Seed rain in a successional gradient in a tropical montane cloud forest area

Tropical montane cloud forests (TMCFs) are among the most endangered ecosystems in the world. As a result of slash and burn agriculture, TMCFs areas in southern Mexico are usually a mosaic of corn fields and forests of different ages after abandonment.   Natural regeneration of forest depends almost entirely on seed rain.  However, little is known about this process in this kind of ecosystem.  We monthly monitored seed rain during one year in three chronosequences comprising six successional stages in Sierra Norte, Oaxaca, Mexico, using 66, 0.8 m ² seed traps.  We identified a total of 143 morphospecies of seeds of which 65 % could be identified taxonomically.  We found that seed abundance and seed diversity increased significantly with the age of the stand.   Seed rain varied seasonally being the fall the season that received the highest abundance of seeds. We could not detect any difference in the abundance of anemochorous and non-anemochorous seeds along the studied successional gradients.  Seeds of pioneer and late successional species were more abundant in their native habitats, than in any other habitat. Thus, limited seed dispersal appears to be a factor that limit species composition and abundance in TMCFs areas, and may help explain the high beta diversity observed in these areas in the neotropics.  On the other hand, the high diversity of seeds observed in late successional habitats points to the importance of these habitats as reservoirs of biodiversity and as a targets for conservation practices