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Schwartz G.,Wageningen University | Schwartz G.,Forest Management and Conservation Group | Lopes J.C.A.,Forest Management and Conservation Group | Mohren G.M.J.,Wageningen University | Pena-Claros M.,Wageningen University
Forest Ecology and Management | Year: 2013

Despite greatly improved forest management in recent decades, long-term assessments show that if current harvesting volumes and cutting cycles are maintained, future volume yields of commercial species will decrease. A possible solution is to apply post-harvesting silvicultural treatments to increase the number of valuable trees. In this study we compared during 4years two treatments: tending naturally established seedlings/saplings of commercial species in logging gaps, and enrichment planting+tending seedlings of commercial species. In both treatments, competition was artificially reduced by liberating each focal seedling/sapling from competitors (i.e. other tree seedlings/saplings, lianas, or herbs). The experiment was carried out in an area of ombrophilous dense forest managed by the Orsa Florestal forestry company in Jari Valley, eastern Amazon, Brazil (01°09'S and 52°38'W). The company applies reduced-impact logging in a polycyclic silvicultural system. We sampled 64 2-year-old logging gaps (average area 427.2m2). Thirty-four gaps were used for the planting+tending, 15 gaps underwent the tending treatment, and there were 15 gaps in the control treatment (i.e. no intervention). The tending treatment showed lower mortality rate, faster growth rate, and required less liberation from overstorey plants and lianas than the other two treatments. Half of the species responded positively to tending: the long-lived pioneers Goupia glabra and Laetia procera, and the partially shade-tolerant Dinizia excelsa, Tachigali myrmecophila, and Trattinnickia sp. Similarly to tending, individuals subjected to the enrichment planting+tending treatment also presented higher growth rates. Based on these results we recommend tending be applied to areas with sufficient natural regeneration of commercial species. Enrichment planting+tending should be applied when regeneration of commercial species is scare, ideally using species that have high initial growth rates, and high commercial or conservation value. © 2013 Elsevier B.V.

Schwartz G.,Wageningen University | Schwartz G.,Forest Management and Conservation Group | Pena-Claros M.,Wageningen University | Lopes J.C.A.,Forest Management and Conservation Group | And 2 more authors.
Forest Ecology and Management | Year: 2012

Reduced-impact logging (RIL) is a set of techniques aimed to maintain forest structure and functions of the harvested forest as similar as possible to pre-logging status, while reducing adverse impacts from logging activity on the remaining forest. We analysed the mid-term effects of RIL on the regeneration of the long-lived pioneers (LLP) Bagassa guianensis and Jacaranda copaia; the partially shade tolerant (PST) Hymenaea courbaril, Dipteryx odorata, and Carapa guianensis and the total shade tolerant species (TST) Symphonia globulifera and Manilkara huberi. This study was carried out in an intensive study plot in the 600,000-ha Tapajós National Forest, Eastern Amazon - Brazil (03°02'S and 54°56'W). Three transects split in 10×10m plots, adding up to 2.37ha were sampled in an area where RIL was applied, and compared with a same size sampling in an unlogged area. The regeneration of individuals ≤20cm in dbh was inventoried and measured before logging in 2003 and three times after logging (2004, 2006, and 2009). RIL modified the forest structure creating more gap-phase plots, with the consequences of such disturbance still remaining after 6years. Densities of B. guianensis, J. copaia, and S. globulifera increased, while C. guianensis diminished. The positive effect on the density of LLP species was, however, ephemeral and disappeared 2years after logging. RIL had a positive effect on the height growth rate of S. globulifera and on the dbh growth rate of C. guianensis. Plants growing in the gap-phase plots had higher height growth rates (ANOVA, F 2;2980=33.3, p<0.001) than plants growing in other phases, but the same difference was not observed for dbh growth rates (ANOVA, F 1;364=0.9, p=0.33). Crown position had positive effects on height and dbh growth rates: the higher the crown position, the faster the plant grows in height (ANOVA, F 3;2979=148.4, p<0.001) and dbh (ANOVA, F 3;362=26.1, p<0.001). The application of RIL following the Brazilian regulations, may be considered a silvicultural technique for increasing density and growth rates of commercial species, but additional silvicultural interventions, as liberation for example, might be required for maintaining the ecological outcomes of RIL in the long run. © 2012 Elsevier B.V..

Schwartz G.,Wageningen University | Schwartz G.,Forest Management and Conservation Group | Lopes J.C.,Forest Management and Conservation Group | Kanashiro M.,Forest Management and Conservation Group | And 2 more authors.
Biotropica | Year: 2014

The effects of reduced-impact logging (RIL) on the regeneration of commercial tree species were investigated, as long-term timber yields depend partly on the availability of seedlings in a managed forest. On four occasions during a 20-month period in the Tapajós National Forest (Eastern Amazon, Brazil), seven commercial tree species were assessed as follows: the long-lived pioneers Bagassa guianensis and Jacaranda copaia; the partially shade-tolerant Hymenaea courbaril, Dipteryx odorata, and Carapa guianensis; and the totally shade-tolerant Symphonia globulifera and Manilkara huberi. In 2439 10 × 10 m plots, all individuals < 20 cm diameter at breast height (dbh) were assessed over three intervals, before, during, and after the forest being logged. Before logging, the density of seedlings and saplings of the seven species did not change. Logged trees were spatially aggregated, with 9.2 percent of the plots being heavily impacted by logging. After logging, the recruitment rate increased more than the mortality rate, so that post-harvesting densities of seedlings and saplings increased. The increase in density was concentrated in logged plots with more disturbances. It is concluded that post-harvesting heterogeneity of micro-environments created by RIL may be an important component to be taken into account for sustainable forest management and conservation of commercial species. © 2014 The Association for Tropical Biology and Conservation.

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