Land-use history and forest regeneration in the Cayey Mountains, Puerto Rico

Although deforestation continues to be a major threat to tropical biodivers ity, abandonment of agricultural land in Puerto Rico provides an opportunit y to study long-term patterns of secondary forest regeneration. Using aeria l photographs from 1937, 1967, and 1995, we determined land-use history for 2443 ha in the Cayey Mountains. Pastures were the dominant land cover in 1 937 and <20% of the area was classified as forest. Between 1937 and 1995, f orest cover increased to 62% due to widespread abandonment of agriculture. To examine the effect of historic land use on current forest structure and species composition, we sampled secondary forests in 24 abandoned pastures, 9 abandoned coffee plantations and 4 old-growth forest sites. Sites were l ocated on two soil types along an elevational gradient (125-710 m) and incl uded a chronosequence from 4 to over 80 years old. After 25-30 years, basal area and species richness in secondary forest sites derived from abandoned pastures and coffee plantations were similar to old-growth forest sites. T he species composition of secondary forests derived from abandoned pastures and coffee plantations remained distinct from old-growth forest. In additi on to historic land use, age and elevation were important environmental var iables explaining variation in secondary forest species composition. Nonind igenous species were common in recently abandoned pastures and coffee plant ations, but their importance declined in the older sites. This study demons trates that secondary forests on private land can be an important component of the conservation of tropical tree biodiversity.