Short Rotation Coppice Culture Research Articles

Field and saccharification performances of poplars severely downregulated in CAD1.

Lignin is one of the main factors causing lignocellulosic biomass recalcitrance to enzymatic hydrolysis. Glasshouse-grown poplars severely downregulated for CINNAMYL ALCOHOL DEHYDROGENASE 1 (CAD1), the enzyme catalysing the last step in the monolignol-specific branch of lignin biosynthesis, have increased saccharification yields and normal growth. Here, we assess the performance of these hpCAD poplars in the field under short rotation coppice culture for two consecutive rotations of 1 yr and 3 yr. While 1-yr-old hpCAD wood had 10% less lignin, 3-yr-old hpCAD wood had wild-type lignin levels. Because of their altered cell wall composition, including elevated levels of cinnamaldehydes, both 1-yr-old and 3-yr-old hpCAD wood showed enhanced saccharification yields upon harsh alkaline pretreatments (up to +85% and +77%, respectively). In contrast with previous field trials with poplars less severely downregulated for CINNAMYL ALCOHOL DEHYDROGENASE (CAD), the hpCAD poplars displayed leaning phenotypes, early bud set, early flowering and yield penalties. Moreover, hpCAD wood had enlarged vessels, decreased wood density and reduced relative and free water contents. Our data show that the phenotypes of CAD-deficient poplars are strongly dependent on the environment and underpin the importance of field trials in translating basic research towards applications.

Productivity of low-input short-rotation coppice American sycamore (Platanus occidentalis L.) grown at different planting densities as a bioenergy feedstock over two rotation cycles

Short rotation coppice culture of woody crop species (SRWCs) has long been considered a sustainable method of producing biomass for bioenergy that does not compete with current food production practices. In this study, we grew American sycamore (Platanus occidentalis L.) for nine years corresponding to two rotation cycles (first rotation (FR) = 2010–2014, second rotation (SR) = 2015–2019). This was done at varying tree planting densities (1250, 2500, 5000, and 10,000 trees per hectare (tph)) on a degraded agricultural landscape under low-input (e.g. no fertilizer and low herbicide application) culture, in the Piedmont physiographic region of eastern North Carolina. Tree productivity was proportional to planting density, with the highest cumulative aboveground wood biomass in the 10,000 tph treatment, at 23.2 ± 0.9 Mg ha−1 and 39.1 ± 2.4 Mg ha−1 in the first and second rotations, respectively. These results demonstrate increasing productivity under a low-input SRWC management regime over the first two rotations. Biomass partitioning was strongly affected by planting density during FR, allocating less biomass to stems relative to other plant parts at low planting density (44–59% from 1250 to 10,000 tph, respectively). This effect disappeared during SR, however, with biomass partitioning to stems ranging from 74 to 79% across planting densities. Taken together, our results suggest that American sycamore has the potential to be effectively managed as a bioenergy feedstock with low input culture on marginal agriculture lands.

Transpiration at leaf and tree level in a poplar short-rotation coppice culture: seasonal and genotypic differences

Poplar (Populus spp.) is one of the most commonly cultivated genera in experimental and commercial short-rotation coppice (SRC) plantations. The genus is among the fastest growing in temperate latitudes, but the success of highly productive poplar SRC plantations strongly depends on soil water availability. We examined the transpiration at the leaf and the individual tree levels of four different poplar genotypes under an SRC regime. Measurements were performed for the entire growing season of 2016, during the seventh growth year of the plantation and before the third coppice on four poplar genotypes (three individual multiple-stem trees per genotype) belonging to different species and from a different genetic background. The experimental site was a commercial scale multi-genotype SRC plantation, established in Flanders (Belgium). Measurements at the leaf level were performed on specific days of the growing season that differed in evaporative demand, temperature and incoming radiation. To determine the transpiration at the stem level, we measured single-stem sap flow using the stem heat balance (SHB) method and daily stem diameter variation measurements. The whole-tree transpiration was estimated by summing the sap flow rates from all stems. Measurements at the stem level were continuously monitored during the entire growing season. Sap flow was tightly connected to the phenological stage of the trees, thus onset of spring (leaf area development) and late autumn (leaf fall) were easily identifiable from sap flow measurements, showing differences among the four genotypes. The dynamics of transpiration at the leaf and tree level were driven by photosynthetic photon flux density (PPFD), but the sap flow intensity was controlled by vapour pressure deficit (VPD). The four poplar genotypes showed different water use strategies, based on determination of transpiration and other plant water status indicators.

Efficacy of Growth Regulators in Enhancing Biopolymer Production from a Short-Rotation Coppice Culture of Eucommia ulmoides Olive: The First Rotation Report

Efficacy of Growth Regulators in Enhancing Biopolymer Production from a Short-Rotation Coppice Culture of <i>Eucommia ulmoides</i> Olive: The First Rotation Report

A comparative study of four approaches to assess phenology of Populus in a short-rotation coppice culture

We compared four approaches to assess phenology in a short-rotation coppice culture with 12 poplar (Populus) genotypes. The four approaches quantified phenology at different spatial scales and with different temporal resolutions: (i) visual observations of bud phenology; (ii) measurements of leaf area index; (iii) webcam images; and (iv) satellite images. For validation purposes we applied the four approaches during two years: the year preceding a coppice event and the year following the coppice event. The delayed spring greenup and the faster canopy development in the year after coppicing (as compared to the year before coppicing) were similarly quantified by the four approaches. The four approaches detected very similar seasonal changes in phenology, although they had different spatial scales and a different temporal resolution. The onset of autumn senescence after coppicing remained the same as in the year before coppicing according to the bud set observations, but it started earlier according to the webcam images, and later according to the MODIS images. In comparison to the year before coppicing, the growing season - in terms of leaf area duration - was shorter in the year after coppicing, while the leaf area index was higher.

Evaluation of Indirect Measurement Method of Seasonal Patterns of Leaf Area Index in a High-Density Short Rotation Coppice Culture of Poplar

Leaf area index (LAI) is an important determinant of biomass production and yield of short rotation bio-energy plantation. An accurate measurement of LAI is critical for quantifying light interception and penetration within the canopy, and subsequently understanding its influence on the stand carbon and energy balance. The aim of the current study is validation of the Sunscan Plant Canopy Analyzer which serves as an indirect method for the evaluation of the seasonal patterns of LAI, relation between LAI and above ground woody dry biomass and to determine the specific leaf area in short-rotation poplar hybrid clone J-105 (Populus nigra × P. maximowiczii) in uncoppiced (1st rotation) and coppiced (2nd rotation), respectively. LAI was measured in uncoppiced and coppiced by two different methods using indirect (SunScan Plant Canopy Analyzer) and direct (litterfall collection). Sunscan Plant Canopy Analyzer was compared against litterfall collection (only way to retrieve the actual LAI). Simple regression (R2 = 0.82) model was fitted to validate indirect measurement method and a very good agreement (82%) was observed in LAI values estimated from SunScan Plant Canopy Analyzer and from litterfall collection. Seasonal variability of LAI in a short rotation coppice (SRC) culture of poplar clone J-105 was evaluated over six years period (2008–2013), for uncoppiced (2008 and 2009) and coppiced (2010, 2011, 2012 and 2013) culture. The maximum canopy LAI (LAImax) reached 7.3 (uncoppiced) and 9.5 (coppiced). The linear regression (R2 = 0.93) for average LAI and above ground woody dry biomass was determined, and it was found that LAI acts an indicator of biomass productivity. Specific leaf area (SLA) was estimated in both uncoppiced and coppiced culture of poplar. The maximum SLA was found to be 138.9 cm2g−1 in uncoppiced and 126.9 cm2g−1 in coppiced. To conclude, the evaluated indirect LAI measurement method is portable, reliable and faster than direct LAI measurement in high density poplar short-rotation coppice culture.

Net ecosystem production and carbon balance of an SRC poplar plantation during its first rotation

To evaluate the potential of woody bioenergy crops as an alternative energy source, there is need for a more comprehensive understanding of their carbon cycling and their allocation patterns throughout the lifespan. We therefore quantified the net ecosystem production (NEP) of a poplar (Populus) short rotation coppice (SRC) culture in Flanders during its second growing season.Eddy covariance (EC) techniques were applied to obtain the annual net ecosystem exchange (NEE) of the plantation. Further, by applying a component-flux-based approach NEP was calculated as the difference between the modelled gross photosynthesis and the respiratory fluxes from foliage, stem and soil obtained via upscaling from chamber measurements. A combination of biomass sampling, inventories and upscaling techniques was used to determine NEP via a pool-change-based approach.Across the three approaches, the net carbon balance ranged from 96 to 199 g m−2 y−1 indicating a significant net carbon uptake by the SRC culture. During the establishment year the SRC culture was a net source of carbon to the atmosphere, but already during the second growing season there was a significant net uptake. Both the component-flux-based and pool-change-based approaches resulted in higher values (47–108%) than the EC-estimation of NEE, though the results were comparable considering the considerable and variable uncertainty levels involved in the different approaches. The efficient biomass production – with the highest part of the total carbon uptake allocated to the aboveground wood – led the poplars to counterbalance the soil carbon losses resulting from land use change in a short period of time.

Fine root biomass and turnover of two fast-growing poplar genotypes in a short-rotation coppice culture.

Background and aimsThe quantification of root dynamics remains a major challenge in ecological research because root sampling is laborious and prone to error due to unavoidable disturbance of the delicate soil-root interface. The objective of the present study was to quantify the distribution of the biomass and turnover of roots of poplars (Populus) and associated understory vegetation during the second growing season of a high-density short rotation coppice culture.MethodsRoots were manually picked from soil samples collected with a soil core from narrow (75 cm apart) and wide rows (150 cm apart) of the double-row planting system from two genetically contrasting poplar genotypes. Several methods of estimating root production and turnover were compared.ResultsPoplar fine root biomass was higher in the narrow rows than in the wide rows. In spite of genetic differences in above-ground biomass, annual fine root productivity was similar for both genotypes (ca. 44 g DM m−2 year−1). Weed root biomass was equally distributed over the ground surface, and root productivity was more than two times higher compared to poplar fine roots (ca. 109 g DM m−2 year−1).ConclusionsEarly in SRC plantation development, weeds result in significant root competition to the crop tree poplars, but may confer certain ecosystem services such as carbon input to soil and retention of available soil N until the trees fully occupy the site.

Science, society and biosafety of a field trial with transgenic biofuel poplars

Background Global warming, environmental disasters, and increasing oil prices have catalyzed a worldwide trend to use plant biomass as a renewable source for liquid biofuels and bio-based materials. Plant biomass can be processed into fermentable sugars by enzymatic depolymerization of the cell wall polysaccharides, followed by fermentation. However, the presence of lignin in the cell wall constitutes a major recalcitrance factor because it limits the accessibility of polysaccharidases to the cellulose microfibrils. To overcome this hurdle, plant biomass is pretreated in a costly and energyrequiring process. One approach to overcome the recalcitrance problem is to engineer lignin amount or alter its composition to make lignin more susceptible to chemical degradation [1]. Cinnamoyl-CoA reductase (CCR), the enzyme that converts feruloyl-CoA into coniferaldehyde, is considered the first enzyme in the monolignol-specific branch of the phenylpropanoid pathway. Poplar trees down-regulated in CCR have been produced in the early nineties and planted in a field trial in France to produce sufficient wood for small scale chemical pulping tests [2]. These trees had 20% lower lignin levels and relatively more cellulose per gram of wood [2]. Given that lignin is one of the main limiting factors limiting the conversion of plant biomass into fermentable sugars, and that poplar is considered as a promising second generation biofuel crop, we have re-grown these trees in the greenhouse and in the field, and evaluated wood produced from these trees by saccharification experiments. Methods Cinnamoyl-CoA reductase (CCR) expression was downregulated in poplar by sense and antisense strategies [2]. Transgenic trees were evaluated for lignin amount and composition [2] and for sugar release by saccharification assays [3]. After obtaining permission from the regulatory authorities, two transgenic lines were planted in a field trial in Belgium and two in a field trial in France, both under short rotation coppice culture to maximize biomass production. Wood was saccharified with and without acid pretreatment.

Short Rotation Coppice Culture of Willows and Poplars as Energy Crops on Metal Contaminated Agricultural Soils

Phytoremediation, more precisely phytoextraction, has been placed forward as an environmental friendly remediation technique, that can gradually reduce increased soil metal concentrations, in particular the bioavailable fractions. The aim of this study was to investigate the possibilities of growing willows and poplars under short rotation coppice (SRC) on an acid, poor, sandy metal contaminated soil, to combine in this way soil remediation by phytoextraction on one hand, and production of biomass for energy purposes on the other. Above ground biomass productivities were low for poplars to moderate for willows, which was not surprising, taking into account the soil conditions that are not very favorable for growth of these trees. Calculated phytoextraction efficiency was much longer for poplars than these for willows. We calculated that for phytoextraction in this particular case it would take at least 36 years to reach the legal threshold values for cadmium, but in combination with production of feedstock for bioenergy processes, this type of land use can offer an alternative income for local farmers. Based on the data of the first growing cycle, for this particular case, SRC of willows should be recommended.

Growth and production of a short-rotation coppice culture of poplar—IV: Fine root characteristics of five poplar clones

Abstract Below-ground characteristics of five Populus clones, belonging to different species and parentages, were studied during the second growing season of the third rotation of a high-density coppice culture. Size (length, area and volume), biomass, nitrogen and carbon concentrations of three classes of fine roots (diameter classes of 0–1, 1–2 and 2–5 mm) were determined for four different soil layers. Fine root biomass varied significantly among clones and among soil layers. Clone Primo (Populus deltoides×Populus nigra) had the highest root biomass and the longest fine roots, while clone Hazendans (Populus trichocarpa×P. deltoides) had the lowest root biomass and shortest fine roots. The topsoil layer (0–5 cm) was very rich in fine roots; the fine root biomass and distribution of all clones decreased with increasing soil depth. Fine root area index (diameter classes of 0–1 and 1–2 mm) varied among clones, with higher values for clones Wolterson and Primo (3.6 and 3.7, respectively), while clones Hazendans and Columbia River had lower values (1.7 and 2.2, respectively). The absence of a significant correlation between fine root traits and above-ground biomass leads to the conclusion that above-ground biomass was not a reliable indicator of below-ground biomass in poplar, probably because of the age of the plantation in our study (stump age of 10 years). Fine root area index was positively correlated with leaf area index for all clones and at all soil depths, i.e., clones with a high fine root area index also had a high leaf area index. We conclude that leaf area index can be an indicator of root area.

Dynamics of biomass production in a poplar coppice culture over three rotations (11 years)

Short rotation coppice culture systems are characterized by a high stool and shoot density, and by rotation durations between 2 and 3 years for species showing an extremely fast growth such as poplar. With the objective to study the long-term biomass production evolution and dynamic of such systems, a high-density plantation with 17 poplar ( Populus) clones belonging to six parentages was established in April 1996 and coppiced in December 1996, January 2001, and February 2004. At the end of each growing season, stool survival, shoot diameter, and the number of shoots per stool were measured. Biomass production was estimated directly by harvesting a number of shoots or indirectly via allometric power equations. Stool survival rates differed among parentages and from year to year irrespective of number of rotations; the highest rates were for P. nigra and the lowest rates were for P. deltoides × P. nigra and P. deltoides × P. trichocarpa parentages. In the second and third rotations, the P. trichocarpa × P. deltoides hybrids showed very high mortality rates. The number of shoots per stool varied among rotations and parentages, and shoot elimination was parentage specific. The number of shoots per stool increased with increasing rotation number, while they decreased from year to year within each rotation. A single general allometric equation linking shoot diameter to shoot biomass could be used to estimate biomass production for most years and most clones. Exceptions were found for the year 2001 and for clone Hazendans. Biomass production differed among parentages and among rotations. The different parentages also differed in their strategy of biomass accumulation. Although P. nigra had the highest biomass production over 11 years, the parentage ranking of biomass production shifted over rotations. The P. trichocarpa × P. deltoides hybrids showed high biomass production in the first rotation, but low in the second and third rotations. Biomass production increased from year to year within one rotation, while it decreased with rotation number. Among the parentages examined, P. nigra and P. trichocarpa were the best performing ones and the best adapted to the multiple coppice rotations.

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

Abstract 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.

Impact of elevated CO 2 and nitrogen fertilization on foliar elemental composition in a short rotation poplar plantation

The experiment was carried out on a short rotation coppice culture of poplars (POP-EUROFACE, Central Italy), growing in a free air carbon dioxide enriched atmosphere (FACE). The specific objective of this work was to study whether elevated CO 2 and fertilization (two CO 2 treatments, elevated CO 2 and control, two N fertilization treatments, fertilized and unfertilized), as well as the interaction between treatments caused an unbalanced nutritional status of leaves in three poplar species ( P. x euramericana, P. nigra and P. alba). Finally, we discuss the ecological implications of a possible change in foliar nutrients concentration. CO 2 enrichment reduced foliar nitrogen and increased the concentration of magnesium; whereas nitrogen fertilization had opposite effects on leaf nitrogen and magnesium concentrations. Moreover, the interaction between elevated CO 2 and N fertilization amplified some element unbalances such as the K/N-ratio.

Clonal variation in stomatal characteristics related to biomass production of 12 poplar ( Populus) clones in a short rotation coppice culture

Twelve poplar ( Populus) clones, belonging to different species and interspecific hybrids, were studied during the third growing season of the second rotation of a high density coppice culture. Stomatal characteristics, as stomatal density and stomatal length, were examined for fully expanded leaves from all clones and at two canopy positions (upper and lower canopy). Above-ground biomass production was assessed by destructive harvesting and varied significantly among clones. Leaves of all clones were amphistomatous except for clones belonging to the Populus trichocarpa parentage. Abaxial stomatal density was higher than adaxial stomatal density for all clones and for both canopy positions. Significant clonal variations in stomatal density and length were observed. Significant differences were also found between the two canopy positions for both stomatal density and length. Upper canopy leaves had higher stomatal density than lower canopy leaves. Variations in stomatal characteristics were related to the parentage of the clones and to the canopy position within each clone. Biomass was positively and significantly correlated with abaxial stomatal density, i.e., clones with high density showed high biomass production. We conclude that stomatal density of different poplar clones affected biomass production.

06/00177 Growth and production of a short rotation coppice culture of poplar. II. Clonal and year-to-year differences in leaf and petiole characteristics and stand leaf area index: Afas, N. A. et al. Biomass and Bioenergy, 2005, 28, (6), 536–547

06/00177 Growth and production of a short rotation coppice culture of poplar. II. Clonal and year-to-year differences in leaf and petiole characteristics and stand leaf area index: Afas, N. A. et al. Biomass and Bioenergy, 2005, 28, (6), 536–547

06/00178 Growth and production of a short rotation coppice culture of poplar. III. Second rotation results: Laureysens, I. et al. Biomass and Bioenergy, 2005, 29, (1), 10–21

06/00178 Growth and production of a short rotation coppice culture of poplar. III. Second rotation results: Laureysens, I. et al. Biomass and Bioenergy, 2005, 29, (1), 10–21

Growth and production of a short rotation coppice culture of poplar. III. Second rotation results

Abstract This study describes production and growth of the second rotation of 17 poplar ( Populus spp.) clones in a short rotation coppice culture (SRC). In addition, the link with leaf characteristics was studied. In April 1996, an experimental field plantation with 10,000 cuttings ha −1 was established on a former waste disposal site. In December 1996, January 2001 and February 2004, all stools were coppiced. At the end of the second rotation (2001–2003), highest biomass production was found for P. nigra clone Wolterson with 9.7 Mg ha −1 y −1 . The best performers of the first rotation, i.e. P. trichocarpa × P. deltoides clones Hoogvorst and Hazendans, performed poorly in the second rotation, due to heavy rust infections. Two growth strategies were evident: Wolterson had a slow elimination of smaller shoots and had lots of smaller leaves; Hazendans and Hoogvorst had a rapid elimination of smaller shoots and had fewer, larger leaves. We conclude that shoot growth dynamics and leaf size were not the primary production determinants in our poplar SRC. But Melampsora larici-populina remained an important external determinant of biomass production.

Growth and production of a short rotation coppice culture of poplar. II. Clonal and year-to-year differences in leaf and petiole characteristics and stand leaf area index

Twelve different poplar ( Populus ) clones, belonging to different species and interspecific hybrids were studied during the first and second growing seasons of the second rotation of a high density coppice culture. Leaf size, leaf area, leaf nitrogen and specific leaf area (SLA) were examined at two different canopy levels, together with petiole length and petiole diameter. Leaves in the upper canopy layer were larger, heavier and had a lower SLA. They also had longer and thicker petioles, as well as a higher nitrogen concentration per unit dry weight than lower canopy leaves. Significant clonal variation was observed in leaf and petiole characteristics in both growing seasons. Leaf area index (LAI), scaled-up from allometric relationships, showed significant clonal variation in the two growing seasons, and increased for all clones in the second growing season. LAI increment was related to a significantly increased diameter of all shoots. Our study demonstrates (i) that light significantly affects leaf and petiolar characteristics, and nitrogen concentrations of foliage elements, and (ii) that year-to-year differences in foliar characteristics are related to stand aging rather than to increased shading due to larger LAI.

Elevated CO2 concentration, fertilization and their interaction: growth stimulation in a short-rotation poplar coppice (EUROFACE)

We investigated the individual and combined effects of elevated CO2 concentration and fertilization on aboveground growth of three poplar species (Populus alba L. Clone 2AS-11, P. nigra L. Clone Jean Pourtet and P. x euramericana Clone I-214) growing in a short-rotation coppice culture for two growing seasons after coppicing. Free-air carbon dioxide enrichment (FACE) stimulated the number of shoots per stool, leaf area index measured with a fish-eye-type plant canopy analyzer (LAIoptical), and annual leaf production, but did not affect dominant shoot height or canopy productivity index. Comparison of LAIoptical with LAI estimates from litter collections and from allometric relationships showed considerable differences. The increase in biomass in response to FACE was caused by an initial stimulation of absolute and relative growth rates, which disappeared after the first growing season following coppicing. An ontogenetic decline in growth in the FACE treatment, together with strong competition inside the dense plantation, may have caused this decrease. Fertilization did not influence aboveground growth, although some FACE responses were more pronounced in fertilized trees. A species effect was observed for most parameters.