SOIL SEED BANKS IN PLANTATIONS AND TROPICAL SEASONAL RAINFORESTS OF XISHUANGBANNA, SOUTHWEST CHINA

The impacts of land conversion from forests to plantations on seed availability are poorly appraised in terms of future restoration potentials. Seed storage and species composition of soil seed banks were characterised in five natural forests and three plantations. Mean soil seed storage differed significantly between study sites, ranging from 2444 seeds/m2 in a selectively logged forest to 17,946 seeds/m2 in a pomelo orchard. For all sites except for secondary forest 2, herb seeds dominated the soil seed bank. More seeds of pioneer tree species were found in the soil seed banks of secondary forests than in primary rainforests. This suggests that secondary forests have higher seed availability and stronger potential for forest restoration than primary forests. Anthropogenic management activities resulted in abundant but less diverse soil seed bank due to the dominance of a few herbaceous species in the pomelo orchards and rubber plantations. Low tree seed storage was found in soil seed banks of pomelo orchards and rubber plantations and might decelerate forest succession. Thus, the seeds of pioneer trees in soil seed banks of secondary forests could promote natural forest regeneration in abandoned plantations.