No abstract

For vegetation on white sand in Amazonia, the topography, soil nutrients, level of the water table, and rainfall combine to result in distinct formations, each with a characteristic physiognomy and each with a rather distinct floristic composition and very distinct dominants. We describe the physiognomies and present the floristic composition of nine formations, based on intensive fieldwork in NW Acre state, Brazil, where on six sites we have documented 222 species; 170 of them are woody plants or trunked palms ≥5 cm diam. Herbaceous species are good indicators for some of the formations. Distribution patterns and habitat specialization can be difficult to interpret because they often require familiarity with the localities and local terminologies involved. Many of the species show disjunct distributions congruent with the occurrence of other white-sand areas in northern South America. The nine formations within Acre are strongly dissimilar, with only two pairwise comparisons showing >50 percent similarity. Comparison of the Acre white-sand flora with datasets from Peruvian and Central + Eastern Amazonia show striking differences in composition and in taxonomic dominance, with more than 95 percent dissimilarity. White-sand formations in Acre and elsewhere are gravely affected by expanding human settlement; little is known about the regeneration and recovery of the degraded white-sand habitats. This complex sector of Acre's biological diversity is still virtually unrepresented in conservation units anywhere in Brazil's part of southwestern Amazonia, so it should be made an immediate conservation priority.Abstract in Portuguese is available with online material.

Even though it is well known that the flora of Amazonia is severely under-documented, botanical research in the region has been stagnant for the past two decades or more. An exception to this trend has been the international collaboration in the state of Acre, Brazil. The objective of this study was to assess botanical progress in Southwestern Amazonia, specifically the evolution of our knowledge of the flora of the state of Acre five years after production of the first catalogue of its flora. Between 2006-2011, the Acre data-base recorded 2,110 determinations, and among these were 347 new records for Acre, representing an increase of 8.6% in the known flora, which as of 2011 comprised 4351 species. Of the new records, 6.6% (23) were new records for Brazil and 14.4% (50) represented genera new to Acre. The new records comprised 322 species of vascular plants and 22 of non-vascular plants. The most significant finding was that one of every six identifications was a new record for Acre; the total flora of Acre is estimated to be at about 8,000 species. Advances in documentation of the Acre flora have been achieved through institutional partnerships, attention to rescuing and "cleaning" data, mobilizing taxonomic specialists, distributing duplicates to herbaria with significant Amazon collections, and undertaking expeditions to regions of the state that were poorly known or unknown. Indeed, the botanical inventory of Amazonia overall and the management and conservation of the Amazon flora can be realized only through programs that are systematic, integrative and participatory. Every effort must be made to guarantee that the inventory of Amazonia proceeds at least as rapidly as deforestation and development. This necessarily means far greater investment in training, employing, and supporting the field work of productive taxonomists.

Forestry managers have been searching for ways to reduce the impacts of logging on Amazonian biodiversity, but some basic factors are still not considered in native forestry operations, among them the diversity of epiphytes associated with the logged trees. Our goals in this study were to determine the floristic composition, quantify the species richness, and characterize the species diversity of the vascular epiphytic community present in three timber tree species in Acre State, Brazil. We collected and identified all epiphytes in 30 randomly selected trees C35 cm DBH of each of three important timber species, Tabebuia serratifolia, Manilkara inundata and Couratari macrosperma. We also documented the epiphyte diversity in 120 randomly selected trees C35 cm DBH of 56 other species to determine whether the three timber species have different epiphyte diversity than the tree community at large. The epiphyte samples in the three timber species showed 77 species, 13 of which were new records for the flora of Acre state. The epiphyte community in the randomly selected trees presented a total of 56 species. The timber species phorophytes hosted on average three times more epiphyte species per tree than the other 120 randomly selected trees. These results show that a substantial portion of local floristic richness can be lost during logging activity due if not properly managed by rescuing epiphytes after felling the trees. Although these epiphytes could contribute positively to forestry sustainability due to their ornamental value, increasing the economic yield per hectare, there are no local initiatives for economic use of epiphytes.

Vascular epiphytes are common in tropical forests and represent a considerable part of the biodiversity in Southwestern Amazonia. The aim of this study was to determine the floristic composition, patterns of species richness, and geographical distribution and knowledge gaps (collection effort) of the epiphytic vascular flora of the Brazilian State of Acre. We analyzed the database of the Flora of Acre and found a total of 331 species and 32 families of angiosperms and ferns. Almost half of the epiphytic flora of Acre (48% of species) occurs only in Northern Brazil. Of the total species, 56% are restricted to Amazonia. The distribution of the number of collections of epiphytes is concentrated in a few locations in the state and there is a positive correlation between the number of collections of epiphytes and the general index of collection density. The low and unequal sampling effort of epiphytes across the State, the high proportion of specimens identified at best to genus, and the still steep species/sampling curve indicates that the true diversity of epiphytes in Southwestern Amazonia is expressively higher than recorded thus far. This highlights the need for efforts specifically focused on documenting under-represented taxonomic groups as well as more thorough inventory of the canopy flora in this region of Amazonia.