Manuel R. Guariguata

Neotropical secondary forest succession: changes in structural and functional characteristics

Abstract In this review, we highlight the main biotic and abiotic factors that influence the patterns of Neotropical secondary forest successions, referred as the woody vegetation that regrows after complete forest clearance due to human activities. We focus on both patterns of species replacement and various processes that occur during succession, and suggest that the sequence of processes may be predictable even if species composition is not. We describe forest recovery with respect to old-growth conditions, which we define as the structure, function, and composition of the original forest before conversion, and we examine this recovery process within the context of type and intensity of past land use. The various phases of the recovery process are described in detail: from factors affecting early colonization, changes in light and soil properties, soil–vegetation feedbacks at initial and later successional stages, biomass accumulation, forest productivity, rates of species accumulation, and species composition. The consensus of these analyses is that the regenerative power of Neotropical forest vegetation is high, if propagule sources are close by and land use intensity before abandonment has not been severe. Nevertheless, 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. We attempt, throughout this review, to integrate the structural and functional characteristics of secondary succession as a way to enhance our ability both to predict and manage successional forest ecosystems due to their increasing importance as timber sources, providers of environmental services, and templates for restoration purposes.

SEED AND SEEDLING ECOLOGY OF TREE SPECIES IN NEOTROPICAL SECONDARY FORESTS: MANAGEMENT IMPLICATIONS

In spite of the growing importance of neotropical secondary forests as sources of timber and environmental services, the baseline information needed to develop silvicultural options is still limited. In this paper I describe interspecific patterns of seed longevity in the soil, germination, and survival and growth of transplanted seedlings under closed canopy of nine tree species that are common in secondary forest stands in wet, lowland Costa Rica and most of which are timber species in the region: Cordia alliodora, Hampea appendiculata, Jacaranda copaia, Laetia procera, Rollinia microsepala, Simarouba amara, Stryphnodendron microstachyum, Trichospermum grewiifolium, and Vochysia ferruginea. Many of these species also occur throughout the lowland neotropics. Experiments were carried out in three replicate secondary-forest stands (20–30 yr old after pasture abandonment) located at La Selva Biological Station in northeastern Costa Rica. Longevity of experimental seed cohorts differed markedly among species...

Strategies for genetic conservation of trees in the Peruvian Amazon

Forestry practices and high rates of land clearance for agriculture are causing genetic erosion of valuable tree species in the Peruvian Amazon, thereby endangering the economic sustainability of rural communities and limiting Perus opportunities for the development of new timber and non-timber forest products. The potential utility and limitations of six low-input interventions to help forestall further genetic erosion in the region are discussed, with a focus on local community involvement. Improved agroforestry systems may help reduce deforestation by increasing farm productivity, although methods to increase the currently low adoption rate of these technologies need to be developed. Use of strategic tree domestication techniques can also improve farm productivity and prevent inadvertent genetic drift and inbreeding associated with traditional domestication practices, although to have a major impact, current programs need to be extended across the region. Woodlot forestry could supplant selective extraction of timber and offers an attractive opportunity for poverty alleviation if appropriate credit and land tenure policies can be developed. However, it may also result in increased deforestation if activities on public land cannot be controlled. The implementation of improved seed collection systems and simple seed transfer guidelines would help to reduce the collection of seed of poor quality and low genetic diversity, and avoid maladapted plantings, although such programs are difficult to monitor and seed costs may increase. Strategic identification and design of in situ conservation areas would help to ensure the viability of conserved populations, but requires the forfeiture of significant revenue from timber concessions.

Demographic response of tree juveniles to reduced-impact logging in a Costa Rican montane forest

Abstract We assessed diameter and height growth, and mortality in seedlings (individuals ≥0.3, but