Aboveground Yield and Biomass Quality of Giant Reed (Arundo donax L.) as Affected by Harvest Time and Frequency

Giant reed (Arundo donax L.) is a perennial rhizomatous grass producing high biomass yields in temperate and warm climates under rainfed and reduced input conditions. Harvest time and frequency typically affect the productivity and suitability for energy conversion of energy crops. In order to evaluate the effect of different cutting managements on biomass yield and quality of giant reed, three single harvest (SH) and six double harvest (DH) systems were compared. Biomass yield, leaf mass ratio, dry matter (DM), and ash content were assessed for each harvest. Over the 2 years of study, giant reed demonstrated good productivity levels both when harvested once a year and twice a year (about 30 Mg ha−1) without significant differences between the treatments. Regarding double-cut regimes, overall yields were significantly reduced by delaying the second cut from autumn to winter (32.9 vs 30.2 Mg ha−1), and the percentage of the first cut with respect to the overall yield varied from 55 to 80 %. Biomass quality was also significantly affected by harvest time and frequency. The biomass obtained in double harvest systems showed higher average moisture levels (about 40 % DM) and ash concentrations ranging from 4.7 to 8.7 %. In contrast, single harvest systems led to a drier biomass (47–57 % DM) and reduced mineral contents (3.4–4.8 % ash). The feasibility of double-cut management should therefore be considered in terms of the specific giant reed-based supply chain, with particular regards to the storage and conversion technology adopted

Carbon Budget of an Agroforestry System after Being Converted from a Poplar Short Rotation Coppice

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 ± 40 g C m−2 year−1), highlighting that the system was a net carbon sink (i.e., NBP > 0). However, the ACS registered a net C loss (i.e., NBP < 0), since the NBP was −93 ± 56 g C m−2 year−1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial effect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses

Carbon Budget of an Agroforestry System after Being Converted from a Poplar Short Rotation Coppice

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 40 g C m2 year1), highlighting that the system was a net carbon sink (i.e., NBP &gt; 0). However, the ACS registered a net C loss (i.e., NBP &lt; 0), since the NBP was 93 56 g C m2 year1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial eect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses

Giant reed (Arundo donax L.) for biogas production: land use saving and nitrogen utilisation efficiency compared with arable crops

Aiming to improve the sustainability of biogas supply chains, the research for alternative feedstocks is a key issue and giant reed (Arundo donax L.) is a promising no-food crop to be used in anaerobic digestion. In fact, giant reed is a perennial species characterised by low nutrient requirements and is able to provide promising biogas yields. Its suitability for anaerobic digestion is influenced by harvest time, since plant characteristics vary noticeably along the season. Moreover, ensiling is a storage technique that can assure a good preservation of the biomass over time, but also influence the methane yields. Therefore, the aim of this study was to assess the suitability for biogas production of giant reed silage, according to different cutting regimes, and to evaluate the efficiency in saving land and nitrogen for fuelling biogas plants, in comparison with maize and two sorghum varieties. Methane yields per hectare (Nm3 CH4 ha–1) were determined by multiplying the biochemical methane potential of each substrate by the aboveground biomass of the corresponding crop. The land use coefficient (LU), namely the land needed to fuel one kW power (ha kWe–1), was calculated from the estimated methane yields per hectare. Finally, nitrogen utilisation efficiency (NUtE), which is the ratio between the estimated methane yield and the nitrogen uptake per hectare (Nm3 CH4 kgN–1), was determined for each crop species and according to the harvest time and frequency of giant reed. Overall, a good suitability for ensiling was observed in giant reed. When harvested in September, the crop yielded about 9900 Nm3 CH4 ha–1, while in double harvest systems biomethane was about 12,000 Nm3 CH4 ha–1, +35% and +70% than maize and sorghum respectively. Moreover, giant reed under double harvest management was the most land-conservative option, as LU was about 0.22 ha kWe–1, while in annual crops it was about 0.35 ha kWe–1. The higher NUtE was observed in single harvests (up to 64 Nm3 CH4 kgN–1), while double harvests showed remarkably lower values, averaging 48 Nm3 CH4 kgN–1. Annual crops were less efficient, since NUtE ranged from 28 Nm3 CH4 kgN–1 (maize) to 40 Nm3 CH4 kgN–1 (fibre sorghum). In conclusion, giant reed can be an alternative for biogas making, potentially providing land and nitrogen savings compared with conventional annual crops

Climate control of terrestrial carbon exchange across biomes and continents

Peer reviewe

Asperity distribution of the 1964 great Alaska earthquake and its relation to subsequent seismicity inthe region

The 1964 Alaska earthquake was the second largest seismic events in the 20th century. The aim of this work is the use of surface deformation data to determine asperity and slip distributions on the fault plane of the Alaska earthquake: these distributions are calculated by a Monte Carlo method. To this aim, we decompose the fault plane in a large number of small square asperity units with a side of 25 km; this allows us to obtain plane surfaces with an irregular shape. In the first stage, each asperity unit is allowed to slip a constant amount or not to slip at all, providing the geometry of the dislocation surface that best reproduces the observed displacements. To this purpose, a large number of slip distributions have been tried by the use of the Monte Carlo method. The slip amplitude is the same for all the asperities and is equal to the average fault slip inferred from the seismic moment. In the second stage, we evaluate the slip distribution in the dislocation area determined by the Monte Carlo inversion: in this case, we allow unit cells to undergo different values of slip in order to refine the initial dislocation model. The results confirm the previous finding that the slip distribution of the great Alaska earthquake was essentially made of two dislocation areas with a higher slip, the Prince William Sound and the Kodiak asperities. Analysis of the post-1964 seismicity in the rupture region shows a strong correlation between the larger earthquakes (Mw z 6) and the distribution of locked asperities following the 1964 event, which can be considered as an independent test of the validity of the model. We do not find slip values higher than 25 m for any of the patches, and we determine two separate high-slip zones: one correspondent to the Prince William Sound asperity, and one ( f 18 m slip) to the Kodiak asperity. The slip distribution connected with the 1964 shock appears to be consistent with the following seismicity in the region

Asperity distribution of the 1964 Great Alaska earthquake and its relation to subsequent seismicity in the region (vol 367, pg 219, 2003)

Figs. 1, 4, 5, 6, 7, 8 and 9 in this paper should have been printed in colour. They were printed in black and white in error but can be viewed in colour in the online version of the paper on ScienceDirect. The publisher apologises to the authors and to readers for the inconvenience caused

Il "nuovo" effetto fotoelettrico di Quirino Majorana

Si discute, alla luce delle teorie moderne, il lavoro svolto da Ettore e Quirino Majorana su possibili nuovi aspetti dell'effetto fotoelettrico, non individuati dalla teoria di Einstein. Sulla base di argomenti qualitative, si suggerisce che, con buona probabilit\ue0, le misure effettuate da Quirino sull'effetto fotoelettrico dovuto a illuminazione periodica del campione, potrebbero essere interpretate dalla teoria di Einstein, con opportune modifiche dovute alla specifit\ue0 dell'esperimento. In sostanza, come era gi\ue0 avvenuto per la Relativit\ue0, anche in questo caso Quirino sembra impiegare il proprio straordinario talento di sperimentatore nel tentativo di smentire una teoria che poi i suoi stessi esperimenti confermano. In questo caso, tuttavia, la questione non pu\uf2 dirsi completamente chiarita, n\ue9 sul piano teorico, n\ue9 su quello sperimentale. Si sottolinea l'illuminante chiarezza dell'intervento teorico di Ettore, puramente basato sulla fisica classica, peraltro

Asperity distribution of the 1964 great Alaska earthquake and its relation to subsequent seismicity inthe region

The 1964 Alaska earthquake was the second largest seismic events in the 20th century. The aim of this work is the use of surface deformation data to determine asperity and slip distributions on the fault plane of the Alaska earthquake: these distributions are calculated by a Monte Carlo method. To this aim, we decompose the fault plane in a large number of small square asperity units with a side of 25 km; this allows us to obtain plane surfaces with an irregular shape. In the first stage, each asperity unit is allowed to slip a constant amount or not to slip at all, providing the geometry of the dislocation surface that best reproduces the observed displacements. To this purpose, a large number of slip distributions have been tried by the use of the Monte Carlo method. The slip amplitude is the same for all the asperities and is equal to the average fault slip inferred from the seismic moment. In the second stage, we evaluate the slip distribution in the dislocation area determined by the Monte Carlo inversion: in this case, we allow unit cells to undergo different values of slip in order to refine the initial dislocation model. The results confirm the previous finding that the slip distribution of the great Alaska earthquake was essentially made of two dislocation areas with a higher slip, the Prince William Sound and the Kodiak asperities. Analysis of the post-1964 seismicity in the rupture region shows a strong correlation between the larger earthquakes (Mw z 6) and the distribution of locked asperities following the 1964 event, which can be considered as an independent test of the validity of the model. We do not find slip values higher than 25 m for any of the patches, and we determine two separate high-slip zones: one correspondent to the Prince William Sound asperity, and one ( f 18 m slip) to the Kodiak asperity. The slip distribution connected with the 1964 shock appears to be consistent with the following seismicity in the region