Biometric Measures of Carbon Cycling Before and After Selective Logging in Tapajós National Forest - Para - Brasil 1,2 Figueira, A.M.S.; 3 Sousa,C.A.; 4 Maia,A.; 5 Menton, M.; 1 Miller, S.D. ; 6 Goulden, M.; 2 Rocha, H.; 1 State University of New York at Albany, 2 Universidade de S. Paulo, 3 IBAMA, Manaus-AM, 4 Universidade Federal do Para, 5 University of Florida, 6 University of California, Irvine The study of disturbed areas of the Amazon region helps to provide understanding of how current land-use models affect the forest ecosystem and its capacity to recover over time. The present study examines the seasonal variability of litter biomass and tree DBH increment, before and after selective logging, in order to better understand the effects of logging on forest structure, tree growth and forest recovery. This poster is based on a dataset that includes about 800 trees equipped with dendrometers, providing measurements of tree growth over 3-5 years. Litter collection in the same study area was done for ~ 5 years, and immediate logging effects (slash, roads, skid trails, canopy gap fraction) were also investigated. For this poster, the results were based on about 200 selected trees with clean time series measurements (bands with no spring oxidation over time, and/or no dendrometer band adjustment or replacement). In addition, only the leaf portion of the litter was considered (which comprises about 70% of the total litterfall). Leaf biomass: We installed 30 1m2 litterfall traps (Fig.1), which were arrayed at 25-m intervals along two east-west transects in an 18-ha block (300m N-S, 600m E-W) upwind of the eddy covariance tower (Fig.2). Litter was collected bi-weekly beginning in September The material was separated into leaves, wood and other parts (mainly flowers and fruits), oven dried and weighed. Overview Methods - RESULTS SUMMARY _LITTER PRE-LOGGING T ha -1 yr -1 (leaves = 6.3Tha -1 yr -1 ) POST-LOGGING T ha -1 yr -1 (leaves=5.2 T ha -1 yr -1 ) Figure 1: Litterfall trap Figure 2: Grid The temporal variation of dry weight shows a peak of leaf fall around September, which coincides with the dry season in the region. Comparison of rainfall and leaf fall (Fig.) shows that litterfall increases when rainfall decreases. There is a peak in leaf fall immediately after selective logging, suggesting a large litter input caused by the logging (~50 g/m 2 ). Dendrometer measurements: ~ 800 trees equipped with dendrometers bands Measurements were taken every 6 weeks (3-5 years of measurements) Before selective logging: ~ 400 trees equipped with dendrometers bands ~ 200 trees with DBH > 35cm and ~ 200 trees with DBH < 35cm After logging: we installed bands in ~ 400 trees, primarily near gaps Small trees (<35cm dbh) near gaps present higher rates of 6 week increments compared to small trees placed in undisturbed areas. This rate of increment of trees near gaps was about 2 times greater than the rate in trees of intact areas. Figure 3: Dendrometer band Figure 2: Gap caused by logging Conclusions The dendrometry and litterfall measurements before logging indicated growth and litter production rates comparable to other published studies in tropical forests (Vieira et al 2006, Rice et al, 2005). Our measurements indicate that litterfall production increased during the logging, but then decreased to the production rate before logging occurred. As indicated by the dendrometer measurements, trees near or in gaps caused by logging show an increase in growth rate compared to those in undisturbed areas. Row data showing the accumulated increment (mm) in different classes of trees. Acknowledgments: References:. Vieira, S.; Trumbore, S.; Camargo, P.; Selhorst, D.; Chambers, J; Higuchi, N.; Martinelli, L.A Slow growth rates of Amazonian trees:Consequences for carbon cycling. SUMMARY_ DENDROMETRY Classescm y -1 Trees <35cm DBH0.30 Trees 35-50cm DBH0.34 Trees >50cm DBH0.33 Trees <35cm DBH - near gaps0.45