SEED BANK OF NATURAL FOREST REMAINDERS AND REFORESTATION AREAS IN A MOGI-GUACU RIVER FLOODPLAIN, LUIZ ANTONIO COUNTY, SAO PAULO STATE, BRAZIL

The objective of this study was to evaluate qualitative and quantitatively the seed bank of two natural forest remainders, one Eucalyptus robusta plantation and three reforestation areas with native species, located in a riparian area of Mogi-Guacu River floodplain, in Luiz Antonio County (21 degrees 31'S and 47 degrees 55'W), Sao Paulo State, Brazil. The evaluation was carried out in 12 plots of 10 x 10 m systematically distributed in each area. Four subplots of 0.5 m x 0.5 m were randomly distributed in each plot. Two subplots were used to evaluate the seed bank in the litter and two in the soil sample at the 0 - 5 cm depth. The sampling was accomplished in September 2001 in the natural forest remainders and in the eucalyptus plantation and, in September 2002, in the reforested areas. The soil and the litter were conditioned in plastic pots, and incubated with periodic irrigations for the seed germination during seven months, in two greenhouse environment conditions: one at 100% sunlight and the other, under a screen that provides a 70% sunlight reduction. In the composition of all sample area seed banks, there was a predomination of pioneer species at the early successional stages. The most important arboreal species were Aloysia virgata and Cecropia hololeuca. The reforestation with native species provided a seed bank with a greater diversity of native arboreal species than the eucalyptus plantation. The present study indicates that the similarity between the planted and natural forest should be enhanced over the time.