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Lara W.,Sustainable Forest Management Research Institute | Lara W.,Research Center on Ecosystems and Global Change | Bravo F.,Sustainable Forest Management Research Institute | Sierra C.A.,Max Planck Institute for Biogeochemistry | Sierra C.A.,Research Center on Ecosystems and Global Change
Dendrochronologia | Year: 2015

A new tool for the detection and measurement of tree-ring widths in wood was developed for the R environment. This tool, the measuRing package, integrates measurement of tree-ring widths with powerful statistical analyses within the R environment. The package assists in the identification of ring borders on scanned image sections from dendrochronological samples. It processes the image section and computes luminance data from images producing a matrix of gray values and a time series of smoothed gray values. Luminance data is plotted on segmented images for users to perform both visual identification of ring borders, or manual control of automatic detection. The package provides functions to visually include/exclude ring borders on the R graphical device, or automatically detect ring borders using a linear detection algorithm. This algorithm detects ring borders according to negative extreme values in the smoothed time-series of gray values. Users of the package can also implement other algorithms for automatic detection. © 2015 Elsevier GmbH. Source


Sierra C.A.,Max Planck Institute for Biogeochemistry | Sierra C.A.,Research Center on Ecosystems and Global Change | Yepes A.P.,Research Center on Ecosystems and Global Change
Eos | Year: 2010

Ecosystems and Global Change in the Context of the Neotropics; Medelln, Colombia, 19-20 May 2010; Research in most areas of global environmental change is overwhelmingly produced outside developing countries, which are usually consumers rather than producers of the knowledge associated with their natural resources. While there have been important recent advances in understanding the causes of global-scale changes and their consequences to the functioning of tropical ecosystems, there is still an important gap in the understanding of these changes at regional and national levels (where important political decisions are usually made). A symposium was held with the aim of surveying the current state of research activities in a small, developing country such as Colombia. It was jointly organized by the Research Center on Ecosystems and Global Change, Carbono and Bosques; the National University of Colombia at Medelln; and the Colombian Ministry of the Environment, Housing, and Regional Development. This 2-day symposium gathered Colombian and international scientists involved in different areas of global environmental change, tropical ecosystems, and human societies. Source


Lara W.,University of Valladolid | Lara W.,Research Center on Ecosystems and Global Change | Bravo F.,University of Valladolid | Maguire D.A.,Resources and Management
Agricultural and Forest Meteorology | Year: 2013

We established a new approach for incorporating dynamic tree biomass variables into dendrochronological studies. A multi-level algorithm was developed for modeling biomass growth from tree-ring chronologies, and for establishing temporal relationships between biomass dynamics and drought. The algorithm, BIOdry, integrates conventional procedures for modeling patterns between tree biomass growth and drought, using dendrochronological data from Mediterranean ecosystems, accounting for multiple sources of variation from sample design, and comparing patterns from contrasting climatic portions of study site during last 50 years. The modeling approach was validated by exploring principal factors affecting annual biomass increments and annual aridity indexes in two Mediterranean pine forests: Pinus pinaster and P. sylvestris. BIOdry corrected several statistical problems related with dendrochronological sampling and modeling of biomass growth. The most important factors affecting relationships between the series were time span of the analysis, regional variations and adaptive strategies of species. Series from trees in the Atlantic region were not sensitive to increasing drought while responses of trees in the Mediterranean regions depended on species. Series from P. pinaster were more sensitive to drought oscillations than series of P. sylvestris. Both species growing in southern Spain have experienced increasing sensitivity to drought during last 50 years. Southern forests are little adapted to decreasing precipitations of autumns and winters. BIOdry can be used for assessing spatial and temporal vulnerabilities of growth attributes derived from tree-ring chronologies to increasing drought. © 2013 Elsevier B.V. Source

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