Populational ecology of seven tree species in a selective logging area in Central Amazon

Author(s)

Maria Rosa Darrigo

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2011-07-29

Examining board members

Flavio Antonio Maës dos Santos; Gislene Maria da Silva Ganade; Simone Aparecida Vieira; Jochen Schöngart; John Du Vall Hay

• Advisor: Eduardo Martins Venticinque; Flavio Antonio Maës dos Santos

Abstract

Reduced-impact logging systems have been considered one way to diminish deforestation rate in Amazonia. However, we do not have enough knowledge about the effects of such systems, due to a lack of data about regeneration and dynamics of tree species. In this thesis we investigated the impact of selective logging on regeneration and dynamics of five commercial species (Goupia glabra, Manilkara huberi, Manilkara bidentata, Minquartia guianensis and Zygia racemosa) and two non-exploited species (Pouteria anomala and Protium hebetatum). We investigated effects of selective logging on the abiotic factors as well as in the regeneration of small individuals (10 to 100cm tall, Chapter I). Through models and simulations, we verified the sustainability of the parameters currently used in the major management plans, proposed for logging activities in Amazon (Chapter II). Finally, we assessed whether variations in light conditions found in the exploited areas could change herbivore-plant interactions, resulting in effects on the mortality of small individuals and their regeneration. Our results pointed to higher light and soil fertility in the exploited areas. We also found an increment in growth rate, due to canopy opening, which should last five years after exploitation. The higher soil fertility found in the exploited areas did not increase the growth rate. The mortality rate was higher in the exploited areas, even in those after 12 year regeneration period. The variation in the vital rates was verified in both exploited and non exploited species, which indicates that logging environmental alteration might also affect the regeneration of noncommercial species. We found higher herbivory and growth rates in gaps and in exploited areas, due to higher light intensity. However, in the control areas the herbivory was higher in the gaps than in the understory, thus responding to the increase in light conditions. In the exploited areas, the herbivore rate was the same in gaps and understory. Herbivory was an important factor conditioning the mortality of small individuals, but this interaction has equally influenced mortality in exploited and non-exploited areas. Therefore, this interaction should not be considered a cause of higher small individuals mortality rates found in the exploited areas. Population growth rates indicate stability or population growth of the tree species in the control areas, but in the exploited ones we found a shrinking population (exception to P. hebetatum, non-exploited species). We concluded that the reduced impact selective logging is not sufficient to warrant sustainability. Higher mortality of small individuals and logging intensity seems to be an important factor that contributes to the lower population growth rates verified in the exploited areas (AU)