Populus

Hybrid poplar plantations offer opportunities for enhancing carbon sinks, but accurate assignment of carbon credits requires accurate estimation of the amount of carbon stored in poplar biomass. Here we present individual-tree bole and branch biomass equations derived for Populus trichocarpa Torr. and Gray  P. deltoides Marsh. hybrids from plantations in coastal British Columbia, Canada. Trees ranged in age from 4 to 13 years old and were planted at a density of 1111 stems ha À1 . Equations were applied to similar short-rotation intensive-culture plantations near or at rotation age to derive estimates of aboveground leafless biomass production and amount of carbon sequestered. After 12 years, predicted aboveground leafless biomass accumulation ranged from 9.2 to 13.6 Mg ha À1 year À1 ; predicted bole biomass accumulation ranged from 7.5 to 11.3 Mg ha À1 year À1 . Total carbon in aboveground leafless biomass at age 12 ranged from 51.2 to 75.7 Mg ha À1 . Three of the stands reached 14 years of age prior to harvest. Predicted carbon content of aboveground leafless biomass at 14 years of age ranged from 73.7 to 88.7 Mg ha À1 .

This is the first study reporting the presence of endogenous caffeine, theobromine, and theophylline in all organs of poplar plants. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was used in order to evaluate the uptake, translocation, and metabolism of caffeine-(trimethyl-(13)C) in Populus alba L. Villafranca clone grown in hydroponic conditions. We investigated the remediation of caffeine since it is one of the most widely consumed drugs and it is frequently detected in wastewater treatment plant effluents, surface water, and groundwater worldwide. Our results demonstrated that poplar can absorb and degrade exogenous caffeine without negative effects on plant health. Data showed that concentrations of all endogenous compounds varied depending on caffeine-(trimethyl-(13)C) treatments. In particular, in control conditions, endogenous caffeine, theobromine, and theophylline were mainly distributed in roots. On the other hand, once caffeine-(trimethyl-(13)C) was provided, this compound and its dimethy-(13)C metabolites are mainly localized at leaf level. In conclusion, our results support the possible use of Villafranca clone in association with other water treatment systems in order to complete the process of caffeine remediation.

Background: Fragmentary conservation of synteny has been reported between map-anchored Prunus sequences and Arabidopsis. With the availability of genome sequence for fellow rosid I members Populus and Medicago, we analyzed the synteny between Prunus and the three model genomes. Eight Prunus BAC sequences and map-anchored Prunus sequences were used in the comparison.

Finnish wood heat treatment technology, Ther-moWood, was recently introduced to Québec, Canada by Ohlin Thermo Tech. Subsequently, a large number of initial trials were conducted on five commercially important Québec wood species, spruce (Picea spp.), pine (Pinus spp.), fir (Abies spp.), aspen (Populus spp.), and birch (Betula spp.). These species were thermally-modified in different batches at temperatures of 200 • C or higher. The static bending and hardness of the thermally-modified wood were examined. Decreases of 0% to 49% were observed in modulus of rupture of heat-treated spruce, pine, fir, and aspen depending on species and treatment schedules used; modulus of rupture of birch increased slightly after the heat treatment. The decrease in modulus of elasticity of heat-treated spruce and pine ranged from 4% to 28%; but the modulus of elasticity of heat-treated fir, aspen, and birch increased except one trial for fir. Hardness of the heat-treated wood increased or decreased depending on the species, test directions (radial, tangential, and longitudinal), and treatment schedules.

refers to molecular-level characteristics such as elemental composition, functional groups, and molecular con-Formation of chemically resistant humic substances might be an formation that influence the inherent biodegradability important process controlling recycling of soil C to the atmosphere. of the molecule. Interactions refers to the intermolecular Humic substances are believed to be resistant to microbial decomposition because they accumulate in soil, but there is little direct experi-interactions with other inorganic or organic molecules mental evidence for their inherent recalcitrance. My objective was to that influence biodegradability-for example, complexcompare the microbial mineralization rates of the humic and fulvic ation with Al. Physical accessibility refers to the location acid fraction to other fractions of decayed plant matter in soil. Uniof the molecule with respect to enzymes or cells. For formly 14 C labeled Populus fremontii leaf litter that had decomposed example, substrates may be located in submicrometer for 180 d was fractionated into the NaOH-insoluble residue, phenolic, pores too small for microbial cells to enter (Sollins et humic acid, fulvic acid, hydrophilic acid, and hydrophilic neutral fracal., 1996). These conditions do not necessarily occur extions. Humic acid comprised 22.7% of the C in the decomposed litter.

The vigorous vegetative reproduction of intolerant deciduous competition limits the efficacy of mechanical release operations in young softwood plantations. Applying bioherbicides such as the fungus Chondrostereum purpureum (Pers. ex Fr.) Pouzar could improve the effectiveness of release by reducing stump sprouting while gaining public acceptance. A field experiment was conducted in Québec (Canada) in two white spruce (Picea glauca [Moench]

Atmospheric transport models are used in studies of atmospheric chemistry as well as aerobiology. Atmospheric transport models in general needs accurate emissions inventories, which includes biogenic emissions such as Volatile Organic Compounds (VOCs) and pollen. Trees are important VOC and pollen sources and a needed requirement is specie distribution which takes into account important species such as Betula and Alnus. We present here a detailed tree species inventory covering Europe, parts of Africa and parts of Asia.

Models which combine the abstract (eg, physiological) function of a plant with its architecture have more and more come into the focus of international research in recent years. In the wake of this development, an entirely new class of models has arisen, generally known as ...

We use the stratigraphy of floodplains on Alaska's North Slope to describe how tundra watersheds responded to climate changes over the last 15,000 calibrated years BP (15 cal ka BP). Two episodes of extremely rapid floodplain alluviation occurred during the PleistoceneeHolocene transition, one between 14 and 12.8 cal ka BP and the other between 11.5 and 9.5 cal ka BP. These aggradation episodes coincided with periods of warming in summer when cottonwood (Populus balsamifera L.) expanded its range, peatlands became established, and widespread thermokarst occurred. The two aggradation episodes were separated by a period of floodplain incision during the Younger Dryas under cooler and possibly drier conditions. At times of increasing summer warmth, melting permafrost and enhanced precipitation probably triggered widespread mass wasting on hillslopes that overwhelmed the capacity of streams to transport sediment downstream, and rapid floodplain aggradation resulted. After peatlands became widespread in the early Holocene, rivers slowly incised their valley fills. Because major pulses of sediment input were limited to times of rapid thaw and increasing moisture, many floodplains on the North Slope have been effectively decoupled from upstream hillslopes for much of the past 15,000 years. Our findings: (a) confirm the sensitivity of arctic watersheds to rapid warming in summer, (b) emphasize the importance of hillslope mass wasting in landscape-scale responses to climate change, and (c) suggest that the presence of peatland on this arctic landscape today has raised its geomorphic response threshold to climate warming compared to what it was 14,000 years ago.

Complete Populus genome sequences are available for the nucleus (P. trichocarpa; section Tacamahaca) and for chloroplasts (seven species), but not for mitochondria. Here, we provide the complete genome sequences of the chloroplast and the mitochondrion for the clones P. tremula W52 and P. tremula x P. alba 717-1B4 (section Populus). The organization of the chloroplast genomes of both Populus clones is described. A phylogenetic tree constructed from all available complete chloroplast DNA sequences of Populus was not congruent with the assignment of the related species to different Populus sections. In total, 3,024 variable nucleotide positions were identified among all compared Populus chloroplast DNA sequences. The 5-prime part of the LSC from trnH to atpA showed the highest frequency of variations. The variable positions included 163 positions with SNPs allowing for differentiating the two clones with P. tremula chloroplast genomes (W52, 717-1B4) from the other seven Populus indivi...

Isoprene emission capacity measurements are presented from 18 North American oak (Quercus) species and species from six other genera previously found to emit signi"cant quantities of isoprene. Sampling was conducted at physiographically diverse locations in North Carolina, Central California, and Northern Oregon. Emissions from several sun leaves of each species were measured at or near standard conditions (leaf temperature of 303C and photosynthetically active radiation of 1000 mol m\ s\) using environmentally controlled cuvette systems and gas chromatography with reduction gas detectors. Species mean emission capacity ranged from 39 to 158 g C g\ h\ (mean of 86), or 22 to 79 nmol m\ s\ (mean of 44). These rates are 2}28 times higher than those previously reported from the same species, which were summarized in a recent study where isoprene emission rates were assigned based on published data and taxonomy. These discrepancies were attributed to di!erences in leaf environment during development, measurement technique (branch or plant enclosure versus leaf enclosure), and lack of environmental measurements associated with some of the earlier branch enclosure measurements. Mass-based emission capacities for 15 of 18 oak species, sweetgum (Liquidambar styraciyua), and poplars (Populus trichocarpa and P. deltoides) were within ranges used in current biogenic volatile organic compound (BVOC) emission models, while measured rates for the remaining three oak species, Nyssa sylvatica, Platanus occidentalis, Robinia pseudoacacia, Salix nigra, and Populus hybrids (Populus trichocarpa ; P. deltoides) were considerably higher. In addition, mean speci"c leaf mass of the oak species was 30% higher than assumed in current emission models. Emission rates reported here and in other recent studies support recent conclusions that isoprene emission capacities for sun leaves of high emitting species may be better represented by a value of 100$50 g C g\ h\ during hot summer conditions. We also "nd that intermediate isoprene emission rates previously suggested for some tree species may not represent their true emission capacities, and that broadleaf plant species may have either low ( (1.0 g C g\ h\) or very high ( &100 g C g\ h\) genetic capacity to emit isoprene when mature foliage is exposed to a high ambient temperature and light environment. Published by Elsevier Science Ltd.

Studying the elements (Al, Ba, Ca, Cu, Fe, K, Mg, Na, P, S, Sr, Zn) in dust and leaves along an urbanization gradient in Wien, Austria we found that the elemental concentrations of foliage dust were significantly higher in the urban area than in the rural area for Al, Ba, Fe, Pb, P and Se, and concentrations of leaves were significantly higher in urban than in rural area for Mn and Sr.

We describe the calibration and structure of a multi-species, two-scale light transmission model, and demonstrate its effectiveness for predicting instantaneous light availability at the stand scale across a wide range of forest stand compositions. The model, MIXLIGHT, calculates light transmission through the forest overstory at the stand or microsite scale using standard forest inventory data and two other parameters, foliage area density and foliage inclination. Since MIXLIGHT simulations on both scales are based on a list of individual tree characteristics, it allows for simple manipulation of stand structure to study the effects of silvicultural options on light availability. The two scales allow the input of various kinds of data, allowing predictions from data of different sources and completeness. A simple and rapid method of calibrating the foliage parameters for the species of interest is presented, using measurements of direct-beam light transmission measurements made in the shadows of newly isolated trees. In an independent validation, MIXLIGHT predicted light transmission at the stand level closely for 17 forest inventory plots with a wide range of density and species composition, during leaf-on and leaf-off seasons and under sunny and cloudy conditions. A sensitivity analysis indicated that the influence of the parameters in the model on stand level light transmission predictions was (highest to lowest): foliage area density, crown radius, crown length, and foliage inclination. Nonetheless, a test of the common assumption that the foliage is spherically inclined caused significant underestimation of light transmission. With this flexibility and demonstrated accuracy, we believe MIXLIGHT will provide an accessible and effective tool for forest stand management and regeneration modeling.

A mass spectrometer was coupled to high-performance anion-exchange chromatography (HPAEC) with the help of electrochemical neutralization of the eluent and post-column addition of lithium chloride for carbohydrate analysis. Parallel selective channels (single ion monitoring) were used to decrease the detection limits and separate unresolved peaks. The mass specific detection allowed the simultaneous analysis of a wide range of sugar alcohols, mono-, di-and oligosaccharides. Carbohydrates extracted from leaves of poplar submitted to drought stress were analyzed using pulsed amperometric detection (PAD), then mass spectrometry. It allowed the confirmation of peak attribution and the identification of salicin as a major compound in the extracts. Different responses to water deficit and re-hydration were obtained for several carbohydrates, suggesting different roles in osmoprotection processes.

Fire history and stand structure was examined in twelve virgin forest stands situated within forest reserves in northern Sweden. The selected stands represented fire refuges as well as different successional stages after fire. Six of the stands were dominated by Norway spruce (Piceu abies L. Karst.), three were dominated by Scats pine (Pinus sylvestris L.), and three were dominated by hairy birch (Be&a pubescens Ehrh.) or aspen (Populus tremulu L.). In 3 of the southernmost stands, the average fire interval was 34 to 65 years during the late 1600s to late 18OOs, but since 1888 no fires had occurred in any of the stands. The absence of fire disturbance since 1888 is probably caused by the fire suppression in the overall landscape. The standing volume of living trees ranged between 87 and 5 11 m3 ha-' while the volume of dead trees, including both snags and logs, ranged between 27 and 201 m3 ha-'. The volume of dead trees constituted ca. 30% of the total stem volume. In the conifer dominated stands, there was a statistically significant relationship between total stem volume, including both living and dead trees, and site productivity. A comparison between the amount of dead and living trees indicated substantial changes in tree species composition in several stands. It is suggested that data on the amount of dead trees, especially logs, and its distribution over decay classes could be used to examine the continuity of certain tree species. All stands had a multi-sized tree diameter distribution, which in most cases was similar to a reversed J-shaped distribution. In general spruce was numerous in the seedling cohort and in small diameter classes, indicating that its proportion in the stands was stable, or was increasing at the expense of pioneer tree species such as pine, aspen and silver birch (Beth pendulu Roth.). The most numerous species in the seedling cohort, rowan (Sorbus aucupuriu L.), was almost totally missing in the tree layer, indicating a high browsing pressure preventing rowan seedlings from growing into trees. The general increase of spruce and the sparse regeneration of pioneer species, in the stands previously affected by fire, are discussed in relation to natural disturbance regimes, biological diversity and nature conservation policies. It is proposed that reintroduction of fire disturbance is a necessity for future management plans of forest reserves. Other management practices to increase species diversity within forest reserves are also discussed. 0 1997 Elsevier Science B.V.

Some Acacia mangium Willd. plantations in Asia grow poorly due to low soil fertility and the absence of compatible mycorrhizal fungi. This legume tree can be colonized by arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi but inoculation is not routinely practiced. This study aimed to compare the effectiveness of AM fungi and four isolates of the ECM fungus Pisolithus tinctorius (Pers.) Coker and Couch (Pt) in promoting growth of A. mangium seedlings under glasshouse conditions. AM inoculants were: Glomus etunicatum, G. fasciculatum, G. macrocarpum and Gigaspora margarita and mixed species extracted from rhizosphere soil of a Populus stand in Suwon (AMKFRI), and Carex (AMM6) and Populus (AMM7) growing in mine tailings in Korea. Pisolithus isolates were from Philippines (PtPhil) and Korea (PtKFRI, PtMKACC, PtKACC). Generally, ECM fungi promoted height and diameter growth of A. mangium more than the AM inoculants. The Korean Pisolithus increased plant dry weight by 122-145%, mixed AM inoculants by 61-97%, and Glomus and Gigaspora by 45-72% over the control. PtKACC gave the highest root colonization and promoted the highest growth and concentration of most nutrients. Mycorrhizal root colonization was positively correlated with plant dry weight, Na, Fe and Cu concentrations and N, P, K, Ca, Na, Fe and Cu contents. In conclusion, the results provide strong evidence for benefits of mycorrhizal inoculation on A. mangium seedlings under glasshouse conditions. The Korean Pisolithus isolates (particularly PtKACC), and two AM fungi (AMKFRI and AMM6) are potential mycorrhizal inoculants but their effectiveness and persistence should be determined on degraded lands in tropical countries where A. mangium is being planted for rehabilitation.

The use of plants to decontaminate soils polluted by heavy metals has received considerable attention in recent years as a low-cost technique. Poplars (Populus spp.) can accumulate relatively high levels of certain metals, and have the added advantage of producing biomass that can be used for energy production. A short rotation coppice culture with 13 poplar clones was established on a former waste disposal site, which was moderately polluted with heavy metals. Total content of metals in leaves, wood and bark were determined in August and October/November. Significant clonal differences in accumulation were found for most metals, although clones with the highest concentration of all metals were not found. Cadmium, zinc and aluminium were most efficiently taken up. The lowest concentration was found in wood; the highest concentrations were generally found in senescing leaves, making removal and treatment of fallen leaves necessary.

Bu çalışmada, farklı ağaç türlerinden hazırlanan, polivinilasetat (PVAc) ve üre-formaldehit (ÜF) tutkallarıyla yapıştırılmış lamine malzemelerin (LVL), liflere dik ve paralel doğrultudaki alyan vida tutma performansları, masif ağaç malzemelerle karşılaştırmalı olarak incelenmiştir. Deney örnekleri, Türkiye Mobilya Endüstrisi'ndeki yaygın kullanımları nedeniyle Doğu kayını (Fagus orientalis L.), sarıçam (Pinus sylvestris L.) ve kavak (Populus nigra) odunlarından hazırlanmıştır. Deneylerde 5 mm çapında ve 70 mm boyunda alyan vida kullanılmıştır. 3 malzeme çeşidi, 3 ağaç türü, 2 lif doğrultusu ve her örnekten 10 adet olmak üzere toplam 180 adet örnek statik yük altında alyan vida çekme deneyine alınmıştır. Deneyler sonucunda, en yüksek alyan vida tutma mukavemeti, masif Doğu kayını malzemelerde liflere paralel yönde, en düşük ise masif kavak malzemede liflere dik yönde elde edilmiştir. Ayrıca, masif ağaç malzemeye göre teknik ve ekonomik yönlerden birçok avantajları olan lamine malzemeler, kendi ağaç türlerinin masif malzemelerine yakın performans değerleri göstermişlerdir. Buna göre, lamine malzemelerin, çerçeve (iskelet) mobilya üretiminde kullanıldığı taktirde, özellikle alyan vidalı birleştirme uygulamalarında mukavemet açısından problem çıkarmayacağı ifade edilebilir.

Native tree plots have been established in river irrigation districts in the western U.S. to provide habitat for threatened and endangered birds. Information is needed on the effective irrigation requirements of the target species. Cottonwood (Populus spp.) and willow (Salix gooddingii) trees were grown for seven years in an outdoor plot in a desert environment in Tucson, Arizona. Plants were allowed to achieve a nearly complete canopy cover over the first four years, then were subjected to three daily summer irrigation schedules of 6.20 mm d−1; 8.26 mm d−1 and 15.7 mm d−1. The lowest irrigation rate was sufficient to maintain growth and high leaf area index for cottonwoods over three years, while willows suffered considerable die-back on this rate in years six and seven. These irrigation rates were applied April 15–September 15, but only 0.88 mm d−1 was applied during the dormant period of the year. Expressed as a fraction of reference crop evapotranspiration (ETo), recommended annual water applications plus precipitation (and including some deep drainage) were 0.83 ETo for cottonwood and 1.01 ETo for willow. Current practices tend to over-irrigate restoration plots, and this study can provide guidelines for more efficient water use.

Xerocomus silwoodensis sp. nov., a new species within the European X. subtomentosus complex Host specificity ITS sequence data Molecular taxonomy a b s t r a c t A recent analysis of the Xerocomus subtomentosus complex in Europe using rDNA-ITS sequence data distinguished four taxa in Europe. Two of these corresponded to the established taxa X. subtomentosus and X. ferrugineus, and a new taxon, X. chrysonemus, was described. The fourth taxon was noted but left undescribed owing to lack of material.

This study used classification and ordination techniques to characterize the composition and distribution of woody vegetation along the Tana River floodplain near Bura in eastern Kenya. Results obtained from cluster analysis of tree and shrub vegetation corroborated the results from nonmetric multidimensional scaling (NMS), separating the forests into seven fairly well-defined assemblages of species. The primary vegetation gradient summarized by the ordination was significantly correlated (0.257-0.394, p < 0.01) with soil texture and soil carbon at depths of 50-120 cm. The secondary vegetation gradient was significantly correlated (0.480-0.483, p < 0.01) with indicators of river flood regime. Measured environmental variables, however, only partially explained observed vegetation patterns. Many overstory species were well represented in the regeneration layer of low-lying point-bar and oxbow forests, but were poorly represented in the higher elevation levee forests. There were significant correlations (0.278-0.320, p < 0.01) between the first ordination axis for the regeneration layer and flood regime of the river, and between the second ordination axis and soil texture (0.321-0.346, p < 0.01) in the top 20 cm where seedling roots are likely to be settled. Spirostachys venenifera and Acacia elatior had the widest environmental tolerance, occurring in 78% and 60% of all sample plots, respectively. Populus ilicifolia had the narrowest environmental tolerance, occurring in less than 1% of plots, all located on point-bars. #

This study used experiments at several spatial scales to determine whether (1) intraspecific competition occurs among larvae of the leafmining sawfly Profenusa thomsoni (Konow) (Hymenoptera: Tenthredinidae) on birch (Betula spp.), (2) oviposition site preferences of P. thomsoni maximize offspring performance, and (3) early-season damage by external folivores or the leafminer Fenusa pumila Leach (Hymenoptera: Tenthredinidae) affects oviposition preferences or larval performance of P. thomsoni.Larval P. thomsoni competed at natural densities; survival and weight of larvae were reduced under crowded conditions. Despite this, females of P. thomsoni tended to lay eggs on leaves already bearing eggs from other females and discriminated only weakly among leaves of different sizes on a branch. Both damage by F. pumila and artificial damage to leaves early in the season decreased survival of P. thomsoni larvae on the same branch, and ovipositing P. thomsoni females avoided damaged leaves but not other leaves on the same branch. In general, oviposition choices by P. thomsoni reduced larval survival. Possible reasons for the lack of a strong preference–performance relationship in P. thomsoni are discussed.

Groundwater and surface flow depletions are altering riparian ecosystems throughout the southwestern United States. Due in large part to hydrologic alterations and land use changes, forests of the pioneer trees Populus fremontii (Fremont cottonwood) and Salix gooddingii (Goodding willow) have declined. In many areas these forests have been replaced by shrublands and woodlands of Tamarix ramosissima (salt cedar). Previous work has focused on the physiological responses of these riparian plant species to decreases in water availability, but little attention has been given to shifts in community and population structure (size class diversity, canopy cover, basal area, vegetation volume, and stem density) in response to declines in surface flow duration and groundwater levels. This study identified hydrologic thresholds above which P. fremontii-S. gooddingii maintain tall dense stands with diverse age classes, and above which they are more abundant than T. ramosissima stands along the San Pedro River in Arizona. Populus fremontii and S. gooddingii were dominant at sites where average maximum depth to groundwater was less than 2.9 meters (m), annual groundwater fluctuation was less than 0.6 m, and surface flow was present more than 73% of the months during a two-year period of data collection. Because T. ramosissima is a shrub species with smaller leaves and lower canopy heights than P. fremontii and S. gooddingii, these shifts in species composition corresponded to decreases in maximum canopy height and upper stratum (above 8 m) vegetation volume as site water availability declined. Sites with deeper water tables and lower flow frequencies had greater areal coverage of shrublands and less woodland coverage. The altered vegetation structure along dewatered rivers may provide poorer quality wildlife habitat. This study provides river managers with quantitative hydrologic guidelines for conserving tall dense P. fremontii-S. gooddingii stands and emphasizes the importance of maintaining long-term hydrologic conditions that are favorable to these species. This project has four components with each addressing an aspect of how humanimposed drought stress, as well as subsequent rewatering of rivers, influences competitive abilities and relative abundances of native (Fremont cottonwood and Goodding willow) and exotic (salt cedar) riparian tree species.

Although the primary structure of proteins, nucleic acids, and carbohydrates can be readily determined, no sequencing method has been described yet for the second most abundant biopolymer on earth (i.e. lignin). Within secondary-thickened plant cell walls, lignin forms an aromatic mesh arising from the combinatorial radical-radical coupling of monolignols and many other less abundant monomers. This polymerization process leads to a plethora of units and linkage types that affect the physicochemical characteristics of the cell wall. Current methods to analyze the lignin structure focus only on the frequency of the major monomeric units and interunit linkage types but do not provide information on the presence of less abundant unknown units and linkage types, nor on how linkages affect the formation of neighboring linkages. Such information can only be obtained using a sequencing approach. Here, we describe, to our knowledge for the first time, a sequencing strategy for lignin oligome...

Tutti i diritti riservati. È vietata la riproduzione di testi e illustrazioni senza il permesso scritto dell'Editore Il volume è stato sottoposto a procedura di Peer-Review POPULARITAS-Pursuit of consensus and populism in ancient Rome This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement N o 792476 Gianpaolo Urso (a cura di) Popularitas. Ricerca del consenso e "populismo" in Roma antica-Roma: «L'ERMA» di BRETSCHNEIDER, 2021-312 p.-24 cm.

The feedbacks between plant and soil processes play an important role in driving forest succession. One poorly understood feedback mechanism is the interaction between plant secondary chemicals and soil microbes. In the Alaskan taiga, changes in nutrient cycling caused by balsam poplar (Populus balsamifera) secondary chemicals may affect the transition from alder (Alnus tenuifolia) to balsam poplar on river oodplains. We examined the effects of four poplar condensed tannin fractions on N cycling in alder and poplar soils. Tannins were added to forest¯oor samples from both poplar and alder sites. Samples were incubated for 1 month in the laboratory with soil respiration rates measured over the course of the incubation. At the end of the incubation we measured both net and gross nitrogen mineralization and nitri®cation, microbial biomass C and N, and the activity of various exoenzymes. In all soils, tannin additions reduced N availability, however, the mechanisms differed depending on the molecular weight of the tannin and the native soil microbial community. Low molecular weight tannin fractions served as a labile C source in poplar Oi, poplar Oe, and alder Oe horizons but were toxic to microbes in alder Oi. High molecular weight tannin fractions appeared to act primarily by binding extracellular substrates and thus limiting C and N mineralization, with the strongest effects observed in the alder soils. q

The Augustan principate has many elements of a monarchical system. However, this does not allow to question the reality of the Augustan restoration and to emphasize the ambiguity of the regime. The hypotheses such as “monarchy with republican façade” or a “republican fiction” are misleading. Indeed, the restoration of res publica hasn’t prevented institutional developments or monarchical inclinations. The whole basis of res publica was the respect of “ways of doing” and procedures, a frame considered as immutable. Augustan restoration didn’t aim to restore a prior state but to restore this frame (that of senatus populusque romanus). And this could be done with the establishment of a new political regime. Therefore, the Augustan principate cannot be considered as a cover intented to give a republican façade to a monarchical power.

Le fait que le principat augustéen ait une composante monarchique marquée appelée à s’affirmer de plus en plus avec le temps n’autorise pas à douter de la réalité de la restauration augustéenne et à dénoncer l’ambiguïté du régime. L’hypothèse d’une « monarchie à façade républicaine » ou d’une« fiction républicaine » est trompeuse dans la mesure où le rétablissement de la res publica n’interdisait ni les évolutions institutionnelles ni les velléités monarchiques. C’était dans les « manières de faire », dans le respect de certaines procédures, que résidait la res publica. La restauration augustéenne ne visa pas à rétablir dans le détail un état ante mais à restaurer un cadre (celui du senatus populusque romanus) considéré, lui, comme immuable mais qui n’interdisait pas l’établissement d’un régime nouveau. Le principat augustéen ne saurait donc être entendu comme un simple habillage destiné à donner une « façade républicaine » à un régime en réalité monarchique.

Pretreatment is commonly used to reduce recalcitrance of the lignin-carbohydrate matrix. In this study, leading pretreatment technologies, including dilute sulfuric acid, liquid hot water, alkaline, and organosolv pretreatments, were applied to the selected Populus trichocarpa genotype with relatively low lignin content to elucidate cellulose physicochemical property changes and digestibility-related factors. Pretreated Populus trichocarpa (BESC 131) exhibited higher accessibility and glucose yield than the untreated biomass. Chemical composition and Fourier transform infrared (FTIR) analysis results revealed that hemicellulose and lignin were removed to a varying extent depending on the pretreatment techniques applied. The degree of polymerization of the cellulose was decreased to the largest extent after dilute acid pretreatment, followed by organosolv, alkaline, and liquid hot water pretreatments. Cellulose crystallinity index was slightly changed after the pretreatments; however, its differences were not remarkable between those pretreatment techniques. Among four different pretreatments, organosolv was the most effective pretreatment technology in terms of sugar release, which was three times higher than that of the untreated native biomass. Among all of the tested cell wall traits, the lignin content of Populus trichocarpa was the most remarkable feature associated with glucose release, though Populus trichocarpa recalcitrance was not solely dependent on any single factor.

In 1961, Walter Ullmann studied the characteristics of Politics and Government in the Middle Ages and he theorized two different models of power and law: the Ascending and Descending Themes of Government. In the same years, Francesco Calasso encouraged a renewal of Legal History and he developed the system of ius commune. Going through the famous theory proposed by Ullmann in Principles of Government and Politics in the Middle Ages, this paper aims at analyzing the concept of power during the period of ius commune and connecting these observations with the Calasso’s lesson.

The objective of this research was to evaluate screw and nail withdrawal strength properties of veneer laminated lumber manufactured from poplar (Populus nigra) and beech (Fagus orientalis L.) in transverse, radial, and tangential directions. Ten and 13 layer laminated samples were produced in different thickness veneers of both species using two types of resins, namely polyvinylacetate (PVAc) and polyurethane (PU). Based on the results of this study it was found that layer thickness did not influence the withdrawal strength in transverse direction but strength values increased with increasing specific gravity of the samples in this direction. Overall strength properties in radial direction were found to be higher than that of tangential direction. Based on the statistical analyses resin type did not significantly effect withdrawal strength of both species.

Trees are effective in the capture of particles from urban air to the extent that they can significantly improve urban air quality. As a result of their aerodynamic properties conifers, with their smaller leaves and more complex shoot structures, have been shown to capture larger amounts of particle matter than broadleaved trees. This study focuses on the effects of particle size on the deposition velocity of particles (Vg) to five urban tree species (coniferous and broadleaved) measured at two field sites, one urban and polluted and a second more rural. The larger uptake to conifers is confirmed, and for broadleaves and conifers Vg values are shown to be greater for ultra-fine particles (Dp &amp;amp;amp;lt; 1.0 microm) than for fine and coarse particles. This is important since finer particles are more likely to be deposited deep in the alveoli of the human lung causing adverse health effects. The finer particle fraction is also shown to be transported further from the emission source; in this study a busy urban road. In further sets of data the aqueous soluble and insoluble fractions of the ultra-fines were separated, indicating that aqueous insoluble particles made up only a small proportion of the ultra-fines. Much of the ultra-fine fraction is present as aerosol. Chemical analysis of the aqueous soluble fractions of coarse, fine and ultra-fine particles showed the importance of nitrates, chloride and phosphates in all three size categories at the polluted and more rural location.

Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) · tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon (C) flow into various cell wall components, and the mechanisms important for the formation of the gelatinous cell wall layer (G-layer). A specific effort was made to identify carbohydrate-active enzymes with a putative function in cell wall biosynthesis. An increased C flux to cellulose was suggested by a higher abundance of sucrose synthase transcripts. However, genes related to the cellulose biosynthetic machinery were not generally affected, although the expression of secondary wall-specific CesA genes was modified in both directions. Other pathways for which the data suggested increased activity included lipid and glucosamine biosynthesis and the pectin degradation machinery. In addition, transcripts encoding fasciclin-like arabinogalactan proteins were particularly increased and found to lack true Arabidopsis orthologs. Major pathways for which the transcriptome and metabolome analysis suggested decreased activity were the pathway for C flux through guanosine 5¢-diphosphate (GDP) sugars to mannans, the pentose phosphate pathway, lignin biosynthesis, and biosynthesis of cell wall matrix carbohydrates. Several differentially expressed auxin-and ethylene-related genes and transcription factors were also identified.

Currently, significant academic and industrial activity is focused on sourcing feed stocks from non-food biomass crops for the sustainable production of energy, power and chemical products. Crops identified as suitable for Northern Europe include Miscanthus, switchgrass (Panicum virgatum), reed canary grass (Phalaris arundinacea) and short rotation coppice willow and poplar (Salix and Populus spp.). All of these crops provide biomass that is amenable for conversion by thermochemical processes i.e. those based on heat and pressure. There are concerns that for some processes the conversion efficiency of biomass is poor compared with coal and oil due to comparatively low energy density, high moisture content, and poor storage and handling properties. Many of these parameters can be improved by pre-processing feed stock materials prior to their conversion. We examine the energy crop species that are suitable for Northern Europe; discuss the processes of combustion, gasification and pyrolysis, and explore how differences in chemical composition influence conversion efficiency. Finally, we review biomass upgrading (pelletisation, torrefaction and treatment with sub-critical (hydrothermal upgrading) and with supercritical water).

Riparian ecosystems in the south-western United States have undergone extensive physical and biological changes, due, in part, to alteration of natural flow regimes and suppression of fluvial processes. Many riparian ecosystem restoration projects are achieving success because they recognize the importance of restoring the hydrologic regime. In other words, these projects are restoring flows of water and sediment in sufficient quantities and with appropriate temporal and spatial patterns. Other projects have proceeded without recognition of the need to incorporate environmental stream flow requirements into management plans. To increase success rate of riparian ecosystem restoration, this paper describes some changes that have occurred within riparian ecosystems of the southwestern United States, reviews the role of stream flow regimes in structuring riparian plant communities, and assesses various ways in which riparian plant communities can be restored by naturalizing ecological processes.