Post-harvesting silvicultural treatments in logging gaps: A comparison between enrichment planting and tending of natural regeneration

Summary

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 4 years 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 427.2 m2). 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.