Luciana F. Alves

An estimate of the number of tropical tree species

Significance People are fascinated by the amazing diversity of tropical forests and will be surprised to learn that robust estimates of the number of tropical tree species are lacking. We show that there are at least 40,000, but possibly more than 53,000, tree species in the tropics, in contrast to only 124 across temperate Europe. Almost all tropical tree species are restricted to their respective continents, and the Indo-Pacific region appears to be as species-rich as tropical America, with each of these two regions being almost five times as rich in tree species as African tropical forests. Our study shows that most tree species are extremely rare, meaning that they may be under serious risk of extinction at current deforestation rates. The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

Tree allometry and crown shape of four tree species in Atlantic rain forest, south-east Brazil

The allometry of crown shape and trunk diameter with tree height were analysed for four tree species in a tropical lowland rain forest, southeast Brazil. The dimensional relationships of a subcanopy species (Garcinia gardneriana) were contrasted with those of two canopy (Chrysophyllum flexuosum and Swartzia simplex) and one emergent species (Sloanea guianensis). For all trees 1 cm dbh, we recorded dbh, total height, branching height, crown area, crown width and crown length. Observed allometric relationships indicated interspecific variation in trunk diameter and crown shape with height. All species conformed to the elastic similarity model, except the emergent one that showed thicker trunks and a scaling exponent conforming to the constant stress model. The general allometric function used to describe the overall relationship (all sizes combined) did not specify exceptional variation in crown shape between species of contrasting adult stature (emergent vs. subcanopy species). However, when allometric relationships through ontogeny were considered, different strategies of growth, maintenance and expansion of crown became evident. Crown shapes were much more variable in canopy and emergent species than in the subcanopy one, suggesting that larger- statured species might be more flexible inthe relative allocationof en ergy to height, diameter, and crown growth than smaller-statured ones. Notwithstanding, it is suggested that it is not possible adequately to predict allometric relationships only by adult stature/canopy position. Allometric variation may be also related to size-dependent changes in demographic traits and/or different responses to light availability among tree species.

Uma área de relevante interesse biológico, porém pouco conhecida: a Reserva Florestal do Morro Grande

The Morro Grande Forest Reserve (10,870 ha) is one of the biggest forest areas in the Atlantic Plateau. This region was intensively deforested for agriculture, wood and charcoal production, and more recently by the expansion of urban areas. The Reserve is located in the cristalline Plateau of Ibiuna, just above the Paranapiacaba Mountain (860 1075 m above sea level), in a transition region between the rainy climate from the Atlantic coast, and the seasonal climate from inland Sao Paulo state. As a consequence, species composition in Morro Grande Reserve combines elements from the tropical rainforest and the semideciduous forest. Despite this particularity, few studies were carried out in the forests from Morro Grande. It is only in 2000 that a group of scientist related to the BIOTA/FAPESP program began a systematic analysis of the species composition of different taxonomic groups, as well as the analysis of ecological processes related with forest regeneration. The present manuscript introduces a series of nine articles with the biological data obtained in the Reserve these last four years, and aims also to present an historical and abiotic description of the Reserve, highlighting aspects of the relief, geologic and pedological conditions, climate, hydrography, land use and land cover.

Stocks of carbon and nitrogen and partitioning between above- and belowground pools in the Brazilian coastal Atlantic Forest elevation range

We estimated carbon and nitrogen stocks in aboveground biomass (AGB) and belowground biomass (BGB) along an elevation range in forest sites located on the steep slopes of the Serra do Mar on the north coast of the State of São Paulo, southeast Brazil. In elevations of 100 m (lowland), 400 m (submontane), and 1000 m (montane) four 1-ha plots were established, and above- (live and dead) and belowground (live and dead) biomass were determined. Carbon and nitrogen concentrations in each compartment were determined and used to convert biomass into carbon and nitrogen stocks. The carbon aboveground stock (CAGB) varied along the elevation range from approximately 110 to 150 Mg·ha−1, and nitrogen aboveground stock (NAGB), varied from approximately 1.0 to 1.9 Mg·ha−1. The carbon belowground stock (CBGB) and the nitrogen belowground stock (NBGB) were significantly higher than the AGB and varied along the elevation range from approximately 200–300 Mg·ha−1, and from 14 to 20 Mg·ha−1, respectively. Finally, the total carbon stock (CTOTAL) varied from approximately 320 to 460 Mg·ha−1, and the nitrogen total stock (NTOTAL) from approximately 15 to 22 Mg·ha−1. Most of the carbon and nitrogen stocks were found belowground and not aboveground as normally found in lowland tropical forests. The above- and belowground stocks, and consequently, the total stocks of carbon and nitrogen increased significantly with elevation. As the soil and air temperature also decreased significantly with elevation, we found a significantly inverse relationship between carbon and nitrogen stocks and temperature. Using this inverse relationship, we made a first approach estimate that an increase of 1°C in soil temperature would decrease the carbon and nitrogen stocks in approximately 17 Mg·ha−1 and 1 Mg·ha−1 of carbon and nitrogen, respectively.

Florestas de restinga e de terras baixas na planície costeira do sudeste do Brasil: vegetação e heterogeneidade ambiental

It was evaluated the floristic similarity between two Atlantic Rainforest physiognomies in Brazilian coast area, herein called Restinga and Lowland forests. The hypothesis was that, due the differences in geomorphologic processes, these forests would differ on soil physical and chemical properties, floristic composition, live above-ground biomass and litterfall production. It was sampled 1 ha (100 × 100 m) for each site located in Ubatuba, Sao Paulo state, SE Brazil. Within each hectare it was recorded trees with DBH > 4.8 cm in all 10 × 10 m contiguous plots, and collected soil and litterfall samples. The cluster and ordination analyses indicated the two communities as distinct groups considering soil and floristic composition, agreeing with the initial hypothesis. Species diversity was higher (p 0.05) between the two forests. This apparent paradox could be explained assuming that, since different species establish themselves in the Restinga or Lowland forests and find a favorable spectrum of conditions and resources, they would tend to persist and to develop in that place; even so the edaphic conditions differ between the Restinga and Lowland forests, each species could respond in a particular way to these variations, and then both forests could reach similar values of biomass and litterfall production. It is probable that the environmental filter conditioned by soils has being important for the strong floristic segregation between these two forests.

A regeneração florestal em áreas de floresta secundária na Reserva Florestal do Morro Grande, Cotia, SP

Notwithstanding its complexity, a more integrated knowledge of the regeneration process in tropical forests subject to natural as well as human disturbance is necessary. Given the great extent of secondary forests in the Neotropics, an important topic to be considered is the potential of secondary forest patches to preserve the biological diversity of old-growth, less disturbed forests. The main objective of this study was to evaluate tree seedling community structure and its potential as source of regeneration in areas of secondary forest within the Morro Grande Forest Reserve (RFMG), one of the most important areas of Atlantic Rain Forest on the Atlantic Plateau. The structure and composition of the tree seedling community was sampled in 1 m2 plots randomly placed in three areas of secondary forest. We recognized 106 species among 742 sampled tree seedlings, distributed in 35 families and 69 genera. The richest families (Myrtaceae, Fabaceae, Rubiaceae and Lauraceae) represented 47% of the species total, and the five more abundant species were Myrcia fallax, Ocotea dispersa, Psychotria vellosiana, Psychotria suterella, and Matayba elaeagnoides. Woody species regeneration was predominantly composed of zoochoric and shade tolerant species, characteristics of more advanced stages of Atlantic Rain Forest succession. Tree seedling community did not vary in abundance and size structure, but species composition and richness varied significantly among areas. Our results suggest that woody regeneration in secondary forest areas of the RFMG has a high potential of maintaining tree biological diversity of old-growth forests and, consequently, contributing to forest restoration at the regional scale. Spatial heterogeneity in floristic composition and species richness of the seed rain, as well as of the tree seedling community in secondary forest patches, represent important components that influence the sucessional process and the maintenance of species diversity, therefore acting as sources of recruitment of new individuals and species.

NEON terrestrial field observations: designing continental‐scale, standardized sampling

Rapid changes in climate and land use and the resulting shifts in species distributions and ecosystem functions have motivated the development of the National Ecological Observatory Network (NEON). Integrating across spatial scales from ground sampling to remote sensing, NEON will provide data for users to address ecological responses to changes in climate, land use, and species invasion across the United States for at least 30 years. Although NEON remote sensing and tower sensor elements are relatively well known, the biological measurements are not. This manuscript describes NEON terrestrial sampling, which targets organisms across a range of generation and turnover times, and a hierarchy of measurable biological states. Measurements encompass species diversity, abundance, phenology, demography, infectious disease, ecohydrology, and biogeochemistry. The continental-scale sampling requires collection of comparable and calibrated data using transparent methods. Data will be publicly available in a variety of formats and suitable for integration with other long-term efforts. NEON will provide users with the data necessary to address large-scale questions, challenge current ecological paradigms, and forecast ecological change.

Height-diameter relationships of tropical Atlantic moist forest trees in southeastern Brazil

Site-specific height-diameter models may be used to improve biomass estimates for forest inventories where only diameter at breast height (DBH) measurements are available. In this study, we fit height-diameter models for vegetation types of a tropical Atlantic forest using field measurements of height across plots along an altitudinal gradient. To fit height-diameter models, we sampled trees by DBH class and measured tree height within 13 one-hectare permanent plots established at four altitude classes. To select the best model we tested the performance of 11 height-diameter models using the Akaike Information Criterion (AIC). The Weibull and Chapman-Richards height-diameter models performed better than other models, and regional site-specific models performed better than the general model. In addition, there is a slight variation of height-diameter relationships across the altitudinal gradient and an extensive difference in the stature between the Atlantic and Amazon forests. The results showed the effect of altitude on tree height estimates and emphasize the need for altitude-specific models that produce more accurate results than a general model that encompasses all altitudes. To improve biomass estimation, the development of regional height-diameter models that estimate tree height using a subset of randomly sampled trees presents an approach to supplement surveys where only diameter has been measured.

Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography

Forest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change.

Allometry of a neotropical palm, Euterpe edulis Mart.

Neste trabalho foram analisadas as relacoes entre o diâmetro e a altura de uma palmeira Neotropical (Euterpe edulis) comum na Floresta Atlântica do SE do Brasil. As relacoes observadas entre a altura e o diâmetro ao longo do estipe (diâmetro ao nivel do solo (DAS), e diâmetro ao nivel do peito (DAP) foram comparadas a tres modelos teoricos de estabilidade mecânica: similaridade elastica, similaridade de estresse e similaridade geometrica. As inclinacoes das regressoes altura-diâmetro nao se ajustaram a nenhum dos modelos de estabilidade mecânica. Diferencas significativas na alometria do estipe foram encontradas comparando-se as relacoes altura-DAS com altura-DAP, sugerindo maior incremento em DAP com a altura. A relacao entre o fator de seguranca do diâmetro contra quebra e a altura mostrou que tanto o DAS como o DAP encontram-se acima do limite teorico de quebra de McMahon para arvores, mas alguns individuos aproximam-se deste limite em relacao ao DAP. Apesar de apresentarem padrao similar de decrescimo do fator de seguranca com a altura, as diferencas encontradas para o fator de seguranca ao longo do estipe - maior fator de seguranca para o DAS quando comparado com o DAP - indicam que o risco de quebra em palmeiras depende do tamanho e varia ao longo do estipe. As relacoes alometricas distintas ao longo do estipe obtidas para Euterpe edulis podem estar refletindo possiveis diferencas na forma do estipe e nas estrategias de crescimento.