest growing hardwoods for bioenergy production. Currently, few modeling tools exist to simultaneously estimate soil hydrological processes, nitrogen (N) uptake, and biomass production in a eucalyptus plantation. In this study, a STELLA (Structural Thinking and Experiential Learning Laboratory with Animation)-based model was developed to meet this need. After the model calibration and validation, a simulation scenario was developed to assess eucalyptus (E. grandis × urophylla) annual net primary production (ANPP), woody biomass production (WBP), water use efficiency (WUE), and N use efficiency (NUE) for a simulation period of 20 years. Simulation results showed that a typical annual variation pattern was predicted for water use, N uptake, and ANPP, increasing from spring to fall and decreasing from fall to the following winter. Overall, the average NUE during the growth stage was 700 kg/kg. To produce 1000 kg eucalyptus biomass, it required 114.84 m3 of water and 0.92 kg of N. This study suggests that the STELLA-based model is a useful tool to estimate ANPP, WBP, WUE, and NUE in a eucalyptus plantation.

Spatially variable hydrologic impact and biomass production tradeoffs associated with Eucalyptus (E. grandis) cultivation for biofuel production in Entre Rios, Argentina

AbstractClimate change and energy security promote using renewable sources of energy such as biofuels. High woody biomass production achieved from short‐rotation intensive plantations is a strategy that is increasing in many parts of the world. However, broad expansion of bioenergy feedstock production may have significant environmental consequences. This study investigates the watershed‐scale hydrological impacts of Eucalyptus (E. grandis) plantations for energy production in a humid subtropical watershed in Entre Rios province, Argentina. A Soil and Water Assessment Tool (SWAT) model was calibrated and validated for streamflow, leaf area index (LAI), and biomass production cycles. The model was used to simulate various Eucalyptus plantation scenarios that followed physically based rules for land use conversion (in various extents and locations in the watershed) to study hydrological effects, biomass production, and the green water footprint of energy production. SWAT simulations indicated that the most limiting factor for plant growth was shallow soils causing seasonal water stress. This resulted in a wide range of biomass productivity throughout the watershed. An optimization algorithm was developed to find the best location for Eucalyptus development regarding highest productivity with least water impact. E. grandis plantations had higher evapotranspiration rates compared to existing terrestrial land cover classes; therefore, intensive land use conversion to E. grandis caused a decline in streamflow, with January through March being the most affected months. October was the least‐affected month hydrologically, since high rainfall rates overcame the canopy interception and higher ET rates of E. grandis in this month. Results indicate that, on average, producing 1 kg of biomass in this region uses 0.8 m3 of water, and the green water footprint of producing 1 m3 fuel is approximately 2150 m3 water, or 57 m3 water per GJ of energy, which is lower than reported values for wood‐based ethanol, sugar cane ethanol, and soybean biodiesel.

Altered plant carbon partitioning enhanced forest ecosystem carbon storage after 25 years of nitrogen additions.

Decades of atmospheric nitrogen (N) deposition in the northeastern USA have enhanced this globally important forest carbon (C) sink by relieving N limitation. While many N fertilization experiments found increased forest C storage, the mechanisms driving this response at the ecosystem scale remain uncertain. Following the optimal allocation theory, augmented N availability may reduce belowground C investment by trees to roots and soil symbionts. To test this prediction and its implications on soil biogeochemistry, we constructed C and N budgets for a long-term, whole-watershed N fertilization study at the Fernow Experimental Forest, WV, USA. Nitrogen fertilization increased C storage by shifting C partitioning away from belowground components and towards aboveground woody biomass production. Fertilization also reduced the C cost of N acquisition, allowing for greater C sequestration in vegetation. Despite equal fine litter inputs, the C and N stocks and C:N ratio of the upper mineral soil were greater in the fertilized watershed, likely due to reduced decomposition of plant litter. By combining aboveground and belowground data at the watershed scale, this study demonstrates how plant C allocation responses to N additions may result in greater C storage in both vegetation and soil.

Effects of Intra-Seasonal Drought on Kinetics of Tracheid Differentiation and Seasonal Growth Dynamics of Norway Spruce along an Elevational Gradient

Research Highlights: Our results provide novel perspectives on the effectiveness and collapse of compensatory mechanisms of tracheid development of Norway spruce during intra-seasonal drought and the environmental control of intra-annual density fluctuations. Background and Objectives: This study aimed to compare and integrate complementary methods for investigating intra-annual wood formation dynamics to gain a better understanding of the endogenous and environmental control of tree-ring development and the impact of anticipated climatic changes on forest growth and productivity. Materials and Methods: We performed an integrated analysis of xylogenesis observations, quantitative wood anatomy, and point-dendrometer measurements of Norway spruce (Picea abies (L.) Karst.) trees growing along an elevational gradient in South-western Germany during a growing season with an anomalous dry June followed by an extraordinary humid July. Results: Strong endogenous control of tree-ring formation was suggested at the highest elevation where the decreasing rates of tracheid enlargement and wall thickening during drought were effectively compensated by increased cell differentiation duration. A shift to environmental control of tree-ring formation during drought was indicated at the lowest elevation, where we detected absence of compensatory mechanisms, eventually stimulating the formation of an intra-annual density fluctuation. Transient drought stress in June also led to bimodal patterns and decreasing daily rates of stem radial displacement, radial xylem growth, and woody biomass production. Comparing xylogenesis data with dendrometer measurements showed ambivalent results and it appears that, with decreasing daily rates of radial xylem growth, the signal-to-noise ratio in dendrometer time series between growth and fluctuations of tree water status becomes increasingly detrimental. Conclusions: Our study provides new perspectives into the complex interplay between rates and durations of tracheid development during dry-wet cycles, and, thereby, contributes to an improved and mechanistic understanding of the environmental control of wood formation processes, leading to the formation of intra-annual density fluctuations in tree-rings of Norway spruce.

Climate and soil mediate the effects of liana density on forest dynamics

AbstractForest community dynamics is a topic of great interest in times when the global carbon budget is a widespread concern due to climate change. Among its effects, longer periods of drought and liana proliferation, coupled with land use change, may endanger tropical forest carbon sinks. Here, in a 10.3 ha sampling of six Atlantic semideciduous forests, we investigated the effects of liana crown occupancy and large‐stemmed lianas, as well as their interactions with climate and soil, on forest dynamics. We expected that harsh environmental conditions would enhance the negative effects of lianas on forest productivity. Our hypothesis was corroborated by the findings that the positive effect of lianas on tree mortality increases under drier conditions, as well as their negative effect on tree recruitment. In addition, liana crown occupancy was the best predictor of net aboveground woody biomass productivity, which decreases as liana crown occupancy increases. Our study provides additional evidence of indirect climate change impacts on the tropical forest carbon sink by increasing the negative effects of liana crown occupancy on tree biomass productivity.Abstract in Portuguese is available with online material.

Enhancing hybrid Liquidambar somatic seedling production using a temporary immersion bioreactor

Temporary immersion bioreactors can improve hybrid sweetgum somatic embryo conversion and somatic seedling growth rates compared to semisolid medium, significantly improving somatic seedling production efficiency for hybrid sweetgum, an emerging woody biomass crop. Fast-growing hybrid southern hardwood trees should make excellent material for woody biomass production in the Southeastern US, if elite clones can be identified and efficiently propagated. We have enhanced the potential of sweetgum (Liquidambar styraciflua) as a biomass species by generating hybrids between the tree and its Chinese relative, Liquidambar formosana, and propagating the most promising clones via somatic embryogenesis. Some of the hybrid clones have already demonstrated superior biomass productivity compared to elite L. styraciflua trees. However, production of somatic seedlings from these clones remains labor-intensive. Bioreactors, specifically temporary immersion designs, such as the RITA®, have been applied to improve the efficiency of in vitro propagation of a number of woody species. We tested RITA® bioreactors for their potential to improve the production efficiency of high-quality hybrid sweetgum somatic seedlings. In one tested genotype, a RITA® with 50 somatic embryos had about 66% higher conversion frequency (p < 0.05) and produced about 40% more “high-quality” somatic seedlings (p < 0.05) than when somatic embryos were germinated on semisolid medium in GA-7 vessels. In all the genotypes we tested, somatic seedlings produced in RITA® bioreactors had higher survival percentages by the end of acclimatization than somatic seedlings produced on semisolid medium in GA-7 vessels.

Modelling and simulation of the wood biomass supply from the sustainable management of natural forests

Wood biomass is an important energy resource, which can contribute to reduce the dependence on fossil fuels. The research undertakes the microeconomic approach to estimate the technical availability and operational costs of woody biomass production with a higher level of precision than other models present in the literature, as it considers the entire supply chain of the sustainable management of natural forests. This study introduces a tool, which is applied to estimate supply curves and costs of wood biomass extraction from natural forests in the 7th Region of Chile. The simulation indicates that 531,015 tons/year of wood biomass is available in natural forests of the Region under study, with extraction costs ranging from 24.51 to 56.68 US$/ton, or an average total cost of 40.97 US$/ton. The parametric analysis revealed that the maximum admissible distance to the nearest transport route and the transportation costs are the two most influential variables in the estimation of wood biomass supply and cost. Reducing the admissible distance from 5 km to 1 km reduced the availability of biomass by 80%, while a variation of ±50% of transportation costs translated into ±18.3% variation of total extraction costs.The proposed method can be used to identify the technical-economic potential of wood biomass from natural forests in any commune, province, region, or country; as it has the flexibility to allow tests with multiple scenarios and parameters depending on the specific characteristics of the area to be analysed. Essentially, the purpose of this tool is to serve the assessment processes of the identification of new wood biomass resources, allowing decision makers to increase the potential of sustainable and cost-effective woody biomass for heat and electricity generation, and at the same time reduce greenhouse gas emissions and the dependence on fossil fuels.

Fire as a driver of wood mechanical traits in the boreal forest

In boreal forests where the fire return interval is long, the high structural variability of stands may affect wood traits. Here, we build on earlier work that revealed a difference in wood mechanical traits of black spruce between regular (regenerated from fire in the last 200 years) and irregular (undisturbed by fire for at least 200 years) stands. This study aimed to identify the ecological drivers of this variation in wood traits. To do so, we first sought to corroborate existing results on the effects of stand structure induced by the time since the last stand-replacing fire (TSLF) on wood mechanical stiffness in the eastern boreal forest of Canada. Results confirmed that black spruce from regular stands tend to produce wood with higher modulus of elasticity (MOE) than those from irregular stands. For both regular and irregular stands, we compared a set of linear models that were defined a priori to determine the structural and site productivity variables having the largest influence on MOE. The ‘growth efficiency index’ (aboveground woody biomass production per unit leaf area) was the best predictor of MOE variation among regular stands. For irregular stands, the model with TSLF as the sole explanatory variable was a better predictor of MOE than any other candidate model. However, we did not find strong evidence of a direct relationship between TSLF and wood traits, since our best models explained a relatively small proportion of the variance. Our results suggest that differences in wood traits could be attributable to the seed or layer origin of the trees and/or to the length of time trees remain in the understory. We propose that intensive wood production strategies focus on stands of the first post-fire cohort.

3-04 木質バイオマス生産からエネルギー利用までの要素連関性について～コストの観点から～

3-04 木質バイオマス生産からエネルギー利用までの要素連関性について～コストの観点から～

Eucalyptus Are Unlikely to Escape Plantations and Invade Surrounding Forests Managed with Prescribed Fire in Southeastern US

Woody biomass production can increase through establishment of non-native tree species exhibiting greater growth potential than traditional native species. Interest in growing Eucalyptus in the southeastern US has raised concern over its potential spread and invasion, which could impact ecosystem properties and functions. Within the matrix of land use where Eucalyptus establishment is being considered in the southeastern US, surrounding pine forests managed with fire represent a likely pathway for invasion. We used greenhouse and field experiments to evaluate the potential invasion risk of Eucalyptus benthamii. We were specifically interested in determining if seeds could successfully germinate in fire-maintained pine forests and if fire-return intervals influenced germination through impacts on litter accumulation and light availability. The greenhouse experiment investigated the influence of light availability on germination success, whereas the field study investigated the influence of time since fire, and thus litter accumulation and light availability, on germination success. Percent germination was similar under non-shaded controls and moderate shade, but complete shade resulted in low germination rates. Germination was lower in the field compared to the greenhouse and was influenced by litter and light availability, which varied according to fire-return intervals. Litter increased, and light availability decreased, with time since burn. Germination was negatively related to litter depth and positively related to light availability, thereby decreasing with time since fire. Germination increased with litter removal but remained positively related to light availability after litter removal. Higher germination with litter removal suggests germination is influenced by litter, but higher germination with increased light availability, regardless of raking, suggests germination is also influenced by light availability. Despite these relationships, no seedlings persisted through the growing season. The low germination rates under a variety of field conditions coupled with the lack of persistence suggests establishment may be unlikely, regardless of the surrounding land matrix.

Deciphering support for woody biomass production for electric power using an ecosystem service framework

There is well established literature that focuses on measuring the public (social) value of ecosystem services, alongside traditional economic valuations, with the aim of better informing natural resource management decision-making. However, few studies have considered the role of ecosystem service values directly in the context of the general public's support for specific natural resource management decisions and practices. This leaves open the possibility that policy makers and resource managers may be relying on criteria that have negligible influence on public preferences. In this paper, we consider this gap, by testing hypotheses concerning the public's willingness to support forest harvesting for biomass material that will facilitate electricity generation based on a survey of households in Tomahawk, Wisconsin, U.S. An ecosystem service valuation model was developed and subjected to multivariate statistical analyses (factor analysis and OLS linear regression). The findings show that respondents in biomass producing communities may be more supportive of biomass sources such as forestry residues and forest thinnings than dedicated energy wood harvesting operations. In addition, the findings indicate that using an ecosystem service approach can help explain differences in support between these respondents and provide insight into socially acceptable forms of biomass harvesting operations.

High productivity in hybrid-poplar plantations without isoprene emission to the atmosphere

Hybrid-poplar tree plantations provide a source for biofuel and biomass, but they also increase forest isoprene emissions. The consequences of increased isoprene emissions include higher rates of tropospheric ozone production, increases in the lifetime of methane, and increases in atmospheric aerosol production, all of which affect the global energy budget and/or lead to the degradation of air quality. Using RNA interference (RNAi) to suppress isoprene emission, we show that this trait, which is thought to be required for the tolerance of abiotic stress, is not required for high rates of photosynthesis and woody biomass production in the agroforest plantation environment, even in areas with high levels of climatic stress. Biomass production over 4 y in plantations in Arizona and Oregon was similar among genetic lines that emitted or did not emit significant amounts of isoprene. Lines that had substantially reduced isoprene emission rates also showed decreases in flavonol pigments, which reduce oxidative damage during extremes of abiotic stress, a pattern that would be expected to amplify metabolic dysfunction in the absence of isoprene production in stress-prone climate regimes. However, compensatory increases in the expression of other proteomic components, especially those associated with the production of protective compounds, such as carotenoids and terpenoids, and the fact that most biomass is produced prior to the hottest and driest part of the growing season explain the observed pattern of high biomass production with low isoprene emission. Our results show that it is possible to reduce the deleterious influences of isoprene on the atmosphere, while sustaining woody biomass production in temperate agroforest plantations.

O-09 木質バイオマスの利用拡大に向けた技術評価 バイオマス生産の観点から

O-09 木質バイオマスの利用拡大に向けた技術評価 バイオマス生産の観点から

Adverse and Beneficial Effects of Woody Biomass Feedstock Plantations on Biodiversity and Wildlife Habitats

Abstract Woody biomass feedstock is suitable for direct combustion, gasification, pyrolysis, ethanol or methanol production yielding heat, charcoal, pyrolysis oil, green electricity and bio-propellants. However, there are several issues concerning the environmental, social and economic sustainability of woody biomass production connected to land use, protection of wildlife habitats, conservation and remediation of landscapes. Establishing energy plantations on arable lands or on grasslands is generally considered as working against nature conservation, while setting them up in polluted areas or wastelands could be advantageous for wildlife, because of 1. more permanent cover that provides shelter and biomass for feeding, which is especially important in winter periods; 2. higher architectural complexity of vegetation providing more place for nesting and feeding for wildlife; 3. exploiting the advantages of root filtration, phytoremediation, or using less chemicals; 4. forbs in the undergrowth and young shoots able to provide better quality food for wildlife than the intensive monocultures. The solution is a complex management system, including land use, phytoremediation, waste and wastewater management and ecosystem-based planning incorporated in one dynamic structure.

Effect of spacing, parental genotype and harvesting cycle on biomass production in two half-sib progenies of Robinia pseudoacacia L.

Abstract This study investigated the influence of spacing, parental genotype and harvesting cycle on woody biomass production in open-pollinated families of the locally selected black locust (Robinia pseudoacacia L.) clones ‘Tsarevets’ and ‘Srebarna’ at specific site conditions. A Nelder experiment with 16, varying along the spokes, nearly-square spacings and two black locust families arranged in alternating sectors, was established in North Central Bulgaria. Alternative harvesting options (‘harvesting cycles’), consisting of one, two or three successive coppicings, were applied and the amounts of dry shoot dendromass collected per plant were accumulated to calculate and analyse the total yield of woody biomass, achievable within 2-, 3- and 4-year periods (‘production period’). The one-coppicing cycle proved superior for both families, regardless of the length of the production period. Biomass yield in the family of ‘Srebarna’ exceeded that of ‘Tsarevets’ at the wider spacings, when 1 and 2 year-old shoots were harvested, while dendromass production of ‘Tsarevets’ was substantially higher in the 4-year-old shoots. The woody biomass yield per plant increased with spacing, and growth tended to saturation at the lowest densities, enabling derivation of optimal planting densities. The total dendromass yield per hectare was maximized at growing space of around 0.5 m2 per plant for the 2-year production period, while spacing of 1.2–2 m2 was required for production periods of 3 and 4 years. If the results from this experiment can be reliably scaled up in practice then short rotation crops of ‘Srebarna’ and ‘Tsarevets’ families at comparable site conditions should be able to produce annual biomass yields of 9–11 Mg.ha−1.year−1 within a 4-year period, given the optimal planting densities and harvesting regimes prescribed.

Additive effects of high growth rate and low transpiration rate drive differences in whole plant transpiration efficiency among black poplar genotypes

Poplar plantations, widely used for the production of woody biomass, might be at high risk from the climate change-induced increase in the frequency of drought periods. Therefore, selecting improved genotypes, which are highly productive but with a high water use efficiency (WUE), is becoming a major target. The use of automated weighing systems in controlled environments facilitates the estimation of cumulated water loss and whole plant transpiration efficiency (TE). Differences in TE and leaf level intrinsic WUE as well as the contribution of underlying ecophysiological traits were determined in three contrasting P. nigra genotypes. Strong differences in TE among the selected genotypes were congruent with differences in leaf level intrinsic WUE. Our data show that a high total leaf area was overcompensated by a low per leaf area transpiration rate, leading to higher TE in highly productive genotypes originating from cool locations. Nocturnal water loss was relatively low but contributed to variations in TE among genotypes. In response to drought, leaf level WUE increased but not TE, suggesting that carbon losses due to whole plant respiration could offset the drought-induced increase in intrinsic WUE.

Quantifying intra-annual dynamics of carbon sequestration in the forming wood: a novel histologic approach

This study presents a novel histologic approach to quantify the intra-annual dynamics of carbon sequestration in forming wood. This innovative approach, based on repeated measurements of xylem apparent density, is more direct, and more accurate than the previously published cellular-based approach. Moreover, this new approach, which was tested here on softwoods, is also applicable to hardwoods without any modification. Forest ecosystems are key players of the terrestrial carbon cycle. Indeed, wood represents the principal carbon pool of terrestrial biomass, accumulated in trees through cambial activity. Here, we present a novel, simple, and fast approach to accurately estimate the intra-annual dynamics of aboveground woody biomass production based on image analysis of forming xylem sections. During the 2015 growing season, we weekly collected wood samples (microcores) containing the forming xylem on seven Norway spruces (Picea abies (L.) Karst), grown in Hesse forest (North-East France). The microcores were prepared to allow the observation of the forming tissues with an optical microscope. Xylem apparent density and radial increment were then measured directly on images of the histological sections. In order to compare our “histologic approach” with the previously published “cellular approach,” we also counted the number of tracheids in each differentiation zones, and measured the tracheid dimensions all along the last-formed tree ring. The two approaches yielded comparable meaningful results, describing xylem size increase and aboveground woody biomass production as bell-shaped curves culminating in May and June respectively. However, the histologic approach provided a shorter time lag between xylem size increase and biomass production than the cellular one. Better quantification of the shift between stem growth in size and in biomass will require addressing the knowledge gap regarding lignin deposition kinetics. Nevertheless, our novel histologic approach is simpler and more direct than the cellular one, and may open the way to a first quantification of intra-annual dynamics of woody biomass production in angiosperms, where the cellular approach is hardly applicable.

Abscisic acid signalling mediates biomass trade-off and allocation in poplar.

Abscisic acid (ABA) is a well known stress hormone regulating drought adaptation of plants. Here, we hypothesised that genetic engineering of genes involved in ABA stress signalling and photoperiodic regulation affected drought resistance by trade-off with biomass production in perennial poplar trees. We grew Populus tremula×tremuloides wild-type (T89) and various transgenic lines (two transformation events of 35S::abi1-1, 35S::RCAR, RCAR:RNAi, 35S::ABI3, 35S::AREB3, 35S::FDL1, FDL1:RNAi, 35S::FDL2 and FDL2:RNAi) outdoors and exposed them to drought in the second growth period. After the winter, the surviving lines showed a huge variation in stomatal conductance, leaf size, whole-plant leaf area, tree height, stem diameter, and biomass. Whole-plant leaf area was a strong predictor for woody biomass production. The 35S::AREB3 lines were compromised in biomass production under well irrigated conditions compared with wild-type poplars but were resilient to drought. ABA signalling regulated FDL1 and FDL2 expression under stress. Poplar lines overexpressing FDL1 or FDL2 were drought-sensitive; they shed leaves and lost root biomass, whereas the FDL RNAi lines showed higher biomass allocation to roots under drought. These results assign a new function in drought acclimation to FDL genes aside from photoperiodic regulation. Our results imply a critical role for ABA-mediated processes in balancing biomass production and climate adaptation.