Potencial de regeneração natural de Virola surinamensis (Rol. ex Rottb.) Wab. em florestas inundadas com e sem exploração madeireira na Amazônia Oriental.

Abstract

Actually, there are many studies testing the effect of flood in the Amazonian floodplain forests plants. However, the majority performed in the community levei. There area few studied performed in population levei, mainly in plant species with economic values. The species Virola surinamensis is a typical dioecious tree in the Amazonian floodplain forests with great economic importance due the value of wood used by timber industry. These uses result in a drastic reduction ofnatural population ofthis species in the natural conditions. Them objectives ofthis study are: (1) Compare to density ofseedlings established between the igapo and varzea floodplain forests without human intervention; (2) Compare to density ofseedling established in three locations submit the different wood extractions; (3) Compare to seed germination, the growth between the varzea and igapo floodplain forests without human intervention and (4) Compare to survival and biomass production of seedling established in three different levei of inundation. Ali studies were carried in the estuarine floodplain forests in the Pará State, Brazil. In the objectives 1 and 2 were establish 20 plots of 2 x 2 meters in the igapo and varzea floodplain forests unexploited and also in the three locations subject to different leveis oftimber extractions. In the objective 3 were collected seeds of Virola in the igapo and varzea floodplain forests unexploited. In the germination and growth experiraents were divided in four treatments: Tl-Seeds ofigapo planted in igapó soils; T2-Seeds of varzea planted in igapo soils; T3-Seeds of varzea planted in várzea soils and T4- Seeds of igapo planted in varzea soils. The measured data were height and diameter ofplants and dry mass of leaves, stems and roots. In the flooding experiment the plants were divided in three treatments: (1) control (without food); (2) partially flood and (3) total flood. The experiment had duration of 120 days and also was measured of height of plants, the total number of leaves and the formation of lenticels and adventitious roots. The density of seedling was significantly lower in the igapo forest in comparison to varzea. The relative frequency of seedling in the plots varied from 30% in the areas with actual timber exploration and areas exploited and abandoned to 85% in the areas without timber exploration. There is no difference in the seedling germination between the varzea and igapo soils. However, the seeds planted in the varzea soils have higher increment in height and dry biomass. The seedlings of Virola are tolerant to flood. The plants totally submerse had a significantly decreased in the mean height in comparison the plants partially food and the control (not flood) that grown on average 7.3% and 8%, respectively. There was no variation in biomass production in plants among the treatments. In the partially and fully submerged plants presented morphological modifícations, such as, the formation of lenticels and adventitious roots and the presence of chlorosis and foliar senescence.