Woody Crop Systems Research Articles

A functional trait framework for integrating nitrogen‐fixing cover crops into short‐rotation woody crop systems

AbstractDeveloping approaches to simultaneously maximize short‐rotation woody crop (SRWC) productivity while minimizing footprints associated with intensive management is imperative to profitable and sustainable bioenergy production systems. Intercropping nitrogen (N)‐fixing cover crops in SRWC systems is an overlooked approach to sustainably intensify SRWC production by increasing N availability using less environmentally costly inputs. Here, we discuss how functional traits (e.g., seasonal activity, lifespan, leaf habit, soil exploration) of cover crops and SRWCs may interact through space and time influencing access to light, water, and nutrients to provide a framework for successful integration of cover crops into SRWCs. Next, we summarize the literature on intercropping forest plantations with N‐fixing cover crops to identity research gaps and outline future research needs and opportunities. And then, using empirical N demand and productivity data from SRWCs and cover crop N inputs from the literature, we illustrate how SRWC leaf habit (conifer evergreens and deciduous hardwoods) would influence successful integration of cover crops and potential N fixation. We estimate that integrating cover crops into SRWCs could supply 27% and 72% of the N demand across a 10‐year rotation for an evergreen and a deciduous hardwood, respectively. These figures suggest theseintegratedSRWC systems may approach a virtual minimal external N input when other biogeochemical cycles are considered. The guiding principles presented here are grounded in ecological theory and provide a framework for sustainable intensification of forest production.

Biochar restructures plant–soil–microbe relationships in a woody cropping system

AbstractBiochars are porous charcoal‐like materials that can enhance soil health and plant growth, but their use has not been adequately evaluated in woody cropping systems. To fill this knowledge gap, we investigated the effects of two slow pyrolysis pine biochars on plant performance, soil physicochemical properties, extracellular enzyme activities, and root‐associated fungal community composition in an experimental Christmas tree plantation over 3 yr. Both biochars stimulated the activities of five extracellular enzyme activities between 67 and 446%, but appeared to reduce N availability. Structural equation modelling identified increased soil moisture as a potential mechanism of biochar's effects on all measured enzyme activities, whereas increased dissolved organic C was a possible mechanism of biochar's effect on N and P targeting enzymes. This finding suggests that biochar‐induced increases to dissolved organic C have a specific effect on nutrient targeting enzymes. Biochar was found to negatively impact tree growth and survival, but impacts varied between tree species and biochar type. High‐throughput sequencing showed that biochar decreased the diversity of root‐associated fungal communities, with the ectendomycorrhizal species Wilcoxina mikolae becoming hyper‐dominant on balsam fir in response to one of the biochars. Changes to root‐associated fungal communities may have been partially responsible for negative effects on conifer performance. Although our study identified negative effects of biochar on plant performance and fungal diversity, we also found widespread changes to soil chemistry and microbial function that might be leveraged in systems with more acidic soils or different crops to increase plant performance.

Short-term impact of crop diversification on soil carbon fluxes and balance in rainfed and irrigated woody cropping systems under semiarid Mediterranean conditions

PurposeDiversification practices such as intercropping in woody cropping systems have recently been proposed as a promising management strategy for addressing problems related to soil degradation, climate change mitigation and food security. In this study, we assess the impact of several diversification practices in different management regimes on the main carbon fluxes regulating the soil carbon balance under semiarid Mediterranean conditions.MethodsThe study was conducted in two nearby cropping systems: (i) a low input rainfed almond (Prunus dulcis Mill.) orchard cultivated on terraces and (ii) a levelled intensively irrigated mandarin (Citrus reticulata Blanco) orchard with a street-ridge morphology. The almond trees were intercropped with Capparis spinosa or with Thymus hyemalis While the mandarin trees were intercropped with a mixture of barley and vetch followed by fava bean. Changes caused by crop diversifications on C inputs into the soil and C outputs from the soil were estimated.ResultsCrop diversification did not affect soil organic carbon stocks but did affect the carbon inputs and outputs regulating the soil carbon balance of above Mediterranean agroecosystems. Crop diversification with perennials in the low-input rainfed woody crop system significantly improved the annual soil C balance in the short-term. However, crop diversification with annual species in the intensively managed woody crop system had not effect on the annual soil C balance.ConclusionsOur results highlight the potential of intercropping with perennials in rainfed woody crop systems for climate change mitigation through soil carbon sequestration.

Soil respiration and net ecosystem productivity in a chronosequence of hybrid poplar plantations

Forest stand age can affect ecosystem carbon (C) cycling and net ecosystem productivity (NEP). In Canada, establishment of short-rotation plantations on previously agricultural lands has been ongoing, but the effect of stand development on soil respiration (Rs) and NEP in such plantations is poorly understood. These types of data are essential for constraining ecosystem models that simulate C dynamics over the rotation of a plantation. We studied Rs (including autotrophic, Ra, and heterotrophic, Rh) and NEP in 2008 and 2009 in a chronosequence of 5-, 8-, 14-, and 16-yr-old (ages in 2009) hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantations in northern Alberta. The highest Rs and NEP were generally found in the 14-yr-old stand. Seasonal variations in Rs were similar among the plantations, with most of the variation explained by soil temperature at the 10 cm depth in 2008 with far less explained in 2009, a much drier year. In diurnal measurements, hysteresis was found between soil respiration and soil temperature, with the patterns of hysteresis different among stand ages. Soil respiration in the 14-yr-old plantation had the greatest sensitivity to temperature changes. Stand age did not affect the Rh:Rs ratio, whereas the NEP exhibited strong inter-annual variability. We conclude that stand age was a major factor affecting Rs and NEP, and such effects should be considered in empirical models used to simulate ecosystem C dynamics to evaluate potentials for C sequestration and the C source–sink relationship in short-rotation woody crop systems.

Long-Term Monitoring of Soil Carbon Sequestration in Woody and Herbaceous Bioenergy Crop Production Systems on Marginal Lands in Southern Ontario, Canada

Enhancement of terrestrial carbon (C) sequestration on marginal lands in Canada using bioenergy crops has been proposed. However, factors influencing system-level C gain (SLCG) potentials of maturing bioenergy cropping systems, including belowground biomass C and soil organic carbon (SOC) accumulation, are not well documented. This study, therefore, quantified the long-term C sequestration potentials at the system-level in nine-year-old (2009–2018) woody (poplar clone 2293–29 (Populus spp.), hybrid willow clone SX-67 (Salix miyabeana)), and herbaceous (miscanthus (Miscanthus giganteus var. Nagara), switchgrass (Panicum virgatum)) bioenergy crop production systems on marginal lands in Southern Ontario, Canada. Results showed that woody cropping systems had significantly higher aboveground biomass C stock of 10.02 compared to 7.65 Mg C ha−1 in herbaceous cropping systems, although their belowground biomass C was not significantly different. Woody crops and switchgrass were able to increase SOC significantly over the tested period. However, when long term soil organic carbon (∆SOC) gains were compared, woody and herbaceous biomass crops gained 11.0 and 9.8 Mg C ha−1, respectively, which were not statistically different. Results also indicate a significantly higher total C pool [aboveground + belowground + soil organic carbon] in the willow (103 Mg ha−1) biomass system compared to other bioenergy crops. In the nine-year study period, woody crops had only 1.35 Mg C ha−1 more SLCG, suggesting that the influence of woody and herbaceous biomass crops on SLCG and ∆SOC sequestrations were similar. Further, among all tested biomass crops, willow had the highest annual SLCG of 1.66 Mg C ha−1 y−1.

Cut‐and‐chip harvester material capacity and fuel performance on commercial‐scale willow fields for varying ground and crop conditions

AbstractShrub willow (Salix spp.) is capable of producing commercially attractive amounts of biomass in short rotations, but harvesting costs and logistics remain a concern. There is a particular need for information about harvesting operations on larger, commercial short‐rotation woody crop systems. Another recent issue on commercial fields in northern New York is commercial growers conducting harvests during the growing season rather than the recommended dormant season when fields may be too wet to harvest. This study evaluated and modeled the in‐field performance of a cut‐and‐chip harvester for almost 700 wagonloads of chips operating in commercial willow fields in a wider array of crop and field conditions than have been previously reported. Analysis indicated that the time of harvest (leaf‐on or leaf‐off) and whether site conditions were wet or dry affected the harvester's material capacity. Mean material capacity was greatest for leaf‐off, dry conditions (71.8 Mg/hr) and lowest for leaf‐on harvests, which were similar for wet (30.4 Mg/hr) and dry conditions (29.7 Mg/hr). Mean crop specific fuel consumption ranged between 1.3 and 3.3 L/Mg, but can get considerably higher for standing biomasses below 40 Mg/ha. Wet ground conditions and leaf‐on harvests tend to decrease material capacity and increase fuel consumption as the harvester has to divert power to forward movement and material processing. Relationships for material capacity and fuel consumption based on standing biomass, time of harvest and ground conditions will be essential for evaluating and modeling the economic and environmental impacts of commercial‐scale willow operations.

A historical perspective on soil organic carbon in Mediterranean cropland (Spain, 1900–2008)

Soil organic carbon (SOC) management is key for soil fertility and for mitigation and adaptation to climate change, particularly in desertification-prone areas such as Mediterranean croplands. Industrialization and global change processes affect SOC dynamics in multiple, often opposing, ways. Here we present a detailed SOC balance in Spanish cropland from 1900 to 2008, as a model of a Mediterranean, industrialized agriculture. Net Primary Productivity (NPP) and soil C inputs were estimated based on yield and management data. Changes in SOC stocks were modeled using HSOC, a simple model with one inert and two active C pools, which combines RothC model parameters with humification coefficients. Crop yields increased by 227% during the studied period, but total C exported from the agroecosystem only increased by 73%, total NPP by 30%, and soil C inputs by 20%. There was a continued decline in SOC during the 20th century, and cropland SOC levels in 2008 were 17% below their 1933 peak. SOC trends were driven by historical changes in land uses, management practices and climate. Cropland expansion was the main driver of SOC loss until mid-20th century, followed by the decline in soil C inputs during the fast agricultural industrialization starting in the 1950s, which reduced harvest indices and weed biomass production, particularly in woody cropping systems. C inputs started recovering in the 1980s, mainly through increasing crop residue return. The upward trend in SOC mineralization rates was an increasingly important driver of SOC losses, triggered by irrigation expansion, soil cover loss and climate change-driven temperature rise.

Impact of biases in gridded weather datasets on biomass estimates of short rotation woody cropping systems

Short rotation woody crop (SRWC) systems continue to be investigated as energy crops for a range of energy products including liquid biofuels and electricity. To understand their market potential and economic viability, regional biomass yield and production estimates are used as primary inputs. Biomass is generally estimated using growth models which often utilize gridded weather datasets when implemented for regional simulations. With such models, the accuracy of weather data will affect the uncertainty of estimated biomass and subsequent bioenergy analyses. This study evaluates the biases in weather variables of commonly used high resolution gridded datasets including PRISM, Daymet, NARR, and NLDAS in comparison with observed weather at five flux tower stations. Further, impacts of inaccuracies in gridded data sources on biomass estimates of SRWC hybrid poplar was investigated at site and regional levels using a version of the 3-PG growth model modified to model production with multiple harvests through coppicing or periodic cutting of the trees with regrowth from the tree stump.Results suggest that weather variables in all gridded datasets are characterized by some degree of bias leading to considerable bias in biomass estimates, in some cases up to 45%. PRISM and Daymet were shown to have lower uncertainty in most of the weather variables, likely due to their higher spatial resolution and higher dependency on station weather. Site level simulations indicate that relative to the reference biomass estimates based on actual weather measurements, NARR data yielded 4.1Mgha−1y−1 higher biomass while NLDAS, Daymet, and PRISM resulted in 3.3, 1.2 and 0.3Mgha−1y−1 lower biomass. Regional simulations suggest that total biomass varied substantially with gridded data sources ranging between 47.4 and 58.3Tg on the croplands and rangelands in the region (Columbia Plateau), which subsequently led up to 23% variation in the estimate of poplar based jet fuel production from the SRWC resource. Therefore, findings of this study reinforce the need to account for uncertainties in biomass estimates introduced by biases in gridded weather when modeling bioenergy production.

Orchard and horticulture systems in Spanish Mediterranean coastal areas: Is there a real possibility to contribute to C sequestration?

Agriculture in the Mediterranean basin is currently contributing to greenhouse gas emissions (GHG) and in the future is expected to be strongly affected by climate change. Increasing soil organic carbon (SOC) via soil organic matter (SOM) improvement is widely regarded as a way to both mitigate and adapt to climate change. Using as a case study the Mediterranean coastal area in Spain, which is regarded as one of the most intensively managed areas in Europe for orchards and horticultural cropping, we analyzed the potential for climate change mitigation of introducing different practices that are expected to increase SOC. We selected both as a single measure and in combination, cover cropping and application to the soil of the available underutilized exogenous organic matter (EOM), treated (e.g. composted or digested) or non-treated. These practices were compared against a baseline scenario that intended to reflect the current practices in the area (e.g. all livestock manure produced in the area is applied to the agricultural soil). We carried out a modelling exercise at the regional scale using the agricultural activity data and current climatic conditions as inputs. Modelling runs were performed coupling a widely used dynamic model of SOC turnover (RothC) with a model to simulate the GHG emissions from EOM processing or storage prior to soil application (SIMSWASTE).Results indicate that the most promising practice, considered as a single measure and with respect to the baseline, was introducing cover crops in woody cropping systems. This practice resulted in an increase of 0.44MgCha−1 yr−1 during the first 20 years (range 0.41–0.52MgCha−1 yr−1) and led to a total SOC accumulation of about 30TgC after 100 years. Amendment of all agricultural land with available underutilized EOM resulted in an increase of up to 0.09MgCha−1 yr−1 (range 0.07–0.16MgCha−1 yr−1) as a single measure (urban waste) and 0.13MgCha−1 yr−1 (range 0.11–0.21MgCha−1 yr−1) as a combined measure (urban waste and composted agroindustry by-products), leading to a total SOC accumulation of about 7TgC (urban waste) and 10Tg C (urban waste and composted agroindustry by-products) after 100 years. Manure anaerobic digestion or composting as a single measure did not result in significant SOC changes but, if GHG emissions and savings from manure storage and processing management stages are considered, they could help to reduce about 4.3 (anaerobic digestion) or 1.1Tg CO2eq yr−1 (composting) in the study area, which represents a significant amount compared with total agricultural emissions in Spain.

Carbon and nutrient dynamics in short-rotation coppice of poplar and willow in a converted marginal land, a case study in central France

Bioenergy woody biomass production shortens the life cycle of carbon and secures energy supplies. However, using fast growing trees in these woody crop systems such as in short rotation coppices (SRCs), implies an increasing risk of depleting the soil nutrient stocks by direct biomass removal and low nutrient return. The aim of this study was to quantify the impact of these woody crop systems after 4 years of growth on the soil quality (C and nutrient cycling) by monitoring tree components (i.e. shoot, litterfall, root system) instead of soils; C and nutrient contents in weed strips were also included into these analyses. Our results indicated that shoot biomass was similar in SRC-P and SRC-W 2 years after planting (4 t ha−1). However, after 4 years, willow outperformed poplar (21.9 vs. 8.6 t ha−1, respectively) removing until 30 % of K soil pool. Litterfall increased between first and second rotation coppices (0.85 vs. 4 t ha−1) similarly for SRC-P and SRC-W, indicating biomass exportation and return were strongly imbalanced in SRCs crop systems. N pool in weed strips represented a significant contribution to N cycling in these SRC woody crop systems due to the presence of N2-fixing plants. However, no differences were detected between poplar and willow crops. In low quality agricultural soils, which are the likely host for SRC implementation, we demonstrated that willow has a higher nutrient accumulation rate than poplar, particularly for K, Mg and P. Weed strips constitute an important reservoir of C and nutrients and should be studied further.

Peer review report 1 on “Impact of Biases in Gridded Weather Datasets on Biomass Estimates of Short Rotation Woody Cropping Systems”

Peer review report 1 on “Impact of Biases in Gridded Weather Datasets on Biomass Estimates of Short Rotation Woody Cropping Systems”

Peer review report 2 on “Impact of Biases in Gridded Weather Datasets on Biomass Estimates of Short Rotation Woody Cropping Systems”

Peer review report 2 on “Impact of Biases in Gridded Weather Datasets on Biomass Estimates of Short Rotation Woody Cropping Systems”

Forecasting the deployment of short-rotation intensive culture of willow or hybrid poplar: Insights from a Delphi study

Short-rotation intensive culture (SRIC) of willow (Salix spp.) or hybrid poplar (Populus spp.) is currently at a precommercial stage with a potential to be applied economically across important areas to produce lignocellulosic biomass and environmental services in Canada. A two-round Delphi survey was conducted among 50 experts to assess the future deployment of SRIC in this country. The total area in 10 years (2011 base year) was forecasted as 1330, 4100, and 11 400 ha under pessimistic, realistic, and optimistic scenarios, respectively. The deployment of SRIC in the next decade depends mainly on the development of the demand for SRIC biomass and services, that of production technologies, and the establishment of policies and programs promoting its application. In the short term, research and development (R&D) and policy initiatives should be funded or implemented by various stakeholders to facilitate the deployment of the system. On average, respondents deemed that the potential for long-term (20 years) deployment of SRIC in Canada was good. Some of the conclusions and the methodological approach of this study could apply to short-rotation woody crop systems and to agroforestry systems in Canada and elsewhere.

History and Status ofEucalyptusImprovement in Florida

The first organizedEucalyptusresearch in Florida was begun by the Florida Forests Foundation in 1959 in southern Florida. This research was absorbed by the USDA Forest Service and the Florida Division of Forestry in 1968. In the early 1970s, the Eucalyptus Research Cooperative formed to provide additional support emphasizedE. grandis,E. robusta,E. camaldulensis, andE. tereticornisand developed cultural practices for commercial plantations in southern Florida. In 1978, this cooperative united with the Hardwood Research Cooperative at North Carolina State University until 1985 when the 14-year effort ended after three severe freezes from 1983 to 1985.Eucalyptusplanting and research were continued with a Florida-wide focus by the University of Florida and collaborators starting in 1980. The collective accomplishments in terms of genetic resources and commercial planting are summarized. For example, fast-growing, freeze-resilientE. grandisseedlings are produced by advanced generation seed orchards, fiveE. grandiscultivars are commercially available, as areE. amplifoliaandCorymbia torellianaseeds. Genetic improvement of these and other species is ongoing due to beneficial collaborations. Short Rotation Woody Crop systems are promising for increasing productivity and extending uses beyond conventional pulpwood to applications such as windbreaks, dendroremediation, and energy wood.

Functional groups show distinct differences in nitrogen cycling during early stand development: implications for forest management

Nutrient acquisition of forest stands is controlled by soil resource availability and belowground production, but tree species are rarely compared in this regard. Here, we examine ecological and management implications of nitrogen (N) dynamics during early forest stand development in productive commercial tree species with narrow (Populus deltoides Bartr. and Platanus occidentalis L.) and broad (Liquidambar styraciflua L. and Pinus taeda L.) site requirements while grown with a range of nutrient and water resources. We constructed N budgets by measuring N concentration ([N]) and N content (N C ) of above- and belowground perennial and ephemeral tissues, determined N uptake (N UP ), and calculated N use efficiency (NUE). Forest stands regulated [N] within species-specific operating ranges without clear temporal or treatment patterns, thus demonstrating equilibrium between tissue [N] and biomass accumulation. Forest stand N C and N UP increased with stand development and paralleled treatment patterns of biomass accumulation, suggesting productivity is tightly linked to N UP . Inclusion of above- and belowground ephemeral tissue turnover in N UP calculations demonstrated that maximum N demand for narrow-sites adapted species exceeded 200 kg N ha−1 year−1 while demand for broad-site adapted species was below this level. NUE was species dependent but not consistently influenced by N availability, suggesting relationships between NUE and resource availability were species dependent. Based on early stand development, species with broad site adaptability are favored for woody cropping systems because they maintain high above- and belowground productivity with minimal fertilization requirements due to higher NUE than narrow site adapted species.

Cottonwood Leaf Beetle (Coleoptera: Chrysomelidae) Larval Performance on EightPopulusClones

The cottonwood leaf beetle, Chrysomela scripta F., is the most serious defoliator of young plantation-grown Populus in the eastern United States, yet there is a paucity of data on larval feeding performance across Populus clones used in tree breeding. Field experiments were conducted in 1998 and 1999 to determine the overall feeding performance of larval C. scripta on 8 Populus selections from a pedigree family. Using a randomized complete block design, entire trees were enclosed in mesh cages, and female C. scripta were allowed to oviposit in sleeve cages on each tree. Larval cohorts were culled to 10 upon hatch and allowed to develop to pupation within each sleeve cage. Larval survival, pupal weight, adult emergence, and total mortality were recorded as performance parameters. Significant but inconsistent performance differences were found among clones, suggesting that some clones were less suitable for C. scripta larval development in some insect generations. Larval performance was generally poorer on clones with higher P. trichocarpa parentage. C. scripta performance was significantly poorer in 1999 and showed a decline throughout the 1999 growing season, but it is not clear whether this was caused by conditions of the host plants, weather patterns, or changes made in the source of insects for infestation. Clones with foliar characteristics detrimental to larval C. scripta performance could be used for plantings or in developing C. scripta-resistant hybrid Populus selections for short-rotation woody crop systems.

Short-rotation woody crop systems, atmospheric carbon dioxide and carbon management: A U.S. case study

Atmospheric concentrations of carbon dioxide (CO2) are increasing along with global use of fossil fuels and worldwide rates of deforestation. These trends have led international panels and organizations to devise carbon management strategies in an effort to curb increases in CO2. The goal of this paper is to explore the potential role of short-rotation woody crops (SRWC) in the U.S. as one option in a carbon-managed future economy. On a scale of 40 × 106 ha, and at an average productivity rate of 21 Mg oven-dry biomass ha−1 yr−1, SRWC systems could account for an average of 0.30 Pg of C yr−1 when prorated over the 50-year deployment life of a typical SRWC system. Most of the accounted carbon (76%) would come from fossil fuel displacement as opposed to direct carbon sequestration. The proportion of accounted carbon associated with fossil fuel displacement increases with longer time frames due to the relatively rapid saturation of the carbon sequestration pool. Key words: Populus, biomass, carbon sequestration, carbon displacement, Kyoto Protocol, CO2

An Iowa Demonstration of Agroforestry: Short-Rotation Woody Crops

Results of a "wood-for-energy" demonstration and research study are presented. Three short-rotation woody crop (SRWC) systems were planted in 1986 on an old agriculture field. One system has a one-year rotation and a 0.3 × 0.3 m spacing. The second has a 3-5 year rotation and a 1.8 × 0.9 m spacing, and the last has a 7-10 year rotation and a 1.8 × 1.8 m spacing. Three different Populus clones and sliver maple (Acer saccharinum L.) were used for the systems. All plantings, except the annual system, were 0.2 ha in size. Site preparation included discing, rototilling, and application of pre-emergent herbicides. Planting was done with a conventional single row tree planter, with the exception of the wood grass, which was hand planted. Early growth and yield varied by system and were affected by severe drought conditions in 1988 and 1989. Average height and diameter growth for the first three years were significantly greater for the two Populus clones than for the silver maple. For the annually harvested 0.3 × 0.3 m system, the average yields were 7.2, 9.2, 9.4, and 6.6 dry metric tons per ha (dmt ha−1 yr−1) from 1986 to 1989. Populus clones NC-5326 and NC-5328 in the 1.8 × 0.9 m system produced similar yields since establishment in 1986. After the first four growing seasons, there was a moderate difference in growth and yield between the Populus clones in the 1.8 × 1.8 m system. The NC-5326 produced 50% more than NC-5328. The annual system was costly to establish, with costs exceeding $7,069 ha−1 The 1986 establishment costs were $1,648 ha−1 or the Populus clones and $1,665 ha−1 for silver maple, both included in the 1.8 × 0.9 m system. In comparison, a 1987 planting of this system had a 18% reduction in costs. The 1986 establishment costs for the 18 × 1 8 m system were $1,023 ha−1for the Populus clones and $1,038 ha−1for silver maple, with a 23% cost savings in a 1987 planting. Pest problems were limited to a cottonwood leaf beetle infestation in the summer of 1987, which was easily controlled with a pesticide. Early growth and yields are encouraging given the severe drought conditions of 1988 and 1989. Moreover, the cost reductions from subsequent plantings (1987) indicate a trend towards cost-efficient short-rotation woody crop systems producing biomass for energy in the Iowa agricultural landscape.

Economic evaluations for short-rotation biomass production systems

Economic evaluations were added, for the first time, as a formal ‘Activity’ in the 1986 International Energy Agency Bioenergy Agreement task II. The objective of the ‘Activity’ was to economically evaluate the state of the art for short-rotation biomass production systems. This was done through three significant economic workshops, a comprehensive annotated bibliography, the development and testing of a standardized cost accounting spreadsheet for reporting cost informations, and the publishing of numerous technical papers. Given the economic climate during 1986–88, short-rotation woody crop systems for energy appeared marginal in most instances without government incentives.