Improving our understanding of the growth dynamics of trees along elevation gradients could help us predict their potential to store carbon and their vulnerability to changes in local and global environmental conditions, such as deforestation and climate change. This study is a review and analysis of the results obtained in recent dendrochronological studies of the effect of elevation and climate (temperature and precipitation) on the radial growth of trees in temperate zones, mainly in the Northern Hemisphere. Only 18 (32.1%) of the 56 studies analyzed found a correlation between radial growth of the trees (total chronologies) and elevation. The analysis of 56 chronologies of 46 tree species included in the 110 works reviewed, showed that only in 28.2% of them the correlation between radial growth versus temperature and precipitation was significant: positive in 3.6%, negative in 2.7%, and positive and negative in 21.8%, depending on the season of the year. The wide variation found in the radial growth response of the trees to elevation gradients may be related to multiple environmental factors at a local or regional scale, but also to the different sampling methods used in the studies. However, a moderate proportion of the studies analyzed (close to 30%) show that temperature and rainfall are related to trends in radial growth in different elevation ranges and regions of the world.

Introduction: Magnolia rzedowskianaVázquez, Domínguez & Pedraza is a tree species endemic to the cloud forest of the Sierra Madre Oriental; its scanty (distributed) and isolated populations are considered at danger of extinction.Objective: To describe the microscopic anatomical characteristics of M. rzedowskiana wood to contribute to the biological knowledge of this species.Materials and methods: Wood samples were determined by a non-destructive method, extracting two growth cores from five adult trees in each of the four sampling sites located in Chilijapa and Zotictla in Hidalgo, La Yesca in Querétaro and ejido La Trinidad in San Luis Potosí. Cores were sectioned into subsamples to elaborate fixed preparations from tangential, transversal and radial cuts. Characteristics were identified using an optical microscopy and described according to IAWA (International Association of Wood Anatomists) criteria.Results and discussion: Growth zones, diffuse porosity, solitary and multiple radial pores in intermediate arrangement between radial and tangential; scalariform perforation plate and libriform fibers; diffuse and scanty paratracheal and apotracheal axial parenchyma; biseriate rays combined with triserial, uniseriate and heterocellular rays composed of procumbent cells with a row above and below of marginal square cells with oil bodies. The wood is distinguished by mesomorphism and resistance to drought.Conclusion: The anatomical description of M. rzedowskiana is a contribution to biological knowledge. From an economic point of view, this wood has potential use to produce pulp for paper.