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Red spruce (RS; Picea rubens Sarg.)-black spruce (BS; Picea mariana (Mill.) B.S.P.) controlled crosses (100%, 75%, 50%, 25%, and 0% RS, balance BS) showed increasingly greater height with increasing proportion of BS in each successive year. Height growth of 4-year-old ambient C[O.sub.2] (aC[O.sub.2]) grown trees was highly correlated with height of 22-year-old field-grown trees of the same or similar crosses. Bud flush was earliest in BS and declined linearly with increasing proportion of RS with no significant C[O.sub.2] effect. Percent stem (stem + branches) mass increased under elevated C[O.sub.2] (eC[O.sub.2]), a quarter of which was due to ontogeny. Conversely, percent needle mass had a significant negative relationship with increasing tree size, and there was a C[O.sub.2] x tree size interaction. Shoot-to-root ratio was greatest for BS, whereas RS had among the lowest. Hybrid index (HI) 50 had the greatest root mass allocation, lowest shoot-to-root ratio, and among the greatest total mass under eC[O.sub.2]. Growth efficiency increased with tree size and eC[O.sub.2] but decreased with HI. Percent total biomass stimulation under eC[O.sub.2] was lowest for BS at 6.5%, greatest for HI 50 at 20.3%, and RS had 17.5%. Key words: allocation, black spruce, elevated C[O.sub.2], growth, fitness, interspecific hybridization, red spruce. Des croisements diriges entre l'epinette rouge (ER; Picea rubens Sarg.) et l'epinette noire (EN; Picea mariana (Mill.) B.S.P.) (composes a 100, 75,50, 25 et0% de ER et le reste de EN) ont produit des individus dont la hauteur augmentait avec la proportion grandissante de EN pour chaque annee consecutive. La croissance en hauteur a 4 ans des arbres sous des conditions de C[O.sub.2] ambiant (aC[O.sub.2]) etait fortement correlee a la hauteur a 22 ans d'arbres ayant pousse au champ et provenant des memes croisements ou de croisements similaires. Le debourrement des bourgeons etait le plus hatif chez EN et declinait lineairement avec une proportion grandissante de ER, sans effet significatif du C[O.sub.2]. La masse de la tige (tige + branches) en pourcentage augmentait sous des conditions d'enrichissement en C[O.sub.2] (eC[O.sub.2]) et le quart de cette augmentation etait du a l'ontogenie. A l'inverse, il y avait une relation negative significative entre la masse des aiguilles en pourcentage et l'augmentation de la taille des arbres, ainsi qu'une interaction entre le C[O.sub.2] et la taille des arbres. Le rapport entre la tige et les racines de EN etait le plus eleve, alors que celui de ER etait parmi les plus faibles. Les individus avec l'indice d'hybridation (IH) 50 allouaient le plus de masse aux racines, avaient le rapport le plus faible entre la tige et les racines et parmi la plus grande masse totale sous des conditions d'eC[O.sub.2]. L'efficacite de croissance augmentait avec la taille des arbres et l'eC[O.sub.2], mais elle diminuait avec l'IH. Le pourcentage de la biomasse totale attribuable a la stimulation par l'eC[O.sub.2] etait le plus faible chez EN avec 6,5 %, le plus eleve chez les individus d'IH 50 avec 20,3 % et atteignait 17,5 % chez ER. [Traduit par la Redaction] Mots-cles : allocation, epinette noire, enrichissement en C[O.sub.2], croissance, aptitude, hybridation interspecifique, epinette rouge., Introduction Red spruce (RS; Picea rubens (Sarg.)) is an important and characteristic component of the late-successional forest of the Acadian Forest Region in eastern Canada and the northeastern United States. [...]

Longleaf pine (Pinus palustris Mill.) restoration in the south eastern United States offers opportunities for carbon (C) sequestration. Ecosystem C stocks are not well understood in longleaf pine forests, which are typically of low density and maintained by prescribed fire. The objectives of this research were to develop allometric equations for above- and below-ground biomass and quantify ecosystem C stocks in five longleaf pine forests ranging in age from 5 to 87 years and in basal area from 0.4 to 22.6 [m.sup.2] x [ha.sup.-1]. Live aboveground C (woody plant + ground cover) and live root C (longleaf pine below stump + plot level coarse roots + plot level fine roots) ranged from 1.4 and 2.9 Mg C x [ha.sup.-1], respectively, in the 5-year-old stand to 78.4 and 19.2 Mg C x [ha.sup.-1], respectively, in the 87-year-old stand. Total ecosystem C (live plant + dead organic matter + mineral soil) values were 71.6, 110.1, 124.6,141.4, and 185.4 Mg C x [ha.sup.-1] in the 5-, 12-, 21-, 64-, and 87-year-old stands, respectively, and dominated by tree C and soil C. In the 5- year-old stand, ground cover C and residual taproot C were significant C stocks. This unique, in-depth assessment of above and below-ground C across a series of longleaf pine stands will improve estimates of C in longleaf pine ecosystems and contribute to development of general biomass models that account for variation in climate, site, and management history in an important but understudied ecosystem. Key words: longleaf pine, carbon sequestration, allometry, roots, ground- penetrating radar. La restauration du pin des marais (Pinus palustris Mill.) dans le sud-est des Etats-Unis off re une opportunity de stocker du carbone (C). Les stocks de C de l'ecosysteme ne sont pas bien connus dans les forets de pin des marais qui ont typiquementune faible densite et se maintiennent grace au brulage dirigee. Les objectifs de ces travaux de recherche consistaient a elaborer des equations allometriques pour la biomasse aerienne et souterraine et a quantifier les stocks de C de l'ecosysteme dans cinq forets de pin des marais dont l'age allait de 5 a 87 ans et dont la surface terriere variait de 0,4 a 22,6 [m.sup.2] x [ha.sup.-1]. Le C aerien vert (plantes ligneuses + couverture vegetale) et le C des racines vivantes (souches de pin des marais + grosses racines et racines fines presentes dans les placettes) variaient respectivement de 1,4 et 2,9 Mg C x [ha.sup.-1]dans le peuplement age de 5 ans a 78,4 et 19,2 Mg C x [ha.sup.-1] dans le peuplement age de 87 ans. Le C total de l'ecosysteme (plantes vivantes + matiere organique morte + sol mineral) atteignait respectivement 71,6,110,1,124,6,141,4 et 185,4 Mg C x [ha.sup.-1] dans les peuplements ages de 5,12, 21, 64 et 87 ans et etait domine par le C des arbres et du sol. Dans le peuplement age de 5 ans, le C contenu dans la couverture vegetale et les racines pivotantes residuelles constituait un stock important de C. Cette evaluation unique et approfondie du C aerien et souterrain dans une serie de peuplements de pin des marais ameliorera les estimations du C dans les ecosystemes domines par cette essence et contribuera au developpement de modeles generaux de biomasse qui tiennent compte de la variation dans le climat, la station et l'historique d'amenagement dans un ecosysteme important mais peu etudie. [Traduit par la Redaction] Mots-cles: pin des marais, sequestration du carbone, allometrie, racines, georadar., Introduction Forests serve as a means for mitigating climate change by acting as sinks for atmospheric C[O.sub.2] and storing carbon (C) in plant biomass, detritus, and forest soils. In the [...]

Total belowground biomass, soil C, and N mass were measured in plots of 32-year-old black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) from four full-sib families studied previously for drought tolerance and differential productivity on a dry and a wet site. Stump root biomass was greater on the wet than on the dry site; however, combined fine and coarse root biomass was greater on the dry than on the wet site, resulting in no site root biomass differences. There were no site differences in root distribution by soil depth. Drought-tolerant families had greater stump root biomass and allocated relatively less to combined coarse and fine roots than drought-intolerant families. Fine roots ( Resume: La biomasse souterraine totale ainsi que la masse de C et de N dans le sol ont ete mesurees dans des places echantillons ou croissaient des epinettes noires (Picea mariana (Mill.) Britton, Sterns & Poggenb.) agees de 32 ans. Quatre descendances biparentales etudiees precedemment pour leur tolerance a la secheresse et leurs differences de productivite selon qu'elles croissaient dans une station seche ou humide etaient representees. La biomasse des racines de souche etait plus importante dans la station humide que dans la station seche. Cependant, la biomasse combinee des racines fines et des grosses racines etait plus grande dans la station seche que dans la station humide, de telle sorte qu'il n'y avait pas de difference entre les stations dans la biomasse des racines. Il n'y avait pas de difference entre les stations dans la distribution des racines en fonction de la profondeur dans le sol. La biomasse des racines de souche etaient plus importante chez les descendances tolerantes a la secheresse qui allouaient relativement moins de ressources aux racines fines et aux grosses racines combinees que les descendances intolerantes. Les racines fines ( [Traduit par la Redaction], Introduction Efforts to reduce atmospheric [CO.SUB.2] are being explored both by reducing emissions and by sequestering more C. Forests are important C sinks because they sequester C both in situ [...]

Fine and coarse root biomass, C, and N mass parameters were assessed by root size and soil depths from soil cores in plots of 32-year-old black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) from four full-sib families studied previously for drought tolerance and differential productivity on a dry and wet site. All fine and coarse root size categories had greater root biomass on the dry than on the wet site. Most of the site differences resided in 0 -20 cm soil depth. The wet site had greater root N concentration than the dry site, despite the same soil N; thus, virtually no differences were observed in total fine and coarse root N mass between sites. Root N concentration declined with increases in both soil depth and root size. Fine roots ( Resume: La biomasse des racines fines et celle des grosses racines, ainsi que les parametres de masse du C et du N, ont ete evalues en fonction de la dimension des racines et de la profondeur dans le sol a partir de carottes de sol prelevees dans des places echantillons ou croissent des epinettes noires (Picea mariana (Mill.) Britton, Sterns & Poggenb.). Les arbres etaient ages de 32 ans et representaient quatre descendances biparentales etudiees precedemment pour leur tolerance a la secheresse et leurs differences de productivite selon qu'ils croissaient dans une station seche ou humide. La plupart des differences entre les stations ont ete observees dans les premiers 20 cm de sol. La concentration de N dans les racines etait plus elevee dans la station humide meme si la concentration de N dans le sol etait la meme dans les deux stations. Par consequent, pratiquement aucune difference entre les stations n'a ete observee dans la masse totale de N de l'ensemble des racines. La concentration de N dans les racines diminuait avec l'augmentation de la profondeur dans le sol et la dimension des racines. Les racines fines representaient respectivement 73% et 38% de la masse totale de N et C dans l'ensemble des racines. La masse d'aiguilles etait plus faible et la masse de racines fines plus elevee dans la station seche que dans la station humide, ce qui implique une adaptation au changement de stress hydrique via le reequilibrage des organes qui consomment des ressources. Les descendances tolerantes a la secheresse avaient la meme quantite de racines fines que les descendances intolerantes mais elles pouvaient supporter plus de feuillage et de masse aerienne par unite de masse de racines fines que les descendances intolerantes. [Traduit par la Redaction], Introduction Water availability is a predominant factor in determining the geographic distribution of vegetation, and water stress has long been known to decrease plant growth and gas exchange and change [...]

: Growth, allocation to woody root biomass, wood properties, leaf physiology, and shoot morphology were examined in a 47-year-old loblolly pine (Pinus taeda L.) density trial located in Maui, Hawaii, to determine if stands continued to carry the high density, basal area, and volume reported at younger ages and to identify potential factors controlling expression of maximum growth potential. Basal area and volume were similar among spacings (square: 1.8, 2.4, 3.0, and 3.7 m) and averaged 93 [m.sup.2]*[ha.sup.-1] and 1076 [m.sup.3]*[ha.sup.-1], respectively, and were double the maxima reported for loblolly pine in its native range. Spacing had a significant influence on density, quadratic mean diameter, and height. Ring-specific gravity and percent latewood were similar among spacing treatments but values were high compared to mainland stands. Leaf light-saturated net photosynthesis, dark respiration, stomatal conductance, and quantum yield were comparable with values reported for loblolly pine in its native range. Foliar calcium concentrations, specific leaf area, and flush number were high in the Hawaii study. Higher carrying capacity in Hawaii may be related to a more favorable climate conducive to yearround leaf carbon gain, high nutrient availability, increased flushing, and less allocation to belowground mass. Resume: Nous avons etudie la croissance, l'allocation des ressources a la biomasse racinaire ligneuse, les proprietes du bois, la physiologie foliaire et la morphologie des pousses dans un peuplement de pin a encens (Pinus taeda L.) age de 47 ans situe a Maui, a Hawaii, et qui faisait partie d'une experience de densite variable. Le but de l'etude etait de determiner si les peuplements continuaient de soutenir les valeurs elevees de densite, de surface terriere et de volume observees en jeune age et d'identifier les facteurs qui pourraient etre associes a l'expression de la croissance potentielle maximale. La surface terriere et le volume n'ont pas varie selon l'espacement (espacements carres de 1,8, 2,4, 3,0 et 3,7 m) et ont respectivement atteint 93 [m.sup.2]*[ha.sup.-1] et 1076 [m.sup.3]*[ha.sup.-1], en moyenne, ce qui correspond au double des valeurs maximales observees dans l'habitat naturel du pin a encens. L'espacement a eu un effet significatif sur la densite, le diametre moyen quadratique et la hauteur des arbres. La densite du bois et le pourcentage de bois final etaient semblables parmi les traitements d'espacement, mais leurs valeurs etaient elevees comparativement aux peuplements continentaux. La photosynthese foliaire nette sous une lumiere saturante, la respiration a l'obscurite, la conductance stomatique et le rendement quantique avaient des valeurs semblables a celles qui ont ete rapportees pour le pin a encens dans son habitat naturel. La concentration foliaire en calcium, la surface foliaire specifique et le nombre de pousses etaient eleves dans l'etude hawaiienne. La plus forte capacite de support du milieu a Hawaii peut etre reliee a un climat plus favorable qui est propice a un gain foliaire en carbone a longueur d'annee, a une disponibilite elevee en nutriments, a une augmentation du nombre de pousses et a une plus faible allocation des ressources a la biomasse souterraine. [Traduit par la Redaction, Introduction Production rates of loblolly pine (Pinus taeda L.) in Hawaii, Brazil, Argentina, and South Africa indicate that full biological expression of growth potential in loblolly pine has not yet [...]

Carbon is an essential component of life and, in its organic form, plays a pivotal role in the soil's fertility, productivity, and water retention. It is an integral part of the atmospheric-terrestrial C exchange cycle mediated via photosynthesis; furthermore, it emerged recently as a new trading commodity, i.e., 'carbon credits.' When carefully manipulated, C sequestration by the soil could balance and mitigate anthropogenic C[O.sub.2] emissions into the atmosphere that are believed to contribute to global warming. The pressing need for assessing the soil's C stocks at local, regional, and global scales, now in the forefront of much research, is considerably hindered by the problems besetting dry-combustion chemical analyses, even with state-of-the-art procedures. To overcome these issues, we developed a new method based on gamma-ray spectroscopy induced by inelastic neutron scattering (INS). The INS method is an in situ, nondestructive, multielemental technique that can be used in stationary or continuous-scanning modes of operation. The results from data acquired from an investigated soil mass of a few hundred kilograms to an approximate depth of 30 cm are reported immediately. Our initial experiments have demonstrated the feasibility of our proposed approach; we obtained a linear response with C concentration and a detection limit between 0.5 and 1% C by weight. Abbreviations: INS, inelastic neutron scattering; LIBS, laser-induced breakdown spectroscopy; MDL, minimum detectable limit; NG, neutron generator; TNC, thermal neutron capture.

Author(s): Ram Oren (corresponding author) [1]; David S. Ellsworth [2, 3]; Kurt H. Johnsen [4]; Nathan Phillips [5]; Brent E. Ewers [1]; Chris Maier [4]; Karina V.R. Schäfer [1]; Heather [...]

Elevated atmospheric CO2 (eCO2) typically increases aboveground growth in both growth chamber and free‐air carbon enrichment (FACE) studies. Here we report on the impacts of eCO2 and nitrogen amendment on coarse root biomass and net primary productivity (NPP) at the Duke FACE study, where half of the eight plots in a 30‐year‐old loblolly pine (Pinus taeda, L.) plantation, including competing naturally regenerated broadleaved species, were subjected to eCO2 (ambient, aCO2 plus 200 ppm) for 15–17 years, combined with annual nitrogen amendments (11.2 g N m−2) for 6 years. Allometric equations were developed following harvest to estimate coarse root (>2 mm diameter) biomass. Pine root biomass under eCO2 increased 32%, 1.80 kg m−2 above the 5.66 kg m−2 observed in aCO2, largely accumulating in the top 30 cm of soil. In contrast, eCO2 increased broadleaved root biomass more than twofold (aCO2: 0.81, eCO2: 2.07 kg m−2), primarily accumulating in the 30–60 cm soil depth. Combined, pine and broadleaved root biomass increased 3.08 kg m−2 over aCO2 of 6.46 kg m−2, a 48% increase. Elevated CO2 did not increase pine root:shoot ratio (average 0.24) but increased the ratio from 0.57 to 1.12 in broadleaved species. Averaged over the study (1997–2010), eCO2 increased pine, broadleaved and total coarse root NPP by 49%, 373% and 86% respectively. Nitrogen amendment had smaller effects on any component, singly or interacting with eCO2. A sustained increase in root NPP under eCO2 over the study period indicates that soil nutrients were sufficient to maintain root growth response to eCO2. These responses must be considered in computing coarse root carbon sequestration of the extensive southern pine and similar forests, and in modelling the responses of coarse root biomass of pine–broadleaved forests to CO2 concentration over a range of soil N availability. [ABSTRACT FROM AUTHOR]

Inadequate cold tolerance of Eucalyptus spp. has limited a broader deployment beyond subtropical regions of the United States. We examined growth, photosynthetic rate, and cold tolerance of a cold-hardy Eucalypt (Eucalyptus benthamii) planted in North Carolina and compared the results with native Pinus taeda. After two growing seasons, E. benthamii surpassed P. taeda in both height (5.06 m, 1.34 m) and diameter (5.0 cm, 0.7 cm) growth, respectively. From April through November, E. benthamii's mean photosynthetic rate (Ps) (13.82 µmol CO2 m-2s-1) was more than twice that of P. taeda (6.21 µmol CO2 m-2s-1). Similarly, mean Ps during winter months was 6.09 µmol CO2 m-2s-1 for E. benthamii compared to 2.73 µmol CO2 m-2s-1 for P. taeda. Laboratory assessments of cold tolerance demonstrated that, unlike P. taeda, E. benthamii had a limited ability to acclimate to seasonal temperature changes. The coldest temperature (Tm) where >50% of the tissue was damaged and recovery unlikely for E. benthamii was -13.4°C for leaves and -14.3°C for stems, whereas for P. taeda it was -29.9°C for leaves and -36.5°C for stems. The exceptional productivity of E. benthamii was not without trade-offs as all trees died after experiencing air temperatures of -12.8°C on January 7, 2014. [ABSTRACT FROM AUTHOR]