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Loblolly pine (Pinus taeda L.) productivity over the past century has increased significantly from genetic improvements and more intensive management practices. The current study concludes a series of assessments of loblolly pine growth/physiological responses to continuous resource management treatments of weed control (W), weed control plus irrigation (WI), and weed control plus irrigation and fertigation (WIF). Increment cores were analyzed by X-ray densitometry to assess treatment impacts on wood properties. Plotting the wood property data against assigned years allowed results to be compared with available weather data. Mean values for all wood property determinations were similar between the W and WI treatments. Increased ring width for the WIF treatment was consistent with other studies demonstrating substantial increases in loblolly pine productivity by fertilization. Since decreases in ring specific gravity (SG) from fertilization can be offset by increases in ring SG from irrigation, gains in productivity were achieved without reducing wood quality. Key words: earlywood, fertilization, irrigation, latewood, southern pine, specific gravity Au cours du siecle dernier, la productivite du pin Loblolly (Pinus taeda L.) a augmente de maniere significative grace aux ameliorations genetiques et aux pratiques de gestion plus intensives. L'etude actuelle conclut une serie d'evaluations de la croissance et des reactions physiologiques du pin Loblolly aux traitements de gestion continue des ressources : desherbage (D), desherbage plus irrigation (DI), et desherbage plus irrigation et fertigation (DIF). Des carottes d'accroissement ont ete analysees par densitometrie aux rayons * pour evaluer l'impact des traitements sur les proprietes du bois. Le trace des donnees sur les proprietes du bois en fonction des annees attribuees a permis de comparer les resultats aux donnees meteorologiques disponibles. Les valeurs moyennes pour toutes les determinations des proprietes du bois etaient similaires entre les traitements D et DI. L'augmentation de la largeur des cernes pour le traitement DIF etait conforme a d'autres etudes demontrant une augmentation substantielle de la productivite des pins Loblolly par la fertilisation. Etant donne que les diminutions de la largeur des cernes en fonction de la gravite specifique (GS) dues a la fertilisation peuvent etre compensees par les augmentations de la largeur des cernes en fonction de la gravite specifique dues a l'irrigation, les gains de productivite ont ete obtenus sans reduire la qualite du bois. [Traduit par la Redaction] Mots-cles: bois precoce, fertilisation, irrigation, bois tardif, pin du sud, gravite specifique, 1. Introduction The productivity of southern pine plantations throughout the southeastern United States has increased 4-fold within the past century through genetic tree improvement initiatives along with intensive management treatments [...]

High productivity of fertilized loblolly pine (Pinus taeda L.) plantations in the southern United States is related to increased leaf area index (LAI), but higher evaporative leaf surface area may increase drought vulnerability. To determine if the benefits of fertilization are affected by water availability or the effects of drought are exacerbated by fertilization, the interactive effects of throughfall treatment (ambient throughfall versus throughfall reduction) and fertilization treatment (no fertilization versus one-time fertilization) on a loblolly pine plantation were examined over five growing seasons. Enhancement of LAI and growth from fertilization was unaffected by throughfall treatment, and reductions in LAI, tree height, and stand volume increment in response to throughfall reduction were unaffected by fertilization treatment. Leaf-level stomatal conductance ([g.sub.S]) was decreased and water use efficiency was increased by fertilization and by throughfall reduction. Lower [g.sub.S] was associated with decreased leaf predawn water potential in response to throughfall reduction. In contrast, lower gs in response to fertilization was associated with a reduction in the hydraulic allometry index, a measure of the ability of sapwood to supply water to leaves. These results suggest that fertilization may enhance LAI and growth even under mild or moderate drought. Key words: loblolly pine, leaf area index, leaf water potential, hydraulic traits, drought. La productivite elevee des plantations de pin a encens (Pinus taeda L.) dans le sud des Etats-Unis est reliee a l'augmentation de l'indice de surface foliaire (LAI), mais une plus grande surface foliaire augmente l'evaporation et peut accentuer la vulnerabilite a la secheresse. Dans le but de determiner si les benefices de la fertilisation dependent de la disponibilite en eau ou si les effets de la secheresse sont exacerbes par la fertilisation, les effets interactifs de traitements impliquant la precipitation au sol (ambiante ou reduite) et la fertilisation (aucune ou une application) dans une plantation de pin a encens ont ete etudies pendant cinq saisons de croissance. L'amelioration de LAI et de la croissance due a la fertilisation n'etait pas influencee par les changements dans la precipitation au sol. La fertilisation n'a pas eu d'effet sur la reduction de LAI, de la hauteur des arbres et de l'accroissement en volume du peuplement en reaction a la reduction de la precipitation au sol. La conductance stomatique a l'echelle des feuilles ([g.sub.S]) a ete reduite et l'efficacite de l'utilisation de l'eau a ete augmentee par la fertilisation et la reduction de la precipitation au sol. La valeur plus faible de [g.sub.S] etait associee a la diminution du potentiel hydrique de base foliaire en reaction a la reduction de la precipitation au sol. Au contraire, la valeur plus faible de [g.sub.S] en reaction a la fertilisation etait associee a la reduction de l'indice d'allometrie hydraulique, une mesure de la capacite du bois d'aubier a approvisionner les feuilles en eau. Ces resultats indiquent que la fertilisation peut ameliorer LAI et la croissance meme en presence d'une secheresse legere ou moderee. [Traduit par la Redaction] Mots-cles : pin a encens, indice de surface foliaire, potentiel hydrique foliaire, caracteristiques hydrauliques, secheresse., Introduction Along with increasing temperature, greater annual and seasonal variability in precipitation, more intense rain events, and longer interstorm periods are predicted for eastern North America (Swain and Hayhoe 2015; [...]

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 [...]

: 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 [...]

Abstract: Leaf physiology and stem growth were assessed in loblolly pine (Pinus taeda L.) in response to 10 to 11 years of treatment with weed control (W), weed control plus [...]