Forest regeneration in abandoned coffee plantations and pastures in the Cordillera Central of Puerto Rico
Humfredo Marcano-Vega 1,2, T. Mitchell Aide 1,* and David Báez 1
Department of Biology, University of Puerto Rico, PO Box 23360, San Juan, Puerto Rico 00931-3360, USA; Current address:Present address: Institute for Tropical Ecosystems Studies University of Puerto Rico, PO Box 363682, San Juan, Puerto Rico 00936-3682, USA; *Author for correspondence (e-mail: email@example.com; phone: (787) 764 0000 ext 1-2580 fax: (787) 764 2610)
Received 24 January 2000; accepted in revised form 17 November 2000
Key words: Abandoned agricultural lands, Beta diversity, Foreststructure, Land-use history, Secondary succession, Tropics Abstract Forest structure and species composition were described in abandoned shade and sun coffee plantations and abandoned pastures in Puerto Rico. Forest structural characteristics were similar to older forest sites after approximately 30 yr of recovery. The historical presence of shade coffee plantations as the dominant agriculturalactivity in the region has resulted in the homogenization of secondary forest composition. The continuous dominance of Coffea arabica and species used for shade in abandoned shade coffee contributed to a slower rate of species composition change in comparison to abandoned pastures. Abandoned pastures were initially colonized by a group of light demanding and/or wind dispersed species and then by shadetolerant species characteristic of abandoned shade coffee plantations, suggesting that the secondary forests of abandoned shade coffee plantation are the major source of species in this landscape. The presence of a few isolated big trees in sun coffee plantations appeared to facilitate colonization of woody species similar in composition to abandoned shade coffee plantations. In a multivariateanalysis, time since abandonment and elevation were the variables that explained the majority of variability in species composition among sites. However, a few native species (e.g. Guarea guidonia, Casearia sylvestris, Ocotea leucoxylon) were common regardless of land use history or elevation. In contrast, important old forest species (e.g. Sloanea berteriana, Dacryodes excelsa, Manilkara bidentata)were rare or absent from most of the secondary forest stands suggesting the need to reintroduce these species. Land management and conservation efforts can be improved by incorporating the effects of land use history on secondary forest dynamics. Introduction Thousands of years of land-use change has resulted in extensive areas of agricultural and pastures lands, plantations, and degraded forestthat have greatly altered the species composition of many landscapes (Ojima et al. 1994). The acceleration of these changes during the last 30 years, particularly tropical deforestation, has generated worldwide concern due to increases in greenhouse gas emissions, loss of biodiversity, and changes in the global climate (Houghton 1994; Brown and Lugo 1994). Although the rate of tropicaldeforestation is much greater than reforestation (Rudel and Roper 1996), secondary forests resulting from human impact account for approximately 40% of the total forested area in the tropics (Brown and Lugo 1990). If these large areas of secondary forest can be properly managed, this could reduce the pressure on the remaining areas of intact forest (Anderson 1990; Brown and Lugo 1990; Finegan 1992). A soundunderstanding of the dynamics of secondary succession after the abandonment of agricultural lands is needed if we intend on managing these forests for conservation or sustained agroforestry uses
76 (Brown and Lugo 1994; Uhl et al. 1990; Finegan 1992). The island of Puerto Rico offers the opportunity to study the effects of different land use practices on secondary forest regeneration (García...