Pioneer Woody Species In Southern Brazilian Grasslands

In southern Brazil, forests colonise grasslands only at a slow rate. Successional pathways and mechanisms are little known. Of selected pioneer woody species, I studied a) seedling emergence, survival and growth, and elder individual regenerative ability - experimentally, b) population structure and short-term dynamics - in permanent plots -, comparing grazed/burnt and abandoned grassland. The study elucidates several factors governing forest expansion: 1) Relative importance of seed and "safe site" limitation, seedling emergence rate and timing. 2) Factors influencing seedling survival and growth. 3) Relative importance of clonal spread and generative reproduction and relative performance of root suckers and seedlings in forest tree establishment. 4) Relative ability of forest trees and grassland shrubs to persist under recurrent disturbance. 5) Inhibition versus faciliation of forest tree establishment by grass and shrub communities and consequences of sudden shrub dieback.