19 research outputs found

    Recovery of above-ground tree biomass after moderate selective logging in a central Amazonian forest

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    We examined the recovery and dynamics of living tree above-ground biomass (AGB) after selective logging in an Amazonian terra firme forest managed by a private company. The forest consisted of 24 blocks (including one set aside for conservation) selectively logged in different years on a managed schedule. Trees ≥10 cm in diameter at breast height (dbh) were surveyed in 2006 in 192 0.25-ha plots, in 2010 in 119 plots, and in 2012-2013 in 54 plots. A logistic growth model factoring in logging dynamics and mean AGB of a block in these years was established. Referencing the mean AGB of the unlogged forest, the model indicated that the logged forest would take on average 14 years to regain its preharvest AGB after selective logging at 1.9 trees ha-1 (dbh > 50 cm). In 2010 and 2012-2013, the AGB increased significantly for small and large trees (10-20 cm and >60 cm dbh, respectively) in the logged forest. In contrast, it decreased significantly for medium-sized trees (30-50 cm dbh) in the unlogged forest. Comparisons with the previous studies mainly conducted in the other regions of Amazon suggested that the estimated AGB recovery period with moderate logging intensity was almost appropriate and likely acceptable to forest managers. © SISEF

    Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

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    Introduction: The productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored. Methods: To fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate. Results: Using linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index). Discussion: Our results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change

    Significance of topographic gradient in stem diameter - Height allometry for precise biomass estimation of a tropical moist forest in the central Amazon

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    We developed a stem diameter D-height H allometric model that included variability in the D-H relationship along a topographic gradient. The study site was located along a belt transect (2500 × 20 m) established in a primary tropical forest near Manaus, Brazil. The transect included typical topography of the region, characterized by plateaus and valleys called "baixios". The D-H allometric model (n = 1307) indicated that potential tree height increased significantly, from 28 m at the lowest baixio plot to 35 m at the highest plateau plot. Consequently, by combining the D-H allometric model and an allometric equation with the variable D2H, biomass was estimated for trees (D > 10 cm) in each sub-plot (20 × 20 m). Ignoring variability in the D-H relationship introduced wide-ranging error to biomass estimation; error values ranged from -5% at a baixio plot to +6% at a plateau plot. Average biomass was 317 ± 28 (SE) Mg ha-1, and tree density and biomass fell significantly with decreasing relative elevation

    Examination of vertical distribution of fine root biomass in a tropical moist forest of the central amazon, Brazil

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    Fine roots are an important component of the carbon flow of forests. Soil properties in tropical forest (terra firme forest) of the Central Amazon differ substantially along topography, and the biomass and vertical distribution of fine roots may also differ accordingly. Information on the vertical distribution of fine roots is essential to obtain unbiased estimates of fine root biomass. Accordingly, we examined fine root biomass and its vertical pattern along the gradient of topography in a typical terra firme forest in this region. The regressions on the cumulative fine root biomass along soil depth (at 5 cm intervals from 0-40 cm in depth) revealed significantly different vertical distribution of fine root biomass among three topographic habitats (lower-slope valley called baixio, mid-slope, and upper-slope plateau). A shallower rooting pattern was observed in the plateau than the other habitats, while fine root biomass was larger in the baixio than the plateau-a difference likely attributable to the soil physical properties than the aboveground stand structures among the sites. More than 74 and 93% of the fine root biomass was estimated to be distributed within the upper 20-and 40-cm soil layers, respectively. Our results suggested that a shallow sampling depth, which is common in fine root research in the Amazon, would be reasonable, though we should examine the consistency of our results in different regions

    Changes in forest structure and biomass over ten years in a lowland amazonian forest

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    The topographic effects on biomass and its increment were evaluated for a terra-firme forest near Manaus, Brazil. We established three plots (60 × 60 m) on a plateau and at the bottom of a valley (namely baixio), and measured stem diameter at breast height D (> 10 cm) for tree and palm species in 2002 and 2012. Small trees (10 cm > D > 5 cm) were measured in subplots (20 × 60 m) within each plot. We also estimated tree height with the D - tree height H relationship model based on a hundred samples of the tree species in each topography. The aboveground biomass AGB was estimated as 315.4 ± 33.2 (average ± SE) Mg ha-1 on the plateau, which was higher than 224.2 ± 20.3 Mg ha-1 in baixio though the difference was statistically marginal (p = 0.09). The difference in AGB was partly ascribed to the decrease of H for large trees and a lack of large trees whose D > 80 cm at the baixio site. The AGB of palm species in baixio was 2.7 ± 0.87 Mg ha-1, which was higher than 0.24 ± 0.08 Mg ha-1 on the plateau though the difference was statistically insignificant (p = 0.11). On the other hand, the increment of AGB did not differ significantly between the two sites (p > 0.05), and the variation of AGB increment among the plots was mainly ascribed to the variation of biomass loss caused by mortality