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

Tree ring studies to estimate carbon-uptake in Amazonian lowland forestsSack, M. 1 , Worbes, M. 1 & Piedade, M. T. F. 21 Forstbotanisches Institut, Büsgenweg 2, 37077 Göttingen, Germanye-mail: msack@gwdg.dee-mail: mworbes@gwdg.de2 Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, Caixa Postal 478,CEP: 69011-970, Manaus/AM, Brasile-mail: maitepp@internext.com.brContribution to Carbonsink – LBA / WP5 - Historical and spatial trends in Amazon forestsProposal N o : EVK4-1999- 00191Project Coordinator: Kabat, P.The measurement of forest increment by conventional methods (e.g. repeated diametermeasurements) is widely used. From Amazonian lowland and adjacent regions several long-termobservation plots in forests have been evaluated previously. The data indicate a net increase ofwood biomass in the last decades. However, the method is not appropriate to analyze theinfluencing factors nor to explain this finding. Tree ring analysis allows the estimation of annualwood increment by ring-width measurements and helps to clarify the structural dynamics in woodformation and growth variation over the complete lifespan of individual trees. Together with themeasure of wood density and allometric functions of bole volume, the wood biomass incrementcan be calculated. This method is appropriate for examining the inter-annual variability in woodformation and its relation to climatic factors, to estimate the age of the investigated individualtrees, and to quantify long-term historical trends in forest productivity and carbon stocks. Most ofthe dendroecological investigations between extrinsic and intrinsic factors and the cambialgrowth dynamics of tropical trees were carried out with a strong emphasis on the influence ofclimatic factors and the significance of soil water supply for the cambial activity of the trees.According to recent investigations, we can show that repeated cambial wounding (“pinning”) isan appropriate method for growth rate determination, the characterization of the cambial activity,and the proof of annual tree rings in tropical trees.We found in our experimental plots in a forest 90 km north of Manaus a high diversity of about150 tree species per hectare. Congruent with species diversity there is a high diversity in woodstructure. Most of the investigated overstorey trees show a distinct tree ring structure. First resultsindicate a seasonal growth rhythm of many trees of the Amazonian terra firme. This serves forage determination of the trees and the estimation of current and long term growth increments.