Regrowth rates and types

Under light-to-moderate land use intensity, and when seed sources are nearby, (woody) plant species richness rapidly increases during the first years of secondary forest succession, and it takes no more than a few decades after abandonment to reach values comparable to old-growth forest. However, as intensity of past land use increases, slower recovery of species richness is expected due to soil compaction, propagule dispersal limitation, and fire occurrence.
    
Plant size class needs to be taken into account when examining recovery of species richness during succession, because richness and abundance are positively correlated.  Thus, species richness in secondary stands tends to be more similar to old-growth forest when dealing with smaller (i.e., more abundant per unit area) than larger size classes. In slash-and-burn sites in the upper Rio Negro basin of Venezuela and Colombia, at least 40 years were required for species richness of stems 10 cm DBH to attain similar values to that of mature forest, although species richness recovered much more rapidly (between 10 and 20 years) in smaller (>1 cm DBH) individuals. Similarly, in 16¯18-year-old secondary forests that regrew in moderately used pastures in Costa Rica, plant species richness was much lower than that of old-growth forest for stems 10 cm DBH, but comparable in smaller-sized stems (Guariguata et al., 1997). In a replicated forest chronosequence in central Panamá, also reported no obvious variation in species richness of woody seedlings as a function of stand age compared to old-growth levels. In subtropical Puerto Rico, plant species richness of woody stems 1 cm DBH in abandoned pastures was similar to that of old-growth forest but not before 40 years after abandonment (Aide et al., 1996), an estimate slightly higher than those mentioned above. The fact that plant species richness in small size classes rapidly reaches old-growth forest values in all these studies mentioned, also suggests unlimited propagule dispersal from nearby sources.

While plant species richness in secondary forests can approach old-growth values within a few decades after site abandonment, returning to a species composition similar to old-growth forest will be a much longer process, particularly for canopy trees due to their slow turnover time
 
Accumulation of biomass

Typically, secondary forest succession is characterized by shifts in the biomass allocation of the plant community. In early succession, relatively more biomass is allocated to resource acquiring tissues (leaves and fine roots) and in later stages more is allocated towards structural materials (woody stems and coarse roots). Fine root (<2 mm diameter) biomass accumulates at a slower rate than leaf biomass, but its recovery can still be quite rapid. Secondary forests can have greater fine root biomass than plantations of similar age (Cuevas et al., 1991). Secondary forests can also have similar or higher fine root biomass than old-growth forest. Fine root length densities (cm root/cm3 of soil) in 15 year secondary forest can be higher than in old-growth forest in eastern Amazonia .
The regenerative power of Neotropical forest vegetation is clearly high, if propagule sources and land use intensity before abandonment has not been severe. Nonetheless, the recovery of biophysical properties and vegetation is heavily dependent on the interactions between site-specific factors and land use, which makes it extremely difficult to predict successional trajectories in anthropogenic settings. Considerations of site history have provided many useful insights into how Neotropical forest structure and function is influenced by human activity (e.g., Garcia-Montiel and Scatena, 1994; Foster et al., 1999), but as yet we are unable to develop a deterministic model of how land use history and intensity affects tropical forests.