Friday, August 10, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
Roel J. W. Brienen, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Morelia, Mexico, Edwin Lebrija-Trejos, Forest Resources, University of Minnesota, Saint Paul, MN, Michiel van Breugel, Smithsonian Tropical Research Institution, Panama and Miguel Martinez-Ramos, Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autonoma de Mexico, Morelia, Mexico
Studies on secondary forest succession strongly depend on chronosequences to estimate forest recovery rates in terms of biomass and diversity. Relying on historical information of landowners alone to determine ages of patches in such chronosequences introduces uncertainties regarding exact patch ages. Annual tree rings in those species that appear immediately after abandonment could greatly help to overcome such uncertainties by providing reliable and independent age determinations. Moreover, tree rings might prove useful in reconstructing stand dynamics and revealing species´ succession.In this study, we examine the occurrence of tree rings in 70 pioneer and early-successional species in a dry and a wet area in the south of Mexico. Discs or increment cores of more than 450 trees were collected from patches of different ages (3-36 years).
In both areas a relatively large percentage of species (65% for dry area and 40% for wet area) showed distinct growth boundaries, but we also observed problems such as intra-annual and wedging rings, impeding the use of complete stem discs. Comparison of patch ages and the number of rings confirms that rings are mostly formed annual and demonstrates the potential of several typical neotropical pioneer species to provide independent dating of patch ages.
Ranking of species according to time required to appear after abandonment provides a good picture of successional appearance of species and maybe used to test prevailing hypotheses about secondary forest succession in the tropics.
