Search

Climate change may have spatially variable impacts on growth of trees in topographically diverse environments, making generalizing across broad spatial and temporal extents inappropriate. Therefore, topography must be considered when analyzing growth response to climate. We address these topo-climatic relationships in the Canadian Rocky Mountains, focusing on lodgepole pine (Pinus contorta Douglas ex Louden) and interior spruce (Picea glauca (Moench) Voss * Picea engelmannii hybrid Parry) growth response to climate, Palmer drought severity index (PDSI), aspect, and slope angle. Climate variables correlate with older lodgepole pine growth on south- and west-facing slopes, including previous August temperature, winter and spring precipitation, and previous late-summer and current spring PDSI, but younger lodgepole pine were generally less sensitive to climate. Climate variables correlate with interior spruce growth on all slope aspects, with winter temperature and PDSI important for young and old individuals. Numerous monthly growth-climate correlations are not temporally stable, with shifts over the past century, and response differs by slope aspect and angle. Both species are likely to be negatively affected by moisture stress in the future in some, but not all, topographic environments. Results suggest species-specific and site-specific spatiotemporally diverse climate-growth responses, indicating that climate change is likely to have spatially variable impacts on radial growth response in mountainous environments. Key words: lodgepole pine (Pinus contorta), interior spruce (Picea glauca, Picea engelmannii), dendroclimatology, biogeography, climate change. Le changement climatique pourrait avoir des impacts sur la croissance des arbres qui varient dans l'espace dans les environnements topographiquement heterogenes, de telles sorte qu'il serait inapproprie de generaliser sur de vastes etendues spatiales et temporelles. Par consequent, on doit tenir compte de la topographie lorsqu'on analyse la reaction de la croissance au climat. Nous abordons ces relations entre la topographie et le climat dans les montagnes Rocheuses canadiennes, en mettant l'accent sur la reaction de la croissance du pin tordu (Pinus contorta Douglas ex Louden) et de l'epicea de l'interieur (un hybride entre Picea glauca (Moench) Voss et P. engelmannii Parry) au climat, a l'indice Palmer de gravite de secheresse (IPGS), a l'orientation et a l'inclinaison de la pente. Les variables du climat sont correlees avec la croissance des pins tordus plus vieux sur les pentes orientees au sud et a l'ouest, incluant la temperature du mois d'aout de l'annee precedente, la precipitation hivernale et printaniere ainsi que l'IPGS a la fin de l'ete de l'annee precedente et du printemps de l'annee en cours, mais les pins tordus plus jeunes etaient generalement moins sensibles au climat. Les variations du climat sont correlees avec la croissance de l'epicea de l'interieur peu importe l'orientation de la pente; la temperature et l'IPGS durant la saison hivernale sont importants pour tous les individus, jeunes ou vieux. De nombreuses correlations entre le climat et la croissance mensuelle ne sont pas stables dans le temps et ont varie au cours du siecle passe; la reaction differe selon l'orientation et l'inclinaison de la pente. Les deux especes ont des chances d'etre negativement affectees dans l'avenir par le stress hydrique dans certaines, mais pas toutes les situations geographiques. Les resultats suggerent des reactions de la croissance au climat variees du point de vue spatiotemporel et propres a chaque espece et a chaque site, ce qui indique que le changement climatique aura vraisemblablement des impacts variables selon l'endroit sur la reaction de la croissance radiale dans les environnements montagneux. Mots-cles : pin tordu (Pinus contorta), epicea de l'interieur (Picea glauca, Picea engelmannii), dendroclimatologie, biogeographie, changement climatique., Introduction Forests are a key component of the global carbon cycle and other ecosystem services, in many places are a significant economic resource, and contribute to recreational activities. Given the [...]

Purpose: To describe a patient who developed major topographical changes mimicking post-laser in situ keratomileusis (LASIK) ectasia during breast cancer treatment with tamoxifen. Methods: Case report and literature review. Results: A 36-year-old woman who had had 10 years of stable vision after LASIK surgery was diagnosed as having breast cancer 6 months before presentation. As therapy, the patient received tamoxifen, a selective estrogen receptor modulator. After the initiation of therapy, the patient experienced rapidly decreasing vision in her left eye. Assessment of corneal tomography showed marked steepening with irregular astigmatism, leading to the diagnosis of postoperative ectasia in the left eye. After 3 months of treatment with tamoxifen, the anterior cornea showed marked flattening again and improvement of corrected distance visual acuity, both of which were maintained at the 6-month follow-up visit. Conclusions: Serum estrogen level changes during breast cancer treatment may induce major topographical changes, mimicking postoperative ectasia after LASIK. [Journal of Refractive Surgery Case Reports. 2024;4(1):e20–e23.] [ABSTRACT FROM AUTHOR]

Using in situ light curves and understory seasonal light measurements the importance of canopy avoidance was evaluated for a population of sugar maple (Acer saccharum Marsh.) seedlings living at the boreal ecotone in Lake Superior Provincial Park, Ontario, Canada. At higher latitudes, the time period associated with canopy avoidance is shorter and occurs at cooler temperatures, increasing the risk of frost damage. In 2008, leaf-out began 5 days prior to the last frost of the season. By modeling the potential carbon gain of seedlings, it is clear that the short time period prior to canopy leaf-out still contributes a disproportionate amount of carbon to the overall budget of seedlings. Of the total seasonal carbon gain, 80.6% was assimilated in the initial 15 days following sugar maple seedling leaf-out. Based on our model, by leafing out only 6 days earlier than the average seedling leaf-out date, ~200% more carbon could be assimilated during the course of the growing season. Vegetation phenology is cued by climatic triggers--as climate changes so too will phenological responses. These mechanisms add to the overall carbon budget of seedlings; recognizing these mechanisms is essential to thoroughly understand the natural history of this species. Resume: En utilisant des courbes de reaction a la lumiere in situ et des mesures saisonnieres de lumiere sous le couvert, l'importance de la periode d'absence de couvert a ete evaluee pour une population de semis d'erable a sucre (Acer saccharum Marsh.) dans un ecotone boreal du Parc provincial du lac Superieur, en Ontario, au Canada. Aux plus hautes latitudes, la periode d'absence de couvert est plus courte et est associee a des temperatures plus froides, ce qui augmente les risques de dommages causes par le gel. En 2008, le debourrement a debute cinq jours avant le dernier gel saisonnier. A l'aide dun modele du gain potentiel de carbone par les semis, il est clair que la courte periode de temps avant l'emergence des feuilles dans la canopee contribue de facon disproportionnee au bilan total du carbone des semis. Par rapport au gain total saisonnier en carbone, 80,6 % du carbone etait assimile pendant les premiers 15 jours qui ont suivi le debourrement des semis derable a sucre. De plus, selon notre modele, en debourrant seulement six jours avant la date moyenne de debourrement des semis, environ 200 % plus de carbone pourrait etre assimile sur l'ensemble de la saison de croissance. La phenologie de la vegetation est controlee par des declencheurs climatiques, de telle sorte que les reactions phenologiques vont changer a mesure que le climat se modifie. Ces mecanismes sajoutent au bilan total du carbone des semis et la reconnaissance de ces mecanismes est essentielle a une comprehension approfondie de l'historique naturelle de cette espece. [Traduit par la Redaction], Introduction Sugar maple (Acer saccharum Marsh.) is an extremely shade-tolerant species (Godman et al. 1990), regenerating underneath dark overstories created by adults. The darkness of the overstory suppresses seedling development, [...]