Search

We investigated radial growth of post oak (Quercus stellata Wangenh.) growing in a range of stand structures (forest to savanna) created in 1984 by different harvesting, thinning, and prescribed fire intervals. We related ring width index (RWI) to monthly and seasonal climate variables and time since fire to assess impacts of climate variability and interactions with management on radial growth. The RWI of all treatments was positively correlated to minimum daily temperature the previous September and precipitation late spring and early summer the current year, and negatively correlated to maximum daily temperatures and drought index late spring--early summer. June weather was most strongly correlated in four of five treatments. While stand structure affected absolute diameter growth, the RWI of savanna and forest stands responded similarly to climate variability, and low intensity prescribed fire did not influence RWI. On average, a 100 mm reduction in June precipitation decreased RWI by 7%, a 1 [degrees]C increase in previous-year September daily minimum temperature increased RWI by 3.5%, and a 1 [degrees]C increase in June maximum daily temperature decreased RWI by 3.7%. Therefore, negative effects of drought and warmer spring and summer temperatures may be reduced by a longer growing season under warmer climate scenarios. However, management did not appear to influence RWI. Key words: dendrochronology, climate, drought, radial growth, fire frequency. Nous avons etudie la croissance radiale du chene etoile (Quercus stellata Wangenh.) croissant dans une variete de structures de peuplement (forets a savanes) creees en 1984 apres avoir applique differents traitements d'eclaircie et de recolte suivis de differents intervalles entre des brulages diriges. Nous avons relie l'indice de largeur des cernes (ILC) aux variables climatiques mensuelles et saisonnieres ainsi qu'au temps ecoule depuis le feu pour evaluer les impacts de la variation du climat et des interactions avec l'amenagement sur la croissance radiale. Dans tous les traitements l'ILC etait positivement correle a la temperature minimale quotidienne au mois de septembre de l'annee precedente ainsi qu'a la precipitation a la fin du printemps et au debut de l'ete de l'annee en cours, et negativement correle a la temperature maximale quotidienne et a l'indice de secheresse a la fin du printemps et au debut de l'ete. Les variables meteorologiques du mois de juin etaient le plus etroitement correlees dans quatre des cinq traitements. Tandis que la structure du peuplement influenqait la croissance absolue en diametre, l'ILC des peuplements de forets et de savanes reagissait de faqon similaire a la variation du climat et le brulage dirige de faible intensite n'influenqait pas l'ILC. En moyenne, une diminution de la precipitation de 100 mm en juin a provoque une reduction de l'ILC de 8 %; une augmentation de la temperature minimale quotidienne de 1 [degrees]C en septembre de l'annee precedente a entraine une augmentation de l'ILC de 3,5 %; et une augmentation de la temperature maximale quotidienne de 1 [degrees]C en juin a cause une reduction de l'ILC de 3,7 %. Par consequent, les effets negatifs de la secheresse et des temperatures plus chaudes au printemps et a l'ete pourraient etre attenues par des saisons de croissance plus longues sous des scenarios climatiques plus chauds. Cependant, l'amenagement n'a pas semble influencer l'ILC. [Traduit par la Redaction] Mots-cles: dendrochronologie, secheresse, largeur des cernes annuels, bois annuel, frequence des feux., Introduction Radial growth is an indicator of past climate variability that can be used to predict future climate change impacts on tree growth and ecosystem dynamics (Cullen et al. 2001; [...]

Hybrid sweetgum (Liquidambar styraciflua  ×  L. formosana) has received considerable attention as a potential feedstock for traditional and nontraditional forest-based enterprises due to its fast growth and large specific gravity. However, the perceptions of landowners are important to understand the degree of acceptance concerning land use change to consider this opportunity in the United States. We administered a survey instrument to three thousand landowners representing the states of Texas, Oklahoma, Louisiana, and Arkansas where hybrid sweetgum plantations would be feasible. A seemingly unrelated regression analysis was used to explore the attributes that may influence the environmental and economic obstacles in land use change for hybrid sweetgum plantations. Study results suggest that landowners who perceived higher importance of marketing aspects of hybrid sweetgum expressed greater economic concerns for land use change. In contrast, those having higher planted pine acres had higher environmental concerns about land use change. Female landowners were more concerned than their male counterparts. Landowners need access to accurate information from their trusted sources to make informed management decisions, especially when making decisions to adopt new opportunities such as hybrid sweetgum. Study Implications: Study results reveal the need for outreach to landowners in the south central United States, as many were not aware of fast-growing hardwood species such as hybrid sweetgum. Information on growth potential, economics, and management techniques can help facilitate the adoption of hybrid sweetgum. Field visits and peer-to-peer learning facilitated by early adopters can be effective strategies for outreach. [ABSTRACT FROM AUTHOR]

Hybridization between shortleaf pine (Pinus echinata Mill.) and loblolly pine (Pinus taeda L.) has dramatically increased and may threaten the genetic integrity of shortleaf pine. Shortleaf pine is presumed to be more drought tolerant than loblolly pine, but the drought hardiness of the hybrid pine is not known. We determined biomass partitioning in response to water stress and measured whole-plant transpiration of shortleaf, loblolly, and hybrid pine seedlings. Water stress decreased total seedling biomass, increased biomass partitioning to foliage, and decreased biomass partitioning to coarse roots. Shortleaf pine seedlings partitioned more biomass to coarse roots than loblolly pine, and hybrid pine was intermediate between the parent species. We found no differences in the level of soil moisture at which seedlings of different species began to limit transpiration. Our results suggest that the transpiration response of shortleaf pine and hybrid pine is similar to that of loblolly pine when exposed to water stress. However, greater partitioning to coarse root may allow shortleaf and hybrid pines to better withstand drought due to greater potential belowground carbohydrate supply. Key words: Pinus echinata, Pinus taeda, biomass partitioning, drought, transpiration. L'hybridation entre le pin a courtes feuilles (Pinus echinata Mill.) et le pin a encens (Pinus taeda L.) a augmente de facon dramatique et pourrait menacer l'integrite genetique du pin a courtes feuilles. On presume que le pin a courtes feuilles est plus tolerant a la secheresse que le pin a encens mais on ne connait pas la resistance a la secheresse du pin hybride. Nous avons determine la repartition de la biomasse en reaction a un stress hydrique et mesure la transpiration de semis entiers de pins a courtes feuilles, a encens et hybrides. Le stress hydrique a reduit la biomasse totale des semis et modifie la repartition de la biomasse en favorisant le feuillage au detriment des grosses racines. Les semis de pin a courtes feuilles ont alloue plus de biomasse aux grosses racines que le pin a encens alors que ceux du pin hybride etaient a mi-chemin entre les especes parentes. Nous n'avons observe aucune difference dans le niveau d'humidite du sol auquel les semis des differentes especes commencaient a limiter leur transpiration. Nos resultats indiquent que la reaction de la transpiration des pins a courtes feuilles et hybrides est semblable a celle du pin a encens lorsqu'ils sont exposes aun stress hydrique. Cependant, une plus grande allocation de biomasse vers les grosses racines peut permettre aux pins a courtes feuilles et hybrides de mieux tolerer la secheresse a cause de la plus grande reserve potentielle souterraine d'hydrate de carbone. [Traduit par la Redaction] Mots-cles: Pinus echinata, Pinus taeda, repartition de la biomasse, secheresse, transpiration., Introduction Compared with loblolly pine (Pinus taeda L.), shortleaf pine (Pinus echinata Mill.) is more cold tolerant (Lawson 1990), ice tolerant (Boggess and McMillan 1954), fire tolerant (Stewart et al. [...]

Over half of the standing pine timber volume in the southeastern USA is composed of loblolly pine (Pinus taeda L.), making it the most important tree species in the region. Future climate variability may impact productivity of these forests due to reduced water availability. To determine the effects of nutrient availability and decreased water availability on stand-level water use efficiency and growth efficiency, we examined the interactive effects of fertilization and reduced throughfall on whole-tree water use, stand-level canopy transpiration, leaf area index (LAI), and stand-level stem volume growth. This study was conducted over the 6th and 7th growing seasons (2013-2014) of a loblolly pine plantation in southeastern Oklahoma. Across all plots, throughfall reduction reduced volumetric soil water content (VWC) from 13.6% to 10.9% for soil depths of 0-12 cm and from 22.3% to 19.9% for soil depths of 12-45 cm and reduced stand volume growth from 20.9 to 17.9 [m.sup.3] x [ha.sup.-1]. Across all plots, fertilization increased LAI by 12%, increased stand volume growth from 18.3 to 20.5 [m.sup.3] x [ha.sup.-1], and increased water use efficiency of stem volume production by 18%. These results indicate that fertilization can benefit stand growth of loblolly pine plantations even when soil moisture is limiting, in part, by increasing the efficiency of water use. Key words: water use efficiency, growth efficiency, throughfall reduction, fertilization, Pinus taeda. Plus de la moitie du volume en bois de pin sur pied dans le sud-est des Etats-Unis est constitue de pin a encens (Pinus teada L.), ce qui en fait la plus importante espece d'arbre dans la region. La variabilite du climat futur peut avoir un impact sur la productivite de ces forets a cause de la diminution de la disponibilite en eau. Afin de determiner les effets de la disponibilite des nutriments et de la diminution de la disponibilite en eau sur l'efficacite de l'utilisation de l'eau et l'efficacite de la croissance a l'echelle du peuplement, nous avons etudie les effets interactifs de la fertilisation et de la reduction de la pluie au sol sur l'utilisation de l'eau a l'echelle de l'arbre, la transpiration du couvert forestier a l'echelle du peuplement, l'indice de surface foliaire (LAI) et la croissance en volume de la tige a l'echelle du peuplement. L'etude a ete realisee au cours des 6e et 7e saisons de croissance (2013-2014) d'une plantation de pin a encens dans le sud-est de l'Oklahoma. Dans l'ensemble des places echantillons, la diminution de la pluie au sol a reduit la teneur volumetrique en eau du sol de 13,6 a 10,9 % et de 22,3 a 19,9 % a des profondeurs de respectivement 0-12 cm et 12-45 cm et reduit la croissance en volume du peuplement de 20,9 a 17,9 [m.sup.3] x [ha.sup.-1]. Dans l'ensemble des places echantillons, la fertilisation a augmente la valeur de LAI de 12 %, la croissance en volume du peuplement de 18,3 a 20,5 [m.sup.3] x [ha.sup.-1] et l'efficacite de l'utilisation de l'eau pour la production du volume de la tige de 18 %. Ces resultats indiquent que la fertilisation peut etre benefique pour la croissance des peuplements de pin a encens malgre un deficit d'humidite du sol en partie a cause de l'augmentation de l'efficacite de l'utilisation de l'eau. [Traduit par la Redaction] Mots-cles: efficacite de l'utilisation de l'eau, efficacite de la croissance, reduction de la pluie au sol, fertilisation, Pinus teada., Introduction The Southeast is the wood basket of the USA (Schultz 1997), producing more timber volume than any other region in the country (Oswalt et al. 2014). Over half of [...]

Fire suppression and other anthropogenic activities have the potential to eliminate ecological barriers that previously kept related, sympatric species from interbreeding. We compared artificial F1 shortleaf pine (Pinus echinata Mill.) x loblolly pine (Pinus taeda L.) hybrids with their parents to determine potential traits that have allowed hybrid seedlings to dramatically increase in abundance since 1950s. Six open-pollinated families each of loblolly and shortleaf pine as well as 12 controlled crosses were compared over 2 years in Oklahoma, USA. Loblolly and hybrid seedlings had higher establishment and growth rates than shortleaf pine. The hybrid seedlings had similar numbers of sprouts following top-clipping as shortleaf, which were higher than those of loblolly pine. Formation of a strong basal crook, an adaptation to protect dormant buds from fire, was greatest in shortleaf and lower in hybrid and loblolly pine. Instantaneous water use efficiency indicated that hybrid pine had similar high water use efficiency as shortleaf pine compared with loblolly pine. In the absence of fire, the hybrid seedlings perform at least as well as the parent species, which points out the importance of fire to eliminate hybrids and maintain the genetic integrity of shortleaf pine native to fire-prone, xeric sites. Resume: La suppression du feu et d'autres activites anthropiques ont la capacite d'eliminer les barrieres ecologiques qui empechaient autrefois les croisements entre les especes sympatriques qui sont reliees. Nous avons compare des hybrides artificiels F1 entre le pin a courtes feuilles (Pinus echinata Mill.) et le pin a encens (Pinus taeda L.) a leurs parents pour determiner les traits potentiels qui ont permis aux semis des hybrides d'augmenter de facon dramatique en abondance depuis les annees 1950. Six familles a pollinisation libre de pin a courtes feuilles et six autres de pin a encens ainsi que 12 croisements controles ont ete compares sur une periode de deux ans en Oklahoma, aux Etats-Unis. Les semis de pin a encens et des hybrides avaient des taux d'etablissement et de croissance plus eleves que les semis de pin a courtes feuilles. A la suite d'un etetage, les semis des hybrides avaient un nombre de rejets semblables a ceux du pin a courtes feuilles et plus grand que ceux du pin a encens. La formation d'un coude basal robuste, une adaptation qui protege les bourgeons dormants du feu, etait plus importante chez le pin a courtes feuilles et moins importante chez le pin a encens et les hybrides. L'efficacite d'utilisation de l'eau instantanee indiquait que les pins hybrides avaient une efficacite d'utilisation de l'eau elevee, semblable a celle du pin a courtes feuilles, comparativement a celle du pin a encens. En l'absence de feu, les semis des pins hybrides performaient au moins aussi bien que les especes parentales, ce qui fait ressortir l'importance du feu pour eliminer les hybrides et conserver l'integrite genetique du pin a courtes feuilles qui est present naturellement dans les stations xeriques sujettes aux incendies. [Traduit par la Redaction], Introduction Rapid introgression, i.e., the flow of genes into a species through hybridization and backcrossing with another, implies human causation and can lead to extinction (Allendorf et al. 2001). Species [...]