Eduardo van den Berg

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.

Composição florística e estrutura fitossociológica de uma floresta ripária em Itutinga, MG, e comparação com outras áreas

The floristic composition and phytosociological structure were investigated in an area of 7.55 ha of a riparian forest in Itutinga, State of Minas Gerais, Southeastern Brazil. This forest locates alongside a narrow creek, and is sharply bounded by montane grasslands. The phytosociological survey was done on 28 plots of 10 x 30 m where all individuals with diameter at the base of the trunk equal to or larger than 5 cm were recorded and had their diameter measured and height estimated. The floristic survey was based on specimens collected both in and outside the plots. The study area was compared with other forests of Sao Paulo and Minas Gerais States using multivariate analyses. The floristic survey recorded 162 species and 54 families. The forests with flora most similar to the study area were those in the same region (upper rio Grande). We suggest rainfall seasonality and altitude as the variables most strongly influencing the floristic differences among the forests compared. The phytosociological survey recorded 2145 individuals in 141 species. The highest structural similarities occurred with forests in Itutinga and Bom Sucesso, followed by Madre de Deus and Poco Bonito. We suggest differences and similarities in soil properties, topographic features and the occurrence of seasonal floods as the main variables influencing the pattern of similarity observed.

Comunidade arbórea de um continuum entre floresta paludosa e de encosta em Coqueiral, Minas Gerais, Brasil

The purpose of the present contribution was to describe the community of trees of a continuum extending from swampy to upland forest in Coqueiral, SE Brazil, assessing the correlations between the variations of community structure and those of the environment. Sampling was carried out in 25 plots of 20 X 20 m laid on the forest fragment to survey trees with a minimum circumference of 15.5 cm (registering their circumference, height and species) as well as topographic and soil variables. Species-environment correlations were analyzed using canonical correspondence analysis (CCA) and Spearmans test. The swampy and upland habitats differed substantially in both community structure and floristic composition. The general floristic profile was similar to that of other riparian forests of the Mid and Upper Rio Grande region, whilst the swampy portion of the forest differed from what is commonly found in SE Brazil. The species distribution was correlated mainly to soil drainage and proximity to the lake. The high soil diversity and the strong soil moisture gradient found over a small area resulted in different habitats and a diverse community of trees and shrubs that combined phyto-physiognomies of semideciduous and swampy forests, along with cerrado patches.

Dinâmica do componente arbustivo-arbóreo de uma floresta de galeria aluvial no planalto de Poços de Caldas, MG, Brasil

The dynamics of the shrub-tree component was investigated in an alluvial gallery forest in Pocos de Caldas, Minas Gerais, from 1998 to 2005. The main objective of this study was to verify if the rates of the dynamics of the alluvial gallery forests are less than other tropical riparian forest formations. Seasonal flooding was also studied to see if it generates a spatial variation in the dynamics of going from the stream side towards the forest border. The sample consisted of 101, 10×10-meter plots that were distributed in five blocks extending approximately 8 km along the Antas Rivers forest. Each block was divided into three sectors (stream side, forest interior, and forest edge). Compared with other tropical forests, especially the riparian ones, this forest showed lower rates in terms of structural alterations. The forest edge is more dynamic, mainly due to the greater amount of sunlight, which supplies an adequate environment for species with a short life cycle.

Comparação florística de florestas inundáveis das regiões Sudeste e Sul do Brasil

This study evaluated the variation of tree species composition of 35 wetland forest areas in Southeast and South Brazil. The analysis of the floristic composition was based on a floristic checklist containing 602 species of 23 alluvial forests (seasonally inundated) and 12 swamp forests (permanently waterlogged). The species were classified, using a c2 test, according to the habitat preference in: 1) swamp forest species, e.g. Magnolia ovata (A. St.-Hil.) Spreng., Dendropanax cuneatus (DC.) Decne & Planch. and Calophyllum brasiliense Cambess.; 2) alluvial forest species, e.g. Sebastiania commersoniana (Baill.) L.B. Sm. & Downs, Ocotea pulchella Mart. and Sorocea bonplandii (Baill.) W. Burger et al. and 3) non preferential species, e.g. Luehea divaricata Mart. & Zucc., Syagrus romanzoffiana (Cham.) Glassman and Copaifera langsdorffii Desf. Multivariate gradient analysis (Detrended Correspondence Analysis) showed higher clustering of swamp forest areas than aluvial forest areas, indicating close florist similarity in the first group. The results indicated that the environmental heterogeneity associated to different flood regimes is determinant in defining the phytogeographic patterns of wetland forest areas.

Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems

Ervas-de-passarinho tem sim sido regularmente estudadas em paises temperados por afetar negativamente especies cultivadas e florestas manejadas. Em comparacao com ambientes temperados pouco se conhece sobre a ecologia das ervas-de-passarinho neotropicais. Desta forma, e necessario maior conhecimento sobre o grupo porque sao importantes elementos de comunidades vegetais, atuando como recurso-chave para polinizadores, dispersores de sementes e herbivoros. Atraves de uma combinacao de trabalhos classicos ja publicados com evidencias empiricas recentes, nos apresentamos padroes emergentes da interacao entre ervas-de-passarinho com os organismos associados e questionamentos para estudos adicionais. Existe um crescente interesse neste grupo no Brasil. E embora existam informacoes sobre dispersao de sementes, estudos sobre biologia reprodutiva sao raros e representam um campo a ser explorado. O conhecimento da biologia basica das ervas-de-passarinho sera relevante para modelar sua distribuicao espacial usando uma abordagem metapopulacional ou epidemiologica. Nesta revisao nos sumarizamos os principais estudos conduzidos na regiao Neotropical para fornecer um panorama atual das pesquisas desenvolvidas, bem como novas ideias para futuras investigacoes, especialmente no Brasil.

Tree community floristic and structure of alluvial forest fragments in São Sebastião da Bela Vista, Minas Gerais, Brazil

Fragments of alluvial forest in the South of Minas Gerais, Brazil, were studied in order to assess the vegetation structure, tree diversity and the most influential environmental variables on vegetation variations. The environment and vegetation data (dbh ³ 5 cm) were collected in 54, 20 × 10 m, permanents plots allocated in a riverine forest and in five fragments of alluvial forests. In the plots, the survey totalled 2,064 tree individuals, distributed in 51 species. The canonical correspondence analysis detected a tree composition gradient in the first axis, related to Mg, organic matter and H + Al soil content, sand and clay percentage and soil water table level. The CCA second axis was associated with canopy coverage and soil silte percentage. Theses variables caused a plot group formation related to species distribution.

Factors influencing early secondary succession and ecosystem carbon stocks in Brazilian Atlantic Forest

Abstract Ecologically relevant restoration of secondary Atlantic forest on abandoned land offers a potential means to recover biodiversity and improve crucial ecosystem services, including carbon sequestration. Early secondary successional trajectories are determined by a range of environmental factors that influence plant community development. Context-specific understanding of forest vegetation communities, their dynamics, and underlying drivers is needed for future restoration strategies. In this study we examined relationships between soil (chemical and physical) and environmental (landscape and topographical) characteristics, plant community attributes, and carbon stocks during early secondary succession. Data were collected at two sites undergoing early secondary succession in seasonally-dry Atlantic Forest (Rio de Janeiro State, Brazil). Both sites were previously used for pasture and abandoned at similar times, but showed differing vegetation communities. We found tree biomass and diversity and ecosystem carbon storage to be strongly positively related to the amount of surrounding forest, less steep slopes and clay soils, and negatively to the abundance of the shrub Leandra aurea. Soil carbon pools significantly increased with aboveground tree biomass. The only factor significantly affecting the metric of overall successional development (combining tree biomass and diversity) was total surrounding forest cover. Our findings suggest recovery of secondary forest and below- and aboveground carbon storage is limited by the amount of adjacent forest, some soil properties and dense shrub establishment down-regulating the succession process. Overall we offer evidence of potential to improve recovery of Atlantic forest with ecologically relevant seeding/planting programmes and selective shrub removal that could benefit ecosystem carbon storage.

Metapopulation Dynamics of the Mistletoe and Its Host in Savanna Areas with Different Fire Occurrence

Mistletoes are aerial hemiparasitic plants which occupy patches of favorable habitat (host trees) surrounded by unfavorable habitat and may be possibly modeled as a metapopulation. A metapopulation is defined as a subdivided population that persists due to the balance between colonization and extinction in discrete habitat patches. Our aim was to evaluate the dynamics of the mistletoe Psittacanthus robustus and its host Vochysia thyrsoidea in three Brazilian savanna areas using a metapopulation approach. We also evaluated how the differences in terms of fire occurrence affected the dynamic of those populations (two areas burned during the study and one was fire protected). We monitored the populations at six-month intervals. P. robustus population structure and dynamics met the expected criteria for a metapopulation: i) the suitable habitats for the mistletoe occur in discrete patches; (ii) local populations went extinct during the study and (iii) colonization of previously non-occupied patches occurred. The ratio of occupied patches decreased in all areas with time. Local mistletoe populations went extinct due to two different causes: patch extinction in area with no fire and fire killing in the burned areas. In a burned area, the largest decrease of occupied patch ratios occurred due to a fire event that killed the parasites without, however, killing the host trees. The greatest mortality of V. thyrsoidea occurred in the area without fire. In this area, all the dead trees supported mistletoe individuals and no mortality was observed for parasite-free trees. Because P. robustus is a fire sensitive species and V. thyrsoidea is fire tolerant, P. robustus seems to increase host mortality, but its effect is lessened by periodic burning that reduces the parasite loads.

Dinâmica de uma comunidade arbórea após enchente em fragmentos florestais no sul de Minas Gerais

In order to evaluate the impact of a catastrophic flooding on tree individuals, it was carried out, in 2007, evaluation of an alluvial area in Sao Sebastiao da Bela Vista, MG, where it was sampled five alluvial fragments and a riparian forest, which was inventoried in 2005. Results show that after the flooding, a short-term dynamics was characterized by a mortality rate higher than recruitment rate and loss rate was higher than gain rate in basal area. However, the structure of the community was not affected, because frequency of surviving and dead trees in the diametric classes was proportional to the initial number of individual in each class. The results allowed to conclude that although there was no alteration in the diametric structure, the tree community dynamics reflected the disturbance caused by the flooding.