A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Tree Growth History, Stand Structure, and Biomass of PremontaneForest Types at the Cerro Tambo, Alto Mayo, Northern PeruViviana Horna 1,2) , Reiner Zimmermann 1,2) , Henry Soplin 1) , AnnettBörner 1,2) , Tobias Mette 1)1)Forest Ecology and Remote Sensing Group, Ecological-Botanical Gardens ÖBG,University of Bayreuth, 95440 Bayreuth, Germany2) Max-Planck-Institute for Biogeochemistry, Jena, Germany.viviana.horna@bgc-jena.mpg.de Phone: ++49-3641-686731 Fax: ++49-3641-686710AbstractTree growth and biomass accumulation were studied for two structurally contrasting premontane foresttypes occuring from 1200 -1600 m a.s.l. at the Cerro Tambo, Region Alto Mayo in Peru. The premontanevegetation at the Cerro Tambo consists of a mosaic of poor heath forests and well developed premontanerain forests.Within each forest type, the variation in species composition and aboveground biomass is small comparedto the dramatic differences apparent between the heath and rain forests. Edaphic variations and severedrought damage during prolonged dry seasons as agent for such differences was excluded by studies onsoils and water consumption by vegetation. Mosaic type heath forest establishment in a zone with potentialdense rain forest cover can be the result of recurring destructive events like natural fires or landslides,occuring on a decadal to secular scale. Such events may trigger a series of successional stages which lead toirreversible deterioration of site quality under current conditions.Stand structure, tree growth rates, and tree age was measured to describe the growth dynamics of thecontrasting forests and to detect stand growth depressions within the life span of old growth individuals.Tree ring analysis of 106 trees showed that all forests of the Cerro Tambo area have low annual tree growthrates. Heath forests and tall rain forests show no pronounced difference in growth rates. However, heathforests are young and no individuals older than 45 years were found. Tall rain forests trees of more than150 years in age were found. We conclude that heath forests are most likely successional stages after fairlyrecent disturbance.A slight and linear positive increase in rainforest tree growth in all forest plots was found for the pastcentury and may be attributed to the globally increasing atmospheric CO 2 concentration. A further observedincrease in tree growth in all forest plots during the last two decades may be attributed to atmosphericdeposition of nutrients due to massive deforestation followed by rural development in this region.