• Energy Research
• Open Access close
• Restricted close
• US close
• PK close
• Trees and Timber Institute close

This is the longest continuous experiment where ethylenediurea (EDU) was used to protect plants from ozone (O3). Effects of long-term ambient O3 exposure (23 ppm h AOT40) on biomass of an O3 sensitive poplar clone (Oxford) were examined after six years from in-ground planting. Trees were irrigated with either water or 450 ppm EDU. Above (-51%) and below-ground biomass (-47%) was reduced by O3 although the effect was significant only for stem and coarse roots. Ambient O3 decreased diameter of the lower stem, and increased moisture content along the stem of not-protected plants (+16%). No other change in the physical wood structure was observed. A comparison with a previous assessment in the same experiment suggested that O3 effects on biomass partitioning to above-ground organs depend on the tree ontogenetic stage. The root/shoot ratios did not change, suggesting that previous short-term observations of reduced allocation to tree roots may be overestimated.

Recovery of tree root biomass can be attractive, since the stump-root system represents a substantial portion of the tree mass and its removal may prove instrumental to re-cultivation. Most available studies concern Nordic technologies, particularly suited to mature conifer stands. Unlike spruce, plantation poplar develops a deep taproot, whose extraction requires completely different methods. The aim of the study was to investigate poplar root recovery operations in plantations with time studies, and to determine the productivity and delivery costs of the operations. Seven operation systems developed to work with poplar plantations in Italian conditions were studied. Extraction and cleaning units were based on general-purpose prime movers. Under favourable conditions extraction and cleaning units achieved a very high productivity: 150 stumps per hour for the extraction unit and 170 for the cleaning unit. Delivered cost varied widely, ranging from 28 to 66 Euros Mg. Transportation was the most expensive single work task. It accounted for about 40% of the total recovery cost. Extraction and cleaning contributed approximately 25% each to the total cost, and loading 9%. Guidelines to recovery system improvement and efficient operation are provided.–1

The functional reasons for isoprene emission are still a matter of hot debate. It was hypothesized that isoprene biosynthesis evolved as an ancestral mechanism in plants adapted to high water availability, to cope with transient and recurrent oxidative stresses during their water-to-land transition. There is a tight association between isoprene emission and species hygrophily, suggesting that isoprene emission may be a favorable trait to cope with occasional exposure to stresses in mesic environments. The suite of morpho-anatomical traits does not allow a conservative water use in hygrophilic mesophytes challenged by the environmental pressures imposed or exacerbated by drought and heat stress. There is evidence that in stressed plants the biosynthesis of isoprene is uncoupled from photosynthesis. Because the biosynthesis of isoprene is costly, the great investment of carbon and energy into isoprene must have relevant functional reasons. Isoprene is effective in preserving the integrity of thylakoid membranes, not only through direct interaction with their lipid acyl chains, but also by up-regulating proteins associated with photosynthetic complexes and enhancing the biosynthesis of relevant membrane components, such as mono- and di-galactosyl-diacyl glycerols and unsaturated fatty acids. Isoprene may additionally protect photosynthetic membranes by scavenging reactive oxygen species. Here we explore the mode of actions and the potential significance of isoprene in the response of hygrophilic plants when challenged by severe stress conditions associated to rapid climate change in temperate climates, with special emphasis to the concomitant effect of drought and heat. We suggest that isoprene emission may be not a good estimate for its biosynthesis and concentration in severely droughted leaves, being the internal concentration of isoprene the important trait for stress protection.

Abstract Background and Aims The development of Arundo donax as a biomass crop for use on drought-prone marginal lands in areas with warm to hot climates is constrained by the lack of variation within this species. We investigated the effect of morphological and physiological variation on growth and tolerance to drought under field conditions in three ecotypes of A. donax collected from habitats representing a climate gradient: a pre-desert in Morocco, a semi-arid Mediterranean climate in southern Italy and a warm sub-humid region of central Italy. Methods The three A. donax ecotypes were grown under irrigated and rain-fed conditions in a common garden field trial in a region with a semi-arid Mediterranean climate. Physiological and morphological characteristics, and carbohydrate metabolism of the ecotypes were recorded to establish which traits were associated with yield and/or drought tolerance. Key Results Variation was observed between the A. donax ecotypes. The ecotype from the most arid habitat produced the highest biomass yield. Stem height and the retention of photosynthetic capacity later in the year were key traits associated with differences in biomass yield. The downregulation of photosynthetic capacity was not associated with changes in foliar concentrations of sugars or starch. Rain-fed plants maintained photosynthesis and growth later in the year compared with irrigated plants that began to senescence earlier, thus minimizing the difference in yield. Effective stomatal control prevented excessive water loss, and the emission of isoprene stabilized photosynthetic membranes under drought and heat stress in A. donax plants grown under rain-fed conditions without supplementary irrigation. Conclusions Arundo donax is well adapted to cultivation in drought-prone areas with warm to hot climates. None of the A. donax ecotypes exhibited all of the desired traits consistent with an ‘ideotype’. Breeding or genetic (identification of quantitative trait loci) improvement of A. donax should select ecotypes on the basis of stem morphology and the retention of photosynthetic capacity.

In the alpine Autonomous Province of Bolzano (N-E Italy), about 40 % of the biomass used for bioenergy production is currently imported. This share is expected to further increase in the near future owing to growing renewable energy needs. The residual biomass harvestable from the local agronomic sector, mostly based on the cultivation of apple, is a promising option to supply relatively cheap bioenergy feedstock. In this study, we investigate the use of woody residues from apple orchards (apple orchard´s woody residues, AWRs) for the production of bioenergy using the life cycle assessment (LCA) methodology. The system boundaries include the harvesting and chipping of AWRs, their transport to the energy plant and conversion into heat and power in a gasification unit. The life cycle inventory (LCI) data rely on field measurements for AWRs harvesting and chipping operations, as well as for their chemical and energy characterization. In the life cycle impact assessment (LCIA) phase, we consider various environmental impact categories like climate change, acidification, fossil depletion, and others. We benchmark the outcomes with two alternative reference systems based on fossils fuels. Our results show that the energy production using AWRs generally presents better environmental indicators than the reference systems, although some trade-offs exist. For instance, whereas the bioenergy system saves up to about 85% of greenhouse gas (GHG) emissions and about 95% of non-renewable resources, it is usually associated with higher toxicity impact potentials.

AbstractThe photosynthetic, optical, and morphological characteristics of a chlorophyll‐deficient (Chl‐deficient) “yellow” soybean mutant (MinnGold) were examined in comparison with 2 green varieties (MN0095 and Eiko). Despite the large difference in Chl content, similar leaf photosynthesis rates were maintained in the Chl‐deficient mutant by offsetting the reduced absorption of red photons by a small increase in photochemical efficiency and lower non‐photochemical quenching. When grown in the field, at full canopy cover, the mutants reflected a significantly larger proportion of incoming shortwave radiation, but the total canopy light absorption was only slightly reduced, most likely due to a deeper penetration of light into the canopy space. As a consequence, canopy‐scale gross primary production and ecosystem respiration were comparable between the Chl‐deficient mutant and the green variety. However, total biomass production was lower in the mutant, which indicates that processes other than steady state photosynthesis caused a reduction in biomass accumulation over time. Analysis of non‐photochemical quenching relaxation and gas exchange in Chl‐deficient and green leaves after transitions from high to low light conditions suggested that dynamic photosynthesis might be responsible for the reduced biomass production in the Chl‐deficient mutant under field conditions.