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Abstract Industrial hemp, (Cannabis sativa L.), one of the earliest crops spun for fiber, is now used for a variety of commercial products including paper, textiles, clothing, biodegradable plastics, biofuel, food, animal feed etc., all of which are derived from hemp fiber or seeds. Being wind pollinated, dioecious and staminate hemp plants produce large amounts of pollen that are attractive to bees. Hemp flowering in northern Colorado, where this study was conducted, occurs between the end of July and the end of September. This time period coincides with a dearth of pollinator-friendly crop plants in the region, making hemp flowers a potentially valuable source of pollen for foraging bees. Here we present the diversity and abundance of bees collected in the fields of flowering hemp. A total of 23 different genera of bees were collected of which the European honeybee, Apis mellifera at 38% of the total abundance was the most dominant followed by Melissodes bimaculata at 25% and Peponapis pruinosa at 16%. These three genera made up nearly 80% of the total abundance. While hemp does not produce any nectar, the pollen rich nature of the flowers can make hemp an ecologically valuable crop. As cultivation of hemp continues to expand, we expect insect pests on hemp to also become prevalent. Our results documenting bee diversity in flowering hemp provides the impetus for the development of integrated pest management plans that protect pollinators while controlling pests.

Abstract The eddy covariance method was used to investigate carbon fluxes and evapotranspiration (ET) from a high biomass forage sorghum ( Sorghum bicolor L.) field in the Southern U.S. Great Plains for three growing seasons (2013–2015). Above normal precipitation and narrow row spacing (50 cm) led to higher biomass production (25 Mg ha −1 ) and leaf area index (LAI = 7.2) development in 2014. This also resulted in higher carbon uptake or net ecosystem production (NEP) and ET during that year. Early and late season precipitation enhanced ecosystem respiration (R eco ) resulting in lower NEP in 2015. Shorter growing season (119 days) also contributed to lower cumulative NEP in 2015. Estimated gross primary production (GPP) in 2014 (1780 g m −2 ) was 10% higher than the GPP in 2013 (1591 g m −2 ) and 24% higher than the GPP in 2015 (1353 g m −2 ). During all growing seasons, the site was a source of carbon (negative NEP) at the beginning and transitioned to a sink (positive NEP) later in the season. Biomass-GPP relationship indicated that approximately 65% of total GPP was allocated to above ground biomass (AGB). Average monthly ecosystem WUE (expressed as gross carbon gain per unit of ET) ranged from 1.7 g mm −1 to 4.2 g mm −1 . Results from our study indicate that weather conditions, growing season length and crop management are important factors in determining the magnitude of carbon uptake and release, and ET of this cellulosic biofuel feedstock crop in the Southern U.S. Great Plains.

An important and potentially underused source of biomass that could be utilized in energy production is from nonindustrial private woodlands. We employ the Theory of Planned Behavior to estimate the social availability of woody biomass as a function of landowner behavior intent, landowner characteristics, forest land characteristics, and biomass price on stated willingness to harvest biomass in conjunction with a commercial timber harvest. A mail survey was administered to 1109 nonindustrial private woodland owners in a 26county region in northeast Minnesota and northwest Wisconsin during the fall of 2009. Using binary logistic regression, we found payment level offered to harvest biomass plays a significant role in landowners’ decisions, but that non-monetary factors are also important. Landowner attitudes and opinions regarding soil impacts, aesthetics, and energy independence were important predictors of stated willingness to harvest. Social norms as manifested through the influence of neighbors were also significant. These findings expand existing research and are useful for profiling nonindustrial private woodland owners to identify sustainable sources of biomass to supply a burgeoning bioenergy sector in the Lake States.

Water Research Commission (WRC) and National Research Foundation (NRF) of South Africa for funding the project (K5/1480/1/12).

Abstract Calorific values (CV) of plants plays a key role in energy conversion. The red-heart Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the most important commercial timber species in southern China. However, little is known about its CVs. We compared the CVs of C. lanceolata organs, understory, and litter from four different stand ages (9, 15, 26, and 34a). The results showed that the ash-free calorific value (AFCV) can more accurately reflect CV than gross calorific value (GCV). The AFCV of stemwood increased from the lower to upper, and was higher in heartwood than in sapwood. AFCV in organs increases with stand age and was the highest in leaves and lowest in bark. AFCV of litters also increased with stand age. But AFCV of understory reduced with increasing of stand age, and the AFCV of aboveground were higher than that of underground. Ash content (AC) of tree organs was not associated with GCV, but affected AFCV, observably. The biomass of 9a, 15a, 26a and 34a stands were 61.67, 123.57, 171.58, 203.01 t/ha, and the total energy of them were 11.92, 24.28, 33.37, 39.68 × 108 kJ/ha, respectively. The biomass and energy of the tree layer accounted for 90% of the total stand and were greatest in stemwood, which can be simulated by Logistic models, and reached biomass and energy maturity at about 35 years. The results not only be helpful for the decision makers to efficiently obtain more biomass with high energy, but also enrich the content of energy ecology.

Abstract Growth and yield of Populus were examined in a 5-year test of five spacing-harvest regimes in western Washington. Two hybrid clones (D-O1 and H-11) were planted at two woodgrass spacings (0.18 and 0.3 m) and three wider spacings (0.5, 1.0 and 2.0 m). All treatments were replicated three times in a randomized block design; all plots were fertilized, irrigated, and weeded uniformly. Mean annual harvest yields in the woodgrass treatments did not differ significantly between the two clones (D-O1 and H-11) or two spacings (0.18 and 0.3 m), averaging 6.4 to 7.0 Mg ha −1 (tonnes ha −1 ) over the 5-year period. The highest yield in woodgrass treatments was produced in the second year (first year of coppice), and it declined thereafter. Cumulative growth in the wider spacings was significantly greater than in the two woodgrass spacings. Per hectare yields of clone H-11 in the wider spacings at age 5 were two to three times greater than cumulative yields obtained with annually cut woodgrass, averaging 15.7 to 18.8 Mg ha −1 yr −1 . Fifth-year increments in all wider spacings (0.5, 1.0 and 2.0 m) of clone H-11 exceeded 30 Mg ha −1 . Yields of clone D-01 in the wider spacings ranged from 8.1 to 10.9 Mg ha −1 yr −1 , and thus were also substantially greater than cumulative yields of woodgrass. We conclude that annually harvested woodgrass shows little promise as a viable system for growing Populus for biomass. On the other hand, yields in the wider spacings with a longer harvest cycle were substantially higher than previously expected, especially for clone H-11. Thus, possibilities for application of the wide-spaced regimes and longer cutting cycles appear promising.

Abstract Lack of access to modern energy, such as electricity, liquid fuels and gas, limits socio-economic development in developing countries, particularly in rural communities. Primary forest residues are potential bioresources for producing modern forms of energy beyond traditional biomass, which can be supplied to economic activities in the rural communities. However, variations in production of primary forest residues over time exacerbate sustainability challenges for developing sustainable bioenergy systems based on the residues supply chains integrated with timber production. A model is presented showing dynamics of primary forest residues, as bioenergy feedstocks, stemming from forest plantations management, harvesting systems, and stakeholder influence and interest along the bioenergy production value chain. Using a case study of the Viphya forest plantations established for timber production in Malawi, management and harvesting systems, sawmilling technologies, residues production and post harvesting management were assessed and key sustainability challenges along the residues supply chain have been identified. The decreasing stocks of mature stand over time results from over-exploitation for timber production, delayed replanting, high death rate of replanted trees and underinvestment in plantations management. An integrated framework for forest management and bioenergy production can promote sustainable harvesting of mature stand for timber and primary forest residues production through synchronization of harvesting and replanting of timber and establishment of thresholds for harvesting timber to generate residues at a rate that can match with the scale and rate of the bioenergy conversion. The framework can promote stability, availability and reliability of timber and primary forest residues supply for bioenergy production.

Abstract The potential habitat value of commercial short rotation coppice (SRC)-willow plantations for flower-visiting insects was investigated. During 1998–2000, at a single typical intensive Danish farmland site, 11 Salix viminalis plantations were sampled by late April to quantify willow catkin abundance and flower sex. Mean plantation size was 1.1 ha and included one or more of clones: orm, rapp, ulv, jorr, christina and jorrun. Plot-year means of catkin abundance and of proportion of willows flowering were related to the coppicing cycle, i.e. the number of growth years since last harvest of plot (‘year’ 0–4). In 1998, the ground layer vegetation was sampled. Monitoring flower-visiting insects by means of line-transect counts failed due to the local scarcity of bees. At the plantation scale, flowering was discontinuous across the harvest cycle as it was totally absent in the year immediately following harvest. In successive years (1–4), individual willows flowered frequently and, occasionally, at high abundances, and catkin abundance increased with time. Within 3–4 year of harvest cycle, all plots flowered in most years with most plots exhibiting at least some flowering in any 1 year. Thus, willow catkin abundance was generally high in the total area due to: high frequency of flowering in plots, occasional high flowering abundance, plots not being harvested simultaneously and large total number of willows within plots and landscape. Similarly, flower sex ratio, and thus flower value, varied greatly between plots while variation was damped across plots. Alternative simultaneous flower resources in ground layer vegetation were few except for Dandelion. SRC willow may constitute an important resource for bees, even under the stress of the harvest cycle, and recommendations are given for improving this biodiversity aspect.

Abstract Willow (Salix viminalis) irrigated with three different dosages of wastewater has been investigated for leaf damages in four plantations located in Sweden, Northern Ireland, France and Greece, during 3 consecutive years. Control treatments were clean water and/or no water. Additionally, the plantation in Sweden included a human urine/water mix treatment and the one in N. Ireland a sewage sludge treatment. Few effects of the treatments were found. In the Greek trial, all treatments were affected by abiotic stress causing leaf discolouration, necrosis and leaf curling, but the control treatment was least affected. Mite infestations were also less prevalent in the control plots there. In the French trial, control leaves were less galled by Dasineura marginemtorquens than leaves from the lowest dose of wastewater but not compared to the two higher doses of wastewater, during 1 of the 3 years. At the same site, but in another year, Melampsora rust infection was least developed at the highest dose of wastewater but only significantly so when compared to the intermediate dose of wastewater. Urine/water treatment resulted in more rust and leaf margin damages than the control treatments in 1 year. Also, leaf spotting by leafhoppers tended to be more prevalent on the urine treatment. However, since the urine fertilisation favours willow growth as well, a somewhat enhanced biotic damage to leaves is probably no reason for avoiding this application in full-scale plantations. Damage by chrysomelid beetles was very common in the French and the N. Irish plantations, but no significant differences between treatments were found. Neither were there any treatment effects on symptoms by aphids.