Annotated Checklist of the Vascular Plants of the Serranía de Pilón Lajas and the Adjacent Piedmont, Ballivian Province, Beni, Bolivia
Compiled by David N. Smith¹ (deceased) and Timothy J. Killeen²
1. Herbario Nacional de Bolivia
2. Missouri Botanical Garden
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This annotated checklist of the plants of the Serranía Pilón Lajas has been compiled from approximately 1300 specimens that have been collected in an area that includes the Andean piedmont from Rurrenabaque to Yucumo, the valley of the Río Quiquibey, the Serranía Pilón and the adjacent Serranía de Bala. The extensive collections at the Herbario Nacional de Bolivia (LPB) were reviewed and these other specimens were added to produce a preliminary checklist (Smith & Killeen, unpublished manuscript). Most of these collections were made by the senior author prior to his death between 1988 and 1991; additional collections were made by the second author, S. Beck., J. Solomon, A. Fournet, and a few other botanists.
Table 1 presents summary data for the flora of the region, listing the most diverse families in the zone, as well as a general classification of the species with respect to life forms. The list shows low numbers of epiphyte that are typically rich in montane humid forests. This anomaly can be attributed to a sampling bias, as the emphasis of the project was tree inventory with a strong effort dedicated to plot studies; likewise, lianas, shrubs and herbs are probably undersampled. In spite of the emphasis on tree inventory, it remains highly unlikely that the region has been adequately sampled for even this life form. Most collecting has been restricted to the areas immediately surrounding the two plots, and a narrow band of vegetation along the principal highway between Quiquibey and Yucumo. The recently created "Pilón Lajas Biosphere Reserve and Indigenous Territory" encompasses several additional habitat types, such as cloud forest, montane savanna, and riverine forest. The new protected area incorporates the very humid intermontane valley of the Río Quiquibey, the floodplain of the Río Alto Beni to the northwest, and the cloud forest regions of the Serranía de Beau that is the southwestern boundary of the reserve. Nee (1995) lists 1,093 generas and 2,496 species of vascular plants in his Flora of Amboro National Park and estimates that the total flora of that protected area is actually greater than 3,500 species.
The newly created Reserva de la Biosfera y Terretorio Indigena de Pilón Lajas incorporates many of the same vegetation types found in Amboro National Park. However, the altitudinal variation and the intensity of the rain shadow effect on the downwind side of the mountains are substantially less pronounced in comparison to Amboro. As such, the total flora of the Pilón Lajas will probably eventually be documented at around 2500 to 3000 species. This preliminary list then would provide only between 24 to 30% of the total flora of the new protected area.