Abstract ID: 69

Models based on tree-ring analysis for age estimation in igapó, várzea and terra firme forests of central Amazonia

Tree age is a key indicator for tropical forest dynamics, linked to the discussion on sustainable management, conservation and carbon cycle. However, information on tree ages in central Amazonian forest ecosystems is controversial due to the different methodological approaches applied for age determination or estimation such as tree-ring analysis (dendrochronology), repeated diameter measurements and radiocarbon dating. Trees subjected to annual long-term flooding in the central Amazonian nutrient-poor igapó and nutrient-rich várzea form annual tree rings as a consequence of the flood-pulse, while the growth rhythm of species in upland forests (terra firme) is triggered by seasonal variation in precipitation. This has been indicated by several independent dendrochronological methods such as cambial wounding, measurements of the cambial resistance, phenological observations, dendrometer bands, densitometry, radiocarbon dating and climate-growth relationships. Age determinations based on tree rings of 1.455 trees of several species from várzea, igapó and terra firme are used to develop a multiple regression model for each forest type predicting tree age by diameter and wood density. The models explain between 67% and 83% of the variability of tree age and are a powerful instrument for tropical forest research and development. Maximum tree ages are predicted for the igapó characterized by long-term flooding and low nutrient status. This leads to the assumption that trees in Amazonia reach the highest ages at sites where tree growth and the establishment of forests are limited by environmental factors. The same holds for recorded maximum tree ages in the temperate, boreal and semi-arid climates of the northern and southern hemisphere which are indicated for trees growing on marginal sites (e.g., high altitudes, low nutrient status, water-logged and dry sites). These results contrast age determinations and estimations based on radiocarbon dating and repeated diameter measurements indicating much higher tree ages for várzea and terra firme.

Session:  Carbon - Forest dynamics, natural disturbance, and recovery. (B)

Presentation Type:  Oral