Willow short-rotation production systems in Canada and Northern United States: A review

Willow short rotation coppice (SRC) systems are becoming an attractive practice because they are a sustainable system fulfilling multiple ecological objectives with significant environmental benefits. A sustainable supply of bioenergy feedstock can be produced by willow on marginal land using well-adapted or tolerant cultivars. Across Canada and northern U.S.A., there are millions of hectares of available degraded land that have the potential for willow SRC biomass production, with a C sequestration potential capable of offsetting appreciable amount of anthropogenic green-house gas emissions. A fundamental question concerning 1 sustainable SRC willow yields was whether long-term soil productivity is maintained within a multi-rotation SRC system, given the rapid growth rate and associated nutrient exports offsite when harvesting the willow biomass after repeated short rotations. Based on early results from the first willow SRC rotation, it was found willow systems are relatively low nutrient-demanding, with minimal nutrient output other than in harvested biomass. The overall aim of this manuscript is to summarize the literature and present findings and data from ongoing research trials across Canada and northern U.S.A. examining willow SRC system establishment and viability. The research areas of interest presented here are the crop production of willow SRC systems, above- and below-ground biomass dynamics and the C budget, comprehensive soil-willow system nutrient budget, and soil nutrient amendments (via fertilization) in willow SRC systems. Areas of existing research gaps were also identified for the Canadian context

Metatranscriptomics Reveals the Diversity of Genes Expressed by Eukaryotes in Forest Soils

Eukaryotic organisms play essential roles in the biology and fertility of soils. For example the micro and mesofauna contribute to the fragmentation and homogenization of plant organic matter, while its hydrolysis is primarily performed by the fungi. To get a global picture of the activities carried out by soil eukaryotes we sequenced 2×10,000 cDNAs synthesized from polyadenylated mRNA directly extracted from soils sampled in beech (Fagus sylvatica) and spruce (Picea abies) forests. Taxonomic affiliation of both cDNAs and 18S rRNA sequences showed a dominance of sequences from fungi (up to 60%) and metazoans while protists represented less than 12% of the 18S rRNA sequences. Sixty percent of cDNA sequences from beech forest soil and 52% from spruce forest soil had no homologs in the GenBank/EMBL/DDJB protein database. A Gene Ontology term was attributed to 39% and 31.5% of the spruce and beech soil sequences respectively. Altogether 2076 sequences were putative homologs to different enzyme classes participating to 129 KEGG pathways among which several were implicated in the utilisation of soil nutrients such as nitrogen (ammonium, amino acids, oligopeptides), sugars, phosphates and sulfate. Specific annotation of plant cell wall degrading enzymes identified enzymes active on major polymers (cellulose, hemicelluloses, pectin, lignin) and glycoside hydrolases represented 0.5% (beech soil)–0.8% (spruce soil) of the cDNAs. Other sequences coding enzymes active on organic matter (extracellular proteases, lipases, a phytase, P450 monooxygenases) were identified, thus underlining the biotechnological potential of eukaryotic metatranscriptomes. The phylogenetic affiliation of 12 full-length carbohydrate active enzymes showed that most of them were distantly related to sequences from known fungi. For example, a putative GH45 endocellulase was closely associated to molluscan sequences, while a GH7 cellobiohydrolase was closest to crustacean sequences, thus suggesting a potentially significant contribution of non-fungal eukaryotes in the actual hydrolysis of soil organic matter

Effet des essences forestières sur la biodégradation des matières organiques : impact sur la dynamique et le cycle du carbone, de l’azote et des éléments minéraux

Diplôme : Dr. d'UniversitéCette étude visait à déterminer les indicateurs pertinents de la dynamique des matières organiques (MO) et de certaines étapes du cycle du carbone, de l'azote et des éléments minéraux en relation avec la nature des essences. Le site expérimental de Breuil-Chenue (Morvan), permettant dans des conditions identiques, de suivre l'effet des essences, a servi de support aux travaux. Les différentes approches expérimentales (in situ et au laboratoire) montrent que 30 ans après la plantation, l'expression de la forêt native (taillis sous futaie à hêtre dominant, 150 ans) a disparu au profit des jeunes peuplements. On observe des différences marquées dans la décomposition des substrats végétaux, la minéralisation du carbone et de l'azote, et la dynamique des éléments majeurs jusque dans les agrégats de sol. On distingue : les peuplements à bon potentiel de décomposition des MO comme les plantations de Douglas, et de hêtre, dont la MO résiduelle de l'horizon A1 est peu abondante et relativement récalcitrante. La nitrification y est efficace, et mobilise préférentiellement Ca, Mn et Mg. Les peuplements à faible potentiel de décomposition comme la forêt native, et surtout l'épicéa, dont la litière plus riche en lignine, Fe et Al s'accumule à la surface du sol, donnant lieu à une MO minéralisable abondante dans l'horizon A1. La nitrification y est très faible, et Fe et Al sont fortement mobilisés. Le peuplement de chêne aux feuilles pauvres en lignine et plus riches en Ca, Mg, Mn et K, occupe une position intermédiaire. Les substrats végétaux s'y décomposent rapidement. Cependant, la forte production de litière, et sa proportion élevée en bois favorisent son accumulation au sol

Effet des essences forestières sur la biodégradation des matières organiques (impact sur la dynamique et le cycle du carbone, de l'azote et des éléments minéraux)

Cette étude visait à déterminer les indicateurs pertinents de la dynamique des matières organiques (MO) et de certaines étapes du cycle du carbone, de l azote et des éléments minéraux en relation avec la nature des essences. Le site expérimental de Breuil-Chenue (Morvan), permettant dans des conditions identiques, de suivre l effet des essences, a servi de support aux travaux. Les différentes approches expérimentales (in situ et au laboratoire) montrent que 30 ans après la plantation, l expression de la forêt native (taillis sous futaie à hêtre dominant, 150 ans) a disparu au profit des jeunes peuplements. On observe des différences marquées dans la décomposition des substrats végétaux, la minéralisation du carbone et de l azote, et la dynamique des éléments majeurs jusque dans les agrégats de sol. On distingue: les peuplements à bon potentiel de décomposition des MO comme les plantations de Douglas, et de hêtre, dont la MO résiduelle de l horizon A1 est peu abondante et relativement récalcitrante. La nitrification y est efficace, et mobilise préférentiellement Ca, Mn et Mg. Les peuplements à faible potentiel de décomposition comme la forêt native, et surtout l épicéa, dont la litière plus riche en lignine, Fe et Al s accumule à la surface du sol, donnant lieu à une MO minéralisable abondante dans l horizon A1. La nitrification y est très faible, et Fe et Al sont fortement mobilisés. Le peuplement de chêne aux feuilles pauvres en lignine et plus riches en Ca, Mg, Mn et K, occupe une position intermédiaire. Les substrats végétaux s y décomposent rapidement. Cependant, la forte production de litière, et sa proportion élevée en bois favorisent son accumulation au sol.The aim of this study was to determine the relevant indicators of the dynamic of organic matter (OM) and some steps of the cycle of carbon, nitrogen and mineral nutrients in relation with the nature of tree species. The experimental site of Breuil-Chenue (Morvan), which allows on similar conditions, to follow the tree species effect, was used as work support. Field and laboratory experimental approaches show that 30 years after the plantation, the expression of the native forest (a coppice with standards dominated by beech, 150 year-old) disappeared, under the effect of young tree species. Marked differences were observed in litter decomposition, carbon and nitrogen mineralization, and dynamics of major elements, even in soil aggregate fractions. Groups of tree species stands were distinguished: the first one having a good potential of decomposition, concerns Douglas fir and beech, whose OM in the A1 horizon, was not abundant but relatively recalcitrant. Nitrate production was higher and implicated on Ca, Mn and Mg mobility. The second group was characterized by a low potential of decomposition. It includes native forest, and spruce plantation whose needles richest in lignin, Fe and Al accumulate on topsoil. Soil OM from these both stands presented a weak nitrate production, but release much more soluble organic compounds with a great potential of carbon mineralization in lab. Fe and Al were more mobilized. The oak plantation, with leaf litter low in lignin and richer in Ca, Mg, Mn and K, occupied an intermediate position. Plant materials were decomposed rapidly. However, strong production of litter and its high proportion of wood result in it accumulation on topsoil.NANCY1-SCD Sciences & Techniques (545782101) / SudocSudocFranceF

Characterization and genus identification of rhizobial symbionts from Caragana arborescens in western Canada

Naturally occurring nitrogen-fixing symbionts from root nodules of caragana (Caragana arborescens) growing in central Saskatchewan were isolated following surface sterilization of caragana root nodules and squashing and spreading of the contents on yeast extract – mannitol medium. The symbiotic nature of the strains was confirmed following inoculation onto surface-sterilized C. arborescens seed in a gnotobiotic Leonard jar system. The Rhizobium isolates from C. arborescens root nodules were intermediate in generation time (g) (mean g of 5 isolates was 6.41 h) compared with the fast growers, Rhizobium leguminosarum NRG457 (g: 4.44 h), Rhizobium tropici 899 (g: 3.19 h), and Sinorhizobium meliloti BALSAC (g: 3.45 h), but they were faster than the slow-growing Bradyrhizobium japonicum USDA 110 (g: 13.86 h) and similar to Mesorhizobium amorphae (g: 7.76 h). Nitrogen derived from fixation by measuring changes in delta15N natural abundance in plant tissue confirmed the effectiveness of the strains; approximately 80% N2 from fixation. Strain identification was carried out by determining the sequences of 3 genes: 16S rRNA-encoding genes, cpn60, and recA. This analysis determined that the symbiotic partner of Canadian C. arborescens belongs to the genus Mesorhizobium and seems more related to M. loti than to previously described caragana symbionts like M. caraganae. This is the first report of Mesorhizobium sp. nodulating C. arborescens in western Canada

Intercropping Caragana arborescens with Salix miyabeana to satisfy nitrogen demand and maximize growth

Willow shows great promise as a biomass crop and is now used worldwide. However, willow is a nutrient and water demanding plant that often requires the use of nitrogen (N) fertilizer to maximize growth on poor soils. The intercropping of Salix miyabeana with the atmospheric N2-fixing Caragana arborescens on poor soils of the Canadian Prairies could provide a portion of the N demand of the willow. The main objectives were to: (1) determine the yield potential, N nutrition and water use efficiency (WUE) of willow and Caragana grown in pure and mixed plantations across a range of soil productivity and (2) assess the extent of atmospheric N2-fixation by the Caragana within the first rotation in central Saskatchewan. We found large differences in willow yields, foliar N and WUE across the sites. The willow yields (1.24 to 15.6 t dry matter ha−1 over 4 years) were low compared to northeastern North American values and reflect the short and dry summers of the region. The yields were positively correlated to foliar N (ranging between 14.3 and 32.4 mg g−1), whereas higher WUE (expressed as δ13C) were not positively correlated to water availability but to higher yields. Caragana N2-fixation (measured using 15N isotope dilution) was not active at the most productive site but up to 60% of the foliar N was of atmospheric origin at the two other sites. Willow growth increased with Caragana proportions at the least productive site, which is typical of the benefits of N2-fixing plants on the growth of other plants on poor soils. At the most productive site, Caragana decreased the growth of willow early on due to competition for resources, but willow eventually shaded Caragana to a point of significant canopy decline and dieback. It is therefore more appropriate to intercrop the two species on less productive soils as Caragana is more likely to add N to the system via N2-fixation and is less likely to be shaded out by willow

Effect of tree species substitution on organic matter biodegradability and mineral nutrient availability in a temperate topsoil

In the Breuil-Chenue experimental site (Morvan, France), the native forest, a 150-year-old coppice with standards dominated by beech was partly clear-cut thirty years ago and replanted with several tree species. Soil samples were collected from the A1 horizon, in the 0–5 cm layer of the preserved native forest and three plantations: European beech, Douglas-fir and Norway spruce. Aliquots of 0–2 mm sieved soils were incubated for 40 days under laboratory conditions (15 ◦C, water-holding capacity). Carbon-mineralization was monitored; mineral nitrogen, water-extractable organic carbon and mineral elements were determined before and after the incubation. The release of CO2 decreased in the order: spruce > native forest > beech > Douglas-fir, whereas nitrogen net mineralization decreased in the opposite order. Douglas-fir and beech soils were characterised by high nitrification activity and high solubilization of Ca, Mg, and Mn. Native forest and spruce soils were characterized by low nitrification activity, high carbon-mineralization and high solubilization of Fe and Al.Il y a 30 ans, dans le site atelier de Breuil-Chenue (Morvan, France), la forêt native, un taillis sous futaie de 150 ans à dominante de hêtre, était partiellement coupée à blanc, puis replantée avec diverses essences. Des échantillons de sol ont été prélevés dans l’horizon A1 (0–5 cm) sous la forêt native préservée et les plantations de hêtre, Douglas et épicéa. Les fractions de sols (2 mm) ont été incubées au laboratoire (15 ◦C, capacité au champ). La minéralisation du carbone a été suivie périodiquement. L’azote minéral, le carbone et les éléments hydrosolubles ont été quantifiés avant et après incubation. La minéralisation du carbone décroît dans l’ordre : épicéa > forêt native > hêtre > Douglas, alors que celle de l’azote décroît dans l’ordre inverse. Les sols de Douglas et de hêtre se caractérisent par une forte nitrification et solubilisent plus Ca, Mg et Mn. Ceux de la forêt native et d’épicéa nitrifient peu, minéralisent fortement le carbone et solubilisent plus Fe et Al

Spatial and temporal diversity of wood decomposer communities in different forest stands, determined by ITS rDNA targeted TGGE

The aim of this study was to determine the dynamics of colonisation and composition of the wood-decomposer community in a native forest and four monocultures over time. A fingerprinting method of TGGE (temperature gradient gel electrophoresis) with rDNA amplified by ITS1F and ITS2 primer pairs was optimized and used as a culture-independent approach to determine the dominant fungal species and biodiversity over a two-year period of decomposition of beech-wood samples. The bacterial community after two years was also investigated. Data showed that each tree species, as well as sampling date, displayed the characteristic community structure. There was no strong decrease in microbial species richness or Shannon-Wiener diversity index caused by a change of tree species. Nevertheless, a strong shift in decomposer community structure was evident among the tree species both for fungi and bacteria. The effect of environmental conditions was also significant.L’objectif de cette étude était de caractériser la dynamique de colonisation d’un matériau modèle (du bois de hêtre) par les lignivores au cours de la décomposition, dans une forêt native et sous quatre essences de substitution à la forêt native feuillue. La technique d’empreinte génétique de TGGE (électrophorèse sur gel en gradient de température) ciblée sur l’ADN ribosomique, amplifié par les amorces ITS1F et ITS2, a été optimisée et utilisée pour déterminer les espèces fongiques dominantes ainsi que la diversité totale au cours des deux années d’incubation in situ des échantillons. La diversité bactérienne a également été étudiée sur les échantillons prélevés après deux années d’incubation. Les données indiquent que le peuplement et la durée d’incubation modifient la structure des communautés fongiques. Il n’y a cependant pas de forte diminution du nombre d’espèces ni de l’index de diversité de Shannon-Wiener associée au changement d’essence forestière. Toutefois, il y a une forte évolution dans la structure des communautés de décomposeurs entre les peuplements, à la fois pour les champignons et les bactéries. Les effets des paramètres environnementaux sont discutés

Influence of tree species on gross and net N transformations in forest soils

We compared N fluxes in a 150-year-old Fagus sylvatica coppice and five adjacent 25-year-old plantations of Fagus sylvatica, Picea abies, Quercus petraea, Pinus laricio and Pseudotsuga menziesii. We measured net N mineralization fluxes in the upper mineral horizon (A1, 0–5 cm) for 4 weeks and gross N mineralization fluxes for two days. Gross rates were measured during the 48-h period after addition of 15NH4 and 15NO3. Mineralization was measured by the 15NH4 dilution technique and gross nitrification by 15NO3 production from the addition of 15NH4, and by 15NO3 dilution. Net and gross N mineralization was lower in the soil of the old coppice, than in the plantations, both on a soil weight and organic nitrogen basis. Gross nitrification was also very low. Gross nitrification measured by NO3 dilution was slightly higher than measured by 15NO3 production from the addition of 15NH4. In the plantations, gross and net mineralization and nitrification from pool dilution were lowest in the spruce stand and highest in the beech and Corsican pine stands. We concluded that: (1) the low net mineralization in the soil of the old coppice was related to low gross rate of mineralization rather than to the concurrent effect of microbial immobilisation of mineral N; (2) the absence of nitrate in the old coppice was not related to the low rate of mineralization nor to the absence of nitrifyers, but most probably to the inhibition of nitrifyers in the moder humus; (3) substituting the old coppice by young stands favours nitrifyer communities; and (4) heterotrophic nitrifyers may bypass the ammonification step in these acid soils, but further research is needed to check this process and to characterize the microbial communities.Nous avons mesuré les flux de minéralisation nette d’azote au cours d’une incubation de quatre semaines et les flux bruts d’azote au cours d’une incubation de deux jours dans 6 sols prélevés dans une comparaison d’espèces forestières. Nous avons comparé les horizons A1 d’un taillis sous futaie (TSF) de Fagus sylvatica et de cinq plantations adjacentes de 25 ans de Fagus sylvatica, Picea abies, Quercus petraea, Pinus laricio et Pseudotsuga menziesii. Les taux bruts ont été mesurés 48 h après l’addition de 15NH4 et 15NO3. La minéralisation brute a été calculée à partir de la dilution de 15NH4 et la nitrification brute à partir de la dilution de 15NO3 mais aussi de la production de 15NO3 à partir de l’apport de 15NH4. La minéralisation brute et nette est la plus basse dans le TSF, exprimée par gramme de sol ou d’azote organique. La nitrification nette et brute mesurée par enrichissement en 15NO3 est très faible, mais la nitrification brute est sensiblement plus élevée lorsqu’on l’évalue par dilution isotopique du 15NO3. Dans les plantations, la minéralisation et la nitrification brute et nette sont plus faibles sous épicéa et plus élevées sous hêtre et pin Laricio. Nous en concluons que (1) la faible minéralisation d’azote dans le TSF est directement liée à une faible minéralisation brute et non à l’expression d’une immobilisation microbienne de l’azote minéral formé ; (2) l’absence de nitrate dans le TSF n’est pas liée à l’absence de nitrifiants mais plutôt à l’inhibition de leur activité sous le moder ; (3) la coupe rase du TSF et sa plantation entraîne une levée partielle ou totale de cette inhibition ; et (4) l’activité de nitrifiants hétérotrophes sans libération intermédiaire de NH4 est possible dans ces sols acides. Des études plus approfondies devraient permettre de vérifier ce point et d’identifier ces populations