Short Rotation Coppice Plantations Research Articles

First vs. second rotation of a poplar short rotation coppice: Above-ground biomass productivity and shoot dynamics

Within the global search for renewable energy sources, woody biomass from short rotation coppice (SRC) cultures is a valuable option. So far there is a shortage of large-scale field yield data to support stakeholders. We investigated an operational-scale SRC plantation (POPFULL) with 12 poplar genotypes in Flanders during its first two biennial rotations. By inventorying shoot numbers and diameters, combined with allometric relationships, productivity related data were derived after each growing season. We observed significant variation in biomass yield and productivity-related characteristics among the 12 poplar genotypes, of which two recently selected. Genotype Hees (Populus deltoides × Populus nigra) and Skado (Populus trichocarpa × Populus maximowiczii, selected in 2005) reached the highest productivity among genotypes, i.e. 16 Mg ha−1 y−1 of dry matter (DM) yield in the second rotation, which was more than double than the poorest performing genotype Brandaris (a pure P. nigra). However, with many small shoots genotype Hees had a different growth strategy than Skado that resprouted with few, thicker and higher shoots. Biomass production increased from a plantation average of 4.04 Mg ha−1 y−1 of DM in the first (establishment) rotation to 12.24 Mg ha−1 y−1 in the second rotation. Mean height growth raised from 2.08 m y−1 during the first rotation to 2.99 m y−1 during the second rotation. The influence of the first coppicing on tree mortality was negligible. Monitoring of subsequent rotations over the plantations' lifetime – which counts for SRC bioenergy cultures in general – is essential to evaluate productivity in the long term.

Effect of short rotation coppice plantation on the performance and chips quality of a self-propelled harvester

The performance of coppice harvesting machines is influenced by parameters such as field yield, the shape and size of the plantation and the space for turning at the headland. The quality of chips and the effect of the dendrometric characteristic of nine different species (Fraxinus angustifolia, Robinia pseudoacacia, Salix alba, Eucalyptus occidentalis, Populus nigra L. and four genotypes of Populus x euroamericana (Grimminge, Hoogvorst, Muur, Vesten) grown in the same flat plot of about 4.5 ha on the performance rate and quality of the work, was evaluated. Field yields ranged from 33 t ha−1 to ∼95 t ha−1, for the S. alba and E. occidentalis, respectively. The harvester worked with an average speed of 0.91 m s−1 (±0.22) and average productivities of 0.98 ha h−1 (±0.24) and 45.25 t h−1 (±5.56). There was a satisfactory linear correlation between the working speed of the machine and field yield. The quality of the chips showed some variability with values of moisture content ranging between 42.7% and 57.3% (for R. pseudoacacia and S. Alba respectively) and values of bulk density from 273 kg m−3 to 313 kg m−3 (for Populus euroamericana Vesten and E. occidentalis respectively).

Linking biomass production in short rotation coppice with soil protection and nature conservation

Biomass from short rotation coppice (SRC) plantations has attracted widespread attention as a component of new sustainable energy concepts. Nevertheless, as yet the surface area of SRC plantations in Europe is relatively low compared to other biomass producing land-use systems. This is somewhat incomprehensible because it has been shown that SRC systems also offer distinct ecological benefits. Therefore, greater consideration of the related ecosystem services should be incorporated into land-use planning processes. Presented in this study is a conceptual framework for the integration of soil protection and nature conservation into the spatial prioritization of areas suitable for SRC. This approach includes the development of a site-specific yield model and the identification and classification of criteria and indicators for both soil protection and nature conservation. The basic concept for planning procedures was established and tested for the State of Saxony (Germany). Existing constraints were identified, and could be attributed mainly to the availability of adequate information at different spatial scales. The regional-scale study emphasized the considerable biomass potential of SRC and the related synergy effects for soil protection and nature conservation. Future work should focus on the local (district, farm) and catchment scale and attempt to integrate additional aspects such as hydrological ecosystem services and carbon sequestration.

How do urban dwellers react to potential landscape changes in recreation areas? A case study with particular focus on the introduction of dendromass in the Hamburg Metropolitan Region

Recently, many German regions have seen dramatic landscape changes in agricultural areas due to increasing cultivation of bioenergy crops. Especially in regions that are economically dependent on income from recreational use, this development faces opposition by tourist stakeholders, local inhabitants and recreationists. In the future tall bioenergy plants like maize could be replaced by even taller short rotation coppice plantations of willow and poplar. This development raises the question of how people perceive landscape changes and if perceptions are influenced by the landscape where they take place. We surveyed urban residents in the city of Hamburg (n= 400) to see how they perceive potential landscape changes in four recreation areas with different landscape structures in the vicinity of Hamburg (Lüneburg Heath, Harburg Hills, Elbe Marshes and Altes Land). The survey showed that people rated changes significantly different, depending on the specific landscape type of the recreation areas. The survey did not show a clear general preference for reducing or increasing forests. However, the landscape character of each recreation area had a strong influence on the acceptance of landscape changes by planting forests, hedges, and shrubs. People showed a significantly higher negative reaction towards more forests in open landscapes characterized by heath and meadows than in landscapes with a higher share of forests and fields. Interestingly, the introduction of hedges and shrubs was evaluated differently from the introduction of forests depending on the type of open landscape. People preferred the introduction of hedges and shrubs in the landscape rich in meadows and pastures while they rejected the introduction of hedges and shrubs in a historic cultural landscape rich in heathland. In view of these results we recommend that the landscape character and the cultivation system are considered in the assessment and determination of potential short rotation coppice production sites. This may considerably increase the acceptability of dendromass cultivation for energy purposes.

Energy and economic sustainability of woodchip production by black locust (Robinia pseudoacacia L.) plantations in Italy

Growing demand for energy has led to a rise in the price of fossil oil and an increased rate of depletion of fossil resources. This situation has generated a strong interest in the use of biofuel, and many studies have been undertaken on the worldwide potential for biofuel. Among all renewable energy sources, biomass could contribute to meeting the EU’s renewable energy targets in 2020, especially short rotation coppice (SRC). In order to evaluate the energy and economic sustainability of woodchip production by black locust SRC, an ad hoc study was undertaken and a specific calculation model was developed. Data were collected in a black locust SRC plantation site in North West Italy during the period 2006–2012. This involved an SRC duration of six years and a biomass (10Mgha−1 DM per year) harvest at the end of a cycle (six years). The results indicated that black locust plantations are very desirable from an energy point of view since the output/input ratio results are higher than 20. Unfortunately, the results are not so positive from an economic point of view. In fact, in order to obtain economic sustainability for woodchip production, the biomass price should be at least €103Mg−1DM. Consequently, woodchip production by black locust SRC is only possible with economic support for production and with optimisation of agricultural labour and biomass production.

Stumps of Eucalyptus globulus as a source of antioxidant and antimicrobial polyphenols.

These past years have seen an enormous development of the area of natural antioxidants and antimicrobials. Eucalyptus globulus is widely cultivated in subtropical and Mediterranean regions in intensive short rotation coppice plantations. In the Portuguese context, E. globulus is the third species in terms of forest area. The stump is the basal part of the tree, including the near-the-ground stem portion and the woody roots that remain after stem felling. The purpose of this work was to study the phytochemical profile and to evaluate the antioxidant and antimicrobial properties of several crude stump wood and stump bark extracts of E. globulus, comparing it with similar extracts of E. globulus wood (industrial chips). The results showed the presence of high concentrations of total phenolic compounds (>200 mg GAE/g extract) and flavonoids (>10 mg QE/g extract) in E. globulus stump extracts. Generally the stump wood extracts stands out from the other ones, presenting the highest percentages of inhibition of linoleic acid oxidation. It was also possible to conclude that the extracts were more active against Gram-positive bacteria, presenting low MIC values. This study thus provides information supporting the economic valorization of E. globulus stump wood.

Economic evaluation of introduction of poplar as biomass crop in Italy

Abstract Lignocellulosic biomass production deriving from agro forest species, as well as poplar ( Populus spp.), has denoted an increase in last years in UE also thanks to a series of policies aimed at reducing emissions of greenhouse gases and promoting renewable sources. In Italy poplar represents the main agro forest species and it is cultivated according to two different methods: very Short Rotation Coppice (vSRC) and Short Rotation Coppice (SRC). The aim of this paper has been to evaluate the economic feasibility of poplar as energy crop in the southern Italy and specifically to consider its competitiveness with respect to conventional crops. In particular, an economic analysis in a representative case study located in the Sicilian hilly hinterland has been carried out, by comparing the direct costs and incomes of poplar (both vSRC and SRC) and durum wheat. Results showed that only introduction of SRC plantation could increase the farm competitiveness, while vSRC could be economically advantageous only with a substantial increase of biomass market price and/or CAP subsidy. However, the introduction of poplar should grant a better contribution to climate change mitigation with respect to annual crop, improving the greenhouse gases balance and diminishing the environmental impact of agricultural activity.

Evaluation of biomass production potential and heating value of hybrid poplar genotypes in a short-rotation culture in Italy

Ensuring increased and sustainable biomass production is critical for European countries. Short-rotation coppice (SRC) plantations on agricultural lands have a great potential to increase biomass supply for biofuels, bioenergy, and bioproducts. In Italy, SRC is based on the use of fast growing species, high planting density, and short harvesting cycles. In this study, the performance of new genotypes to be used in SRC plantations for biomass production was evaluated after three biennial rotations. At the trial plantation in Mira (Northern Italy), six different poplar (Populus) genotypes, belonging to different interspecific hybrids were studied. This plantation provided the opportunity to study the relationships between survival, biomass production and other growth parameters over multiple rotations and for a wide genotypic range. Biomass production differed significantly among rotations starting from 16Mgha−1year−1 in the first, peaking at 20Mgha−1year−1 in the second, and decreasing to 17Mgha−1year−1 in the third rotation. At the end of each rotation, significant differences among genotypes were observed in number of shoots per stool and per ha, stem diameter, tree height, and biomass production. Mean survival rates became significantly different from the other rotations only in the third rotation during which survival rate ranged from 95% for (P.×generosa)×P. nigra ‘Monviso’ to 75% for (P.×generosa)×P. nigra ‘AF6’, but non-significant difference was observed among genotypes. Skewness and inequality of shoot size distributions were genotype-dependent and increased with rotations. Highest biomass production was found for genotypes P.×canadensis ‘83.148.041’, ‘Monviso’ and (P.×generosa)×P. trichocarpa ‘AF8’ with mean annual dry mass production of 21.7, 19.5 and 19.3Mgha−1year−1, respectively. Genotype×rotation interactions were significant on shoot size, diameter and number, but not on survival and biomass production highlighting that genotypes behaved differently over rotations. Moisture and ash content, wood specific gravity, and higher heating value were determined at the end of the third biennial rotation, and significant differences among genotypes were found. This study is critical for investigating the behavior of novel poplar genotypes with potential for commercial biomass production over multiple coppice rotations.

Potential of Short Rotation Coppice plantations to reinforce functional biodiversity in agricultural landscapes

We compared communities of vascular plants and arthropods in ten Short Rotation Coppice (SRC)–maize pairs, to (1) quantify the difference in diversity and composition between these two alternative land-use types and (2) to assess the potential of SRC plantations to increase functional biodiversity values in agricultural landscapes. In each SRC plantation and maize field, the vegetation was surveyed and arthropods were sampled by applying pitfall and pan trapping. The composition of the vegetation and of the epigeic and vegetation inhabiting arthropod communities strongly differed between the crop types. This differentiation was mainly due to true species turnover and only to a lesser extent to the occurrence of nested subsets. On average, the total cover of the vegetation was 10 times higher in the SRC plantations and taxonomic and trait diversity were also consistently higher in SRC. Arthropod activity densities were significantly higher, sometimes almost double, in SRC plantations. Significantly higher effective species numbers in SRC were only retrieved for Hymenoptera and Coleoptera. Regarding functional groups, the activity densities of omnivores, detritivores, mycophages, phytophages and parasitoids were significantly higher in SRC. While activity densities of predators were not different among the crop types, their effective species number was higher in SRC, indicating a more evenly distributed and diverse predator community. To conclude, we have shown that SRC can significantly increase vegetation and arthropod abundance and/or diversity in agricultural landscapes when replacing annual biomass crops, such as maize.

No general soil carbon sequestration under Central European short rotation coppices

AbstractWood from short rotation coppices (SRCs) is discussed as bioenergy feedstock with good climate mitigation potential inter alia because soil organic carbon (SOC) might be sequestered by a land‐use change (LUC) from cropland to SRC. To test if SOC is generally enhanced by SRC over the long term, we selected the oldest Central European SRC plantations for this study. Following the paired plot approach soils of the 21 SRCs were sampled to 80 cm depth and SOC stocks, C/N ratios, pH and bulk densities were compared to those of adjacent croplands or grasslands. There was no general trend to SOC stock change by SRC establishment on cropland or grassland, but differences were very site specific. The depth distribution of SOC did change. Compared to cropland soils, the SOC density in 0–10 cm was significantly higher under SRC (17 ± 2 in cropland and 21 ± 2 kg C m−3 in SRC). Under SRC established on grassland SOC density in 0–10 cm was significantly lower than under grassland. The change rates of total SOC stocks by LUC from cropland to SRC ranged from −1.3 to 1.4 Mg C ha−1 yr−1 and −0.6 Mg C ha−1 yr−1 to +0.1 Mg C ha−1 yr−1 for LUC from grassland to SRC, respectively. The accumulation of organic carbon in the litter layer was low (0.14 ± 0.08 Mg C ha−1 yr−1). SOC stocks of both cropland and SRC soils were correlated with the clay content. No correlation could be detected between SOC stock change and soil texture or other abiotic factors. In summary, we found no evidence of any general SOC stock change when cropland is converted to SRC and the identification of the factors determining whether carbon may be sequestered under SRC remains a major challenge.

Leaf Litter Decomposition and Nutrient-Release Characteristics of Several Willow Varieties Within Short-Rotation Coppice Plantations in Saskatchewan, Canada

Quantifying short-rotation coppice (SRC) willow leaf litter dynamics will improve our understanding of carbon (C) sequestration and nutrient cycling potentials within these biomass energy plantations and provide valuable data for model validation. The objective of this study was to quantify the decomposition rate constants (k Biomass) and decomposition limit values (LVBiomass), along with associated release rates (k Nutrient) and release limits (LVNutrient) of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg) of leaf litter from several native and exotic willow varieties during an initial 4-year rotation at four sites within Saskatchewan, Canada. The k Biomass, LVBiomass, k Nutrient, and LVNutrient values varied among the willow varieties, sites, and nutrients, with average values of 1.7 year−1, 79 %, 0.9 year−1, and 83 %, respectively. Tissue N had the smallest k Nutrient and LVNutrient values, whereas tissue K and Mg had the largest k Nutrient and LVNutrient values, respectively. The leaf litter production varied among willow varieties and sites with an average biomass accumulation of 7.4 Mg ha−1 after the 4-year rotation and associated C sequestration rate of 0.2 Mg C ha−1 year−1. The average contribution of nutrients released from leaf litter decomposition during the 4-year rotation to the plant available soil nutrient pool across varieties and sites was 22, 4, 47, 10, 112, and 18 kg ha−1 of N, P, K, S, Ca, and Mg, respectively. Principal component analysis identified numerous key relationships between the measured soil, plant tissue, climate, and microclimate variables and observed willow leaf litter decomposition and nutrient-release characteristics. Our findings support the contention that SRC willow leaf litter is capable of enhancing both soil organic C levels and supplementing soil nutrient availability over time.

Introducing nitrogen-fixing species in short rotation coppice

In short rotation coppice (SRC) plantations, there may be a risk of soil fertility decline requiring fertilizer input that is liable to be a source of pollution and reduce the system profitability. One option is the development of mixed-species plantations, associating a nitrogen-fixing species with the species of economic interest (acacia/eucalyptus, alder/poplar, black locust/poplar, etc.). The nitrogen input, resulting from the introduction of the nitrogen-fixing species could enhance the primary production and modify the carbon partitioning between above and belowground parts of the trees. The current studies will allow to precise the positive or negative effects that prevail within a mixed plantation of poplar and black locust. Cecilia GANA INRA Centre de Nancy-Lorraine UMR Ecologie et ecophysiologie forestieres F-54280 CHAMPENOUX (cecilia.gana@nancy.inra.fr)

Simultaneous leaf- and ecosystem-level fluxes of volatile organic compounds from a poplar-based SRC plantation

Emission of carbon from ecosystems in the form of volatile organic compounds (VOC) represents a minor component flux in the global carbon cycle that has a large impact on ground-level ozone, particle and aerosol formation and thus on air chemistry and quality. This study reports exchanges of CO2 and VOC between a poplar-based short rotation coppice (SRC) plantation and the atmosphere, measured simultaneously at two spatial scale, one at stand level and another at leaf level. The first technique combined Proton Transfer Reaction “Time-of-Flight” mass spectrometry (PTR–TOF–MS) with the eddy covariance method, to measure fluxes of a multitude of VOC. Abundant fluxes of isoprene, methanol and, to a lesser extent, fluxes of other oxygenated VOC such as formaldehyde, isoprene oxidation products (methyl vinyl ketone and methacrolein), methyl ethyl ketone, acetaldehyde, acetone and acetic acid, were measured. Under optimal environmental conditions, isoprene flux was mostly controlled by temperature and light. Differently, methanol flux underwent a combined enzymatic and stomatal control, together involving environmental drivers such as vapour pressure deficit (VPD), temperature and light intensity. Moreover fair weather condition favoured ozone deposition to the poplar plantation.The second technique involved trapping the VOCs emitted from leaves followed by gas chromatography-mass spectrometry (GC–MS) analysis. These leaf-level measurements showed that emission of isoprene in adult leaves and of monoterpenes in juvenile leaves are widespread across poplar genotypes. Detection of isoprene oxidation products (iox) emission with leaf-level measurements confirmed that a fraction of isoprene may be already oxidized within leaves, possibly when isoprene copes with foliar reactive oxygen species (ROS) formed during warm and sunny days.

Economics of poplar short rotation coppice plantations on marginal land in Germany

Although there is a need for biomass and a potential for short rotation coppice (SRC), farmers hesitate to establish SRC, even on marginal agricultural land on which annual crops show low productivity. Probably the most important factor explaining this reluctance might be the uncertain economic prospects of the cultivation of SRC. Therefore, the aim of this study is to analyse the economy of a typical SRC supply chain by calculating the annuities which can be expected by German farmers who establish SRC on their marginal land.The result shows that the yearly annuity of a 20-year SRC cultivation is about 70 € y−1 ha−1 when poplar SRC is harvested every 4 years with a forage harvester (one-step system). The result includes the establishment, cultivation and transport of the fresh wood chips to a plant 50 km away. However, this result is not competitive with the result of annual crops (226–462 € y−1 ha−1) and is also lower than the CAP subsidy payments that farmers receive from the EU (300 € y−1 ha−1). To achieve higher annuities, four options were analysed possibly leading either to higher biomass yields or to higher market prices (extension of rotation cycle, implementation of irrigation, technical drying of fresh wood chips, using a two-step harvesting system). The implementation of drip irrigation to increase biomass yield turned out to be uneconomic. An extension of the rotation cycle from 4 to 5 years can be recommended as it leads to an annuity of 255 € y−1 ha−1 (instead of 69 € y−1 ha−1). Results also show that the technical drying of chips using (cheap) surplus heat can be very profitable if the added value is reflected in higher market prices. Furthermore, it is shown that the use of an alternative two-step harvesting system with natural interim drying of the rods can be an attractive option for farmers to increase the annuity of their SRC.

Carbon and water vapor fluxes over four forests in two contrasting climatic zones

The inter- and seasonal patterns of water vapor and canopy carbon fluxes were compared for four forest ecosystems in two contrasting climatic zones in Europe. The eddy covariance and ancillary data were taken from the Carboeurope and FLUXNET databases and a linear modeling statistical analysis was made. The four sites were a high-density poplar (Populus spp.) short rotation coppice plantation (in Lochristi, Belgium) and a mature Scots pine (Pinus sylvestris) forest (in Brasschaat, Belgium) in the Temperate climate versus a fast-growing Eucalypt (Eucalyptus) plantation (in Espirra, Portugal) and a Holm oak (Quercus ilex) forest (in Puechabon, France) in the Mediterranean climate.•The Eucalypt stand showed an efficient stomatal control in response to changes in vapor pressure deficit (VPD), suggesting an ideal adaptation of this species to the severe Mediterranean climate.•The fast-growing poplar stand did not show a similar stomatal control under conditions of moderate water stress. But during an intensive dry period a decrease in the development of the leaf area index (LAI) was observed.•The Holm oak stand showed a low GPP, which is typical for a low productive species with a long rotation cycle. The GPP showed low diurnal variability, even under high solar radiation. This behavior suggested a strong stomatal control caused by the severe water stress, a mechanism that allowed this stand to cope with diurnal and seasonal water deficits.•The mature Scots pine forest in the Temperate climate showed no variation in the GPP – radiation relationship. In this forest no water stress was observed, probably because the trees always had access to the water table. Irrespective of the climate the evapotranspiration of the Scots pine forest presented a tight coupling with the atmosphere, i.e. a low decoupling factor, Ω, comparable with the Holm oak and the Eucalypt forests.The high Ω values of the young poplar plantation were not typical for forest canopies. These values confirmed the strong influence of solar radiation and available energy on evapotranspiration and on the dynamics of this fast-developing canopy. At all four sites the forests showed their capacity to react to the environmental drivers, characteristic from their respective climatic types. However, drastic climatic changes – such as heat waves or long drought spells – may compromise the productivity of fast-growing plantations such as the Eucalypt and poplar stands. The response of the poplars to these events is mainly achieved through LAI control in contrast to the stomatal control in the Eucalypts.

Long-term biomass productivity of willow bioenergy plantations maintained in southern Quebec, Canada

Maintaining the long-term productivity of short-rotation coppice plantations is very important to ensure the large-scale deployment of biomass as a renewable energy source. In Quebec (Canada), willow short rotation coppice has been studied since the early ‘90s, thereby allowing long-term analysis of the dynamic performance of several species and hybrids as well as management practices. In this study, we report on the long-term productivity of two trials maintained in southern Quebec and carried out to compare a) growth and biomass yield of willow Salix viminalis (cultivar 5027) grown for 15 years under fertilized and unfertilized conditions and b) growth of different willow cultivars over three successive rotations (10 years). The first trial showed that after four rotations, sludge-fertilized S. viminalis 5027 produced significantly more biomass, 19.2 odt ha−1 yr−1, whereas unfertilized plots yielded 13.8 odt ha−1 yr−1. The second trial showed that among the wide variety of commercial willow cultivars available, SX64 and SX61 along with some indigenous species (i.e. S25, S365, S546) were the most suitable for short-rotation forestry in southern Quebec.

Land availability and potential biomass production with poplar and willow short rotation coppices in Germany

AbstractSeveral factors influence land availability for the growth of short rotation coppices (SRC) with fast‐growing tree species, including the nationwide availability of agricultural land, economic efficiency, ecological impacts, political boundaries and environmental protection regulations. In this study, we analysed the growing potential of poplar and willow SRC for bioenergy purposes in Germany without negative ecological impacts or land use conflicts. The potential biomass production using SRC on agricultural land in Germany was assessed taking into account ecological, ethical, political and technical restrictions. Using a geographic information system (GIS), digital site maps, climate data and a digital terrain model, the SRC biomass production potential on cropland and grassland was estimated using water supply and mean temperature during the growing season as parameters. From this analysis, a yield model for SRC was developed based on the analysed growth data and site information of 62 short rotation plantations in Germany and France. To assess the technical, ethical and ecological potential of SRC, restrictions in protected areas, technical constraints and competition with food and feed production were investigated. Our results revealed that approximately 18% (2.12 Mio. ha) of cropland and 54% (2.5 Mio. ha) of grassland in Germany were highly suitable for SRC plantations, providing favourable water supplies and mean temperatures during the growing season. These identified sites produced an average yield of more than 14 tons of dry matter per hectare per year. Due to local climate and soil conditions, the federal states in northern and eastern Germany had the highest theoretical SRC potential for agricultural land. After considering all ecological, ethical, political and technical restrictions, as well as future climate predictions, 5.7% (680 000 ha) of cropland and 33% (1.5 Mio. ha) of grassland in Germany were classified as suitable for biomass production with fast‐growing tree species in SRC.

TRANSPIRATION OF POPLAR BASED SHORT ROTATION COPPICE UNDER DROUGHT STRESS

This study compares canopy transpiration (T) of two treatments with different levels of water availability calculated using sap flow (SF) measurements based on thermal dissipation (TD) method. The study was conducted in a poplar based short rotation coppice (SRC) plantation in Czech-Moravian highlands during the summer of 2012 (DOY 154-274). There are 3 pairs of experimental plots under research. Each pair comprises a control plot, and a neighboring plot, equipped with a roof system, draining 40% of incoming rain water away (the water reduced plot). Sap flow of 4 trees within the control plots and 4 trees within the water reduced plots was measured. Data from both treatments were scaled up to stand level separately. Then, potential transpiration (Tp) of SRC for the period DOY 154-183) was successfully (R 2 =0.89) modeled, as a function of global radiation and vapor pressure deficit (VPD), using the Penman-Monteith formula and a parameterized semi-empirical stomatal conductance model. Finally, canopy transpiration from controls (Tc) and water reduced plots (Ts) were compared with modeled Tp and further analyzed. In the period June-September the mean daily Tc=1.86 mm, Ts=1.38 mm and Tp=2.27 mm; daily maximum occurred on 24 June – Tc=3.75 mm, Ts=2.84 mm and Tp=3.89 mm. The T totals over the study period reached Tc= 226 mm, Ts=168 mm and Tp=276 mm. T of both treatments differed depending on actual soil water availability. Our results show that a 40% reduction in throughfall resulted in a 26% reduction in transpiration over the four months study period. Results also confirmed that even a low number of sensors (4+4) can be used for credible estimates of canopy transpiration.

The economic attractiveness of Short Rotation Coppice biomass plantations for bioenergy in Northern Ontario

With an apparent abundance of idled and under-utilized agricultural land in Northern Ontario, there is interest in the ability of short-rotation forests to supply bioenergy and other possible bioproducts. Once established, Short Rotation Coppice (SRC) plantations can be harvested on (roughly) three-year cutting cycles until about age 22. Purpose-grown plantations such as these could be used as stand-alone sources of fibre or used in conjunction with sources such as natural forests or woody residues. Using a recently developed land cover model we found that approximately 405 500 ha of agricultural-type land exists across Northern Ontario. Numerous scenarios were developed to calculate SRC profitability on these areas. The analyses are intended to reflect a broad range of expectations on physical yields and prices, including management costs. Although SRC involves a considerable up-front investment, our simulations suggest a significant amount of land could have a break-even biomass price of $85/oven-dried tonnes (ODT) (+/- $5/ODT) at farm gate. This farm gate biomass price represents roughly current traditional biomass prices paid. Thus SRC would need to produce biomass at a comparable cost to be a competitive option. A number of technological and price changes could increase the attractiveness of SRC systems in Northern Ontario, including decreases in establishment and management costs (while maintaining yield expectations) and improved cultivars offering increased yields.

Soil CO2 efflux in a bioenergy plantation with fast-growing Populus trees - influence of former land use, inter-row spacing and genotype.

AimsIn this study we quantified the annual soil CO2 efflux (annual SCE) of a short rotation coppice plantation in its establishment phase. We aimed to examine the effect of former (agricultural) land use type, inter-row spacing and genotype.MethodsAnnual SCE was quantified during the second growth year of the establishment rotation in a large scale poplar plantation in Flanders. Automated chambers were distributed over the two former land use types, the two different inter-row spacings and under two poplar genotypes. Additional measurements of C, N, P, K, Mg, Ca and Na concentrations of the soil, pH, bulk density, fine root biomass, microbial biomass C, soil mineralization rate, distance to trees and tree diameters were performed at the end of the second growth year.ResultsTotal carbon loss from soil CO2 efflux was valued at 589 g m−2 yr−1. Annual SCE was higher in former pasture as compared to cropland, higher in the narrow than in the wider inter-row spacings, but no effect of genotype was found.ConclusionsSpatial differences in site characteristics are of great importance for understanding the effect of ecosystem management and land use change on soil respiration processes and need to be taken into account in modeling efforts of the carbon balance.