Strong floristic distinctiveness across Neotropical successional forests.

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Wet and dry tropical forests show opposite successional pathways in wood density but converge over time.

Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions.

Can plant DNA barcoding be implemented in species-rich tropical regions? A perspective from São Paulo State, Brazil.

DNA barcoding helps to identify species, especially when identification is based on parts of organisms or life stages such as seeds, pollen, wood, roots or juveniles. However, the implementation of this approach strongly depends on the existence of complete reference libraries of DNA sequences. If such a library is incomplete, DNA-based identification will be inefficient. Here, we assess if DNA barcoding can already be implemented in species-rich tropical regions. We focus on the tree flora of São Paulo state, Brazil, which contains more than 2000 tree species. Using new DNA sequence data and carefully assembled GenBank accessions, we assembled 12,113 sequences from ten different regions. The ITS, rbcL, psbA-trnH, matK and trnL regions were better represented within the available sequences for São Paulo tree flora. Currently, only 58% of the São Paulo tree flora currently have at least one barcoding sequence available. However, these species represent on average 89% of the trees in São Paulo state forests. Therefore, conservation-oriented and ecological studies can already benefit from DNA barcoding to obtain more accurate species identifications. We present which taxa remain underrepresented for the São Paulo tree flora and discuss the implications of this result for other species-rich tropical regions.

Legume abundance along successional and rainfall gradients in Neotropical forests.

The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N2, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.

Plant Species in a tract of insular Atlantic Forest in Ilhabela (SP): Floristics, photographic documentation, and identification keys of arboreal dicotyledons based on vegetative characteristics / Espécies vegetais em um trecho de Mata Atlântica insular em Ilhabela (SP): Florística, documentação fotográfica e chaves de identificação de dicotiledôneas arbóreas baseadas em características vegetativas

Abstract: The Ilhabela State Park (PEIb, for Parque Estadual Ilhabela in Portuguese)-located between 23º 46' 28" south latitude and 45º 21' 20" west latitude-is responsible for the conservation of one of the most important, and most devastated, fragments of insular Atlantic Forest. To catalog the arboreal species along the trails of the Conservation Unit, and to provide a practical instrument to facilitate the recognition of these species, we aimed with this work to conduct a floristic and photographic survey of distinct life forms and create an identification key for arboreal dicotyledonous species based on vegetative characters. We cataloged 123 species belonging to 99 genera and 46 botanical families. The best-represented families were Rubiaceae (15 spp.), Fabaceae (10), Piperaceae (10), Myrtaceae (8), Melatomataceae (7) and Lauraceae (7). We found three species threatened with extinction, two new occurrences for the state of São Paulo, and one plant species new to science, demonstrating the floristic importance of the region. We developed three vegetative dichotomous identification keys: to species with compound leaves; simple and opposite leaves; and alternate simple leaves. The dichotomous keys presents 97 arboreal species, distributed among 37 families, and was based on vegetative characters such as phyllotaxis, composition and shape of the limbus, presence or absence of stipules, exudate, lenticels, indument, glands and dots. We also elaborated a photographic board with 118 species as a supplementary material to support the use of the identification key.

Resumo: O Parque Estadual de Ilhabela - PEIb (23º 46' e 28" de latitude sul e 45º 21' 20" de latitude oeste) é responsável pela conservação de um dos mais importantes e devastados fragmentos de Mata Atlântica insular. Como forma de listar as espécies arbóreas nas trilhas da Unidade de Conservação e fornecer um instrumento prático para auxiliar no reconhecimento dessas espécies, objetivamos nesse trabalho realizar um levantamento florístico e fotográfico com distintas formas de vida para elaborar uma chave de identificação das espécies de Dicotiledôneas arbóreas com base em caracteres vegetativos. Listamos 123 espécies, presentes em 99 gêneros e 46 famílias botânicas. As famílias mais bem representadas foram Rubiaceae (15 spp.), Fabaceae (10), Piperaceae (10), Myrtaceae (8), Melatomataceae (7) e Lauraceae (7). Encontramos três espécies ameaçadas de extinção, duas novas ocorrências para o estado de São Paulo e uma nova espécie de planta para a ciência, demonstrando a importância florística do local. Elaboramos três chaves dicotômicas vegetativas de identificação sendo elas: para espécies com folhas compostas; folhas simples e opostas; e folhas simples e alternas. As chaves apresentando 97 espécies arbóreas, distribuídas em 37 famílias, baseadas em caracteres vegetativos tais como filotaxia, composição e formato do limbo, presença ou ausência de estípulas, exsudado, lenticelas, indumento, glândulas e pontuações. Nós também elaboramos pranchas fotográficas como um material suplementar de auxílio à utilização da chave de identificação.